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Design and fabrication of a low-volume, high-temperature injection mould leveraging a ‘rapid tooling’ approach

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Abstract and Figures

The costs for low-volume production moulds (1–200 production components) are related to the mould material, the process planning time and the fabrication costs. Researchers have explored using additive manufacturing (AM) processes to fabricate moulds directly from their digital models as this reduces the process planning time and some fabrication costs, but there are issues with directly employing an AM solution. Material costs are high for metallic AM processes, and there are thermal conductivity and material compatibility issues when using plastic-based AM processes. Both the metal- and plastic-based AM processes have surface finish issues; so post processing activities must be part of the fabrication plan. In this research, a methodology is found to fabricate low-volume production moulds using a high-temperature moulding material. A general solution is provided, with a case study focusing on an over moulding process in which the injection material being moulded is Technomelt-PA 7846 black. A hybrid mould fabrication is applied where a material extrusion–based process is used to make a sacrificial product-shaped pattern. This pattern is used to form a resin-based insert which is to be assembled into a mould base frame. Customised inserts can be readily built and exchanged to provide a rapid response to a customer request. An assessment of the digital model, the manufacturing, assembly and the final validated assembly model is provided.
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Design and fabrication of a low-volume, high-temperature injection
mould leveraging a rapid toolingapproach
Hamed Kalami
&R. J. Urbanic
Received: 15 August 2018 /Accepted: 17 April 2019
#Springer-Verlag London Ltd., part of Springer Nature 2019
The costs for low-volume production moulds (1200 production components) are related to the mould material, the process
planning time and the fabrication costs. Researchers have explored using additive manufacturing (AM) processes to fabricate
moulds directly from their digital models as this reduces the process planning time and some fabrication costs, but there are issues
with directly employing an AM solution. Material costs are high for metallic AM processes, and there are thermal conductivity
and material compatibility issues when using plastic-based AM processes. Both the metal- and plastic-based AM processes have
surface finish issues; so post processing activities must be part of the fabrication plan. In this research, a methodology is found to
fabricate low-volume production moulds using a high-temperature moulding material. A general solution is provided, with a case
study focusing on an over moulding process in which the injection material being moulded is Technomelt-PA 7846 black. A
hybrid mould fabrication is applied where a materialextrusionbased process is used to make a sacrificial product-shaped pattern.
This pattern is used to form a resin-based insert which is to be assembled into a mould base frame. Customised inserts can be
readily built and exchanged to provide a rapid response to a customer request. An assessment of the digital model, the
manufacturing, assembly and the final validated assembly model is provided.
Keywords Additive manufacturing .Mould fabrication .Low volume .High-temperature moulding materials .Process
planning .Rapid tooling .Assembly
1 Introduction
The competitive landscape in the manufacturing domain is
increasing in our global economy for both mass production
and customised product fabrication; hence, developing new
approaches to address wage and wage disparity issues, econ-
omies of scale and mass customisation, virtualisation and dig-
ital manufacturing, and self-optimisation are research areas
associated with Industry 4.0. The Industry 4.0 approach is
applicable to a wide variety of manufacturing domains, and
applications could leverage the Internet and cloud resources,
digital models (or twins), data analytics, smart sensors, 3D
printing or additive manufacturing, and so forth to allow pro-
ducers to better react to customer demands profitably. The
plastic mouldmaking industry, which is a multi-billion indus-
try consisting of typically small- and medium-size enterprises
(in Canada, there are 502 establishments with 5,300 em-
ployees and $926 million in shipments [1]), is actively pursu-
ing opportunities to reduce tooling costs and processing time.
The design solutions depend on the production volumes and
planning horizons, and different mould materials and fabrica-
tion strategies are required for low-volume, medium-volume,
and high-volume production. The introduction of digital
manufacturing and assembly strategies introduce new oppor-
tunities, especially for complex specialty production applica-
tions. However, to enable mass customisation, lower product
introduction cycles, and so forth, domain-specific detailed
product and process realisation knowledge need to be cap-
tured, and included in the companys design standards or pro-
prietary knowledge base, complementing the digital models.
