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Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m²/hour. However, with the mortar spraying machine, an area of 30m²/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence and compaction of plastering compared to the manual method.
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Available online at www.sciencedirect.com
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2017) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2017 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the 28th C IRP Design Conference 2018.
28th CIRP Design Conference, May 2018, Nantes, France
A new methodology to analyze the functional and physical architecture of
existing products for an assembly oriented product family identification
Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat
École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France
* Corresponding author. Tel.: +33 3 87 37 54 30; E-mail address: paul.stief@ensam.eu
Abstract
In today’s business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of
agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production
systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to
analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and
nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production
system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster
these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable
assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and
a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the
similarity between product families by providing design support to both, production system planners and product designers. An illustrative
example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of
thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.
© 2017 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018.
Keywords: Assembly; Design method; Family identification
1. Introduction
Due to the fast development in the domain of
communication and an ongoing trend of digitization and
digitalization, manufacturing enterprises are facing important
challenges in today’s market environments: a continuing
tendency towards reduction of product development times and
shortened product lifecycles. In addition, there is an increasing
demand of customization, being at the same time in a global
competition with competitors all over the world. This trend,
which is inducing the development from macro to micro
markets, results in diminished lot sizes due to augmenting
product varieties (high-volume to low-volume production) [1].
To cope with this augmenting variety as well as to be able to
identify possible optimization potentials in the existing
production system, it is important to have a precise knowledge
of the product range and characteristics manufactured and/or
assembled in this system. In this context, the main challenge in
modelling and analysis is now not only to cope with single
products, a limited product range or existing product families,
but also to be able to analyze and to compare products to define
new product families. It can be observed that classical existing
product families are regrouped in function of clients or features.
However, assembly oriented product families are hardly to find.
On the product family level, products differ mainly in two
main characteristics: (i) the number of components and (ii) the
type of components (e.g. mechanical, electrical, electronical).
Classical methodologies considering mainly single products
or solitary, already existing product families analyze the
product structure on a physical level (components level) which
causes difficulties regarding an efficient definition and
comparison of different product families. Addressing this
Procedia CIRP 91 (2020) 396–401
2212-8271 © 2020 The Authors. Published by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Peer-review under responsibility of the scientific committee of the CIRP BioManufacturing Conference 2019
10.1016/j.procir.2020.03.105
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2020) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2020.
30th CIRP Design 2020 (CIRP Design 2020)
Conceptualization, development and design of a mortar spraying machine
Wilson R. Nyembaa,c,*, Ngonidzashe L. Shangwaa, Simon Chinguwaa,b, Charles Mbohwac
aDepartment of Mechanical Engineering, University of Zimbabwe, P O Box MP 167, Mount Pleasant, Harare, Zimbabwe
bDepartment of Mechanical Engineering Science, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park 2006,
Johannesburg, South Africa
cDepartment of Quality and Operations Management, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park Bunting
Road Campus, South Africa, Pro Vice Chancellor for Strategic Partnerships and Industrialisation at the Unoversity of Zimbabwe.
* Corresponding author. Tel.: +263772345441; fax: +263-242-303280. E-mail address: nyemba@ yahoo.com
Abstract
Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high
velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the
development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine
was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture
weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders
whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m2/hour. However, with the mortar spraying machine, an
area of 30m2/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it
flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven
by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume
flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a
simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the
construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence
and compaction of plastering compared to the manual method.
© 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference.
Keywords: actuator; mortar; optimisation; plaster.
1. Introduction
Infrastructure development is one of the key economic
drivers in most industrializing countries. The construction
sector is critical in the development of any country as it plays a
pivotal role in industrialization, civilization and transport since
all emanate from construction [1]. The construction industry
takes up a lot of manual labour as it is one of the biggest
employers globally. However, most of the labour is unskilled
resulting in some cases with sub-standard jobs. Quite often,
plastering takes up on average 20-25% of time for construction
for most projects in industrializing countries where this process
is not mechanized [2]. Mechanization of the construction
process will undoubtedly increase human laborers’ efficiency,
which currently stands at 1% - 5.5% [2]. The backbone of any
construction project is mortar as it acts as a binder for strength
and an ornament for better surface finish [3]. Mortar is one of
the most versatile materials used for both binding bricks and
plastering in construction. Plastering is the process of covering
rough walls and inconsistently levelled surfaces in construction
with the application of a plaster [4]. The process of plastering is
vital in construction as it aids in obtaining a good ornamental
surface finish and strength of the structure by not allowing
moisture to weaken the structure. Sprayed mortar has the same
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2020) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2020.
30th CIRP Design 2020 (CIRP Design 2020)
Conceptualization, development and design of a mortar spraying machine
Wilson R. Nyembaa,c,*, Ngonidzashe L. Shangwaa, Simon Chinguwaa,b, Charles Mbohwac
aDepartment of Mechanical Engineering, University of Zimbabwe, P O Box MP 167, Mount Pleasant, Harare, Zimbabwe
bDepartment of Mechanical Engineering Science, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park 2006,
Johannesburg, South Africa
cDepartment of Quality and Operations Management, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park Bunting
Road Campus, South Africa, Pro Vice Chancellor for Strategic Partnerships and Industrialisation at the Unoversity of Zimbabwe.
* Corresponding author. Tel.: +263772345441; fax: +263-242-303280. E-mail address: nyemba@ yahoo.com
Abstract
Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high
velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the
development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine
was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture
weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders
whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m2/hour. However, with the mortar spraying machine, an
area of 30m2/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it
flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven
by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume
flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a
simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the
construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence
and compaction of plastering compared to the manual method.
© 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference.
Keywords: actuator; mortar; optimisation; plaster.
1. Introduction
Infrastructure development is one of the key economic
drivers in most industrializing countries. The construction
sector is critical in the development of any country as it plays a
pivotal role in industrialization, civilization and transport since
all emanate from construction [1]. The construction industry
takes up a lot of manual labour as it is one of the biggest
employers globally. However, most of the labour is unskilled
resulting in some cases with sub-standard jobs. Quite often,
plastering takes up on average 20-25% of time for construction
for most projects in industrializing countries where this process
is not mechanized [2]. Mechanization of the construction
process will undoubtedly increase human laborers’ efficiency,
which currently stands at 1% - 5.5% [2]. The backbone of any
construction project is mortar as it acts as a binder for strength
and an ornament for better surface finish [3]. Mortar is one of
the most versatile materials used for both binding bricks and
plastering in construction. Plastering is the process of covering
rough walls and inconsistently levelled surfaces in construction
with the application of a plaster [4]. The process of plastering is
vital in construction as it aids in obtaining a good ornamental
surface finish and strength of the structure by not allowing
moisture to weaken the structure. Sprayed mortar has the same
© 2020 The Authors. Published by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Peer-review under responsibility of the scientic committee of the CIRP BioManufacturing Conference 2019.
