1. Material Preparation
- Material Selection: Typically uses rigid plastic sheets (e.g., ABS, HDPE, PVC, or PETG) with thicknesses ranging from 1.5 mm to 6 mm or more.
- Pre-Drying: Some hygroscopic materials (like ABS) require drying (e.g., 2–4 hours at 70–80°C) to prevent bubbles or defects.
2. Sheet Heating
- Heating Method: Sheets are uniformly heated in an oven (infrared or convection) until pliable (typically 150–200°C, depending on material).
- Temperature Control: Critical to avoid overheating (causing sagging) or underheating (leading to poor forming).
3. Forming Process
- Vacuum Forming: The heated sheet is placed over a mold, and vacuum pressure (0.7–0.9 bar) pulls it onto the mold surface.
- Pressure Forming: Compressed air (3–6 bar) is applied above the sheet for sharper details and undercuts.
- Mechanical Forming: For complex parts, mechanical assists (plugs or pushers) may be used.
4. Cooling & Solidification
- Cooling Time: Fans or water-cooled molds rapidly cool the part to retain shape (typically 30–60 seconds).
5. Trimming & Finishing
- Demolding: The formed part is removed from the mold.
- Trimming: Excess material is cut using CNC routers, die-cutting, or laser cutting.
- Secondary Operations: Drilling, painting, or assembly may follow.
Key Applications: Automotive panels, medical equipment, industrial enclosures, and large packaging.
Advantages:
✔ Cost-effective for large parts
✔ Faster cycle times vs. injection molding
✔ Design flexibility
Limitations:
✖ Lower dimensional accuracy vs. injection molding
✖ Material waste from trimming