I was on site for process consulting and trouble shooting of a customers mold. They had some issues with gate blush and unbalanced parts in a family mold or 1+1 mold with unlike parts. for more detail in how I come about troubleshooting a problematic mold please read the process page on this site.

By following the scientific molding principles I was able to properly locate the injection stage for the gate area of the part and therefore control the speed of flow for the ABS material and eliminate the gate blush.

Another issue they were having was improper packing of one of the parts. One part was flashing and the other had sink marks (pits or areas that look like shallow pot holes.) This particular mold had good sprue, and runner size, although the gate size was not optimal. It is more difficult to determine proper gate size with dissimilar parts as they have different weights and wall thickness. I suggested we focus on the under filled part only instead of adjusting both sides. The larger part had gates that were under specification for depth and width. The gate depth determines the seal off time and the width determines the amount of volume that can be flowed. I had the customer increase the width by 50% as the optimal depth is usually 80% of wall thickness and width is 150% of gate depth.

Upon putting the mold back in the machine the parts were now balanced and issues resolved. The packing time had been reduced by 50%  or 20 seconds reducing the cycle time by 5 seconds and significantly reducing the machine power usage. It was now sitting under no load in a cooling stage instead of applying pressure during a longer than normal packing stage. I also had the customer remove some of the loops in the cooling lines as the parts were dissipating a lot of heat into the mold which was not being removed.

Related pages

• Process (1)