2 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
ingredients as normal mortar. However, there are additives such
as fibers and accelerators, making it a unique product [5]. One
of the most efficient methods of plastering is spraying the
mortar onto the walls since there is placement and compaction
at the same time. The high velocity with which the mortar is
placed onto the walls ensures good compaction [3]. Currently
in the Zimbabwean construction industry, almost all the
processes are manual, which results in more time being required
for their completion. Lack of mechanization in the local
construction industry has invariably resulted in not only the cost
of buildings remaining high but the quality of work has also
been compromised due to the manual nature in which the mortar
is applied. It was with this in mind and that automation of the
plastering process will make it more efficient [1] that a machine
and system to ease the process of plastering in terms of not only
efficiency but cost reduction, was designed and developed.
2. Background and literature
The quality of mortar is a vital aspect of a mortar spraying
system as the material has to be able to stick to the surface at
high velocity to avoid wastages. Spray mortar can be produced
by either dry mix or wet mix methods.
2.1. Dry Mix
During the dry-mix process, cement and additives are mixed
and fed into a mechanical hopper. The mixture is then
transferred at a calculated speed by a distributor into a stream
of compressed air in a hose directing it to the delivery nozzle.
Inside the nozzle, a perforated manifold is fitted, through which
pressurized water is utilized for mixing with the other
ingredients, before the mixture is applied at high velocity [6].
Fig. 1 shows a flow chart of the dry-mix procedure.
Fig. 1. Schematic flowchart for dry mortar mix
2.2. Wet mix
Wet-mix mortar involves pumping of a pre-mixed and
prepared mortar, usually ready-mixed concrete, to the nozzle as
shown in Fig. 2. The projection of high strength wet mix mortar
requires a calculated compromise between workability and
shoot ability, since at the pumping end it should be fluid enough
to allow for easy movement and stiff material is required at the
other end [7]. Compressed air is introduced at the nozzle to
propel the mixture onto the receiving end, as shown in Fig. 2
while Table 1 shows the essential differences between the two.
Fig 2 Schematic of the wet mortar mix
Table 1. Comparison of wet and dry mix
Wet mix process Dr mix process
Higher water to cement ratio Lower water to cement ratio
Delivery equipment: positive
displacement pump or
pneumatic feed
No pump required
More precise water content
control
Experienced nozzle-man required to
vary water content
Compressed air for transfer of
wet mortar from nozzle to wall
Compressed air for transfer of dry
mortar mix to the nozzle
Healthier working environment Dusty hazardous working environment
2.3. Automated plastering
Modern and automated plastering techniques with
sophisticated technology are now commonplace in
industrialized countries. However, due to limitations in funding
and capacity, such technologies are relatively new and
unaffordable in countries such as Zimbabwe. Construction
companies in such countries appear to be comfortable with the
manual methods of plastering in view of the readily available
cheap labour. The construction costs however remain high due
to the length of time taken to complete such processes.
Notwithstanding the available cheap labour, the trends for the
future in construction technology are to mechanize and
automate operations as local contractors face competition from
those that are contracted from countries such as South Africa
and China [8].
The automated plastering technology utilizes robots to apply
the mortar on vertical walls automatically and intricatel y [9].
These automated robot machines usually have three branches
the mechanical, electronic and software embedded so that they
can execute their tasks. This means a lot more work has to be
done to maintain them and their operation would require time
for a brick layer to operate them efficiently. The automatic
plastering robot innovation has been a huge stride in the
mechanization of the laborious and repetitive process of
plastering. However, it is practically effective when plastering
the wall in the vertical direction only [9]. Such machines have
proved to be very difficult to plaster curved sections of a
building. It also cannot be used to plaster ordinary buildings
since there will be nowhere to anchor the rail guides of the
machine. The automated robot is applicable in buildings with
ceilings.
Wilson R. Nyemba et al. / Procedia CIRP 91 (2020) 396–401 397
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2020) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2020.
30th CIRP Design 2020 (CIRP Design 2020)
Conceptualization, development and design of a mortar spraying machine
Wilson R. Nyembaa,c,*, Ngonidzashe L. Shangwaa, Simon Chinguwaa,b, Charles Mbohwac
aDepartment of Mechanical Engineering, University of Zimbabwe, P O Box MP 167, Mount Pleasant, Harare, Zimbabwe
bDepartment of Mechanical Engineering Science, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park 2006,
Johannesburg, South Africa
cDepartment of Quality and Operations Management, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park Bunting
Road Campus, South Africa, Pro Vice Chancellor for Strategic Partnerships and Industrialisation at the Unoversity of Zimbabwe.
* Corresponding author. Tel.: +263772345441; fax: +263-242-303280. E-mail address: nyemba@ yahoo.com
Abstract
Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high
velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the
development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine
was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture
weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders
whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m2/hour. However, with the mortar spraying machine, an
area of 30m2/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it
flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven
by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume
flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a
simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the
construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence
and compaction of plastering compared to the manual method.
© 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference.
Keywords: actuator; mortar; optimisation; plaster.
1. Introduction
Infrastructure development is one of the key economic
drivers in most industrializing countries. The construction
sector is critical in the development of any country as it plays a
pivotal role in industrialization, civilization and transport since
all emanate from construction [1]. The construction industry
takes up a lot of manual labour as it is one of the biggest
employers globally. However, most of the labour is unskilled
resulting in some cases with sub-standard jobs. Quite often,
plastering takes up on average 20-25% of time for construction
for most projects in industrializing countries where this process
is not mechanized [2]. Mechanization of the construction
process will undoubtedly increase human laborers’ efficiency,
which currently stands at 1% - 5.5% [2]. The backbone of any
construction project is mortar as it acts as a binder for strength
and an ornament for better surface finish [3]. Mortar is one of
the most versatile materials used for both binding bricks and
plastering in construction. Plastering is the process of covering
rough walls and inconsistently levelled surfaces in construction
with the application of a plaster [4]. The process of plastering is
vital in construction as it aids in obtaining a good ornamental
surface finish and strength of the structure by not allowing
moisture to weaken the structure. Sprayed mortar has the same
Available online at www.sciencedirect.com
ScienceDirect
Procedia CIRP 00 (2020) 000–000
www.elsevier.com/locate/procedia
2212-8271 © 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference 2020.
