Pressure Forming

Pressure forming shapes heated plastic sheet against a detailed mold using high pressure, enabling sharp features and molded-in cosmetics similar to injection molding.

Overview

Pressure forming is a thermoforming process that uses compressed air to force a heated plastic sheet against a detailed female mold. The higher pressure delivers sharper corners, finer textures, and better definition than basic vacuum forming, with part aesthetics that can approach injection molding while using lower-cost tooling. It supports large parts, moderate volumes, and complex surface detail like logos, textures, and undercuts with matched or segmented tooling.

You typically use pressure forming for medium production runs where you need high cosmetic quality and good feature detail on one side of the part. Common wall thickness ranges from about 0.060" to 0.250". Tooling cost and cycle time are higher than simple vacuum forming, and tolerances are looser than injection molding, with some wall thinning in deep-draw areas. Secondary trimming and drilling are standard for holes and cutouts, so plan for combined forming plus machining cost when evaluating total piece price.

Common Materials

  • ABS
  • Polycarbonate
  • ABS/PC blends
  • HIPS
  • Acrylic
  • Kydex

Tolerances

±0.010" to ±0.020" on formed features; ±0.005" on CNC-trimmed edges

Applications

  • Medical equipment housings
  • Instrument and electronics enclosures
  • Kiosk and ATM fascias
  • Transportation and aircraft interior panels
  • Industrial machine covers and shrouds
  • Point-of-sale and display housings

When to Choose Pressure Forming

Use pressure forming when you need injection-molding-like cosmetics and detail on one side of a large or medium-sized plastic part without paying for hard steel molds. It suits medium volumes where you can amortize tooling but still want flexibility for design changes. Target parts with complex surfaces, textures, and visible Class A faces that justify higher tooling cost than basic vacuum forming.

vs Vacuum Forming

Choose pressure forming instead of vacuum forming when you need sharper details, tighter radii, and high-end cosmetics on the show surface. Pressure forming justifies its higher tooling and cycle time when the part is customer-facing and must mimic injection molded quality, especially for medical, consumer, or kiosk enclosures.

vs Twin Sheet Forming

Choose pressure forming over twin sheet forming when you only need a single-wall shell or cover with good cosmetics, not a hollow double-wall structure. Pressure forming is simpler and usually cheaper for enclosures, panels, and covers, while twin sheet forming makes more sense for structural, insulated, or fluid-carrying hollow parts.

vs Injection Molding

Choose pressure forming instead of injection molding when you want molded-in detail and texture on one side but can’t justify expensive steel tooling for large parts or moderate volumes. It works well for big panels or housings where injection-molded tools would be extremely large and costly, and where slightly looser tolerances are acceptable.

vs CNC Machining (from solid plastic)

Choose pressure forming over CNC machining when you need repeated production of large plastic covers or panels and care more about cosmetic surfaces than tight internal tolerances. Once tooling is built, pressure forming reduces per-part cost and machining time, especially for curved or contoured surfaces that would be slow to machine.

vs 3D Printing

Choose pressure forming instead of 3D printing for production quantities of large cosmetic parts where surface finish, durability, and material options like ABS or Kydex matter. 3D printing is good for prototypes and complex internal geometries, but pressure forming wins on cost, speed, and cosmetics at scale for relatively thin-walled shells.

Design Considerations

  • Use uniform wall thickness and moderate draw ratios (typically under 2:1–3:1) to control thinning and improve dimensional consistency
  • Add 3–5° of draft on vertical walls facing the mold to aid release and reduce scuffing on cosmetic surfaces
  • Use generous inside corner radii (at least 0.060"–0.080") to improve material flow and avoid thinning or tearing
  • Clearly define Class A cosmetic surfaces, textures, and logo details on drawings so the shop can design appropriate female tooling and vents
  • Design a stable trim flange or datum surfaces for CNC trimming and fixturing; avoid relying on highly contoured edges as primary datums
  • Keep holes, slots, and sharp-edged cutouts as secondary CNC operations and group them where possible to reduce trimming time and cost