Here are some things to consider:
Wear due to the abrasiveness of the material adds to the maintenance frequency a tool requires. Filler and additives are commonly used today to enhance part performance. In these cases, preventative maintenance frequency should be increased beyond the normal recommendation. Cycle time, injection pressure and velocity of the plastic through the hot runner system can also have an influence on the maintenance frequency required for each mold. Much like a car, the harder and faster you push it, the greater the frequency of maintenance.
Some materials require very high melt and mold temperatures. In a valve-gated hot runner system, seals in the valve pin actuator are adversely affected by higher temperatures. With all valve-gated systems, leave mold cooling on after the hot runner has been shut down. This allows removal of heat from the hot runner system and does not allow the mold plates to absorb the residual heat from the heated components. Removal of the heat from the system protects seals and o-rings from damage. Exposing the seals and o-rings to high temperatures repeatedly will accelerate their degradation. Exposure to heat beyond the specifications for the seals will degrade them to a point that they will fail, causing leakage of the air or hydraulic fluid used to actuate the valve pins.
Hot runner systems are much like the barrels on a molding machine in that they require a soak time once the temperature reaches the set point. This soak time allows all material within the system to reach a temperature at which it is thoroughly melted.
Many hot runner systems are damaged when injection pressure is allowed to go to the maximum the machine is capable of—trying to push unmelted plastic through the hot runner.
If you have followed all these steps, you will produce better parts, prevent future problems and keep your molds running at optimal levels.
The article comes from China injection mold manufacturer - Mold Best Assurance Company Limited, website is www.mbamoldanddesign.com