The objective of this research is on low-volume production,
where the production quantities vary between 1 and 200
A shorter version of this paper was presented at the CSME 2018,
May 2018 (Kalami and Urbanic 2018).
*R. J. Urbanic
Hamed Kalami
Department of Mechanical, Automotive, and Materials Engineering,
University of Windsor, Windsor, Ontario N9B 3P4, Canada
The International Journal of Advanced Manufacturing Technology (2019) 105:37973813
/ Published online:
21 May
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... One study conducted by Eiliat et al [9] demonstrated that the existence of voids is unavoidable in an FDM process and these voids can create failure points in FDM-built products. Additionally, using FDM technologies to directly build a tooling is not feasible due to the high pressure and temperatures involved in an IM process [11]. As a result, a new tooling method is needed to accommodate low to medium (10-5000) production volumes. ...
... Besides, they reported that even though their tool had a lower quality in composition and tool life compared to other conventional tools, it could manufacture the final product as accurately as other conventional tools. Kalami et al. [11] designed and fabricated a low volume injection mold and followed a rapid tooling approach that was suitable for a hightemperature material. In their research, they reported that material costs are high for metallic AM technologies and plastic based AM technologies will not be suitable for a tooling solution due to thermal conductivity and material compatibility. ...
... To conduct the injection simulation, the injection temperature (200 ℃), initial mold temperature (18 ℃), and material properties were selected (Technomelt-PA 7846). [11]. ...
... One of the RT options to increase competitiveness is using metal epoxy composite (MEC), which provides greater heat conductivity as mould inserts in RT application and lowers tooling production costs and lead times by 25% and 50%, respectively [3,6]. Using optimisation methods to determine the optimal composition for materials, as recommended in the linked literature, can be considered for future research, such as determining the best amount of Al or Cu to mix with epoxy resin for desirable mechanical properties [27][28][29][30][31][32][33][34][35][36][37]. The use of MEC mould inserts for RT in the injection moulding process, which uses pure metal filler particles combined with epoxy resin, has attracted the attention of many researchers [20,29,[38][39][40]. ...
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The investigation of mould inserts in the injection moulding process using metal epoxy composite (MEC) with pure metal filler particles is gaining popularity among researchers. Therefore, to attain zero emissions, the idea of recycling metal waste from industries and workshops must be investigated (waste free) because metal recycling conserves natural resources while requiring less energy to manufacture new products than virgin raw materials would. The utilisation of metal scrap for rapid tooling (RT) in the injection moulding industry is a fascinating and potentially viable approach. On the other hand, epoxy that can endure high temperatures (>220 °C) is challenging to find and expensive. Meanwhile, industrial scrap from coal-fired power plants can be a precursor to creating geopolymer materials with desired physical and mechanical qualities for RT applications. One intriguing attribute of geopolymer is its ability to endure temperatures up to 1000 °C. Nonetheless, geopolymer has a higher compressive strength of 60–80 MPa (8700–11,600 psi) than epoxy (68.95 MPa) (10,000 psi). Aside from its low cost, geopolymer offers superior resilience to harsh environments and high compressive and flexural strength. This research aims to investigate the possibility of generating a new sustainable material by integrating several types of metals in green geopolymer metal composite (GGMC) mould inserts for RT in the injection moulding process. It is necessary to examine and investigate the optimal formulation of GGMC as mould inserts for RT in the injection moulding process. With less expensive and more ecologically friendly components, the GGMC is expected to be a superior choice as a mould insert for RT. This research substantially impacts environmental preservation, cost reduction, and maintaining and sustaining the metal waste management system. As a result of the lower cost of recycled metals, sectors such as mould-making and machining will profit the most.
... Typically, a metal die accommodates polymeric AM inserts of dies for IM that can be used to produce end components. Kalami and Urbanic [95] highlighted the contribution of such 'soft tooling' or 'temporary moulds', fabricated to produce a limited number of parts (1-200 production components), with the main advantage being that problems with the mould or design modifications can be easily rectified by re-printing the mould [96]. Conversely, the main issue is the lower thermal conductivity of polymeric RT materials, which may negatively affect the warpage, shrinkage, and mechanical properties of moulded end parts, and cause slower cooling rates, therefore resulting in longer packing and cooling times [73,97]. ...
