Vacuum Forming

Vacuum forming shapes heated plastic sheet over a single-sided mold using vacuum, ideal for large, shallow parts with low tooling cost and moderate detail.

Overview

Vacuum forming is a thermoforming process where a heated plastic sheet is drawn over a mold by vacuum, then cooled and trimmed to create the final part. It excels at producing large, lightweight components with one primary cosmetic side, using relatively simple and inexpensive tooling compared to multi-part molds.

Choose vacuum forming for shallow-to-moderate draw parts, moderate feature detail, and wall thicknesses typically from 0.040" to 0.250". It suits low to high production volumes once tooling is built, with quick cycle times and good repeatability for non-critical tolerances. Tradeoffs include non-uniform wall thickness in deep draws, limited sharp detail on the non-tool side, and less precise tolerances than machining or injection molding. It is not ideal for very small features, extremely tight tolerances, or complex undercuts without added tooling complexity and cost.

Common Materials

  • ABS
  • HIPS
  • PETG
  • Polycarbonate
  • PVC
  • HDPE

Tolerances

±0.010" to ±0.030"

Applications

  • Equipment covers and shrouds
  • Instrument and control panels
  • Product and medical trays
  • Automotive interior trim and panels
  • Appliance liners and housings
  • Point-of-purchase displays

When to Choose Vacuum Forming

Use vacuum forming for medium-to-large plastic parts where one side carries most of the cosmetic and geometric detail and tolerances are moderate. It fits low to high volumes when you want low-cost tooling, quick iteration, and sheet-based materials in the 0.040"–0.250" range. It’s especially effective for covers, trays, and panels with relatively simple geometry and limited undercuts.

vs Pressure Forming

Pick vacuum forming when you need lower tooling cost and simpler molds and can accept softer detail and more basic cosmetics on the finished part. For covers, trays, and guards where function matters more than high-end surface definition, vacuum forming is usually more cost-effective than pressure forming.

vs Twin Sheet Forming

Choose vacuum forming when you only need a single wall and don’t require internal cavities or built-in hollow structures. For simple covers, trays, and shields, vacuum forming avoids the higher tooling cost and process complexity of twin sheet forming while still delivering lightweight, rigid parts.

vs Injection Molding

Select vacuum forming when part sizes are large, wall thickness is higher, and you want much lower up-front tooling cost. For medium-volume production of big panels, shrouds, and housings, vacuum forming can be cheaper and faster to tool than injection molding, even though it sacrifices some tolerance and feature precision.

vs CNC machining

Use vacuum forming instead of CNC machining when you need many identical plastic parts and can amortize the tooling cost over the run. For large covers and panels, vacuum forming will usually beat machined-from-solid parts on per-piece cost and weight, as long as you don’t need tight tolerances or heavy structural sections.

vs 3D printing

Favor vacuum forming when you have a stable design, need production volumes, and can work with single-sided detail from sheet stock. 3D printing is better for prototypes and very low volumes, but per-part cost and cycle time are far higher than vacuum forming once tooling is in place.

Design Considerations

  • Use generous draft (typically 3–5° or more) on all vertical faces to release cleanly from the mold and avoid scuffing
  • Avoid deep, narrow draws; keep draw ratios modest or use plug assists to limit wall thinning and improve thickness uniformity
  • Blend sharp corners with large radii to promote smooth material flow and reduce thinning or tearing during forming
  • Place critical dimensions and cosmetic surfaces on the tool side; expect more variation and less detail on the non-tool side
  • Design bosses, ribs, and mounting features to be added via secondary bonded or machined components if they can’t be formed cleanly
  • Provide accurate 3D models of both the formed shape and trim line, and clearly define critical-to-function dimensions and acceptable wall thickness ranges for quoting