Week 8 - Challenge 1 - Draft Analysis on a Fan Cover

Create the tooling axis for the given Fan cover model meeting the requirements of the draft angle and perform the Draft analysis on the model.

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.

In addition to friction, no draft presents the possibility of a vacuum forming during ejection. If the sides of a feature cannot release from the mold, the ejector pins may push on the section until the vacuum becomes so stressed that the part may bend, break, or warp by the time it is pushed out. The alternative is that the part becomes stuck in the mold if the ejector pins are not strong enough to overcome the vacuum. A higher ejection force would be needed to remove a part without draft, which means the part would need to cool longer before it can be ejected successfully. This increase in cycle time and the likelihood of having more rejected parts overall will drive up your production costs.