Serving the UK & IE plastics industry

What Are Vacuum Forming And Thermoforming Machines?

In the case of Vacuum (Vac) Forming, the equipment is designed to turn a flat sheet of plastic material into the required product by heating it until softened, draping it over a single surface mould, then sucking the sheet onto the mould so that it takes its form.

This is a low-pressure process that only requires simple and relatively cheap moulds. For short production runs, even wood is a suitable tooling medium. Relatively large products can be produced, but shapes are generally not complex (without secondary operations such as machining), and the process can be quite slow.

The basic process is:

  • A sheet of plastic of the correct size and thickness is clamped into a frame. Typical material grades used are ABS, PETG, PS, PC, PP, PE, PVC and PMMA
  • The sheet is evenly heated using infrared elements and reflectors, the temperature being specific to the material grade. This takes longer as sheet materials become thicker.
  • More sophisticated equipment can produce deeper or more complex forms by either pre-stretching the sheet or using an actuated device called a plug to push the sheet into the mould prior to the vacuum being applied.
  • A vacuum pumping system then draws out the air between the underside of the sheet and the mould. This sucks the softened plastic onto the mould.
  • Fans or a water mist are used to assist the cooling necessary to fully harden the component before its removal
  • The part is removed, and excess material trimmed. The method employed and the amount of automation depends largely on production volumes required. At this stage, several secondary operations may be performed, such as machining of apertures, printing, assembly with other components etc.
Thermoforming machine

The ‘output’ end of an automated roll-fed thermoforming line, showing the ‘skeletal’ waste material that will be recycled for re-use.

Thermoforming uses many of the same principles as Vacuum forming but tends to be used where high production volumes of smaller items are required. Sheet material tends to be a lot thinner and is typically continuously fed into the machine from a roll or stack. It may sometimes be made up of several differing layers rather than a single (mono) layer.

Typical products produced in this way are food packaging and plastic flower pots. The equipment has a heating station where the sheet material is heated to the required temperature. It then indexes into the forming station, where components are produced through a combination of vacuum application over a series of female mould impressions and being pressed from above by male core plugs. Some tooling also crops out the components as they are formed, but sometimes the sheet is indexed to a separate cropping station.

An automated stacking station frequently handles the removed parts as the skeletal waste exits the machine to be stored prior to recycling.

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