30th CIRP Design 2020 (CIRP Design 2020)
Conceptualization, development and design of a mortar spraying machine
Wilson R. Nyembaa,c,*, Ngonidzashe L. Shangwaa, Simon Chinguwaa,b, Charles Mbohwac
aDepartment of Mechanical Engineering, University of Zimbabwe, P O Box MP 167, Mount Pleasant, Harare, Zimbabwe
bDepartment of Mechanical Engineering Science, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park 2006,
Johannesburg, South Africa
cDepartment of Quality and Operations Management, Faculty of Engineering and the Built Environment, University of Johannesburg, Auckland Park Bunting
Road Campus, South Africa, Pro Vice Chancellor for Strategic Partnerships and Industrialisation at the Unoversity of Zimbabwe.
* Corresponding author. Tel.: +263772345441; fax: +263-242-303280. E-mail address: nyemba@ yahoo.com
Abstract
Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high
velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the
development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine
was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture
weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders
whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m2/hour. However, with the mortar spraying machine, an
area of 30m2/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it
flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven
by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume
flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a
simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the
construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence
and compaction of plastering compared to the manual method.
© 2020 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the scientific committee of the CIRP Design Conference.
Keywords: actuator; mortar; optimisation; plaster.
1. Introduction
Infrastructure development is one of the key economic
drivers in most industrializing countries. The construction
sector is critical in the development of any country as it plays a
pivotal role in industrialization, civilization and transport since
all emanate from construction [1]. The construction industry
takes up a lot of manual labour as it is one of the biggest
employers globally. However, most of the labour is unskilled
resulting in some cases with sub-standard jobs. Quite often,
plastering takes up on average 20-25% of time for construction
for most projects in industrializing countries where this process
is not mechanized [2]. Mechanization of the construction
process will undoubtedly increase human laborers’ efficiency,
which currently stands at 1% - 5.5% [2]. The backbone of any
construction project is mortar as it acts as a binder for strength
and an ornament for better surface finish [3]. Mortar is one of
the most versatile materials used for both binding bricks and
plastering in construction. Plastering is the process of covering
rough walls and inconsistently levelled surfaces in construction
with the application of a plaster [4]. The process of plastering is
vital in construction as it aids in obtaining a good ornamental
surface finish and strength of the structure by not allowing
moisture to weaken the structure. Sprayed mortar has the same
2 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
ingredients as normal mortar. However, there are additives such
as fibers and accelerators, making it a unique product [5]. One
of the most efficient methods of plastering is spraying the
mortar onto the walls since there is placement and compaction
at the same time. The high velocity with which the mortar is
placed onto the walls ensures good compaction [3]. Currently
in the Zimbabwean construction industry, almost all the
processes are manual, which results in more time being required
for their completion. Lack of mechanization in the local
construction industry has invariably resulted in not only the cost
of buildings remaining high but the quality of work has also
been compromised due to the manual nature in which the mortar
is applied. It was with this in mind and that automation of the
plastering process will make it more efficient [1] that a machine
and system to ease the process of plastering in terms of not only
efficiency but cost reduction, was designed and developed.
2. Background and literature
The quality of mortar is a vital aspect of a mortar spraying
system as the material has to be able to stick to the surface at
high velocity to avoid wastages. Spray mortar can be produced
by either dry mix or wet mix methods.
2.1. Dry Mix
During the dry-mix process, cement and additives are mixed
and fed into a mechanical hopper. The mixture is then
transferred at a calculated speed by a distributor into a stream
of compressed air in a hose directing it to the delivery nozzle.
Inside the nozzle, a perforated manifold is fitted, through which
pressurized water is utilized for mixing with the other
ingredients, before the mixture is applied at high velocity [6].
Fig. 1 shows a flow chart of the dry-mix procedure.
Fig. 1. Schematic flowchart for dry mortar mix
2.2. Wet mix
Wet-mix mortar involves pumping of a pre-mixed and
prepared mortar, usually ready-mixed concrete, to the nozzle as
shown in Fig. 2. The projection of high strength wet mix mortar
requires a calculated compromise between workability and
shoot ability, since at the pumping end it should be fluid enough
to allow for easy movement and stiff material is required at the
other end [7]. Compressed air is introduced at the nozzle to
propel the mixture onto the receiving end, as shown in Fig. 2
while Table 1 shows the essential differences between the two.
Fig 2 Schematic of the wet mortar mix
Table 1. Comparison of wet and dry mix
Wet mix process Dr mix process
Higher water to cement ratio Lower water to cement ratio
Delivery equipment: positive
displacement pump or
pneumatic feed
No pump required
More precise water content
control
Experienced nozzle-man required to
vary water content
Compressed air for transfer of
wet mortar from nozzle to wall
Compressed air for transfer of dry
mortar mix to the nozzle
Healthier working environment Dusty hazardous working environment
2.3. Automated plastering
Modern and automated plastering techniques with
sophisticated technology are now commonplace in
industrialized countries. However, due to limitations in funding
and capacity, such technologies are relatively new and
unaffordable in countries such as Zimbabwe. Construction
companies in such countries appear to be comfortable with the
manual methods of plastering in view of the readily available
cheap labour. The construction costs however remain high due
to the length of time taken to complete such processes.
Notwithstanding the available cheap labour, the trends for the
future in construction technology are to mechanize and
automate operations as local contractors face competition from
those that are contracted from countries such as South Africa
and China [8].
The automated plastering technology utilizes robots to apply
the mortar on vertical walls automatically and intricatel y [9].
These automated robot machines usually have three branches
the mechanical, electronic and software embedded so that they
can execute their tasks. This means a lot more work has to be
done to maintain them and their operation would require time
for a brick layer to operate them efficiently. The automatic
plastering robot innovation has been a huge stride in the
mechanization of the laborious and repetitive process of
plastering. However, it is practically effective when plastering
the wall in the vertical direction only [9]. Such machines have
proved to be very difficult to plaster curved sections of a
building. It also cannot be used to plaster ordinary buildings
since there will be nowhere to anchor the rail guides of the
machine. The automated robot is applicable in buildings with
ceilings.
