Designing for Powder Coating

[Travis Covington]

• Do you make dimensional allowances to account for the powder thickness?
  
  Yes - varies by vendor. We have seen thicknesses up to .030 per surface, but usually see .010 or thinner per surface. Don't forget about both sides of a part.
  
  
• What kind of cleaning or surface prep is required before sending your parts out for coating? Do you mask off certain things?
  
  Depends again on vendor. Many will sandblast and clean the surface for you. We always clean the oxidation off welds, but leave everything else. Our sponsor sandblasts most of our parts.
  
  
• What kind of "clean up" is required after you get your powder coated parts back? Are bolt clearance holes OK or do they need to be reamed, tighter tolerance things like bearing pockets, etc?
  
  Minimal based on item 1. Plan ahead for build-up and you can minimize clean-up. Some holes can be easily reamed, etc. Ideally mask bearing bores or do not powdercoat parts with tolerance critical bores, etc. We anodize these parts unless the anodize won't match the desired aesthetic. Reaming or masking bearing bores never comes out nicely. Avoid it if possible. The last few years we have powdercoated fewer and fewer parts based on the re-work time to ream and clean out bearing bores. I do not recommend trying to guess the powdercoat thickness for bearing bores and machining them larger prior to powdercoating. This is risky. Threaded holes can go two different ways. You can ask for the holes to be plugged (which might leave a rough edge right at the thread), or you can chase the threads with a tap after the fact. If it is something simple like a baseplate/bellypan, you can always drill it larger and tap it after powdercoat, using smaller holes as a drill guide for locations.
  
  
• Any other words of wisdom?
  
  Talk to your sponsor. They can better answer all of these questions for you based on their experience and their willingness to walk you through the process/address issues before you get the parts back. You'll also figure out most of this stuff the first few times you do it. Some of it comes with practice.