How to Solve the Deformation in Flat Injection-molded Parts?
Large flat injection-molded parts have a significant area, resulting in substantial shrinkage.
Due to the pronounced molecular orientation in large injection-molded components and uneven mold cooling, inconsistent shrinkage rates occur in various directions of the molded parts.
Consequently, thin large flat injection-molded components are prone to deformation and warping. At times, when one side of a large flat injection-molded part is designed with support ribs, the part tends to bend towards the side with ribs.
Effectively addressing the issue of deformation in large flat injection-molded parts is indeed a challenging task.
Through our production experience, we have identified several measures that have proven to be relatively effective in mitigating deformation issues:
1. Modify the mold to a multi-point gating system (typically using a three-plate mold) for injection molding.
For large flat injection-molded parts exceeding 240 square inches, it’s advisable to utilize four or more gating points. This approach helps alleviate the extent of molecular orientation, reducing disparities in shrinkage across different directions.
2. Raise the mold temperature appropriately.
For ABS materials, maintaining a temperature of at least 60°C serves to decrease the cooling rate of the injection-molded parts.
This reduction minimizes temperature-related deformation due to abrupt cooling transitions and concurrently reduces the degree of molecular orientation.
3. Increase Injection or Holding Pressure
The most crucial measure is to increase the injection or holding pressure significantly and extend the injection or holding time considerably.
By doing so, the dimensions of the injection-molded part expand, reducing its shrinkage and leading to a noticeable improvement in the extent of deformation.
Consequently, prolonging the injection or holding time (e.g., extending by 10 to 15 seconds) has become an important technique commonly employed to address deformation issues.
4. Mold Release Shaping
If the above three measures fail to yield the desired outcomes, resorting to mold release shaping becomes necessary.
This approach requires some finesse, as it is not commonly mastered by most individuals and demands a certain level of skill.
First and foremost, it’s essential to demold the injection-molded part ahead of time.
Then, while it’s still in a state of elevated temperature (it should remain quite hot to the touch, this is crucial), place it on a workbench and use fixtures to shape it. The design of the shaping fixtures is pivotal and needs to be appropriate.
Simultaneously, the resilience of the injection-molded part must be considered.
Typically, the rebound will largely cease after around 12 hours, and the lower the demolding temperature, the greater the rebound.
During production, careful consideration of the amount of overcompensation is necessary.