Vacuum forming, vacuum forming tooling, thermoforming, plastic fabrication, point of sale displays, street lighting, vacuum formed packaging, tooling and finishing
 

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VACUUM FORMING
Vacuum forming (or Thermoforming) is a common method of forming shaped objects by processing plastic materials. Vacuum formed products are all around us and play a major part in our daily lives.
The process involves heating a sheet of plastic until it reaches forming temperature then allowing it to take the shape of a mould. A vacuum is applied to pull the sheet into the mould. The sheet is then ejected from the mould once it has cooled to become harder. In its advanced form, the vacuum forming process uses sophisticated pneumatic, hydraulic and precise heat controls to enable higher production speeds and more detailed vacuum formed applications.

Vacuum forming offers several processing advantages over other forming processes. Low forming pressures are used which allows relatively low cost tooling to be used unlike injection moulding..

Since the process uses low pressures, the moulds can be made of inexpensive materials and mould fabrication time can be reasonably short. Prototype and low quantity requirements of large parts, as well as medium size runs therefore become economical.

More sophisticated machines and moulds are used for continuous automated production of high volume items like packaging.

Unlike other thermoplastic forming processes, where powder or resin are the starting point, vacuum forming uses extruded plastic sheet. With vacuum there are some secondary processes to trim the formed sheet and polish edges to produce the finished item. The trimmed waste can be re-ground and recycled.

Vacuum Forming Process
Clamping
The clamp frame ensures the plastic sheet is held firmly in place during the forming process.

Heating
Radiant heaters are normally used to heat the sheet which has been positioned over the aperture of the vacuum forming machine. For thicker sheet both surfaces are to heated and more sophisticated machines allow this. Heaters move into position both above and below the sheet.

Pre-stretch
Is used to achieve "even" wall thickness. Air is introduced to blow a small "bubble" and the mould is then raised into the pre-stretched sheet.

Vacuum
A vacuum is applied, the sheet is drawn into intimate contact with the mould and the mould detail is picked up.

Plug Assist
Where a deep draw is required a top "plug" may be used to push material into the mould during the forming process.

Cooling and Release
The material is allowed to cool. The cooling process may be shortened with blown air or even a fine water spray. The moulding may then be released from the mould by introducing a small air pressure.

Finishing
After moulding, any mould finishing may be performed, trimming, cutting, drilling, polishing, decorating etc.

Normally, draft angles must be present in the design on the mould, (A recommended minimum of 3°) otherwise release of the formed plastic and the mould is very difficult.

Vacuum forming is usually – but not always - restricted to forming plastic parts that are rather shallow in depth. A thin sheet is formed into rigid cavities for loose objects that are carded or presented as point-of-purchase items. Thick sheet is formed into permanent objects such as road signs and protective covers.

Relatively deep parts can be formed if the sheet is mechanically or pneumatically stretched prior to bringing it in contact with the mould surface and before vacuum is applied

Suitable materials for use in vacuum forming are conventionally thermoplastics, the most common and easiest being High Impact Polystyrene This is moulded around a wooden mould and can form to almost any shape.

Absorbed moisture can expand forming bubbles within the plastic's inner layers. This may be solved by drying the plastic for an extended period at high but sub-melting temperature.

Vacuum forming, vacuum forming tooling, thermoforming, plastic fabrication, point of sale displays, street lighting, vacuum formed packaging, tooling and finishing
Vacuum forming, vacuum forming tooling, thermoforming, plastic fabrication, point of sale displays, street lighting, vacuum formed packaging, tooling and finishing
Vacuum forming, vacuum forming tooling, thermoforming, plastic fabrication, point of sale displays, street lighting, vacuum formed packaging, tooling and finishing