Injection Molding - Science topic

The injection molding process is a manufacturing technique used to produce plastic parts in large volumes with high precision. The working principle of the injection molding process involves several steps:

The injection molding process offers several advantages, including high production efficiency, repeatability, and the ability to produce complex geometries with tight tolerances. However, it also requires significant upfront investment in tooling and equipment and may not be suitable for low-volume production or prototypes.

In the context of comparing the tensile properties of ABS produced by injection molding with those produced by Fused Deposition Modeling (FDM), understanding the principles of each process is essential. Injection molding typically results in parts with higher mechanical properties and surface finish compared to FDM, due to the differences in processing conditions and material behavior. FDM involves layer-by-layer deposition of thermoplastic filament, which can lead to anisotropic properties and lower mechanical performance compared to injection-molded parts. Therefore, a comprehensive review of literature on the principles and processing parameters of each method would provide valuable insights into the differences in tensile properties observed between the two manufacturing processes.

I am collecting values of flexural modulus of several polymers at room temperature: polycarbonate, ABS, polystyrene (large range of values), PTFE, PVDF and polypropylene. Input sent to wkbrostow@gmail.com would be appreciated.

Thanks Ashish Kumar

Yes, but I think it works with balls. Please check the attached file. My Regards

The following document seems intersting.

Dear Kanticha Korsesthakarn , may be the following testing tools would be useful for your work:

Hope it helps.

Dear, Laura Simiyu

I think you should change the filling type and try.

You need a set of experiments. Refer to .

Slope gives the Young's modulus.

better use mould flow analysis software's, easily you can get solution to your problem

Ahmed Z. Naser you should select the right purging material to clean the injection moulding machine and extruder. For me, Dyna-Purge works very well for cleaning PHA and PLA processed injection moulder. So may be you should try this.

Cheers

The dimensional difference should not make huge difference if the material is isotropic, homogeneous polymer. However, your sample being a composite material, the edge effect cannot be ignored. This effect is particularly strong for anisotropic composite (your sample is relatively isotropic, though due to the flow pattern near the mold surface, you will have anisotropy, or skin effect). In a composite, it is said that the certain distance from the edge would have different stress field than in the bulk. So, you do not want to use too narrow a sample. Regarding the thickness, each rheological instruments have its characteristic rigidity. TA Instruments' machine is rather weak and if you have a very thick sample, the sample strength will influence the machine stability. This is not the case for the machine made by the predecessor of TA Instruments, Rheometrics. The machine, RMA-800 has an extremely rigid H-frame and even metallic sample can be evaluated with high reproducibility and thus thickness difference does not matter. Our sample for this RMA-800 machine is typically a few mm thick even with unidirectionally reinforced composites, much stronger than your short fiber reinforced composite.

The reason why you need to clearly indicate the dimension is that G' and G" are shape specific properties. Thus, if the dimension changes the value changes. On the other hand, tan delta is dimension independent as tan delta is calculated by G" devided by G', eliminating the dimension specific contribution from both quantities. This is the reason why tan delta spectrum exhibits better baseline and reproducibility.

The type of testing depends on what is the sample you want to use. If it is a homogeneous polymer, for example, any method is fine. Again, if it is a thin film, three point bending is not appropriate. A rigid slab can be used with any methods, whereas weak, flexible film is with tension. If you have a very strong composite, three point bending or single point cantilever may be appropriate.

My sugestion.

We are talking about the discipline "Material selection". The use of recycled is related to the type of part, mainly to the mechanical and environmental efforts that the part will undergo, properties of the recycled and level of additives that still exist in the recycled, safety factor used in the initial design of the parts. We cannot forget the variability that we can find in the properties of the recycled material. I recommend a statistical analysis, mean, standard deviation, analysis of 6 sigmas, Z= (X- µ )/ σ.

where:

X = project limit

µ = average of tested samples

σ = standard deviation.