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In the Industry 4.0 scenario, additive manufacturing (AM) technologies play a fundamental role in the automotive field, even in more traditional sectors such as the restoration of vintage cars. Car manufacturers and restorers benefit from a digital production workflow to reproduce spare parts that are no longer available on the market, starting with original components, even if they are damaged. This review focuses on this market niche that, due to its growing importance in terms of applications and related industries, can be a significant demonstrator of future trends in the automotive supply chain. Through selected case studies and industrial applications, this study analyses the implications of AM from multiple perspectives. Firstly, various types of AM processes are used, although some are predominant due to their cost-effectiveness and, therefore, their better accessibility and wide diffusion. In some applications, AM is used as an intermediate process to develop production equipment (so-called rapid tooling), with further implications in the digitalisation of conventional primary technologies and the entire production process. Secondly, the additive process allows for on-demand, one-off, or small-batch production. Finally, the ever-growing variety of spare parts introduces new problems and challenges, generating constant opportunities to improve the finish and performance of parts, as well as the types of processes and materials, sometimes directly involving AM solution providers.
... Generally, the AM can produce prototype with complex geometries. Injection mold can be manufactured in a short time and at low cost by RT because RT can shorten the time to the market compared to conventional machining approaches [2][3][4][5][6][7]. It is widely known that computer numerical control (CNC) machining is the most effective method to manufacture components or molds with excellent surface quality, good dimensional accuracy, and microstructures [8]. ...
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Injection molding is cost-effective to manufacture molded products by injection molding machine. A precision part with micro features can be fabricated effectively through the-state-of-art mold. The injection mold with micro features can be manufactured by the metal additive manufacturing technology. However, the surface quality of the injection mold is not acceptable. To cope with these challenges simultaneously, a novel concept was proposed. This work reports a new approach for rapid manufacturing precision injection molds with micro features by integrating additive manufacturing, rapid tooling, and micro-milling. It was found that of the dimensional accuracy of a precision component in the length, width, and height can be controlled at approximately 30 μm. Injection molding was performed using an injection mold with a micro feature of 950 μm and the dimensional accuracy of a precision wax pattern in the length, width, and micro features can be controlled at approximately 60 μm, 50 μm, and 10 μm, respectively. This work builds the foundation needed for hybrid manufacturing to be applicable toward fabrication of precision wax patterns with micro features efficiently and economically for trial production in the investment industry since the quality of wax patterns meets the standards of the general industry completely.
... This has an advantage regarding conventional metal molds which is the freedom of structural construction of 3D printing that can provide unparalleled flexibility in designing the geometry of molds (Dizon et al. 2019). Nevertheless, there are some issues concerning the surface finish of the mold and its dimensional accuracy; this can affect the final molded part (Kalami and Urbanic 2019). There also are some risks that may compromise the mold durability; this is the layer delamination due to the warping stress which is caused by the repeated thermal contraction of a hot layer plastic on top of a cold layer plastic during the material extrusion (Dizon et al. 2019). ...
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Mold injection is an expensive manufacturing method; it involves several engineering-design hours and expensive alloys. Enabling the use of low-cost mold tooling can turn low-run productions economically and sustainably viable. There is a low-cost and more environmentally amicable alternative to injection molding for low-run productions based on epoxy resin molds. However, one drawback is the polymeric nature of the epoxy material, which possess low thermal conductivity, negatively affecting the injection process and thus quality of the molded pieces; as well as its low degradability rate. An opportunity arises for improving the performance of epoxy resin molds by studying the effect of embedding thermally conductive fibers in the matrix. The methodology used in this work consisted in the computational evaluation of a series of molds of composite material models built up from epoxy resin and copper fibers in different geometrical shapes and orientations. Injection simulations were carried out using the software Moldflow and the “effectiveness” of the injected parts was assessed (i.e., injection cycle time, percent volume shrinkage, and injected part deflection). Results suggest that embedding copper fibers within the epoxy matrix resin molds lowers the injection cycle time and reduces volumetric shrinkage while maintaining the deflection amplitude of the injected parts; optimum effectiveness results were obtained when copper is embedded as long fibers oriented along the principal heat flow direction. Moreover, epoxy resin can be replaced by up to a 70% volume of copper fibers, depending upon wall thickness and geometry complexity, thus lowering the impact this resin has on the environment.