398 Wilson R. Nyemba et al. / Procedia CIRP 91 (2020) 396–401
Nyemba et al./ Procedia CIRP 00 (2020) 000–000 3
The robot also has many parts joined together resulting in
more time being required to assemble the parts. This in turn
reduces its maintainability since there are more parts to
maintain. Since the machines are not produced locally, the
sprayed parts will also need to be imported, at probably
unaffordable levels of funding. In Zimbabwe and most
industrializing countries, the process of plastering is still
manual and traditional. Such technology with software would
not be sustainable for small scale construction. None of the
current modern plastering machines are being manufactured in
Zimbabwe.
Local companies are not looking into the mechanization of
the plastering process due to incapacitation in research and
development as well as the general economic recession since
2008 [10]. However, studies in most industrializing countries
have depicted a shortage in skilled labour. This has resulted in
task such as plastering being performed by unskilled personnel.
This has been done in a bid to cut costs. However, this has
resulted in cases of sub-standard work [8]. Plastering
contributes to the strength of a structure. When performing
manual plastering it is difficult to control the thickness and
evenness of the mortar. However, rendering mortar with the
spraying technique, the two can be controlled. Considering the
current foreign exchange shortages crippling Zimbabwe, the
local construction sector is left with no option but to look at
locally available skills and solutions that can mitigate the costs
while being as close as possible to the automated solution.
The ability to locally manufacture the mortar sprayer was a
positive step in the mechanization of the construction sector.
The modern designs are generally for pre-mixed mortar which
the local cement producers in Zimbabwe are not producing
currently. In most industrialized countries, pre-mixed mortar is
produced for different plastering purposes. Hence, the design
would be optimally developed for locally available cement. The
spraying process offers compaction and placement at the same
time. After applying the mortar with the trowel, the builder
normally employs the same tool for compaction and finishing.
2.4. Challenges in local plastering
Locally, the labour intensive and time-consuming traditional
method of plastering is still being utilized but this increases the
total cost of production. The process of plastering is usually
carried out by unskilled labour. Most of the construction work
in Zimbabwe is still manual and requires a lot of skilled labour
to complete the work. The number and quality of low-income
earners’ housing in Zimbabwe is low. This is coupled by the
high cost per unit which is not proportional to the lead
construction time as a result of the repetitive and high labour
demanding plastering process locally. This research aimed at
designing a consumer and environmentally friendly machine
that can assist in reducing the lead time, providing improved
strength to the structure and better surface finish. The overall
objectives were; designing a simple process for conveying the
mortar and spraying it on the wall, selection of materials for
manufacturing the machine from those available locally by
simplification of the process, mobility, portability and
maintainability by semi-skilled contractors. It also aimed at
reducing construction costs by minimizing the labour demand.
2.5. Justification and design specifications
In terms of reduction of costs, the construction process is
highly labour intensive due to the repetitive and manual jobs
that are involved in the process. Mortar spraying can lead to
elimination of formwork hence a saving in cost. The plastering
process manually takes a long time as the worker has to
repeatedly go over the plaster to get the required surface finish.
Mechanization of the process was anticipated to result in the
reduction of the labour cost and in turn reduce the overall cost
of construction.
Sprayed mortar has high ease of access. It can be used to
apply mortar in restricted areas such as curved surfaces. There
is no need to transport and build bulk structures but only the
operator and the machine are required. It is also relatively easier
to apply mortar in high places in comparison to the traditional
method of mortar application. There is also a need for provision
of low permeability and enhanced bond strength. If moisture
penetrates building walls it might result in cracks and the
collapse of the entire structure. However, due to high velocity
of placement it ensures good compaction and high density
coupled with low water absorption. The concrete mixture
contains additives and accelerators which further enhance bond
strength. In terms of maintainability, the design for the mortar
sprayer was assembled from locally and readily available
components hence the maintenance was easier. The design also
had minimal parts to reduce maintenance cost.
The current trowel and manual technique is a repetitive
process and this takes up a lot of time compared to the mortar
spraying and automated technique. Machines can spray a
minimum of 5kg of mortar per minute. This will take less time
than the traditional trowel technique which also has a small
surface area. The process of plastering involves the casting and
placement of mortar and this process is repetitive and time
consuming. The technology of rendering mortar by spraying
came into use in the 20th century following the industrial
revolution. Over the years, the process of mortar spraying has
evolved and is now characterized by high strength, durability
and low absorption [11]. This has been proven to be a far more
superior method of mortar application than the traditional
methods of applying mortar. After such research and with the
problem at hand the machine was designed to have the
following specification as detailed in the sections on design,
construction and results; power: 800
W, hopper capacity:
15 liters, maximum pressure: 25 bar, hose: 25 mm, screw
diameter: 20 mm and compressor: 12-16 cfm.
2.6. Research methodology
An analysis of automated wall plastering machines and
models of spray machines was carried out to familiarize with
the mortar spraying process where it was evident that
automated plastering robots are now commonplace in most
industrialized countries. Data was gathered on the operation of
these machines and their working principles. The information
was retrieved from previous research as contained in journals,
text books and periodicals, in order to come up with ideas on
how best the intended design could be achieved. The evaluation
of the feasibility of the mechanization of the construction
4 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
process was also derived from previous research such as that
carried out in Enugu South in Nigeria [2]. The concept of
plastering with the technique of spraying mortar has not been
extensively exploited in industrializing countries [2]. This was
evident from the surveys and interviews with local builders and
construction companies like the Design Team carried out
during the research. In order to develop and design a machine
that would be effective, it was imperative to carry out these
surveys in one of the low cost housing residential area of
Budiriro in Harare. This was carried out in conjunction with the
CABS consortium and construction project. While the country
still faces the challenges of the economic recession,
construction work was however still going on under such
schemes that are funded by some building societies. The survey
was meant to establish the need for such automated machines
locall y.
A total of 15 house construction sites were visited and
observations made on the trowel plastering technique
employed. The data gathered revealed on average the
contractors managed to cover 4-5 m2 in an hour. The
contractors also revealed that they paid their unskilled labour
on a daily basis for tasks such as plastering. However, it was
also observed that the workers may have been deliberately
delaying the processes in order to get paid more. The purpose
of these interactions, observations and interviews was to
ascertain the need for an automated system for spraying mortar
by analyzing all the available options and challenges. This also
enabled a clear understanding of the mortar design mix for
plastering purposes using the traditional methods which were
key in coming up with design calculations.
