Topics to Address with Your Plastic Injection Molder When Parts are Self-Destructing
Sometimes plastic injection molding companies inadvertently produce molded parts that self-destruct.
There may be one or several reasons why your plastic molded parts are self-destructing, but below are some key topics to address with your plastic injection molder to identify the problem/solution faster!
- You’re using a commodity molder when your intended application requires an engineering molder (find out the differences between engineering molders vs commodity).
- The plastic injection molder is not processing the resin according to the exact requirements of the resin manufacturer’s manual.
- A commodity resin is being used when an engineering resin is required to achieve required part characteristics and physical properties.
Cavity Pressure Issues
- There is not reliable, consistent cavity pressure.
- Cavity pressure can vary in a hot-tip mold design, causing part tolerance variation.
- Very high pressures are required, but the machine does not have a calibrated or correct transducer to accommodate for this. Therefore, the machine cannot knowingly closeloop and control or monitor for correct processing.
- The gate location is incorrect or incorrectly sized.
- Water contamination is occurring.
- Foreign matter is embedded as a contaminate.
Injection Rate Issues
- There is an inconsistent plastic injection rate.
Melt Temperature Issues
- The melt temperature is inconsistent.
- The melt temperature is not homogenous.
- The melt temperature is too cold, causing high levels of stress to be molded in.
Mold Temperature Issues
- The mold temperature is inconsistent.
- The mold temperature is not uniformly in proximity of part cavity.
- The mold temperature is too cold, causing high levels of stress to be molded in.
- The cooling rate of the molded part is not allowed to stay in-mold until cavity pressure decay is no longer a factor, which causes part warpage after ejection.
- A cooling (or sizing) fixture is required if the part is still shrinking after being ejected from the mold.
- The cooling fixture for a molded part could be too cold to prevent a higher level of stress than would prevent warp.
- Inconsistent overall cycle time of molding process.
Multi-Cavity Mold Issues
- Multi-cavity molds cannot maintain reliable consistent cavity pressures between cavities when using hot-tip gate design without individual temperature gate controllers that will control all cavities within desired part tolerances. In other words, just because a transducer is placed on one cavity or the runner system there is no relativity relationship between the other cavities.
- Multi-cavity molds cannot maintain reliable consistent cavity pressures between cavities when using valve gate design systems without mechanical gate shut-off controllers that will control all cavities within desired part tolerances. In other words, just because a transducer is placed on one cavity or the runner system there is no relativity relationship between the other cavities.
- The part is being produced with out-of-tolerance conditions.
- The geometry of the part can be a factor in controlling molded-in stress levels.
- When using a material with a wide spec moleculer weight distribution there may not be a relative relationship between the cavities that’s close enough to maintain all cavities within the required part tolerances.
Why Choose PMC?
Plastic Molded Concepts is a U.S based company that uniquely specializes in molding with engineered resins. We’ve helped dozens of companies resolve issues they were having with an injection molding supplier. Check out our case study to see how we helped resolve a part self-destruction issue for a military and aerospace hardware manufacturing company.
We have been thriving in the plastic molding business for 45 years. We have the experience and certified in-house Master Molders, allowing us to take on projects of any complexity. We provide professional consulting, as well as full plastic injection molding services for well-established parts and innovative prototypes.
Request a quote today for your next project.