Wednesday, July 27, 2016

First Pieces Done

It has been a day of powder coating and learning lessons.  Learning a work flow and how to do everything I've only set up in my mind.  My 10 or 12 year old Sears powder seems to work as if it's new and everything is turning out well.  My only mistake was putting too light a coat on my first pieces.  I'm doing this all on the back porch because of the issues about fumes I mentioned last time.  It's only 90-ish outside, and the sea breeze that starts up mid morning keeps it feeling reasonably comfortable in the shade.  When I work on the metal, I use vinyl gloves to keep skin oil off them.  When I spray the powder, I use a 3M dust mask - and keep the wind at my back. 

First, I decided to do the right angle motor brackets, because these seemed easy with the exception of having six holes that I didn't want filled with paint.  The powder coat kit came with silicone plugs (like these, in a smaller range of sizes) for screw holes, but only four; not enough to fill all of the holes of one bracket.  One bracket got the silicon and two screws, the other got screws in all the holes, wrapped with heat resistant tape (like this) which also came with the gun.  Both of them had a piece of copper wire clamped under a screw to get that metal-to-metal contact with the rack.  I grounded one of them to the gun, but used a test lead jumper wire to connect to the other.  Here's what they looked like after the 20 minute bake at 400F to cure the paint.
You can see the one on the left has the white silicone plugs while the other has 8-32 screws (SHCS) wrapped with the heatproof tape. 

As these were the first parts, I gave them a good look over and while they're certainly usable, the paint on one came out a bit too thin.  Look at the piece on the left. Too light on its left.
So with that lesson learned, I decided to do the Z-axis motor mount - which is a pretty simple piece.  The center of the bore needed to be kept paint free (actually, I'm not 100% sure of that), so I used the heat resistant tape to mask that.  Made a deliberate effort to put on more powder, and this one came out better.
It's resting on the roll of heat resistant tape. 

So far, so good.  I have five big pieces to do - you've seen them all so I won't bore you - and four threaded standoffs that will probably just get the screws with heatproof tape.  I'm not sure how many of these things I can get in the oven at once, and I'm sure my cycle time will go down, so maybe a couple of days of doing this left.  After all that setup work I've done.  That's the nature of doing stuff like this. 


  1. You know, I don't see any problem at all with leaving the holes open and then just running a tap back through them after the coating. Am I missing something?

    1. No, you're not missing anything. That can be done. The places I was reading say that you're chasing the threads, not cutting, and you really want a special chasing tap for that. There are many sets that show up with a web search.

      I can't comment on how critical that is, but I'm curious about how all this works (the silicon plugs and tape), so it's a learning thing.