Of the hundreds of variables involved in injection molding, clamping mechanisms and platens often get less attention than they deserve. Good clamp performance is critical to minimize cycle times, optimize part quality, and maintain process consistency. Alignment and uniformity of the mold halves, platens, and clamping system is therefore critical. When an alignment problem stems from the mold parting line, the platens, or the clamping mechanism and tiebars, the results can be unnecessary machine wear, mold damage, broken tiebars, mold flash, and scrap parts.
One way to ensure proper mating of the tool halves at the parting line is simply by having a level molding machine and parallel platens. Leveling a machine requires three machinist levels. If you have shorts and flash, you could have a mold or clamping alignment problem. This may not be the case if you are running a high-speed, thin-wall product—the problem may be simply not enough clamp force. To help establish whether flash stems from a mold or clamp alignment issue, check parting-line mating. In one typical check for uniform clamp pressure at the parting line, blueing agent applied to one mold half will transfer to the other if there is contact at the parting line, but it will not distinguish between low or high touch force. More detailed information can be obtained with Mold-Align® paper, which changes color relative to the amount of contact force. Mold-Align® is an extremely economical and practical solution for determining proper mold alignment. Mold-Align® is a self contained (single sheet) paper that is quickly implemented, requires no training, and reveals a high resolution image of pressure distribution and void spots between mold plates.