... Unfortunately, the characteristics of plastic physical models printed by AM machine do not usually match the requirements of the end product with the material needed. Thus, rapid tooling technology (RTT) [6][7][8][9][10][11] was then developed. Generally, RTT is considered as a nature extension of AM technology because molds [12] or dies [13] can be manufactured by AM technology for small-volume production. ...
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Vacuum casting (VC) is a highly versatile manufacturing technique capable of producing parts in a wide range of polymers for end use plastic parts or prototypes. VC technology is ideally suited to low volume batch production compared with plastic injection molding since a silicone rubber mold (SRM) can be used to produce up to fifty to eighty parts. The main challenge of this method is that the both dimensional and form accuracies of the VC parts were affected by the fastening force of the SRM using tape due to the fastening force is inconsistent for different operators. In this study, an intelligent SRM clamping mechanism comprising a pressure sensor and Arduino pressure sensing module was developed for reducing the variations in both dimensional and form accuracies of the VC parts. It was found that the 14 kPa is the optimal clamping pressure. The angular deviation of the cuboid VC parts produced by the intelligent clamping mechanism falls within the range of one standard deviation (SD) to the average. The minimum zone circle deviation of the cylinder VC parts produced by the intelligent clamping mechanism falls within the range of − 1 to 2 SDs. In addition, the production cost of the SRM can further be reduced by about 23% using an intelligent clamping mechanism compared with that using the conventional method.
... Currently, the mold or die industry continued to suffer pressure since time and production costs are two major concerns that are needed to develop a new product in the industry. To overcome this obstacle, additive manufacturing (AM) [1] and RT [2] was developed to meet this requirement. RT is cost-effective method for small volume production since it has been proved to a great impact on product development cost [3]. ...
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The molds or dies with complex conformal cooling channel (CCC) can be manufactured by the metal powder additive manufacturing (AM). However, the metal powder AM approaches have a high initial cost of the capital equipment and maintenance. Wax injection molding is a frequently applied manufacturing technique for the production of investment casting wax patterns because of time efficiency. This study demonstrates low-cost alternatives for fabricating wax patterns economically and efficiently was developed via both direct tooling (DT) and indirect tooling (IDT). The Nine pairs of injection mold (IM) containing CCC were manufactured and the cooling performance was evaluated. The characteristics of IM fabricated by DT and IDT were analyzed. The most suitable methods of making injection molding tools fabricated by direct and indirect rapid tooling technologies have been demonstrated based on total production costs, cooling time as well as flexural strength. It was found that there is no significant difference in the cooling time of the molded products fabricated by IM made with virgin polylactic acid filament with different layer thicknesses. The IM fabricated by DT is sensitive to the coolant temperature. The IM fabricated by IDT is not sensitive to the coolant temperature. In addition, there is no significant difference in the cooling time of the molded products by changing the coolant volumetric flow rate.
... Prototype molds also appear in specific injection molding applications [16]. Kalami et al. [17] created a low-volume injection mold for the production of a cable bundle by overmolding. They applied a hybrid mold fabrication methodology, where they extruded a sacrificial product-shaped pattern. ...
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The ever growing demand for reducing costs and decreasing the time to market in today’s plastics industry makes rapid tooling and rapid prototyping a highly researched area. 3D printed injection mould inserts make it possible to produce prototype parts in small series fast and cost-effectively. The mechanical strength and therefore the life expectancy of 3D printed polymeric injection mould inserts are low compared to their traditional steel counterparts. In order to increase the reliability and life expectancy of polymeric mould inserts, in-situ state monitoring during injection moulding is essential. In this paper, we analyse the effect of thermal and mechanical loads on the resulting strains of the mould inserts. Three series of rectangular plate products were injection moulded with a different type of insert in each series. The pressure inside the cavity and the strain of the 3D printed inserts were measured during injection moulding. We correlated maximal cavity pressures and changes in strain with each other in order to set up the deformation characteristic of the inserts. The results indicate a satisfactory correlation between the maximal cavity pressures and the strain change of the inserts. The second important result was that strain gauges can be applied to in-situ monitor the state of the inserts during injection moulding.
