Week 8 - Challenge 4 - Coin Holder Design
Introduction
Having easier ejection from the mold may seem like a minor concern, but draft is crucial to manufacturing parts that meet your quality standard. Without draft, major problems can arise in the injection molding process that increase the time and cost of production.
When no draft is designed into the part, problems can come from friction and vacuums. These issues can damage both your part and even your mold in extreme cases. These problems are a direct result of having insufficient draft. Because plastic shrinks as it cools, portions of the part may pull away from the mold while others grip the core. If there is no draft angle that allows a simple push from the ejector pins to pop the part out of the mold, the part’s surfaces will often drag along the mold as it is being ejected. This friction between the two surfaces can cause scratches or gouges in your part and affect the appearance. This is particularly troublesome if your part is being molded with a surface finish or texture. The friction will scrape away texture and leave you with many rejected parts.
Designing the class B surface from the given class A surface is the next step to be followed
- As the fillets gives problem during the thickening we extract the required surface and offset all the extracted surfaces towards the class B region by 2.5mm and trim them and provide the necessary fillets following the rule(Radius of the fillet of class A surface) ±(the offset value) to get the class B surface
Class C surface
Class C surface are once which lies between the Class A and B surface . while creating the class C surface we have provided the draft greater than 3 degree in such a way that the parting line lies at the B surface. And this is done to prevent flash on the Class A surface.
Class A , B , C surface after the final trim
At the region where the fillet radius where small a minimum fillet of 0.5mm was given at class B surface.
Tree Structure
Conclusion
The coin holder's class B,C surface and the solid body was designed successfully from the give Class A surface. But this is plastic component is not manufacturable as the wall has no draft.