The Process of Scientifically Debugging an Injection Mold [Infographic]

Posted by Al Timm on Jun 28, 2017 9:10:00 AM
Al Timm

 

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The practice and purpose of debugging a mold is at the very core of scientific molding. This critical step ensures consistent and repeatable production of flawless molded parts by having engineers push the mold relentlessly under realistic conditions (and sometimes beyond); their goal is to identify and correct weaknesses before the mold is called into action.

Here’s a look at the basic process of debugging, including an infographic that visually summarizes each step:

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Step 1: The debugging process begins with the tool being put into the press so that the toolmaker and molding engineer can thoroughly and systematically check every aspect of its mechanical functionality. As a starting point, they use the recommendations specified by the supplier of the material to measure the molded part’s characteristics; these recommendations typically include a variety of molding conditions. As an example, a recommendation from a polypropylene (PP) supplier might include temperatures (what temperatures different points of the part can withstand, as well as melt and mold temperatures), pressures (injection, hold and back), speed (fill and screw) and drying (time and temperature, dew point and moisture content).

Step 2: Next, the engineers conduct short-shot testing to assess the dynamic pressure loss and, in a multiple-cavity mold, to check for any imbalance among the cavities. This step also accomplishes a crucial objective: establishing the rheology curve (or viscosity curve) to indicate the best fill rate and pattern.

Step 3: The decoupled process is then set up for further testing. At this point, gate seal studies are performed using both the pressure curve and the weight of the sample parts to determine if the gates seal fully, and at what point on the mold cavity (or multiple cavities). Molding engineers examine the test parts for any defects and record their findings, along with recommendations for any process or tool adjustments that need to be made. They also record data on the melt temperature, fill time, mold temperature, coolant flow, cycle time and pressure curve.

Step 4: Then, the parts proceed to quality control for an examination of their measurements, shot-to-shot consistencies and overall quality. This is done so that any necessary tool adjustments are completed before new samples are made. The new samples then undergo the same quality testing, with necessary adjustments made again as needed.

Step 5: All of the process parameters are recorded, with their acceptable ranges shown, to form the template that will be followed throughout production to ensure consistent quality, efficiency and repeatability.

While it’s a fairly simple process, debugging is one of the most important pre-production phases in injection molding; it’s the part of the process that ensures the mold performs exactly as expected. In the end, debugging is only one step in the scientific molding process performed by specialized engineers. To learn more, download our complete whitepaper.

Scientific Molding: A Molder's Perspective

Topics: Injection Molding, Scientific Molding