... Jahan et al. [18] proposed an optimal cooling channel in 3D-printed dies for plastic injection molding to produce 1.5-mm-thick plastic parts. Rapid tooling technology is an alternative method for batch production because it has proved to a great impact on product development cost [19][20][21][22][23]. The wax injection molding (WIM) is one of the most widely used methods for producing wax patterns [24][25][26]. ...
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Conformal cooling channels (CCCs) are a cooling passageway which follows the profile of the mold cavity or core to perform uniform cooling process effectively in the injection molding process. The production cost is closely related to productivity. To further improve productivity, the injection mold was equipped with CCCs to shorten the cooling time of the injection molded part. To investigate the relationship between the cooling channel layout and cooling efficiency of the CCCs, silicone rubber molds (SRMs) with different layouts of cooling systems were designed and constructed in this study. Simulation software was utilized to study the cooling performance. To verify the results of the simulation, SRM with different cooling systems were fabricated for low-pressure wax injection molding. It was found that the cooling time of the injection molded part is indeed affected by the total surface area of the heat exchange between the coolant and the SRM. The cooling system with four inlets and four outlets seems to be the optimum layout of the SRM in the case study in terms of the difficulty of mold making, total surface area of the heat exchange between the coolant and the SRM, and total cooling flow length of each segment. The saving in the cooling time about 2796 s and improvement of cooling efficiency about 76% can be obtained when the SRM with four inlets and four outlets was used for injection molding. The findings in this study can be used as a reference to design CCCs of injection mold built with AM technology.
... AM technology can provide the mold or die designers to verify a design in a matter of hours. Rapid tooling (RT) technology [5][6][7][8] is divided into soft or hard tooling. Tooling for low volume manufacturing runs is known as soft tooling (ST). ...
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Silicone rubber mold (SRM) is capable of reducing the cost and time in a new product development phase and has many applications for the pilot runs. Unfortunately, the SRM after injection molding has a poor cooling efficiency due to its low thermal conductivity. To improve the cooling efficiency, the thermal conductivity of the SRM was improved by adding fillers into the SRM. An optimal recipe for fabricating a high cooling efficiency low-pressure injection mold with conformal cooling channel fabricated by fused deposition modeling technology was proposed and implemented. This study proposes a recipe combining 52.6 wt.% aluminum powder, 5.3 wt.% graphite powder, and 42.1 wt.% liquid silicon rubber can be used to make SRM with excellent cooling efficiency. The price–performance ratio of this SRM made by the proposed recipe is around 55. The thermal conductivity of the SRM made by the proposed recipe can be increased by up to 77.6% compared with convention SRM. In addition, the actual cooling time of the injection molded product can be shortened up to 69.1% compared with the conventional SRM. The actual cooling time obtained by the experiment is in good agreement with the simulation results with the relative error rate about 20%.
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Product designers and engineers can benefit from the rapid production of prototypes with characteristics that closely resemble those of finished products. In the case of plastic objects which include rubber-like surfaces, existing manufacturing options are either expensive or are impractical, limiting their use of rapid prototypes. This paper presents a method of fabricating rapid prototypes by combining rigid and soft materials through an overmolding process, thus providing a fast and cheap way to obtain feedback regarding form-and-feel characteristics during the design process. Functional objects can be also produced using the proposed method, enhancing part design freedom. Elastomers are injected or cast into molds attached to 3D-printed rigid parts in order to form functional soft surfaces. Several solutions of binding elastomer to parts fabricated using Fused Filament Deposition (FDM) are presented , including multiple ways to produce the bonding of materials. Chemical bonding and mechanical bonding using specifically designed geometries or exploiting the interior structure of 3D-printed parts are proposed. Objects made from rigid plastics overmolded with elastomers are produced for exemplifi-cation. A time and cost analysis is also included as reference and for comparison with other manufacturing methods.
