POM (Polyoxymethylene), also known as acetal, is widely used for high-performance mechanical parts thanks to its high rigidity, self-lubrication, wear resistance, dimensional stability, fatigue resistance, and resistance to oils and chemicals.Typical applications include gears, bearings, bushings, wheels, sliders, and other small, complex components.

When POM overheats or degrades, acidic decomposition products can be generated. Prolonged exposure may affect the screw, barrel, and mold. Yellow streaks, black streaks, and black specks are common warning signs that the machine and hot runner need cleaning.

Case Study: POM Worm Gear

Machine: 100T injection molding machine
Part: POM worm gear
Mold: Hot runner, 4 cavities
Problem: Yellow streaks and occasional black specks
Original Cycle Time: 44 sec → 59–60 sec
Result: High scrap rate and unstable production

Cleaning Challenges

· Complex threaded part geometry

· Part must not stick to the mold

· Hot runner gate could clog during air-shot purging

· Conventional method required screw and hot runner disassembly

Purging Solution

Purging Compound: PlasE® Clean A2503

Because air-shot purging could block the gates, the cleaning process had to combine purging and molding without damaging the mold or affecting part release.

Cleaning Procedure

· 4-cavity mold. Before cleaning, Gate #2 was heavily contaminated, and the molded parts showed black specks, yellow spots, and color streaks. Add PlasE® A2503 and purge through the screw to displace the residual POM.

· Purge through the hot runner and then mold the parts without increasing the temperature.

· After a period of purging, run POM to verify the cleaning result. Yellow streaks were still found at Gate #1, so cleaning was continued.

· Add PlasE® A2503 again, slightly increase the hot-runner temperature, and purge for approximately 10 shots before molding.

· The cleaning was visually confirmed to be complete. Then run POM again, restore the original production parameters, and verify the molded parts from all four gates. No abnormalities were found, and production was successfully resumed.

Cleaning Result

As shown in the cleaning-process photos, only a small amount of yellow streaking was visible on the parts before cleaning. However, after adding the purging compound, a large amount of yellow and black contaminants was purged from the hot runner. This clearly demonstrates the strong cleaning capability of PlasE® A2503 in removing hidden contamination and deposits from the hot-runner system.

· Cycle time: 59 sec → 44 sec

· Machine utilization: increased by approximately 30%

· Scrap rate: returned to normal

· Production stability: restored

· No mold disassembly required

· Lower labor and maintenance costs

· Faster order fulfillment

Key Takeaway

Even when POM contamination appears as only occasional yellow streaks or black specks, significant degraded material can remain inside the screw, barrel, and hot runner.

For complex POM molding applications, PlasE® Clean A2503 provides an effective solution for removing stubborn contamination while minimizing downtime and avoiding unnecessary disassembly.

Sanp Technology has extensive experience with POM purging applications and can recommend suitable PlasE® grades based on the machine, mold, material, and contamination condition.