Hi Basheer,

TiC nanoparticles tend to agglomerate and these agglomerates are not broken down by mixing with coarse metal powder. In addition, fine TiC particles and agglomerates oxidize and therefore do not form any chemical compounds with metal particles. When such mixtures are sintered, the agglomerates impair the sinterability of the metal matrix.

For the reasons mentioned above, you will not find the individual particles in the structure, but rather large and porous TiC / TiO2 agglomerates that not only do not solidify the sintered body, but also massively weaken it. The properties of the material will be correspondingly miserable. The idea of mechanically distributing nanoparticles in a sintered body is not even theoretically feasible.

Regards

Vadim

Dear Kai Kampmeyer, I suggest you to verify the following addresses. I hope they would be useful.

https://www.masterbond.com/applications/rubber-metal-bonding

https://tbbonding.com/glue-silicone-rubber/

Okay Thanks

The dosage and concentration can depend on a lot of factors like the route of injection (i.p, i.m, oral, etc), the buffer in which you want to dissolve.

Hello Rohan,

yes, it is possible. There are different nanofabrication techniques that you can use to control small volumes (even smaller than nl). I guess that one of your challenges is to have a non- deformable material when you are 'pumping' your fluid through the micro/nanochannel as any compliance int eh material would lead to inaccuracies in the fluid control and measurement. You could, for instance, use RIE to create a Si microfluidic or nanofluidic channel. You could also use other etching techniques to fabricate the device in glass. PMMA, as you mention is an option too as it is less deformable that the commonly used PDMS in microfluidics.

You should look into Torlon polyamide-imide from Solvay. It is extremely strong and high heat resistant. Automobile engines have been made from it. Not sure it will make it to 500c though. Have you considered thermosets or ceramics?

There are so many different types of screws out in the market and a lot can be said on many of the screws and or what happens in each zone. To keep it short and simple, depending your resin you are using, plus throughput, will determine how much the screw will have different effect on the polymers. You have your resin entering the feed zone to get it ready for the transition zone and depending the resin type if you need more or less in this zone. The transition zone will do your majority of melting and mixing. When the resin reaches, the metering zone is where you complete your melting and mixing of your polymers. So depending your polymers on what screw would get your resin to mix and flow properly with little shearing in the screw and the mold etc. Therefore your quality can be greatly affected with the wrong screw, due to not preparing your polymers properly without damaging polymers and to have it flow properly and with consistency.

For lab use, you can use Kapton film as suggested, but for industry fast production, you must have mirror shine mould with fast cooling rate as suggested too.

First of all, you need to know at which state your material exists at the operating temperature, does it overcome any phase transition (which is usually accompanied with changes in physical properties). If you know all that, you need do chose an appropriate material with lowest chemical reactivity, lowest viscosity at the operating temperature and lowest tendency to overcome a phase transition prior to in-mold hardening.

Hey

just wondering if you got the answer or not?

Cheers.

Lata Soccalingame, thank you for your answer. About 0.2g of the polymer (30% glass-filled polyamide 6) is put together with 30 ml of formic acid. The mixture is left stirring for around 15 hours at 300 rpm, at 20 °C. Afterwards the solution is put into a centrifuge (1500 rpm) so that the insoluble parts (fiber) sink to the bottom. The solution is filtered before testing. I'm quite sure the tests are accurate.

The MFI is executed at different temperatures (265, 275, 285 °C) and all results show a linear trend (R² > 96%), where MFI increases with regrind percentage.

At the moment, I think that cristallinity might be the reason. The polymer is processed in a mold at around 100 °C, above the glass-transition temperature and below the crystallization temperature. The sprues are ground at about 70 °C.

Another remark is that the Ubbelohde viscosity is measured for the matrix only, while the MFI is for the glass-filled polymer. Could the crystallinity be a possible explanation?

Here is a list:

Most of the polymers with lower RI are fluorinated.

Dear Leelakrishnan,

Nice question, subject for attention and practical interest. I will try to answer mostly based on my practical experience. For facility, let’s go to take the case of polyamides (PA6, PA 6,6, PA11, others).

