If an undercut is mandatory, the mold maker will need to use sliding cores or lifters. This adds mechanical complexity, increases the risk of part defects, and significantly raises the initial cost of the mold. Conclusion
Several software tools can help you design and optimize your parts for injection molding. Some popular options include:
Keep these foundational principles in mind during your next CAD modeling session to bridge the gap between a great digital concept and a perfect physical product.
: The molten plastic is forced into the mold under high pressure. Cool : The plastic stays in the mold until it solidifies. Eject : The mold opens, and pins push the finished part out. Common Beginner Mistakes to Avoid
Draft is the angle or taper you apply to the vertical faces of your part. Why Draft Angles Matter injection molding part design for dummiespdf exclusive
"The part is short (incomplete filling)." Fix: Walls are too thin for the flow length. Increase wall thickness or add flow leaders.
: Sharp corners are "stress concentrators" that make parts brittle. Adding a radius (rounding the corners) improves material flow and significantly increases part strength. A good rule of thumb is an inside radius of at least 50% of the wall thickness. Ribs for Strength
Convert thick solid areas into hollow structures with a constant wall thickness.
Sharp corners are weak points and create stress concentrators, which can lead to part failure. They also make it difficult for plastic to fill the mold completely. If an undercut is mandatory, the mold maker
The of your part (e.g., electronic enclosure, structural bracket) Any cosmetic requirements you have
Bosses are cylindrical protrusions used to mount screws or locate parts. The same 60% rule applies here. The outer diameter of the boss should be carefully designed to avoid creating a thick mass of plastic. Use gussets (small triangular supports) to connect tall bosses to the main wall for added strength.
As molten plastic cools inside a metal mold, it shrinks tightly onto the core side of the tool.Without specialized design modifications, the friction between the plastic and the metal would prevent clean part ejection.This friction can scratch your part, warp your geometries, or freeze the part inside the tool. Implementing Draft Angles
Without draft, the plastic part will stick to the metal mold as it ejects. This causes scrape marks, structural damage, and can even jam the molding machine. Draft allows the part to release cleanly the moment the mold opens. Design Guidelines Eject : The mold opens, and pins push the finished part out
Connect tall bosses to adjacent walls using small ribs (gussets) to prevent them from snapping off under load. 5. Use Radii and Fillets to Avoid Sharp Corners
If you want to tailor these rules to a specific project, please let me know:
Distributes mechanical loads evenly across the geometry, drastically increasing impact resistance.
What is the of the part (cosmetic casing, mechanical gear, flexible clip)?