Pressure Forming

What is Pressure Forming for Plastics? 

Pressure forming uses high vacuum pressure and special tools to form plastic into molds. It produces a finely detailed product. Normal vacuum pressure is limited to an atmospheric pressure of about 14.7 psi.

Pressure forming allows us to utilize more vacuum pressure. This creates a stronger product with precise dimensions and appearance. If you need a perfectly executed product, pressure forming is the way to go.

Common Products Made with Pressure Forming

  • Medical equipment
  • Office equipment
  • Transportation equipment
  • Retail displays
  • Outdoor equipment
  • Embossed logos
  • Control pads and panels
  • Vented equipment enclosures

Beginning Steps

pressure-formed-logo

Plastic pressure forming starts with an extruded sheet of plastic secured in a clamp frame. Next, the plastic moves into an oven and heated until it reaches a malleable temperature.

Afterward, we remove the clamped sheet from the oven. It is then sandwiched between a pressure box and the chosen mold. The heated plastic forms a seal around the mold.

Preventing Thinning

Sometimes the plastic sheet can be stretched too thin. This can create problems in the pressure forming process. If the plastic is too thin, it can crack. Too thin a sheet will also be too weak for certain projects.

To reduce the amount of material thinning in parts with a deep draw, plug assists are often used. This pre-stretches the plastic sheet and reduces the amount of material thinning that can occur.

A plug assist is called for when using a negative mold with pre-stretching. The mold is pushed into the heated plastic sheet to create a seal on the edge. At the same time, the plastic sheet pushes into the mold using the plug assist. This is opposite of what usually occurs with pressure forming.

As it enters the hot sheet, air between the sheet and the mold is compressed, causing the sheet to undulate around the plug. The hot plastic sheeting is prevented from directly contacting the cooler mold as the sheet stretches. This ensures maintaining a consistent material dimension.

Providien uses a thinner starting gauge plastic, which reduces both raw material and processing cost.

Forming the Part

Pressure forming molding

The now heated sheet is placed into a pressure box along with the mold of the desired product. With the sheet secured, a strong vacuum applies up to 85 PSI pressure to the mold side of the sheet. The suction pulls and forms the sheet over the mold.

The vacuum pressure forces the part to match the contours of the mold. At the same time, air pressure is applied to the top of the sheet. Pressure forming gives 3 to 4 times the amount of pressure used in traditional vacuum forming. The combination of both pressures is what gives the product such finesse.

Following forming, the part cools on the mold. The part is then freed of molded stress and ready for finishing. Even before the product is finished, it looks identical to the mold.

Trimming the Part

The molded part may have excess plastic parts sticking off of the product. These parts must be trimmed before the product can be finalized.

The newly pressure formed part gets processed through a 5-axis CNC trimming station. In the CNC station, it is expertly trimmed to its final dimensions.

Further fabrication steps may be performed at this point before the final product is ready for release.

Materials Used

pressure forming materials used

Pressure Forming can bend and meld a variety of materials. Providien Medical primarily uses KYDEX®in it’s pressure forming projects.

KYDEX® is a type of PVC/Acrylic plastic that comes in a variety of colors at low minimums. The plastic can also be aviation grade. It also meets the UL’s strictest flammability rating.

Other common materials include:

  • ABS (Acrylonitrile Butadiene Styrene): range of adaptable resins that meet UL Flammability ratings
  • PMMA (Polymethyl Methacrylate): a common plexiglass with excellent scratch resistance
  • PETG (Polyethylene Terephthalate Glycol): good strength and formability
  • Polycarbonate: a high impact plastic that resists high temperatures
  • PVC/Acrylic: meets highest UL Flammability rankings
  • HIPS (High Impact Polystyrene): low-cost resin
  • TPO (Thermoplastic Polyolefin): great outdoor performance
  • HDPE (High-Density Polyethylene): cost effective for projects requiring high impact strength
  • PC/ABS: achieves high gloss while meeting the same ratings as PVC/Acrylics

Advantages of Pressure Formed Parts

Thermoforming of plastic materials for medical devices

Pressure forming provides many benefits to a product.

These include:

  • Tight tolerances in extreme environments
  • Crisp detail
  • Formed-in texture
  • Formed-in threaded inserts
  • Custom color parts without the need for paint
  • Creates large products
  • Swift prototyping with faster time to market

Pressure formed parts have aesthetics that rival injection molded parts at a fraction of the tooling cost.

The Value of Undercuts

benefits-of-pressure-formed-undercuts

Undercuts are another benefit of pressure formed parts. This allows the attaching of parts to mated pieces.

Undercut parts can also be more easily attached to a chassis or frame. When compared to traditional vacuum forming techniques, this reduces costs and increase repeatability.

This provides a cost great advantage when compared to traditional vacuum forming techniques.

Great Results for Less

pressure formed clamped frame

Pressure formed parts provide cosmetically similar parts that are on par with injection molded parts.

Pressure formed tooling is 60%-80% less expensive than injection mold tooling. Of course, this depends on the part geometry and size of the parts.

Pressure forming competes well against other large part processes such as reaction injection molding (RIM) and structural foam molding.

Total program cost including both tooling and unit cost are typically favorable for pressure forming.

Another value to pressure forming is that it does not require paint. This feature makes it more environmentally friendly.

And at the same time, it provides for better cosmetics when compared to reaction injection molding (RIM) and structural foam.

Your Next Pressure Forming Project

If you have a product that requires immense detail, pressure forming is your best option. Providien Medical can provide you with the expertise you need. Feel free to contact us to discuss your next project.