For injection molding you need polymers usually characterized by high fluidity at the temperature of processing that will allow to fill well your mold at the pressure of injection and finally to obtain in one step very complicated or complex injection molded items. Thus, the adequate choice of polymer grade with adequate molecular characteristics/rheology and of processing parameters (temperature, pressure, etc.) is one key-condition.

The polymer grades designed for processing by extrusion are generally characterized by higher molecular weights and high/higher viscosity in the molten state. This will allow to control better the extrusion as profiles (rods, tubes, plates), films, monofilaments, etc.

I’m not totally excluding that in some cases some polymer grades with mean or high viscosity can be processed by injection molding especially using high temperatures to have the required fluidity to fill the cavity of the mold.

By contrary, an injection molding grade (characterized by low viscosity and high fluidity) will not be recommended for the producing by extrusion of profiles, because the rheological properties are not adequate (NB: a high viscosity in the molten state is imperiously required to obtain rods, tubes, plates, etc.). For some more information please take a look on the web site of BASF for the Ultramid/polyamide products.

Good luck and best regards,

Marius

PS: For more information

Hi,

Is it mould release agent residue?

In general, the steps for designing a standard injection mold based on the design of the plastic part would be;

Design and analysis of the plastic part to avoid defects (analysis of defectology)

Demoldability analysis of the plastic part (verification of undercuts)( location of parting line)

Calculation of the shrinkage of the part (material dependent)

Cycle Time Calculation

Estimation of the Number of Cavities

Sizing of the Cavity and Core Plates

Sizing and selection of the Feeding System

Sizing and choosing the Ejection System

Sizing of the mold venting system

Sizing and selection of the Cooling System

Sizing of sliders and internal pins (if there are undercuts)

Minimum capacities of injection machine( Clamping Force and Injection shot)

Sizing of the mold guiding system

Find attached bibliography related to mold design and part design;

Kazmer, D. O. (2016). Injection mold design engineering. Carl Hanser Verlag GmbH Co KG.

Menges, G. (2001). How to make injection molds.Hanser Verlag

Osswald, T. A., Turng, L. S., & Gramann, P. J. (2008). Injection molding handbook. Hanser Verlag.

Fundamentals of Plastic Mould Design 2012, Dr. Sanjay K Nayak Tata McGraw Hill

Thank you J.C.!

H13 steel, try it.

Dear Prof Seah, It seems the software is discontinued. -JL

HI, Thines,

sorry but I realized you did not get my answer. I do not understand what happened with it.  I try to reproduce it:

The first thing to do this is to determine if you have gel or unmelted polymer.  This can be done very easily with DSC.  Gels do not melt well.  If you do not get a very well defined or any melting peak at all, they are gels (degradated material in form of crosslinked) .  Otherwise you have unmelted polymer.

Degradation is a matter of temperature and residence time.  Screw design and flow channels are critical.  It is important to check this before continuing looking for a solution.

You are welcome. You can find more details in 'Reservoir Stimulation' by Michael J.  Economides and Kenneth G. Nolte.

Dear Dr. Prince

This attach file about the review focuses on the use of composite flour to produce food products, namely bread, biscuits, and pasta, with looks at on its impact, following some improvements made, on the sensory quality, rheology characteristics, and nutritional values as well as its overall acceptance. The blending of wheat flour with various sources of tubers, legumes, cereals and fruit flour in different percentages to produce variety of food products are also reported in this review

Dear Saptarshi,

You can check the website of Kube Electronics in Swizerland. They sell many low cost IR parts for pyroelectric an thermopile sensors.

Good luck with your project.

Christophe

PS. In my lab, we offer testing services for low cost infrared detectors used in automation. Our customers are the manufacturers of occupancy sensors, motions detectors, alarm systems, lighting controls, etc. 

Thank you all for your answers

Thank u all for your responses. I will try it out .

Dear Joauin

Tempilstic crayons may be the answer

www..tempil.com

. I have used them to assess the evenness of heating in textile fabric dying machines. each item has a specific melting temperature and once melted,  the colour change is semi permanent. the temp range is 100 to 2000 F

I think you may need to go through polymer composites as well.