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Injection molds with conformal cooling channels have been deemed increasingly important in the mold manufacturing industry. Selective laser melting (SLM) has proven to be an effective process to fabricate conformal cooling molds. However, the surface quality and morphologies of SLM-fabricated cooling channels are different from that of conventional drilled channels. To investigate the differences in the coolant flow rate and cooling performance between SLM-fabricated and drilled cooling channels, test molds with cooling channel diameters of φ2 mm, φ3 mm, and φ4 mm were fabricated via SLM and the computer numerical control (CNC) process. A test system was designed and set up to investigate the flow rate and cooling performance of two types of test molds. The geometrical shape, dimensional accuracy, and surface morphologies of the SLM-fabricated cooling channels were characterized using optical microscopy and laser microscopy. The results indicated that the SLM-fabricated cooling channel exhibited an elliptic shape due to the lack of support along the building direction. The flow rate of the SLM-fabricated cooling channels was smaller than that of the drilled channels due to the low dimensional accuracy and roughness surface. The cooling performance of the SLM-fabricated cooling channels was also poorer than that of the drilled channels due to the presence of unmolten particles and a loose layer on the SLM-fabricated surface. Theoretical analysis was conducted on the influence of surface roughness on the flow rate and cooling performance of two types of channels and the friction factor; Nusselt number and heat transfer coefficient were obtained.
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Several reports have studied the mechanical properties of the material extrusion additive manufacturing process, specifically referred to as fusion deposition modeling (FDM) developed by Stratasys. As the applications for 3D printed parts continue to grow in diversity (e.g., gears, propellers, and bearings), the loading conditions applied to printed parts have become more complex, and the need for thorough characterization is now paramount for increased adoption of 3D printing. To broaden the understanding of torsional properties, this study focused on the shear strength of specimens to observe the impact from additive manufacturing. A full factorial (4²) design of experiments was used, considering the orientation and the raster angle as factors. XYZ, YXZ, ZXY, and XZY levels were considered for the orientation parameter, as well as 0°, 45°, 90°, and 45°/45° for the raster angle parameter. Ultimate shear strength, 0.2% yield strength, shear modulus, and fracture strain were used as response variables to identify the most optimal build parameters. Additionally, stress-strain diagrams are presented to contrast elastic and plastic regions with traditional injection molding. Results demonstrated an interaction of factors in all mechanical measured variables whenever an orientation and a raster angle were applied. Compared to injection molding, FDM specimens were similar for all measured torsion variables except for the fracture strain; this led to the conclusion that the FDM process can fabricate components with similar elastic properties but with less ductility than injection molding. The orientation in YXZ with the raster angle at 0⁰ resulted in the most suitable combination identified in the response optimization analysis.
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Process planning for hybrid manufacturing, where additive operations can be interlaced with machining operations, is in its infancy. New plastic- and metal-based hybrid manufacturing systems are being developed that integrate both additive manufacturing (AM) and subtractive (machining) operations. This introduces new process planning challenges. The focus of this research is to explore process planning solution approaches when using a hybrid manufacturing approach. Concepts such as localized AM build ups, adding stock to a CAD model or section for subsequent removal, and machining an AM stock model are investigated and illustrated using virtual simulations. A case study using a hybrid laser cladding process is used to demonstrate the opportunities associated with a hybrid solution. However, unlike machining, the process characteristics from system to system vary greatly. These are portrayed via a high power, high material deposition feed rate laser cladding system. There are unique challenges associated with AM processes and hybrid manufacturing. New tools and design rules need to be developed for this manufacturing solution to reach its potential.
This text, now in its second edition, offers an up-to-date, expanded treatment of the behaviour of polymers with regard to material variables and test and use conditions. It highlights general principles, useful empirical rules and practical equations.;Detailing the specific behaviour of many common polymers, the text: places emphasis on time and frequency dependence over temperature dependence; uses contemporary molecular mechanisms to explain creep, stress relaxation, constant strain rate responses and crazing; provides explicit equations to predict responses; supplies a discussion of large deformation multiaxial responses; compares statistical and continuum theories on the same data set; and updates stress-strain behaviour and particulate filled systems.
