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12 April 2016

Manufacture of new technical plastic parts

Quality, Plastic

Today we are going to tell you about the process of manufacturing a new part for one of our customers.

We are going to start from the assumption that the part is not yet fully defined.

In the future we will develop each section further, going into detail in each process.

If you are particularly interested in any of them, do not hesitate to tell us and we will give you the information you need or we will prioritise its publication.

1- Part design

In our technical office we analyse the part or assembly to be manufactured. With this and with our experience, we provide criteria that simplify the final design, facilitate the extraction of the mould in the injection process and optimise costs, both in terms of part manufacture and mould machining. To this end, we use specific technical programmes: CAD / CAM - Catia.

In case the customer requires it, we can help in the definition of the material to be used, as this technical plastic may require specific properties: mechanical resistance, with loads of other compounds, low friction, high flexibility, conductivity, thermosetting, transparency / opacity, predefined colour (RAL / Pantone), visible part, hypoallergenic, UV protection, etc. We can also produce over-injected parts (plastic on metal part) or multi-component parts, by using our bi-component machines or by over-injection of one plastic on another with different properties.

2- Mould design

This is an important stage, as with a good part design and a good mould design, we can greatly optimise the cost of tooling and production start-up times.

We use the aforementioned specific design programmes and, if necessary, injection flow simulation software.

The material to be used and the injection cycles must be taken into account in order to dimension the dimensions according to the dimensional variations of the plastic with temperature.

3- Mould manufacturing

With all of the above, in the machining workshop, the mould is manufactured.

This can be made of different materials and qualities.

Due to the typology of our parts, most of which are long series, we usually use high quality steels. However, on some occasions, we make aluminium moulds for shorter series or pre-series of large-scale projects.

4- Mould tests

Once the mould has been machined, the necessary tests are carried out until the final parts are approved.

To do this, we mount the mould on the appropriate injection moulding machine and simulate its normal operation and functioning, manufacturing some parts. There we check if the part comes out correctly, as we had defined it, or if the mould needs to be retouched in any way.

The usual retouches are usually to eliminate any burrs, bumps, marks in injection areas, adjustments of dimensions, mechanisms and optimisation of cooling.

We repeat this cycle as many times as necessary until the customer approves the final part.

In some of our parts, after this process and before entering the manufacturing phase, we proceed to finish their appearance. This consists of superficially treating some of the parts in contact with the molten plastic mass. This finish is transferred to the final part. This is a very common process in many of our parts, as they are components seen in high added value assemblies.

5- Final part manufacture

Now it is time to manufacture the first batch.

To do this, once the mould has been mounted on the injection moulding machine, we proceed to program all the injection parameters. Briefly, the most important ones are:

  • Temperatures in the different zones and stages of injection, to achieve a suitable state of fluidity in the mass that enters the mould.
  • Plastic mass values, which control how much material enters, its quantity and how long the pressure of its flow is maintained. It is important to control the injection speed of the expected quantity.
  • Different times that make up the whole injection cycle. Relevant to achieve the best crystallisation of the technical plastic for the highest quality of the final part. They include times for: filling, cooling, ejection, mould opening and closing, among others.

6- Quality controls

Throughout the entire production process we carry out quality controls on raw materials, equipment, intermediate products and final parts. The criticality of the part and its final use normally determine the frequency and intensity of these controls.

In general, controls are carried out on:

  • Reception of raw materials.
  • Checking the correct state of the production machinery.
  • Verification of moulds.
  • Monitoring of intermediate processes.
  • Inspection of the final part.
  • Packaging and dispatch conditions

And the most common controls are usually of the following types:

  • Visual: control of aspects, quantities, documentary correspondence, certificates, etc.
  • Mass: weight control.
  • Dimensional: with equipment of varying precision: specific part gauges, calipers, calipers, three-dimensional equipment.
  • Mechanical resistance: traction, compression, bending, adhesive adherence, etc.
  • Charpy impact resistance - Others: temperature cycle tests, fatigue cycles, densities, ash content, hardness, resistance (cold, heat, chemical attacks), colour and transparency tests, tests on pre-assembled assemblies and others.