Dear Sir. Concerning your issue about the reason of changing of  the natural color to yellow when combining PBT (Polybutylene-terephtalate)  with PC compound reinforeced with glass fibers in injection molding . Polybutylene Terephthalate (PBT) is a crystalline, high molecular weight polymer that has an excellent balance of properties and processing characteristics. Because the material crystallizes rapidly, mold cycles are short and molding temperatures can be lower than for many engineering plastics. Particularly preferred are those examples that change from colourless or low visual colour to coloured on exposure to ultraviolet irradiation, and then change to a colour different to the first on subsequent exposure to infrared irradiation. Any type of radiation which performs the colour change reactions can be used. This includes laser or non-coherent, broadband or monochromatic radiation.

Specific radiation types include ultraviolet, near, mid or far infrared, visible, microwave, gamma-ray, x-ray or electron beam. I think the following below link may help you in your issue:

Thanks

One of the most important things is to dry it very well before injection molding. hydrolytic degradation followed by thermo-oxidative degradatio is the most common cause of discoloration in PC. If degratio occurs the flowability of the melt increases.

@Jeyoung Baek: Given the experimental details you just posted, plus the DSC thermograms, it is clear that you need to start at a lower temperature to get a proper baseline to determine your"Tg" transition. This will be clearer if you plot derivative of temperature (with respect to time) against temperature. TA's Universal Analysis software will let you do this easily. Then you'll be able to judge the instantaneous heating rate as a function of time. Since you stated that the heating rate was 10K/min, then you may only interpret the thermogram starting when the actual instantaneous heating rate is very close to (say 5%) of that target heating rate.

Try toluene... nice thing is that it has the same RI, and sticks like crazy as it dissolves the cop a bit. Interface remains totally transparent.

You should develop to system lean manufacturing in factory and Lean Supply chain management 

Temporary mold inserts in case of emergency mold damage on high volume molds would be the most beneficial use case.

Other components would be robot end of arm tool parts.

Hi Alessandro,

no, unfortunately I don't. As I'm not fully aware of the material you are requiring for these molds, this magnetic PLA filament: https://www.matterhackers.com/store/3d-printer-filament/proto-pasta-magnetic-iron-pla might not be applicable for your use case. I was thinking of embedding magnetic components (e.g. Neodymium magnets) into the object while 3D printing.

Cheers

 Felix

Yeah thanks all who spend there valuable time here, structure and properties are different from material to material but i want to know about any possibilities to get LDPE in best same properties like HDPE (any additives, filament or polymer)

Dear Nestor

You can think of using polycarobonate /  perspex /  acrylic sheet or glass sheet . These are available in various dimensions ( l x b x t), you can choose what ever dimensions  serves your purpose. You will have to do the leveling of the sheet.

Best Regards

Pramod

 I hope that following information will be helpful. 

please see the attached paper.

i hope this can help you.

please ask if any doubt.

Thank you very much for your inputs. We will try all of them and see the results.. Best regards!

Sigmasoft and Solidworks are two of the CAE packages capable of doing this task.  I suggest that you contact one or both of these (or another) firms to inquire about their products. But if you want to move ahead with the design without taking time to acquire and learn the methods, these firms could direct you to a university or a contract service firm that has existing expertise that could be paid to assist with this phase ofyour project.

Apply the rule of gating system and risering procedure like Caines method or naval research lab method.

You need to give geometry and solve for the Reynolds equation. Parametrically investigate your simulation.

I strongly suggest you take a look at the work of Xu, particularly his 1999 MIT Doctoral Thesis.  I've attached it for reference.  He lays out a method for determining a 1D cooling formula for a "cooling cell", using this in a 2D cooling lattice for iteratively calculating the required cooling time of more complex geometry.  I'd start on page 39, section 2.2 "Heat transfer model for conformal cooling".

Yes, there are equations to calculate this length. 

The idea is to have a surface with an area enough to transfer the heat from mold to cooling medium.

