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The Meaning of Cavity Pressure Sensors in Custom Plastic Injection Molding

What is the meaning of pressure measurement in Custom Plastic Injection Molding?

Cavity pressure sensors are valuable tools in the plastic injection molding process to maximize productivity and minimize the number of defective parts making it through production and into the “good part” box. With accompanying integrated software, these sensors can detect abnormal conditions and, depending on the type of trouble and software settings, shut down a machine until the fault is corrected, reroute suspect parts for further inspection during the sorting process or reject parts outright.

Cavity pressure sensors are especially valuable if you are engaged in high-volume production of custom precision plastic injection molding, such as parts for body building equipment,medical devices, electronics or the automotive industry. You can employ these sensors to monitor not only cavity pressure but also internal temperature and many other factors to help you on your way to zero defects.

Cavity pressure sensors enable the skilled molder to spot Graph Showing Monitoring common faults such as shrink,short shots, flash, sinks and voids, dimensional problems, and warp. You can even detect cosmetic problems like gloss gradient. In addition to pressure and temperature, pressure sensor systems note other variations, such as in packing, cooling rate and cooling time. All of this is monitored through software output of variations in pressure during injection, packing, compression and cooling — yielding a visual, real-time cavity pressure curve on the equipment’s monitor.

Why do you  put the sensor in the mold?

Typical defects in plastic injection molding production that are detected by pressure sensors include:

  • Shrink.
  • Short shot, the absence of plastic in a portion of the part, results when no pressure developed in the cavity’s unfilled section
  • Flash, essentially the opposite of a short shot, occurs when excess pressure forces a mold to spread enough to allow plastic to spill though the cavity parting line; this not only produces a defective part, it can lead to parts sticking to and damaging the mold.
  • Sinks and voids, result from under packing the cavity and/or the lack of a gate seal, which would be detected as a change in cavity pressure.
  • Dimensional variations, occur when a packed mold is fully compressed and cavity pressure changes at a critical dimensional point
  • Warp, random distortion of a part, often results from variations in packing, cooling rate and cooling time; detected through the pressure curve.
  • Gloss gradient, variations in gloss from the gate area toward the end of the cavity, may be related to the rate of packing; this would show up in the shape of the pressure curve.

For further information on the benefits of cavity pressure sensors for plastic injection molding, contact an experienced supplier of custom plastic injection molding,OK industry via info@okmolding.com.

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