Curing Plastisol (Filters)

Curing involves any process where heat is used to catalyze or initiate chemical and molecular level structural changes in a polymeric materials such as epoxies, phenolics, polyesters and silicones. These materials are applied in many ways to various products for bonding, protective coating, sealing, insulation and other uses.

Jell coating is a partial-curing process whereby a liquid compound is heated (in this case plastisol) enough so it doesn’t run when it is flipped over.

Curing plastisol oil filter seals with induction is a reliable, repeatable, non-contact and energy-efficient process, delivering quality results in a minimal amount of time. Improved temperature ramping cycles can be achieved with computer control of the solid state power supply.

Although induction heating is normally used with metals or other conductive materials, plastics and other non-conductive materials can often be heated very effectively by using a conductive metal susceptor to transfer the heat. Typical RF power supplies for curing applications range from 1 to 5 kW, depending on the parts and application requirements.

Compared with costly oven, time-consuming batch or awkward hot-plate processes, induction curing has a great deal to offer

• smallest footprint: systems require little floorspace, even for line processes
• lowered material costs: lighter mix for gelling
• significant energy savings: delivering energy into the susceptor plate only, minimal vented waste heat
• improved work environment: workers are not exposed to elevated room temperatures, reduced air-conditioning needs
• improved production rates: induction integrates into continuous line production
• improved output and quality: precise control and monitoring enable repeatable high-quality results
• improved safety: fire hazard eliminated with lowered overall process temperature
• unparallelled support: our Applications Lab and Service departments ensure you get and keep the production you need

Filter assemblies are produced by curing a thermosetting material between a paper assembly and a steel or aluminum cover. As shown below, dual pancake induction coils are used in a static setup to provide heat to the top and the bottom plate. A dynamic setup utilizes long pancake coils for the heating. Localized temperatures of 150-175°C associated with such bonds avoid damage to the components and provide a high strength bond upon cooling. Heat cycle times are in the order of 5-10 seconds.

Induction is used to set the gel-set the sealant-flange-paper assembly, which enables inversion of the assembly for the final assembly and cure phase

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This process takes full advantage of induction's benefits by first curing the flange assembly before flipping. Once inverted and assembled, the final induction cure takes place.

"With induction heating we have accelerated the adhesive curing time (on a filter part) from 30 seconds to 6 seconds and have automated what was formerly a manual process. We have been able to cut production times and increase turn-around time"
"Beyond a doubt the reason we chose Ameritherm was because of how responsive they were to our original request for technical assistance. Ameritherm spoke our language and gave us the high value assistance that we needed. There was no need to go anywhere else."

-Automotive filter manufacturer

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"By using induction heating instead of a convection oven we have decreased our production foot print from 86 ft long to 13 feet long. We've also reduced energy consumption and increased employee safety by reducing the fire hazard. But by far the biggest savings for us has been production uptime. Where previously we had a monthly oven downtime of 256 minutes per month we anticipate that the downtime will approach, if not equal, zero minutes."

-Automotive filter manufacturer