The problem has more variables than equations, so you have to assign fix values to some variables.

For example, you have to decide the cooling time you want. It determines the cavity wall temperature if you have the melt temperature, thickness of part, the demolding temperature and effective thermal diffusivity of plastic. With cooling time and enthalpy change (depending of T melt and demolding temperature, and weight of part) you calculate the flow rate of cooling medium for a temperature increase in this medium you have to decide. This Tincrease ranges between 0,5C bis 5C, depending of type of material (semi crystalline or amorphous) and quality of part.

With the temperature of cooling medium (normally you know this from your facility) and flow rate you calculate Reynolds, Prandt and Nussel to obtain the heat transfer coefficient for turbulent flow in circular channels.

With this and the Heat rate to evacuate from mold you can calculate the area of your channels and depending of diameter you choose (machining, drills etc. are practical constrains).  The drop pressure is another constrain for the lenght and diameter.  Normally you will try to get a a this drops which ranges between 0,5 to 3bar, depending of the cooling system in your facility.   And you can or must consider several circuits for cooling, if the length is too big for one circuit.

I recommend to read a masterpiece in this topic: Menges/Mohren "How to Make Injection Molds" Hanser Publisher. The equations were developed by IKV (RWTH Aachen)-researcher like Dr.-Ing. Erich Schürman in his doctor Thesis "Abschätzmethoden für die Auslegung von Spritzgiesswerkzeugen" in 1979.

We at ICIPC (www.icipc.org) developed some tools to calculate a cooling system for injection molds for thermoplastics, based on those equations.

Yes. You can extract rules from the neural network weights. There is software and research about it. Look for "rule extraction from ANN..." or similar.

Dear Sir, Thanks for the references. I'll check them. 

I know how to make the tool - its exactly same as that for CD/DVD. You take a glass plate, coat it with photoresist, shine laser, develop it. Then vaccum deposit metal (200nm thickness) on it, then electroplate it with Nickel to a thickness of 300um. This Nickel plate has all the features (though complimentary) that were present initially on the glass sheet.

Making the nickel 'stamper' is clear to me. My concern is the (extent of) stringent control during the production of plastic component during moulding. Would the features remain intact during the cooling, or would they merge with each other spoiling the details?

The impact strength of glass filled Nylon is excellent.  Three main reasons for a drop are hydrolytic degradation of Nylon due to improper drying, wrong glass fiber sizing (one for PP is used in Nylon for example), and breakage of glass fibers during molding.    There are many nucleating agents which may help to accelerate cooling and reducing crystallite size.  My guess is that your thick section is not filling, and hence, you are using higher pressure or speed to fill it, and your gate is not properly designed causing fiber breakage.

First, you want to check IV or MFR of Nylon you use before and after molding to see any degradation.  Next,  take a thicker section and put in hot oil and see if dimensions change and to determine uneven cooling.   Or you can anneal part in an oven to reduce or remove residual stresses and then check for impact.  Finally, do the ash test on different sections of the part and see if the amount of glass is the same and also check for fiber length.  Most likely degradation of Nylon and Fiber are causing the problem.

Dear Tihomir,

I will think about. I need, to this purpose a sheet with Description and usefull data!

Prof. Kostadinov proposed to me you, as candidate for a AvHumboldt research Post-Doc fellowship! On my side I have good news: the Univ Steinbeis Berlin (SHB) have just prolongate my Professorship with the main domain Research and conducting of research fellows.

I do support with pleasure your application. Please visit, to this purpose, the AvH-internet page for postdoctoral fellows!Let  us keep in touch on :   florin.ionescu@stw.de

The main topics should be not a technologic application, but more a theoretical one, like a development by using theoretical modelling and optimisation algorithmes towards implementation. The application is only on the second

Best regards,

Professor Florin Ionescu

Director of Steinbeis Institute Dynamic Systems Berlin/Konstanz

Steinbeis University Berlin

There are several laser techniques to produce hydrophobic, hydrophilic and omniphobic surfaces. Maybe some of these techniques might be applied to your topic.