3. Materials and methods
The design comprised of a power drill, compressor and
elevated screw. A frustum hopper was used to hold the mortar
and the screw was rotated using a power drill. There was
constant stirring of the mortar by the screw so that it did not dry
out. In addition, the flowing of the mortar was enhanced by
gravity. The wet mix was placed in the hopper and the elevated
chamber was spiraled at the end for transferring the mortar. The
screw was partially immersed in the barrel to direct the mortar
and increase pressure.
3.1. Material selection
Components which are exposed to high stresses during
operation are generally required to be made from a high tensile
steel alloys [12]. AISI 4140 is a high tensile steel grade with
excellent shock resistance combined with high wear resistance.
It has a tensile strength of 850-1000 Nm-2 and is generally used
for applications such as machine tools, spindles, shafts, and
gears [13]. The conveying screw and the barrel are the
components exposed to the highest levels of stress hence they
were made from AISI 4140. Mild steel is a type of carbon steel
with low carbon content. Hence due to this, mild steel is more
ductile, machinable and weldable than high carbon steel. It has
a tensile strength of 400 MPa and is usually utilized in steel
structures due to its machinability [13]. The hopper was made
from mild steel sheet metal and required more machining than
any of the other components. The frame handle was made from
rubber owing to its uniform strength. More specifically,
Ethylene Propylene Diene Terpolymer (EPDM) was chosen for
its excellent weather resistance [14]. It also has good heat and
chemical resistance and can operate in damp or wet conditions.
3.2. Design of components
The hopper was made of a conical frustum which holds a
maximum of 32 kg of material. It was developed and fabricated
from a 2 mm mild steel sheet. Fig. 3 shows a snapshot of the
developed frustum. Taking the bulk density of mortar to be
2162 kg/m3, the generally used value [6] and volume of 32 kg
of mortar was obtained from equation (1) [6];
bulk
m
V
= 0.01480111m3 = 15l (1)
Hence, the hopper can carry a maximum of 15l of mortar.
The upper diameter was taken as 0.4 m and the lower diameter
as 0.15 m. From the volume of a conical frustum (equation 2),
the bottom diameter was 85 mm. The mortar conveying screw
was an integral part of the design and consisted of a shaft and
screw blade. The screw shaft was joint-less to reduce weight.
The capacity that the screw could convey was affected by the
screw and shaft diameters, speed of rotation and inclination.
  
    (2)
Fig. 3. Conical frustum hopper
The design specifications of the screw were
Design speed: 1200 rpm,
Power: 800W,
Volume flow rate: 10 l/min
Flight width: 0.1D.
The torque experienced by the conveying screw can be
obtained using equation 3 [15], from which T = 6.366 Nm.
PT
= 1200 2
800
60
T
(3)
After obtaining the torque the minimum shaft diameter can
be calculated from equation 4 [15]:
3
min
max
16
T
d

= 0.017m (4)
The design standard minimum shaft diameter was taken as
25 mm. In order to get the screw diameter, equation 5 was
applied, where C is the volume flow rate in m3/h, D is the screw
Wilson R. Nyemba et al. / Procedia CIRP 91 (2020) 396–401 399
Nyemba et al./ Procedia CIRP 00 (2020) 000–000 3
The robot also has many parts joined together resulting in
more time being required to assemble the parts. This in turn
reduces its maintainability since there are more parts to
maintain. Since the machines are not produced locally, the
sprayed parts will also need to be imported, at probably
unaffordable levels of funding. In Zimbabwe and most
industrializing countries, the process of plastering is still
manual and traditional. Such technology with software would
not be sustainable for small scale construction. None of the
current modern plastering machines are being manufactured in
Zimbabwe.
Local companies are not looking into the mechanization of
the plastering process due to incapacitation in research and
development as well as the general economic recession since
2008 [10]. However, studies in most industrializing countries
have depicted a shortage in skilled labour. This has resulted in
task such as plastering being performed by unskilled personnel.
This has been done in a bid to cut costs. However, this has
resulted in cases of sub-standard work [8]. Plastering
contributes to the strength of a structure. When performing
manual plastering it is difficult to control the thickness and
evenness of the mortar. However, rendering mortar with the
spraying technique, the two can be controlled. Considering the
current foreign exchange shortages crippling Zimbabwe, the
local construction sector is left with no option but to look at
locally available skills and solutions that can mitigate the costs
while being as close as possible to the automated solution.
The ability to locally manufacture the mortar sprayer was a
positive step in the mechanization of the construction sector.
The modern designs are generally for pre-mixed mortar which
the local cement producers in Zimbabwe are not producing
currently. In most industrialized countries, pre-mixed mortar is
produced for different plastering purposes. Hence, the design
would be optimally developed for locally available cement. The
spraying process offers compaction and placement at the same
time. After applying the mortar with the trowel, the builder
normally employs the same tool for compaction and finishing.
2.4. Challenges in local plastering
Locally, the labour intensive and time-consuming traditional
method of plastering is still being utilized but this increases the
total cost of production. The process of plastering is usually
carried out by unskilled labour. Most of the construction work
in Zimbabwe is still manual and requires a lot of skilled labour
to complete the work. The number and quality of low-income
earners’ housing in Zimbabwe is low. This is coupled by the
high cost per unit which is not proportional to the lead
construction time as a result of the repetitive and high labour
demanding plastering process locally. This research aimed at
designing a consumer and environmentally friendly machine
that can assist in reducing the lead time, providing improved
strength to the structure and better surface finish. The overall
objectives were; designing a simple process for conveying the
mortar and spraying it on the wall, selection of materials for
manufacturing the machine from those available locally by
simplification of the process, mobility, portability and
maintainability by semi-skilled contractors. It also aimed at
reducing construction costs by minimizing the labour demand.
2.5. Justification and design specifications
In terms of reduction of costs, the construction process is
highly labour intensive due to the repetitive and manual jobs
that are involved in the process. Mortar spraying can lead to
elimination of formwork hence a saving in cost. The plastering
process manually takes a long time as the worker has to
repeatedly go over the plaster to get the required surface finish.
Mechanization of the process was anticipated to result in the
reduction of the labour cost and in turn reduce the overall cost
of construction.
