Does your injection molded part not quite fit? Is it a little too big or not as flat as you would like? Fix it with your process, without changing your cycle time.
If your molded part is too large, try heating up the core half of the mold. Twenty degrees Fahrenheit should do it. The additional heat will keep the part hotter during “cooling\cure time” and allow for more post-molding shrinkage after ejection. It can also result in a higher level of crystallinity developing due to the slower cooling rate. The end result will be a smaller part.
Need your part bigger, not smaller? Cool the core half of the mold down and/or leave it on the mold longer by increasing the “cooling/cure time”. The cooler mold temperature will quench the polymer, resulting in a less crystalline, more amorphous part. These conditions will result in less shrinkage and a larger part.
Are you trying to mold a flat part but it warps into something less than flat as it cools? Try heating up the mold by twenty to thirty degrees on one side only. Add the heat to the side that you want the part to shrink\warp toward. The hotter side will develop a more crystalline structure and usually result in a flatter part.
Note: In order to use these techniques a thermometer on each mold half is required. This will not only give you independent temperature control of each mold half, but it will also deliver a higher flow rate and greater cooling to each side. The higher level of process control coupled with greater overall cooling rates will result in better parts faster.
Caution: Never adjust mold halves to a differential of greater than 30°F without consulting your tooling department.
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