Dear Alex

It is experiments, not a model.

Thank you Sir for the information.

The elongation at break and impact strength decreased with increased graphite content because expandable graphite acts as a filler, and if not properly distributed (mixed) within the PC flaws are introduced into the systems. This explains the increased tensile and flexural properties because these are dependent on the mixing, interface, and flaws in the systems. 

Thank you was nice to learn from

Hello Wang, if you "core" is the entire mold-half, then you can use the clamp-force result. Otherwise use the pressure result and the contact area

To do a reasonable job of estimating manufacturing costs for different processes used to produce a product I would suggest you develop a manufacturing cost model for each process type. To start, you will need to be able to define the finished product design and tolerances required, critical to quality attributes, and final product configuration. (Different process types can have dramatically different tolerance capabilities and can require dramatically different downstream processing.) Then for each process type create a theoretical process flow to go from raw materials to finished part. Once the model(s) are created you can start to change variables (material type/cost, rates, etc) and develop a reasonable estimate of manufacturing cost. Using the models you can then develop a statistically based mfg cost answer and also do sensitivity analysis.

If you look only at the cost of producing a pound, square inch, etc of needles you may find that does not estimate the total manufacturing cost because other process step costs dwarf the cost of producing the needles themselves.

Yes your procedure is wrong. You need to blast the SS with alumina, clean with Acetone and dry. make a mixture of 80% EtOH 20% water and 2% Silane. mix for 30 min. apply wait 1 hr. at RT, heat 60-90 C for 1 hr. then inject the PA. good luck!!

Probably gas mains?

Dear Jaap Schut,

no thanks as far as this area is for discussing and exchanging idees and opinions. I would like to add the following that I am sure that it is a very basic for you. Just to extend my previous answer.

Shrinkage is the result of the ability of the chain to be oriented with the ability to store elastic energy which will be used for the chain to recover and regain back an arrengement with high entropy and low enthalpy. This conditions of orientation and storing energy are possoble only for high molecular weight chains. Entaglements (which occur beyond a certain critical molecular weight) play a dramatic role for storing the input energy and for the recovery.

If the end-use of the product does not require high properties, than low molecular weight polymers (with MW lower then the onset of entanglements) will I think have low shrinkability. Regards

Try the lacquer made of polystyrene dissolved in acetone. Cheap as dirt and white.

Refer this link:http://onlinelibrary.wiley.com/doi/10.1002/pen.760301502/abstract

Hi Alagesan

Since your finishing requirement(0.04) is high,you can look into the process like AFM(abrasive flow machining) which is very good in terms of high finish. AFM will work with almost all the materials.Since you mentioned that you need to mass polish the components AFM is better.

With proper binder design and alumina  powder volume loading and debindering schedule, sintered parts should have densities =>98% of theoretical. 

Mohammad

To the best of my knowledge, the following may be potential issues:

- You are using a film grade polymer instead of the extrusion grade, possibly the polymer molecular weight distribution is not favorable for extrusion/injection

- The bioactive glass is possibly increasing the melt viscosity, determine the MFI for your blend versus your base polymer to understand if that is the issue

- The mixture is exposed to moisture and hence upon heating, caking (sic) is not allowing free movement of the screw, conversely if there is outgassing/decomposition, the machine should be vented

- Lastly, the screw, which is usually a general purpose (GP) may not be suitable for this particular blend.

Hope this provides a start form analysis standpoint.

Section 8.1 of Chapter 8 (pp. 238 – 244) in the book A. V. Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker Inc., New York (1996), discusses injection molding and shows simplified calculations for mold-filling during non-isothermal flow of polymer melts.  The derived equations are based on the modified Ostwald-de Waale power-law model which was found to fit best in the shear rate range from 10 – 10³ sec^-1.

The best method you can use to detect those Craks is neutron imaging.

I had used insulin syringe to implant the tumor cells, Although it is well to implant, the pinhole is too small that it may cause cell damage, so it will influence the mission success rate!