Injection Mold Trial and Process Validation Steps Before Mass Production
To avoid unnecessary delays and quality problems during mass production, it is important to carefully adjust and control all processing conditions during mold trials. The goal is to identify the best temperature, pressure, and cycle settings, establish standard testing procedures, and create reliable daily production methods.
1. Confirm the correct material and drying condition
Check whether the plastic material in the barrel is the correct grade and whether it has been dried according to the material specification. Improper material selection or insufficient drying can lead to major differences between trial results and actual production performance.
2. Clean the barrel and material path thoroughly
The barrel, nozzle, and material flow path should be cleaned thoroughly before testing to prevent degraded resin, contamination, or mixed materials from entering the mold. Contaminated material can cause defects, unstable molding conditions, or flow blockage. At the same time, confirm that both barrel temperature and mold temperature are suitable for the raw material being processed.
3. Adjust injection pressure and shot size carefully
Set the injection pressure and shot size to produce a molded part with an acceptable appearance and complete filling. If some cavity parts are not yet fully solidified, do not rush to adjust the process without proper observation. Even a small change in filling rate may result in a significant change in the final part condition.
4. Wait for machine and mold conditions to stabilize
Be patient and allow sufficient time for both the molding machine and the mold to reach stable operating conditions. For medium-sized machines, this may require more than 30 minutes. During this time, monitor the molded parts carefully and observe any changes in appearance, weight, or dimensional stability.
5. Set proper holding and screw forward time
The screw forward time should not be shorter than the gate solidification time. If it is too short, the part weight may decrease and product performance may be affected. When the mold temperature is higher, the screw forward or holding time may also need to be extended to ensure proper packing and part density.
6. Optimize the overall molding cycle
After stable filling and packing conditions are achieved, adjust the process reasonably to reduce the total molding cycle time while maintaining part quality and dimensional consistency.
7. Run the adjusted process long enough to confirm stability
Once the new process settings have been established, run them for at least 30 minutes to allow the process to stabilize fully. After that, produce at least a dozen consecutive full-shot samples for evaluation. For multi-cavity molds, it is especially useful to label the samples with the production date, shot quantity, and cavity number, then store them separately for stability analysis and process tolerance evaluation.
8. Measure samples after cooling to room temperature
All validation samples should be measured only after they have cooled to room temperature. Record the measurement results for all critical dimensions so they can be used for process comparison and production control.
9. Compare samples from each cavity
Compare the dimensions of samples from all cavities and evaluate the following points:
(1) Whether the dimensions are stable.
(2) Whether certain dimensions show an increasing or decreasing trend, which may indicate unstable machine conditions such as poor temperature control or hydraulic pressure fluctuation.
(3) Whether all dimensional changes remain within the specified tolerance range.
If the finished part dimensions remain stable and the molding conditions are normal, the process can be considered reliable. For multi-cavity molds, the parts from each cavity should also be checked individually to confirm that quality is acceptable and dimensional variation remains within tolerance. Any cavity that consistently produces parts larger, smaller, or different from the average should be noted so that the mold dimensions and cavity balance can be reviewed.