Explain the mechanical property issues that could be caused if pressure is not correctly controlled in Injection Molding process.

As soon as the material that is molded contacts the mold in the injection operation, it begins to cool and solidify. For this reason the injection must occur quickly, so that the cavity is filled while the material is molten. This is achieved with a high injection pressure since the compound is very viscous, despite the high temperatures. The molten material must overcome the resistance offered by friction, in the nozzle and cavity, which could not be done if the pressure is lower than required, preventing the proper filling of the mold.

If the injection pressure inside the mold is higher than the appropriate one, it exceeds its closing force, the partition line of the mold is forced to open; allowing the molded compound to escape from the cavity (resulting in burr and additional work is required in order to eliminate it).