Sprayed mortar has high ease of access. It can be used to
apply mortar in restricted areas such as curved surfaces. There
is no need to transport and build bulk structures but only the
operator and the machine are required. It is also relatively easier
to apply mortar in high places in comparison to the traditional
method of mortar application. There is also a need for provision
of low permeability and enhanced bond strength. If moisture
penetrates building walls it might result in cracks and the
collapse of the entire structure. However, due to high velocity
of placement it ensures good compaction and high density
coupled with low water absorption. The concrete mixture
contains additives and accelerators which further enhance bond
strength. In terms of maintainability, the design for the mortar
sprayer was assembled from locally and readily available
components hence the maintenance was easier. The design also
had minimal parts to reduce maintenance cost.
The current trowel and manual technique is a repetitive
process and this takes up a lot of time compared to the mortar
spraying and automated technique. Machines can spray a
minimum of 5kg of mortar per minute. This will take less time
than the traditional trowel technique which also has a small
surface area. The process of plastering involves the casting and
placement of mortar and this process is repetitive and time
consuming. The technology of rendering mortar by spraying
came into use in the 20th century following the industrial
revolution. Over the years, the process of mortar spraying has
evolved and is now characterized by high strength, durability
and low absorption [11]. This has been proven to be a far more
superior method of mortar application than the traditional
methods of applying mortar. After such research and with the
problem at hand the machine was designed to have the
following specification as detailed in the sections on design,
construction and results; power: 800
W, hopper capacity:
15 liters, maximum pressure: 25 bar, hose: 25 mm, screw
diameter: 20 mm and compressor: 12-16 cfm.
2.6. Research methodology
An analysis of automated wall plastering machines and
models of spray machines was carried out to familiarize with
the mortar spraying process where it was evident that
automated plastering robots are now commonplace in most
industrialized countries. Data was gathered on the operation of
these machines and their working principles. The information
was retrieved from previous research as contained in journals,
text books and periodicals, in order to come up with ideas on
how best the intended design could be achieved. The evaluation
of the feasibility of the mechanization of the construction
4 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
process was also derived from previous research such as that
carried out in Enugu South in Nigeria [2]. The concept of
plastering with the technique of spraying mortar has not been
extensively exploited in industrializing countries [2]. This was
evident from the surveys and interviews with local builders and
construction companies like the Design Team carried out
during the research. In order to develop and design a machine
that would be effective, it was imperative to carry out these
surveys in one of the low cost housing residential area of
Budiriro in Harare. This was carried out in conjunction with the
CABS consortium and construction project. While the country
still faces the challenges of the economic recession,
construction work was however still going on under such
schemes that are funded by some building societies. The survey
was meant to establish the need for such automated machines
locall y.
A total of 15 house construction sites were visited and
observations made on the trowel plastering technique
employed. The data gathered revealed on average the
contractors managed to cover 4-5 m2 in an hour. The
contractors also revealed that they paid their unskilled labour
on a daily basis for tasks such as plastering. However, it was
also observed that the workers may have been deliberately
delaying the processes in order to get paid more. The purpose
of these interactions, observations and interviews was to
ascertain the need for an automated system for spraying mortar
by analyzing all the available options and challenges. This also
enabled a clear understanding of the mortar design mix for
plastering purposes using the traditional methods which were
key in coming up with design calculations.
3. Materials and methods
The design comprised of a power drill, compressor and
elevated screw. A frustum hopper was used to hold the mortar
and the screw was rotated using a power drill. There was
constant stirring of the mortar by the screw so that it did not dry
out. In addition, the flowing of the mortar was enhanced by
gravity. The wet mix was placed in the hopper and the elevated
chamber was spiraled at the end for transferring the mortar. The
screw was partially immersed in the barrel to direct the mortar
and increase pressure.
3.1. Material selection
Components which are exposed to high stresses during
operation are generally required to be made from a high tensile
steel alloys [12]. AISI 4140 is a high tensile steel grade with
excellent shock resistance combined with high wear resistance.
It has a tensile strength of 850-1000 Nm-2 and is generally used
for applications such as machine tools, spindles, shafts, and
gears [13]. The conveying screw and the barrel are the
components exposed to the highest levels of stress hence they
were made from AISI 4140. Mild steel is a type of carbon steel
with low carbon content. Hence due to this, mild steel is more
ductile, machinable and weldable than high carbon steel. It has
a tensile strength of 400 MPa and is usually utilized in steel
structures due to its machinability [13]. The hopper was made
from mild steel sheet metal and required more machining than
any of the other components. The frame handle was made from
rubber owing to its uniform strength. More specifically,
Ethylene Propylene Diene Terpolymer (EPDM) was chosen for
its excellent weather resistance [14]. It also has good heat and
chemical resistance and can operate in damp or wet conditions.
3.2. Design of components
The hopper was made of a conical frustum which holds a
maximum of 32 kg of material. It was developed and fabricated
from a 2 mm mild steel sheet. Fig. 3 shows a snapshot of the
developed frustum. Taking the bulk density of mortar to be
2162 kg/m3, the generally used value [6] and volume of 32 kg
of mortar was obtained from equation (1) [6];
bulk
m
V
= 0.01480111m3 = 15l (1)
Hence, the hopper can carry a maximum of 15l of mortar.
The upper diameter was taken as 0.4 m and the lower diameter
as 0.15 m. From the volume of a conical frustum (equation 2),
the bottom diameter was 85 mm. The mortar conveying screw
was an integral part of the design and consisted of a shaft and
screw blade. The screw shaft was joint-less to reduce weight.
The capacity that the screw could convey was affected by the
screw and shaft diameters, speed of rotation and inclination.
  
    (2)
Fig. 3. Conical frustum hopper
The design specifications of the screw were
Design speed: 1200 rpm,
Power: 800W,
Volume flow rate: 10 l/min
Flight width: 0.1D.
The torque experienced by the conveying screw can be
obtained using equation 3 [15], from which T = 6.366 Nm.
PT
= 1200 2
800
60
T
(3)
After obtaining the torque the minimum shaft diameter can
be calculated from equation 4 [15]:
3
min
max
16
T
d

= 0.017m (4)
The design standard minimum shaft diameter was taken as
25 mm. In order to get the screw diameter, equation 5 was
applied, where C is the volume flow rate in m3/h, D is the screw
400 Wilson R. Nyemba et al. / Procedia CIRP 91 (2020) 396–401
Nyemba et al./ Procedia CIRP 00 (2020) 000–000 5
diameter in m, d is the shaft diameter in m, p is the pitch in m
and n is the speed in rpm [15]. From the specifications, the
volume flow rate is 10 l/min or equivalent to 0.6 m3/h.