Fused deposition modelling (FDM) is one of the most widely used cost-effective additive manufacturing (AM) technique for modelling and prototyping of functional/non-functional parts subjected to different industrial applications. However, this technique still possesses substantial problems in-terms of poor surface finish and dimensional accuracy of the prototypes. In the present research work, an effort has been made to improve the surface finish of FDM based benchmarks through chemical (acetone) exposure by using vapor smoothing station (VSS). Experimental analysis has been carried out by using design of experiments (DOE) technique in-order to find out the effect of input factors on surface finish of the benchmarks. The results of the present study highlights the capability of the VSS for improving the surface finish of the FDM based parts to nano-level with negligible dimensional deviations.
The precipitation behavior, mechanical properties and corrosion resistance of a novel Al—Zn—Mg—Sc—Zr alloy aged at different time were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile tests, potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed that with increasing aging time at 120 °C, the hardness and tensile strength of the alloy increased rapidly at first and then slightly decreased. The resistance of exfoliation corrosion (EXCO) and intergranular corrosion (IGC) increased gradually with increasing aging time. The same trend of corrosion properties was demonstrated by electrochemical polarization curves and EIS test. The characteristics of grain boundary precipitates and precipitate free zone (PFZ) had a significant influence on the mechanical and corrosion behaviors of the studied alloy. On the basis of TEM observations, the size of grain boundary precipitates and the width of PFZ became larger, and the distributed spacing of grain boundary precipitates was enhanced with increasing aging time.
Purpose-The purpose of this paper is to characterize mechanical properties (tensile, compressive and flexural) for the three-dimensional printing (3DP) process, using various common recommended infiltrate materials and post-processing conditions. Design/methodology/approach-A literature review is conducted to assess the information available related to the mechanical properties, as well as the experimental methodologies which have been used when investigating the 3D printing process characteristics. Test samples are designed, and a methodology to measure infiltrate depths is presented. A full factorial experiment is conducted to collect the tensile, compressive and benDing forces for a set of infiltrates and build orientations. The impact of the infiltrate type and depth with respect to the observed strength characteristics is evaluated. Findings-For most brittle materials, the ultimate compression strength is much larger than the ultimate tensile strength, which is shown in this work. Unique stress-strain curves are generated from the infiltrate and build orientation conditions; however, the compressive strength trends are more consistent in behavior compared to the tensile and flexural results. This comprehensive study shows that infiltrates can significantly improve the mechanical characteristics, but performance degradation can also occur, which occurred with the Epsom salts infiltrates. Research limitations/implications-More experimental research needs to be performed to develop predictive models for design and fabrication optimization. The material-infiltrate performance characteristics vary per build orientation; hence, experimental testing should be performed on intermediate angles, and a double angle experiment set should also be conducted. By conducting multiple test scenarios, it is now understood that this base material-infiltrate combination does not react similar to other materials, and any performance characteristics cannot be easily predicted from just one study. Practical implications-These results provide a foundation for a process design and post-processing configuration database, and downstream design and optimization models. This research illustrates that there is no best solution when considering material costs, processing options, safety issues and strength considerations. This research also shows that specific testing is required for new machine-material-infiltrate combinations to calibrate a performance model. Originality/value-There is limited published data with respect to the strength characteristics that can be achieved using the 3DP process. No published data with respect to stress-strain curves are available. This research presents tensile, compressive and flexural strength and strain behaviors for a wide variety of infiltrates, and post-processing conditions. A simple, unique process is presented to measure infiltrate depths. The observed behaviors are non-linear and unpredictable.
The Fused Deposition Modeling (FDM) process is a bead deposition based additive manufacturing (AM) process that builds a product from thin layers of molten thermoplastic filaments. The ongoing goal of this research is to develop methodologies for designing and fabricating large complex parts such as complex beta testing prototypes, or sand casting patterns. The unique capabilities of the FDM process are leveraged when designing components and assemblies. Complex geometry can be readily manufactured allowing designers to incorporate non-standard component features, and consider unique solutions; however, there are size, surface finish, and accuracy limitations. Rules are developed to leverage the process characteristics and address the observed limitations. Case studies are presented to highlight the benefits and challenges when using the FDM process.