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Is delaying cure after powder coating inviting trouble?

Often when our powder coat line shuts down for the day, parts are left hanging on our conveyor between the spay booth exit and the cure oven entrance. Sometimes this is overnight, and sometimes over 2 or 3 day-long weekends. Some of these parts are aluminum castings. Is this a bad practice? If so, why?

(Note: we don't have a flash-off area; parts travel through shop air from the booth to the oven.)

Thanks.

David Maijala
quality manager - Huntington Beach, California, USA
September 30, 2010

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October 4, 2010

I think it a practice to avoid, but you should have some feel for the reject rate of your daily first production.
Sprayed uncured material will be subject to dust fallout, moisture absorption and potential insect landings. All these can contribute problems. Dust contamination will cause poor curing, or colour contamination, or inclusions or all of these.
Moisture absorption might cause curing issues (pinholing, pimples), or blowholes due to gassing. You mentioned castings, and these are more subject to this problem than extrusions.
Insect landings will cause blemishes on the material.

But if your reject rate is close to zero on Monday mornings first production, then what is the problem?

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

Thank you, Mr. Crowley, we will test the parts to see if this causes a problem.

David Maijala
- Huntington Beach
October 12, 2010