About Vacuum Forming
Vacuum Forming is when a plastic sheet is heated to a pliable forming temperature and draped over a mold. A vacuum is then applied to force the plastic to take the shape of the mold. The plastic is then cooled, taken off the mold, and trimmed to become a useable part.
The molds are attached to a vacuum box. Molds can be constructed of MDF, Hardwoods, Composites or Aluminum depending on shape, material being formed, quantity, and application.
Below is a list of suitable thermoplastics for vacuum forming:
| Acrylonitrile butadiene styrene (ABS) | Polyacrylonitrile (PAN or Acrylonitrile) | Polyketone (PK) | Polyphthalamide (PPA) |
| Acrylic (PMMA) | Polyamide (PA or Nylon) | Polyester | Polypropylene (PP) |
| Celluloid | Polyamide-imide (PAI) | Polyethylene (PE) | Polystyrene (PS) |
| Cellulose acetate | Polyaryletherketone (PAEK or Ketone) | Polyetheretherketone (PEEK) | Polysulfone (PSU) |
| Cycloolefin Copolymer (COC) | Polybutadiene (PBD) | Polyetherketoneketone (PEKK) | Polytrimethylene terephthalate (PTT) |
| Ethylene-Vinyl Acetate (EVA) | Polybutylene (PB) | Polyetherimide (PEI) | Polyurethane (PU) |
| Ethylene vinyl alcohol (EVOH) | Polybutylene terephthalate (PBT) | Polyethersulfone (PES) | Polyvinyl acetate (PVA) |
| Fluoroplastics (PTFE) | Polycaprolactone (PCL) | Polyethylenechlorinates (PEC) | Polyvinyl chloride (PVC) |
| Ionomers | Polychlorotrifluoroethylene (PCTFE) | Polyimide (PI) | Polyvinylidene chloride (PVDC) |
| Kydex | Polyethylene terephthalate (PET) | Polylactic acid (PLA) | Styrene-acrylonitrile (SAN) |
| Liquid Crystal Polymer (LCP) | Polycyclohexylene dimethylene terephthalate (PCT) | Polymethylpentene (PMP) | |
| Polyacetal (POM or Acetal) | Polycarbonate (PC) | Polyphenylene oxide (PPO) | |
| Polyacrylates (Acrylic) | Polyhydroxyalkanoates (PHAs) | Polyphenylene sulfide (PPS) |
Advantages
- Fast cycle time – Cycles can range from 2-10 minutes per part
- Inexpensive molds – Molds are made to suit the production needs. If a small amount of parts is needed, the mold will be made using less expensive materials.
- Little to No manufacturing evidence. Parts are usually formed using a male mold, allowing for the underside (or back side) of the plastic to show any mold lines & stress marks, leaving the top face untouched.
- Wide range of materials and colors can be used
- Formed parts can be easily reinforced
Disadvantages
- Tall/Deep parts are difficult to form because the plastic can ‘thin out’ and tear while forming.
- Complex shapes can cause ‘webbing’ to occur, leaving a web shape of plastic from the part to the base of the molding board.
Typical Uses
| - signage | - cosmetic surfaces on permanent structures |
| - trays | - interior panels for transport vehicles |
| - various covers | - refrigerator panels |
| - electrical equipment |
Product Design Considerations
- Shrinkage – All thermoplastics will shrink when formed. Shrinkage varies with material, shape of part being formed, thickness etc. Once a material is specified, along with a rough idea of the part shape, shrinkage can be estimated.
- Draft Angles – Draft angles are crucial to the production of vacuum forming. A part cannot be formed without draft angles.
- Undercuts – In Vacuum Forming, absolutely no undercuts can be present.