22
47.2( )
C D d pn
(5)
To allow for optimum transfer of the mortar, the pitch was
set at 0.005 m. Hence to determine the screw diameter capable
of conveying the mortar at the specified volume flow rate,
equation 5 was used to obtain D = 0.05 m. The orientation of
the screw in the hopper increased the conveying efficiency.
Torque requirements decreased due to the effect of gravity. The
conveying screw was inclined at a maximum angle of 30
degrees sloped downwards. Hence, the motor performed less
work in conveying the mortar to the hose. Fig. 4 shows a model
of the designed screw.
Fig. 4. Model of the designed screw shaft
4. Results and cost analysis
In order to establish the effectiveness of the machine, the
quantity of mortar required to plaster a certain area was
important. For instance, the quantity of mortar required to
plaster 1 m2; the maximum thickness of mortar when plastering
was 15 mm, volume of plaster (area × thickness), giving 0.015
m3. In order to get the total volume of mortar, the dry volume
of mortar had to be factored into the calculation; total volume
was the product of the dry volume factor and wet volume (1.27
×0.015), giving 0.01905m3. Hence, to plaster 1 m2, the total
volume of mortar required was 0.01905 m3.
Fig. 5. Model of the exploded view of components
The machine was designed to spray at maximum 0.01
m3/min, equivalent to 0.6 m3/h. Thus, the machine required
0.01905 m3 of mortar and in an hour a total area of 31.5m2 can
be covered. Fig. 5 shows the finite element results obtained
from an analysis of the frame in SolidWorks. It was loaded with
the maximum load of 32kg and the structural analysis showed
the frame would not fail under such stress. The yield strength
of the frame was 4.8x108 N/m2. Fig. 6 shows a picture of the
assembled mortar spraying machine that was designed,
fabricated and tested.
Fig. 6. Snapshot of the designed and fabricated machine
Table 2. Bill of materials and cost of the mortar spray
Item
Description
Quantity
Unit
Price/US$
Total
Cost/US$
1 2mm Mild Steel
(2450x1225)
1 sheet 75 75
2 25mm Round Tubes
(6m)
1 length 15.72 15.72
3 Galvanised Reducer 1 5 5
4 Power Drill 1 80 80
5 25mm Reinforced
Hydraulic Hose
1 10 10
6 Compressor 1 150 150
7 Ball Valve 2 2.50 5
8 400x400mm Auger
Screw
1 20 20
9 Spray Gun 1 12,50 12,50
10
11
Pressure Gauge
Poly wheels
1
4
45
12
45
36
Total Materials Cost
418.22
Approximate Assembling Cost
200
Overheads 100
Grand Total
7
54
.22
Table 2 shows the bill of materials for the major components
of the designed machine together with approximate costs for
assembling it. The total cost of US$754.22 was considered
fairly reasonable for a simple machine such as this in
comparison to the automated mortar spraying machines which
range from US$700 – 1600 for the small ones of the same
capacity and size available on Alibaba.com [16]. A quick
analysis of this cost against the time saved in plastering showed
that the cost of this machine could easily be recovered within a
period of 2 months.
6 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
5. Discussion and recommendations
In order to reduce fall back material, accelerators can be
added to the mortar mix. Accelerators increase the hydration
rate of mortar. They are also capable of reducing the setting
time of the mortar. Accelerators also result in early strength
development of mortar when sprayed onto the wall. Fly ash can
also be added to the mortar mix. Low calcium fly ash can be
introduced to improve the compressive strength of mortar.
During the spraying process, fly ash can aid the fluidity of
mortar. This is when it is utilized as an aggregate.
A mixer could be added to the machine to improve on
consistency of mortar. The spraying machine can only work
with a maximum aggregate size of 2 mm. Hence, an automatic
mixer could help in regulating that. The mortar mix will also
have better evenness and smoothness than the manually mixed
mortar. The mixing of the mortar components was automated
by the drill while the introduction of the mortar ingredients into
the hopper was manual, hence semi-automated. Fig. 7 shows a
snapshot of the mortar spraying machine undergoing some tests
in the laboratory. The addition of simple poly-wheels and the
use of thin mild plate for the hopper made it mobile and easy to
move around with while spraying.
Fig. 7. Snapshot of the mortar spraying machine undergoing tests
6. Conclusions
The construction sector in industrializing countries still
largely rely on manual and often time consuming methods in
processes such as plastering. This is partly attributed to lack of
capacity to invest in modern and automated methods as well as
the availability of cheap labour. This research focused on the
conceptualization, design and development of a semi-
automated mortar spraying machine to mechanize the
plastering process. A simple and user-friendly machine was
designed for local use. The mortar spraying machine was
designed to deliver 10 l/min of mortar, covering an area of
31.5m2/h, thus reducing the lead time for the plastering process
and related costs in the construction sector. The machine was
fabricated using locally available and maintainable materials.
For a total cost of approximately USD754, it was considered as
a reasonable investment for the small scale construction sector,
predominant in industrializing countries. No specialized
training would be required to operate the machine. A number
of recommendations such as the use of accelerators and the
addition of a mixer, were made for future research and
improvement of the developed mortar spraying machine.
Acknowledgements
The authors wish to acknowledge the assistance from the
construction company, Design Team from where the data was
collected and resident of Budiriro in Harare whose homesteads
and construction sites were visited. The financial support by the
Royal Academy of Engineering to promote such innovations
through conferences and publications is acknowledged.
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[15] Childs PN. Mechanical Design Engineering Handbook. Oxford:
Butterworth-Heinemann. 2014.
[16] Alibaba.com. Product: cement mortar spraying machine. Available:
https://www.alibaba.com/showroom/cement-mortar-spraying-
machine.html. Accessed: 3 September 2019.
Wilson R. Nyemba et al. / Procedia CIRP 91 (2020) 396–401 401
Nyemba et al./ Procedia CIRP 00 (2020) 000–000 5
diameter in m, d is the shaft diameter in m, p is the pitch in m
and n is the speed in rpm [15]. From the specifications, the
volume flow rate is 10 l/min or equivalent to 0.6 m3/h.
