A must-have for injection molders! A complete analysis of the top ten "fatal" problems, from shrinkage to flash, all solved in one go!
Injection molding may seem simple, but it actually hides a mystery! Shrinkage, weld marks, warping... Any problem can cause the yield rate to plummet and the cost to soar. This article directly addresses the top ten classic problems that are the most troublesome in the injection molding workshop, and teaches you how to "clear mines" from principles to solutions, so that you can easily say goodbye to rework and customer complaints! 1. Problem 1: Shrinkage (shrinkage) phenomenon: The surface of the product is concave, which is common in thick areas or on the back of the ribs.
Reasons: Insufficient holding pressure or too short holding time; too small gate size or premature solidification; too high material shrinkage.
Solution: Increase the holding pressure and extend the holding time (it is recommended to increase by 5%~10% each time); optimize the gate design (such as using fan-shaped gates and adding shrinkage channels); use low shrinkage materials (such as glass fiber reinforced materials).
Case: The shrinkage problem of a home appliance shell was solved by extending the holding time by 3 seconds, and the yield rate was increased from 70% to 95%. 2. Problem 2: Welding mark (joining line) phenomenon: Obvious linear marks appear at the intersection of two molten materials, affecting the strength and appearance.
Cause: The molten material intersection angle is too small (<135°); the mold temperature is too low or the injection speed is too slow; the material fluidity is poor.
Solution: Adjust the gate position to make the molten material intersection angle>135°; increase the mold temperature (such as ABS mold temperature from 60℃ to 80℃); add fluidity additives or use high-flow grade materials.
Practical skills: Add exhaust grooves in the weld mark area to reduce gas barriers. 3. Problem 3: Warping deformation phenomenon: The product is twisted and uneven after cooling and cannot be assembled.
Cause: Uneven cooling (such as large temperature difference between the core and the cavity); inconsistent molecular orientation; uneven ejection force.
Solution: Optimize the water channel design to ensure uniform mold temperature (within ±3℃); reduce the injection speed to reduce the difference in molecular orientation; increase the number of ejectors or use air ejector demolding. IV. Problem 4: Bubble/vacuum bubble phenomenon: bubbles appear inside or on the surface of the product.
Cause: The moisture content of the material exceeds the standard; the injection speed is too fast to draw in air; the exhaust is poor.
Solution: Dry the material thoroughly (such as PC needs to be dried at 120℃ for more than 4 hours); reduce the injection speed, control the filling in sections; add exhaust grooves (depth 0.02~0.04mm) in the last filling area. (The following is a simplified example, which actually needs to be expanded to ten major issues) Five to ten: Quick question list Problem keywords Solution Flow marks Increase mold temperature, reduce injection speed, use hot runner instead Shortage of glue Check shot size, expand gate, increase material temperature Flash (flashing) Reduce holding pressure, repair mold parting surface, double clamping force Color difference Control barrel temperature fluctuation, clean screw, premix masterbatch Dimensional instability Stabilize cooling time, calibrate mold temperature, control ambient humidity Top white Optimize ejector position, increase demoulding slope, spray release agent Six, general preventive measures: 3 underlying logic Material control: strict drying, batch detection of shrinkage and melt index; mold maintenance: regular cleaning of venting grooves, inspection of wear; process standardization: establishment of parameter database (such as V/P switching point for different materials). Seven, emergency rescue: What should I do if I find problems during mold trial? Step 1: Prioritize adjustment of temperature (material temperature, mold temperature) and injection speed; Step 2: Check whether mold venting and gate are blocked; Step 3: Contact material supplier for modification suggestions. Conclusion: The essence of injection molding problems is the imbalance of the triangle relationship of "material-mold-process". Mastering these ten solutions is equivalent to getting a "stethoscope" for rapid diagnosis. From today on, let your injection molding machine "obediently" produce!
