General Appearance of the Product Parting Line Flash Good molds have venting around most of, if not the whole length of the parting line. As long as the stack and the vents are designed properly, there should never be flash on the parting line. If flashing does occur despite a properly designed and built mold, there could be a number of other causes: The selected molding machine has not enough clamp force (tonnage) for the projected area of the cavity and the required injection pressure or was not adjusted properly. . | Previous Page Copyrighted Materials Copyright 2006 Hanser Publishers Retrieved from General Appearance of the Product---------------------------- 41 Parting Line Flash Good molds have venting around most of if not the whole length of the parting line. As long as the stack and the vents are designed properly there should never be flash on the parting line. If flashing does occur despite a properly designed and built mold there could be a number of other causes The selected molding machine has not enough clamp force tonnage for the projected area of the cavity and the required injection pressure or was not adjusted properly. This is a rather common occurrence especially when the mold is installed in a low-tonnage machine clamping force because a suitable machine was not available. Flashing at the parting line could be caused by a poorly maintained and out of alignment molding machine which could be the result of poorly adjusted tie bars worn tie bar bushings worn or bent machine platen surfaces poor hydraulic system and so forth. Only too often a mold is blamed for flashing when the real reason is a poorly maintained or a too low tonnage machine. There may be hard to see plastic caught between the mold faces. Gaps Between Cavity and or Core Parts and Inserts Mold parts and inserts can be dimensioned for locational clearance fits Standard Geometrical Tolerancing that is they will probably always have a clearance but this clearance must never exceed a size where plastic could flash into it. This means that the so-called standard fits are not always suitable with larger mold components and inserts. Smaller tolerances than given with standard fits must be specified for some mold dimension. This modified method of tolerancing fits is quite suitable for the assembling of molds. Because gates wear out in time and get easily damaged often during startup of the mold molders prefer that the gate be in an insert see Fig. that can be replaced when .
