powder coating - before or after machining?

[BobM3]

Currently we powder coat our aluminum parts after machining. Some of the masked edges are rough looking. I was thinking of powder coating before machining but I don't know how well the powder coating will handle the rough handling in the shop. Also I worry about cleaning. Anyone out there powder coat and then machine your aluminum parts?

 

[IRstuff]

I would think that if you did powder coat before, you'll need to use some sort of protective layer, the blue stuff that's like Saran wrap, only thicker.

But, I'd think that if you had rough edges before, you'd had rough edges after, and there's some possibility that you could get chipping, etc., from the machining operations, on top of whatever lubricants that you might use in machining will probably alter the appearance of the powder coat.

TTFN

 

[kenvlach]

Touch-up machining is sometimes done after anodizing, painting & plating. Very limited, usually, for threads, o-ring areas, electrical contact areas. It's often difficult for a masker to manually apply tape or liquid (with a fine, artists paintbrush) to the precision on the blueprint.

I would recommend machining first. Only do touch-up machining to remove overspray, provide sharp coating lines and expose electrical contact areas. Maybe can save $ not skipping the masking of difficult-to-mask areas.

Also, first take a painted part to your machinists, show them the rough paint edges, and ask how they would do it better & w/o hurting the paint. They can if they want to, so make it their decision as much as possible.

 

[CorBlimeyLimey]

There are varous types of masking materials. Some need to be removed prior to baking (leaving a smooth but rounded/feathered edge), others can withstand the heat but can leave a ragged when removed after baking. They also often require clean-up to remove residual adhesve.

What type of features are you trying to mask?
What machining operations would be involved? (Drilling, Milling, Turning, ???)

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[magic612]

Depending on the areas of the part that require masking, some masking is designed to avoid creating the sharp edges, and custom masks can be designed to "feather" the powder as well.

An alternative method (as described before) is to remove the masking prior to curing the powder. This method often works best to avoid re-working the part and the sharp edges that can occur when masking goes through the cure cycle. In the worst case scenario, only minor machining is required, provided the masking operators are careful when removing the masking plugs.

A number of companies carry masking parts, including tapes and silicone molded parts. Many of them can design custom molded parts for unique masking situations as well, including us at

http://www.viadon.com.

Hope that helps.