Cautions in Mold Tryout

Mold tryout is to test the mold defects through different process conditions and improve it through modifying. For those that cannot be modified for the time being, it is necessary to find out the most reasonable process parameters to guide the subsequent injection molding production.


Pay attention to the following content during the mold tryout:

First: Check the flow balance

Observe the product’s glue feeding by gradually increasing the amount of glue. For a single cavity, flow balance means that the flow front of the melt reaches the end of the cavity. For multiple cavities, flow balance means that the flow front of the melt reaches the end of each cavity . Different product weights or inconsistent shrinkage in multi-cavity molds in injection molding production are generally caused by imbalanced flow.

Second: The inspection of flashing

Check if the parting surface, row position, insert joint line, ejector pin hole and other parts when the product is not shrunk. In this case, more injection molding needs to be adjusted Process, local glue reduction, increase gate or change gate position to improve.

Third: Determination of mold exhaust position

Use a faster injection speed to find the position where the product has scorched, trapped air, water traps, etc., and then set up an exhaust slot at the corresponding position.

Fourth: Determine the key position of the screw of the injection molding machine

By changing the stroke of the screw of the injection molding machine, determine the key position of the screw during product injection. At a minimum, the key positions should include:

  1. The flow channel has just been filled;
  2. From the first gate filling to the last gate filling position (unbalanced gate design);
  3. The location when the water line, burnt, trapped air and other undesirable phenomena that affect the product appear;
  4. The position when the product is 99% filled (that is, the speed and pressure conversion position).

These key positions are the key to adjusting the injection process in the future.

Fifth: Inspection of product appearance
  1. Check the appearance of bad phenomena caused by mold manufacturing, including: piercing, mold surface not smooth, mold surface uneven, mold printing, step difference, poor etching, top white, drag, sticking, etc.
  2. Check the appearance defects caused by the injection molding process, including: air lines, water lines, watermarks, scorching, shrinkage, lack of glue, top white, scratches, material flowers, deformation, etc.
Sixth: Inspection of product size

By adjusting the injection molding process, when the product has a better appearance, a preliminary inspection of the appearance size of the product is carried out. When the size and appearance are restricted, the following principles are followed:

  1. If the product size is too small, the injection molding process should be adjusted until the appearance of the product appears top white, top height, drag, and mold sticking, and find the maximum size that the injection molding process can adjust.
  2. If the product size is too large, the injection molding process should be adjusted until the appearance of the product shrinks, lack of glue, etc., and find the smallest size that the injection molding process can adjust.

As long as this can be done during mold tryout, and the mold problem is discovered and solved. It will provide great convenience for subsequent injection molding production. If you don’t do this during mold trial, the problems in the mold are not found or resolved, and the mold is produced with defects. Not only will the production not proceed smoothly, but the production cost will also be very high.


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