Part design has a strong pertinency to specific applications, but the guiding principles of part design have a certain universality. Some of the guidelines described below may not be appropriate for specific thermoforming parts designed.

1. The outer three-dimensional corner of the convex part of the positive or negative mold generally produces a thick edge. The local surface area of the sheet is larger than that of the die surface. The thick edge will be lightened on a positive die with a limit block. Proper design of local plug pressure aid will often reduce the phenomenon of thick edges in the protruding part of the die.
2. Setting any die inclination on the die surface is better than no die inclination.
3. If it is not possible to design a large radius on the part, chamfering should be considered.
4. One-half to three-fourths of the shrinkage occurs before the component temperature drops to the thermal deformation temperature of the polymer.
5. For vacuum forming, the minimum radius of the two-dimensional or three-dimensional corner should be greater than the thickness of the local sheet, otherwise it will bend when the sheet is stretched to the corner.
6. For most thermoplastics, a radius of four times the thickness of the sheet is easy to form.
7. With the reduction of the three-dimensional corner radius, the plastic sheet is proportionally thinner.
8. For most polymers, a 2D radius of 0.4mm can be achieved by pressure molding.
9. The sheet temperature is higher and the molding time is shorter to achieve a smaller radius. 10. Surface wrinkling indicates that local thickness changes too quickly.
11. The bright spot indicates the enrolling phenomenon due to the lack of local vacuum.
12. Some plastics, such as PMMA and general Purpose polystyrene (GP-PS) are very sensitive to incisions. 13. Sharp corners will be brittle or easy to crack, resulting in damage when the parts are impacted. 14. Parts with internal angles less than 90 degrees may be brittle, regardless of the type of polymer.
15. On thicker parts, in order to obtain accurate local parts thickness, the parts should be formed from thicker sheets and locally shaped to size.
16. Ribs, corrugations, grooves, diamond meshes and multiple cones are typical methods for increasing wall and surface stiffness of thermoformed parts.
17. Parts with larger surface areas increase stiffness by adding 15% of light crown, concentric ribs, radial ribs, or a combination of these structures.
18. The distance between multiple raised ribs shall be at least 150% of the height of the ribs. The same goes for grooves. 19. The shrinkage rate of fiber-reinforced parts is not as important as the size change, because the elastic recovery or rebound occurs after the forming force is removed.
20. The groove on the vertical side of the negative molding part shall be parallel to the sheet plane.
21. The parts shall be designed to be formed around a fully extended removable side core. ,
22. On thin-walled beverage cups, the stiffness of the rolled edge is generally several hundred times that of the flat edge. Small diameter flanges produce adverse core effects.
23. The design of parts is not accurate usually for the following reasons: - mold accuracy is not enough
- Changes in material properties and dimensions between sheets - changes in quality and properties between batches of sheets - lack of understanding of the difference between negative and positive dies - part structure affects molding ability - inappropriate molding techniques are used - poor operator skills
- Improper or inadequate maintenance of machines and molds.
24. When more than 1000 pieces, thick sheet pressure molding is the most economical. 25. The mold cost of pressure molding is one quarter of the injection mold, and the development time is one quarter to one half of the injection molding.
26. Silicone oil release agent can only be used when the parts are not painted.
27. Vegetable oil can be used as a release agent, but all metal surfaces must be cleaned regularly or they will become rancid. Grapeseed oil is one of the most heat-resistant vegetable oils.
28. The molding temperature range of most commonly used plastics is 100-200℃.