CHICAGO — Logic Devices Inc. of Sandy Hook, Conn., promoted a patent-pending injection molding process called Incremental Cavity Ejection at NPE 1997, held June 16-20 in Chicago.
The process allows molded parts with heavy, textured sidewalls, having a minimum draft angle of 0.78 degree, to have no external draft or scuffing. The ICE molding process eliminates scuffing damage and large draft angle requirements, to facilitate the release from the cavity and the large ejection force associated with pushing the part from the core.
When ICE is used, there is not relative movement between the outside of the plastic part and the cavity when the mold first opens, the company said. Ejector pins and stripper rings are kept in the forward position as the mold opens only enough to allow the part to pull away from the cavity surface.
Initial breakaway ejection forces occur when the part is supported more uniformly by the cavity and core, which minimizes the potential for product distortion. More-uniform distributed breakaway stress levels come about because the part is held in place by the ejector pins and cavity undercuts, such as surface texture.
When the part is free from the cavity, the force action on the ejectors is deactivated and the mold opens in the usual manner. Once in the open position, the ejectors are reactivated to eject the part from the core, reducing the potential for part damage.
Other features of the process include adding lettering and logos on side walls without adding costs, reducing the cost of tooling on new molds, being able to use the process on existing machines and faster cycle times.