Injection mold designers must always take into consideration the surface finish required of the finished molded part. The ejection system in the mold that removes the solidified parts out of the mold cavity or cavities has great impact on the part’s surface finish. The most common ejection system uses ejector pins which can leave marks on the part, often referred to as witness lines.
An experienced mold designer will position ejector pins in order to place witness lines in an area acceptable to the part print. The ejection system and ejector pins are housed in the B side of the mold, extending into the cavity during ejection then retracting back into the mold. Restrictions on ejection must be apparent prior to mold design, if ejector pins cannot be used without damaging the part, lifters can be utilized for proper ejection.
The injection mold design must correspond to the ejection pattern and stroke of the press. Michiana Global Mold is an experienced injection mold maker with in-depth knowledge of designing various ejection systems to meet customer specifications. We use CAD/CAM Unigraphics software to design and develop a layout for the ejection system prior to cutting steel.
In some cases, ejection systems must be designed around robotic arms that reach into grab the parts upon ejection. These robotic systems are called ‘sprue pickers’, as sprue is another term for the runner that is also ejected with the part. Some ejection systems automatically separate parts and runners, so that they do not need to be separated later.
Whatever your part design, surface finish, or ejection system is required, Michiana Global Mold will design and construct a superior mold with flawless ejection for the specified part surface finish. We are an ISO registered mold making company with an offshore mold making partner in China. Contact us today for a FREE design consultation and to speak with a skilled mold engineer.