Which parts of plastic molds require clearance (Relief)?
In the design and manufacturing of plastic molds (injection molds), certain component interfaces require clearance (relief) to prevent interference, friction, and jamming, or to ensure proper mold opening/closing and molding functionality.
1. Between Moving and Fixed Mold Components
Core and Cavity: To prevent interference during mold closure, clearance is typically applied.
Only the molding area of the cavity is retained, while other regions are slightly relieved (commonly 0.05–0.1mm).
Non-Molding Areas of Sliders and Mold Inserts: Non-functional areas of sliders and mold inserts are relieved to ensure smooth sliding.
2. Slider-Related Components
Non-Working Surfaces of Sliders and Guiding Mechanisms:
Non-guiding regions are typically relieved by 0.1–0.2mm to avoid interference and friction.
Contact Areas Between Sliders and Front Mold Inserts: Only the molding surfaces are tightly fitted; other areas are relieved.
3. Between Inserts
Inserts and Mold Inserts:
If inserts are not for positioning or molding, their non-functional surfaces are relieved (typically 0.01–0.05mm).
Ejector Pins or Cooling Channels: Insertion holes are appropriately relieved to prevent interference.
4. Sliding Mechanisms
Sliding Blocks and Guiding Blocks: Non-guiding or non-working surfaces require clearance.
Angled Pins and Slider Channels: Avoid full-length contact; only the guiding contact surfaces are tightly fitted.
5. Ejection System
Ejector Pins and Ejector Pin Holes:
Ejector pins are typically 0.01–0.02mm smaller than the holes to ensure smooth ejection while preventing looseness.
Ejector Sleeves and Mold Insert Holes:
Clearance (e.g., 0.02–0.05mm) is required in order to avoid jamming.
6. Venting and Ejection Assistance Structures
Venting Grooves and Contact Surfaces of Mold Inserts:
Non-molding areas near venting grooves are relieved to form micro-channels (e.g., 0.01–0.03mm deep) for gas escape.
