Pressure Forming

Pressure forming thermoforms heated plastic sheet against a mold using high air pressure, delivering sharper detail, better definition, and improved wall thickness control.

Overview

Pressure forming is a thermoforming process where a heated thermoplastic sheet is forced onto a mold using compressed air (often 50–100+ psi). The added pressure drives the sheet into fine features, producing crisper radii, tighter corner fill, and more consistent wall thickness than basic thermoforming methods.

Choose pressure forming for cosmetic housings, panels, and covers that need molded-in texture, sharp feature definition, and medium-volume economics without injection molding tooling cost. It works well for larger parts and moderate draw depths where you still need good surface fidelity.

Tradeoffs: tolerances are looser than injection molding and depend heavily on material, part size, and feature location. Undercuts are limited, deep draws thin the material, and post-trim/secondary ops (CNC trim, drilling, inserts) are common. Tooling and cycle time are higher than low-pressure forming, but the part appearance and feature detail are materially better.

Common Materials

  • ABS
  • HIPS
  • PC
  • PMMA (Acrylic)
  • PETG
  • PVC

Tolerances

±0.010" to ±0.030"

Applications

  • Medical device housings
  • Equipment and instrument covers
  • Kiosk and display bezels
  • Aircraft interior panels
  • Appliance panels and door liners
  • Industrial control enclosures

When to Choose Pressure Forming

Choose pressure forming for medium volumes where you need high cosmetic quality, sharp feature definition, and textured surfaces on a thermoplastic sheet part. It fits larger footprint parts that would be expensive to injection mold and that can tolerate thermoforming-level tolerances plus trimmed edges/holes.

vs Vacuum Forming

Pick pressure forming when you need tighter definition on corners, logos, textures, and small features, or you’re seeing webbing and incomplete corner fill with vacuum alone. It also helps hold wall thickness more consistently on draws where appearance matters.

vs Twin Sheet Forming

Pick pressure forming when you need a single-skin cosmetic panel with strong surface detail rather than a hollow, welded double-wall structure. It’s a better fit for parts where stiffness comes from geometry or ribs rather than a sealed cavity.

vs Injection Molding

Pick pressure forming when the part is large and cosmetic, volumes are moderate, and you want lower tooling cost and faster tooling lead time. It’s also useful when your design can accept formed radii, draft, and secondary trimming instead of molded shutoffs and tight positional tolerances.

vs CNC Machining (plastics)

Pick pressure forming when you need a lightweight shell or cover with smooth contours and texture at lower piece price than machining. It makes sense when the part is defined by surfaces, not thick solid sections, and you can add holes/features with post-trim ops.

Design Considerations

  • Maintain consistent wall thickness expectations: deeper draws and sharp features will thin; place critical bosses/features in low-stretch areas when possible
  • Use generous radii and adequate draft (typically 3–5°+ on formed walls) to improve definition and release
  • Define trim lines clearly and keep critical dimensions off trimmed edges; plan datums around molded surfaces or fixtured trim features
  • Avoid true undercuts; if unavoidable, call them out early for inserts, slides, or secondary assembly strategies
  • Specify cosmetic requirements by surface (A-side/B-side), including texture and gloss; texture increases forming force and can affect release
  • Call out hole patterns and insert locations as secondary ops unless the supplier confirms in-tool forming; provide tolerances appropriate to formed vs trimmed features