#arianaballantyne

[acma-industries]

Injection Moulding

One of the minor manufacturing processes used at ACMA Industries is Injection moulding. “Injection Moulding is a highly efficient and swift way to produce a diverse range of plastic products, form disposable consumer items to specialist and intricate industry components (Philip Howes and Zoe Laughlin)”.  Injection Moulding is simple and allows for great freedom when it comes to complicated form work and designs. This makes it a useful process for ACMA to use. “The process works by way of a heated barrel equipped with a motorised screw feeding a molten… polymer into a hollow slit mould of the required product at high pressure (Philip Howes and Zoe Laughlin)”. The high pressure forces all the air out to fill the cavity completely where the plastic cools and hardens in the shape of the mold cavity. The mold is generally made of metal and is precision machined to create very detailed components. Huge volumes of thermoplastic components in particular are processed annually using injection molding to shape the contours of the piece. This is due to the suitability of thermoplastic properties for injection molding, the ability they have to soften and flow when heated, and the ease of recycling the plastic to remold and reshape the material. Injection molding is one of the simplest processes for molding, it uses more material than blow molding does, as it creates a solid component, this also means that pieces made from injection molding are more durable and have a higher impact resistance than hollow pieces. This process will create a piece that is appropriate for my desired use, and pieces that are appropriate for most uses, so understanding injection molding becomes very important for the design of plastic based components.

  References:

Laughlin, Philip Howes and Zoe. "Material Matters." New Materials In Design. London: Black Dog Publishing Limited, 2012. 136,137. Print.

Xcentric Mold & Engineering, Inc. "About Injection Molding".30 January. Webpage. 2013 http://www.xcentricmold.com/aboutinjectmold.php

  Kate Shepherd 300258946

  Ariana Ballantyne 300227744

[acma-industries]

The Thermoset Process

ACMA Industries uses a thermosetting process to manufacture their plastic products.

M. Joseph Gordon JR. states “Thermosets, unlike thermoplastics, have essentially only one heating style before solidifying in a mold. When thermosets are heated, under high pressure and temperature, in an ejection molding machine… they soften, flow and fuse in a heat-induced crosslinking chemical reaction in the mold”. This explains how the chemical reaction that causes the compounds in the thermoset process form a polymer chain that is irreversibly changed. Thermosets are made out of two compounds and can be in the form of pellets, powders, liquid and gel. The majority of the compounds used are in liquid or gel form and when mixed in the specified proportions they cure through an exothermic reaction.

Gordon JR. also comments how each material system can be “enhanced and modified with varying amounts of process addictive’s and material enhancers as fillers and reinforcement” This is a process ACMA uses regularly for example when they add fire retardants to make their products fire resistant. 

Thermoset compounds cure with an exothermic reaction. “Once thermosets have reacted and cooled, they cannot be re-melted or reformed (Gordon JR).  This is a once off reaction due to the fact that when they undergo a heating process, a chemical reaction, or a suitable irradiation, chemical bonds are formed, and the polymer chain is irreversibly changed into a 3D polymer network. This means that should the plastic ever be broken down it will not be to its original form, and therefore the process cannot be repeated.

The design implication of this is that thermoset polymers are used in situations that call for a permanent material, or in situations where recycling will be too difficult so the material breakdown is not of a high priority.

Thermoset polymers are known for being more suited to high precision final pieces and therefore will probably never be used in the concept phases of design due to its inability to be edited.

ACMA uses a two pot system to make this reaction and processed by injection moulding.

Pros:

Cost Effective

High Temperature Resistance

Can Have Added Properties

Can Be Produced Into Many Shapes Both Small and Large

Can Be Created Into Many Forms Ranging From Hard Cast Plastic to Soft Foam Cushions

High Aesthetic Quality 

Very Stable Forms and Chemical Balance

Durable, Strong and Stable

Abrasion resistant

Can Be Load Bearing

Cons:

Cannot Be Reshaped Or Modelled 

Cannot Be Recycled

More Difficult To Surface Finish

Short Workable time

Can Release Volatile Organic Compound Emissions

(How Stuff Works) (Plastics Modor)

References

JR., M. Joseph Gordon. "Industrial Design Of Plastic Production." New Jersey: John Wiley & Sons, 2003. 118,119. Print.

LGS Chemistry – Thermosoftening and Thermosetting plastics. 2005. Webpage. http://www.lgschemistry.org.uk/PDF/Thermosoftening_and_thermosetting_plastics.pdf

Plastics, Modor. Thermoset VS Thermoplastics. 2013. Web. 09 09 2013.

The Open University (UK). T838 Design and Manufacture with Polymers: Introduction to Polymers, pg. 9. 2000. Milton Keynes: The Open University. Print.

Works, How Stuff. Curiosity.com. 2012. Web. 09 09 2013.

Kate Shepherd 300258946

Ariana Ballantyne 300227744

Emma Cunningham 300259197