TABLE OF CONTENTS It is very important to give careful consideration to the way in which a component is going to be ejected from the tool. The design of the ejection system is one of the major factors in determining how efficient the tool will be in production.
The paramount requirement is that all components are ejected positively, without exhibiting any tendency to twist, distort or hang-back. In determining a satisfactory system, a number of factors have to be taken into account, including:
The part geometry
The material
Gating
Ejection balance
Machine specifications
Component finish requirements
The component geometry will often restrict where ejectors may be placed. Features on the part may make it impossible to eject on certain faces. For example, they may be stepped, or perhaps a face may have several holes all grouped closely together. This type of feature means the face cannot easily be used for ejection.
The component drawing should be checked for suitable draft angles being present in the line of draw. Draft angles are often an essential requirement. Deep drawn parts in particular may tend to scuff or score up when ejecting from parallel-sided cores.
If draft angles are not present on the drawing, the designer should pursue this problem with the customer with a view to obtaining a concession. At the least the customer should be warned of the consequences of continuing in such cases. A draft angle of at least 1 is required for most mouldings,...
