What is Injection Moulding?


  • Operator training and grading system


  • 24 hour availability
  • ISO9001:2015  IATF16949:2016
  • Family owned with long standing employees
  • Smooth transition from design through to tooling and production


  • Low overheads 
  • Reducing stocks
  • Modern machinery with robots and power savers

Injection moulding is a cost-effective way to create plastic components on a large volume basis. Although the initial set-up cost of designing and manufacturing a mould tool can be higher than other plastic moulding processes (such as rotational moulding), the quicker cycle time, durability and repeatability of plastic injection moulding can give a reduction in piece part costs compared to other plastic process methods.

The process

Plastic pellets are melted and extruded through a heated chamber by a screw, then injected into a specialised mould in the filling process. The product cools in the mould until it's firm enough to expel (either mechanically or with compressed air). Mould tools can be manufactured with one or more cavities, and we can assist you with tool design to match your annual volume requirements based on your specifications.

Injection moulding provides a wide range of colour options. Chess Plastics can typically match any Pantone or RAL reference and aid with material selection, polishes, surface textures, and cosmetics as desired.



Injection-Moulding Machinery

The injection moulding machine is made up of two units, namely a clamping and injection unit. Thus, the primary function of the clamping device is to open and close the mould and eject the product. There are two types of mould clamping methods: a toggle type and a hydraulic type. In the latter, the mould is opened and closed directly by the hydraulic cylinder.

Moreover, the injection unit’s function is to melt the plastic by heating and then inject the melted plastic into the mould. The screw rotates to melt the plastic in the hopper. It then accumulates the melted plastic located ahead of a screw. This is known as “metering”.

Following the accumulation of the required amount of molten plastic, the injection process begins. When the molten plastic flows in the mould, the injection machine works to control the screw’s moving speed (injection speed). Alternatively, it also controls the holding pressure after the molten plastic gets filled into the cavity. The change control position from speed to pressure is set to the point that the injection pressure or screw position reaches a specific fixed value.




The mould is a metal, hollow block where molten plastic gets poured into in order to form a fixed shape. And while not shown here, many holes are actually drilled into the metal block to allow for temperature control. This is accomplished with oil, hot water, or heating devices.

The molten plastic then flows into the mould through the gate (sprue) and fills the cavity through the runner and the gate. After cooling, the mould is opened, and an ejector rod component of the injection moulding machine works to push the mould’s ejector plate. This allows for further ejection moulding.


The moulded product is made up of a gate that introduces the molten resin, as well as a runner that guides it to the cavity, and a product. Because the efficiency of producing only a single product at a time is very low, the mould is typically designed with numerous cavities connected to the runner to produce multiple products at a time.

This is essential, as any deviations can result in improper moulding. Thus, the outcome is not likely to be sufficient for the final product.

In this case, if the runner length varies between cavities, these cavities might not get filled at the same time. As such, the size, appearance or performance of the moulded product will often vary from cavity to cavity. Because of this, runners are usually designed to ensure that the length between sprue and runner are in form.

Re-processing Materials

The runner and sprues in the moulded product are not actually considered products. These parts are sometimes discarded, but in other cases, they are reground and then reused as moulding materials.

Moreover, these materials are called reprocessed materials. The reprocessed material is not only used as a moulding material, but is usually used after being mixed with the original particles, because the initial moulding process may reduce various characteristics of the plastic.

The maximum allowable limit for the proportion of reprocessed materials is about 30%. This is because too high a proportion of reprocessed materials may destroy the original properties of the plastic used. Therefore, it is vital that monitoring systems are used by manufacturers to ensure optimal results at all times.

Moulding Conditions

Moulding conditions refer to the following:

  • Cylinder temperature
  • Mould temperature
  • Purge materials
  • Decompression
  • Injection speed
  • Pack and hold
  • Back pressure
  • Screw speed
  • Cushion size

Such conditions are set in the moulding machine to obtain the desired moulded product. What’s more, there are countless combinations of conditions.

And depending on the selected conditions, the appearance, size and mechanical properties of the moulded product will vary greatly.

Therefore, choosing the most suitable moulding conditions requires time-tested technology and experience. At Chess Plastics, we incorporate careful planning and control of our large injection-moulding machinery with the use of our Mattec Real-Time Monitoring System.

This system works in conjunction with our plastic manufacturing software for precision performance among our injection-moulding processes. What’s more, we also offer additional specialised services that allow us to serve our clients better.

Although injection-moulding is our primary service, we also provide welding, plating, printing, assembly and packaging. And in doing so, we can ensure that our clients’ units are ready to be delivered to distributors quickly and efficiently.