Case Study: Optimizing Cycle Time for PTFE Grommets
The Hidden Challenge of Coated Parts
Producing rubber parts destined for secondary coatings introduces unique manufacturing risks that standard molders often miss:
- The base substrate must be flawless; any micro-tear from demolding will cause the coating to fail.
- High scrap rates occur when operators manually pull sticky or fragile parts from the mold.
- Inefficient thermal cycles lead to extended lead times for complex PTFE grommets.
This case study shows how we stabilized the production of a complex coated grommet by engineering the tool, not just the rubber.
The Material Constraint
A client required custom PTFE grommets featuring a silicone core with a specialized friction-reducing coating. This dual-material design provides the elasticity of rubber with the lubricity of plastic. However, the manufacturing process faced a critical bottleneck during the molding of the silicone substrate.
The specific low friction silicone compound required for the coating adhesion exhibited low tear strength while hot. During the initial production trial, manual removal of the parts resulted in frequent tearing. Because the parts were destined for a secondary coating process, even microscopic surface defects resulted in immediate rejection. The inability to clear the mold cleanly led to high scrap rates and stalled production.
⚠ Why Manual Demolding Kills Quality
For parts requiring secondary coatings, the surface finish is non-negotiable. Standard manual air-gun ejection is risky because:
- Stretching: Pulling hot rubber creates invisible micro-fissures that expand during the coating curing stage.
- Deformation: Manual handling can warp the geometry, affecting how the coating is applied.
- Cycle Variance: Fighting with stuck parts cools the mold unpredictably, altering the cure level of the next batch.
The Engineering Solution
Fenlora engineers identified that the issue was not the material formulation, but the mechanical stress applied during ejection. The standard pull method was exceeding the hot-tear limit of the low friction silicone substrate.
We designed and fabricated a custom Synchronized Ejection Fixture (Process Jig). Unlike manual removal, which applies uneven force, this fixture engages the entire perimeter of the grommet simultaneously. It supports the part geometry while mechanically stripping it from the cavity, keeping the stress well below the tear threshold.
The Results
The custom fixture eliminated the tearing immediately, achieving a 100% yield on demolding. Eliminating demolding tears in silicone substrates ensured a flawless finish for custom PTFE grommets.
Furthermore, by stabilizing the ejection process, we optimized the thermal cycle. We successfully reduced the vulcanization time from 380 seconds down to 300 seconds. This 21% efficiency gain allowed us to offset the cost of the extra tooling while delivering a premium, defect-free coated component.
Cycle times too long for cost-effective rubber production?
We work with OEM teams to optimize molding processes, reduce cure time, and stabilize high-volume production. Talk to a Rubber Manufacturing Engineer.