22
47.2( )C D d pn
(5)
To allow for optimum transfer of the mortar, the pitch was
set at 0.005 m. Hence to determine the screw diameter capable
of conveying the mortar at the specified volume flow rate,
equation 5 was used to obtain D = 0.05 m. The orientation of
the screw in the hopper increased the conveying efficiency.
Torque requirements decreased due to the effect of gravity. The
conveying screw was inclined at a maximum angle of 30
degrees sloped downwards. Hence, the motor performed less
work in conveying the mortar to the hose. Fig. 4 shows a model
of the designed screw.
Fig. 4. Model of the designed screw shaft
4. Results and cost analysis
In order to establish the effectiveness of the machine, the
quantity of mortar required to plaster a certain area was
important. For instance, the quantity of mortar required to
plaster 1 m2; the maximum thickness of mortar when plastering
was 15 mm, volume of plaster (area × thickness), giving 0.015
m3. In order to get the total volume of mortar, the dry volume
of mortar had to be factored into the calculation; total volume
was the product of the dry volume factor and wet volume (1.27
×0.015), giving 0.01905m3. Hence, to plaster 1 m2, the total
volume of mortar required was 0.01905 m3.
Fig. 5. Model of the exploded view of components
The machine was designed to spray at maximum 0.01
m3/min, equivalent to 0.6 m3/h. Thus, the machine required
0.01905 m3 of mortar and in an hour a total area of 31.5m2 can
be covered. Fig. 5 shows the finite element results obtained
from an analysis of the frame in SolidWorks. It was loaded with
the maximum load of 32kg and the structural analysis showed
the frame would not fail under such stress. The yield strength
of the frame was 4.8x108 N/m2. Fig. 6 shows a picture of the
assembled mortar spraying machine that was designed,
fabricated and tested.
Fig. 6. Snapshot of the designed and fabricated machine
Table 2. Bill of materials and cost of the mortar spray
Item
Description
Quantity
Unit
Price/US$
Total
Cost/US$
1 2mm Mild Steel
(2450x1225)
1 sheet 75 75
2 25mm Round Tubes
(6m)
1 length 15.72 15.72
3 Galvanised Reducer 1 5 5
4 Power Drill 1 80 80
5 25mm Reinforced
Hydraulic Hose
1 10 10
6 Compressor 1 150 150
7 Ball Valve 2 2.50 5
8 400x400mm Auger
Screw
1 20 20
9 Spray Gun 1 12,50 12,50
10
11
Pressure Gauge
Poly wheels
1
4
45
12
45
36
Total Materials Cost
418.22
Approximate Assembling Cost
200
Overheads 100
Grand Total
7
54
.22
Table 2 shows the bill of materials for the major components
of the designed machine together with approximate costs for
assembling it. The total cost of US$754.22 was considered
fairly reasonable for a simple machine such as this in
comparison to the automated mortar spraying machines which
range from US$700 – 1600 for the small ones of the same
capacity and size available on Alibaba.com [16]. A quick
analysis of this cost against the time saved in plastering showed
that the cost of this machine could easily be recovered within a
period of 2 months.
6 Nyemba et al./ Procedia CIRP 00 (2020) 000–000
5. Discussion and recommendations
In order to reduce fall back material, accelerators can be
added to the mortar mix. Accelerators increase the hydration
rate of mortar. They are also capable of reducing the setting
time of the mortar. Accelerators also result in early strength
development of mortar when sprayed onto the wall. Fly ash can
also be added to the mortar mix. Low calcium fly ash can be
introduced to improve the compressive strength of mortar.
During the spraying process, fly ash can aid the fluidity of
mortar. This is when it is utilized as an aggregate.
A mixer could be added to the machine to improve on
consistency of mortar. The spraying machine can only work
with a maximum aggregate size of 2 mm. Hence, an automatic
mixer could help in regulating that. The mortar mix will also
have better evenness and smoothness than the manually mixed
mortar. The mixing of the mortar components was automated
by the drill while the introduction of the mortar ingredients into
the hopper was manual, hence semi-automated. Fig. 7 shows a
snapshot of the mortar spraying machine undergoing some tests
in the laboratory. The addition of simple poly-wheels and the
use of thin mild plate for the hopper made it mobile and easy to
move around with while spraying.
Fig. 7. Snapshot of the mortar spraying machine undergoing tests
6. Conclusions
The construction sector in industrializing countries still
largely rely on manual and often time consuming methods in
processes such as plastering. This is partly attributed to lack of
capacity to invest in modern and automated methods as well as
the availability of cheap labour. This research focused on the
conceptualization, design and development of a semi-
automated mortar spraying machine to mechanize the
plastering process. A simple and user-friendly machine was
designed for local use. The mortar spraying machine was
designed to deliver 10 l/min of mortar, covering an area of
31.5m2/h, thus reducing the lead time for the plastering process
and related costs in the construction sector. The machine was
fabricated using locally available and maintainable materials.
For a total cost of approximately USD754, it was considered as
a reasonable investment for the small scale construction sector,
predominant in industrializing countries. No specialized
training would be required to operate the machine. A number
of recommendations such as the use of accelerators and the
addition of a mixer, were made for future research and
improvement of the developed mortar spraying machine.
Acknowledgements
The authors wish to acknowledge the assistance from the
construction company, Design Team from where the data was
collected and resident of Budiriro in Harare whose homesteads
and construction sites were visited. The financial support by the
Royal Academy of Engineering to promote such innovations
through conferences and publications is acknowledged.
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Evaluation of mechanization in building production as a way of cost reduction: A study of some construction sites in Enugu South local Government area
  • N B Iheama
  • U Alinta-Abel
  • O Ezeokoli
Iheama NB, Alinta-Abel U, Ezeokoli O. Evaluation of mechanization in building production as a way of cost reduction: A study of some construction sites in Enugu South local Government area. British Journal of Environmental Sciences. 2017;5(2):14-30.
Design and fabrication of automatic wall plastering machine
  • H C Kuttarmare
  • D Dagwar
  • S V Bhoyar
  • S Gothe
  • D Waghmare
  • A Pandit
  • A Raut
Kuttarmare HC, Dagwar D, Bhoyar SV, Gothe S, Waghmare D, Pandit A, Raut A. Design and fabrication of automatic wall plastering machine. International Journal of Advanced Research and Innovative Ideas in Education. 2017;3(2):2333-2340.