Painting rack case question

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JAY X

Well-known member
Joined
Jan 9, 2009
Messages
683
Hi All!

I just finished a prototype of my summing mixer,  https://groupdiy.com/index.php?topic=63515.0
and I painted the case myself. I just painted the case and the cover by the outer side, so inside there is no painting, to provide galvanic conection to connectors.

But now, if i want to make a small run, and have the cases painted professionally (powder coating), the cheapest option is to paint every thing... inside and outside.... and maybe loss the galvanic connection.... :p  it is a dilemma!!...

An option would be to scrap the paint with a file inthe holes of the connectors...
Another idea is to use masking tape to  block the inside rear connectors...
Next option is to have the case  with the cover screwed and then paint the case....

In any case i know that some manual scrapping is necessary for example for the chassis gnd point...

Any idea or suggestion is wellcome... :)

Thanks a lot, and merry christmas!!

Jay x



 
If you decide to have it powder coated, use a kapton tape to cover the area you want to stay as a bare metal.
Most powder achieved a curing temperature at 200C, and the tape withstand up to 250C (some brands even go higher like 300C)

I use an office hole puncher on the tape to make tiny rounded stickers, then stick them to cover all of my M3 size mounting holes.
 
I have honestly never had this problem.  I tend to buy off the shelf boxes, drill them, paint them, load them up with parts, I don't think I've ever seen a case where I couldn't measure case connectivity back to the AC power inlet ground, so I don't think it's that hard to deal with.  I'm sure there are cases which would be more critical. 
 
That's cool. I make my own boxes because off the shelf boxes are a lot more expensive, and they requires manual drilling.
I use kapton tape to cover holes that have self-clinching nuts installed, because I don't want the powder paint to melt and cured inside the thread.
 
Hi All!

Thanks for all ideas,

Kapton tape is a good idea...but quite expensive....I would need 428mm long and 43mm high tape...

I think despite it takes a bit more work, it would be best to have the case with  the top cover screwed on, and paint all with powder coating. Maybe some powder get inside thru the holes, even more with the new top cover i designed, with greater size holes. But maybe just some shadows get inside, preserving  more bare metal for galvanic contact.  Going to ask my supplier...

Jay x
 
You don't need to cover the inside of your case, just the part where you need bare metal for chassis connection.

Note: 5 cm kapton tape is about $6 for 30 meters long where I live.
 
Hi All!

Recently i found there is a Vinyl Spray for painting cars...it forms a plastic vinyl layer over any metal surface. ¿has anyone try this?. seems interesting!

Jay x.
 
JAY X said:
An option would be to scrap the paint with a file inthe holes of the connectors...

Yes. It is the easiest and cheapest method. Masking takes time hence costs money.

Don't forget to use serrated washer to bite into the joint for better contact.
 
JAY X said:
But now, if i want to make a small run, and have the cases painted professionally (powder coating), the cheapest option is to paint every thing... inside and outside....
  Is it? Do you mean you need to paint the inside because it doesn't look right as it is?


  An option would be to scrap the paint with a file inthe holes of the connectors...
Another idea is to use masking tape to  block the inside rear connectors...
Next option is to have the case  with the cover screwed and then paint the case....
Why do you want the case painted? Typically the case would be made out of pre-galvanized steel and need no additional treatment. Only the front panel would need painting.

Now in jurassic times I had boxes painted. The painter would put sticky tape where I told him to put (marked with a permanent marker) and he would apply paint from the outside with the box assembled so there would be only residual paint (in fact powder) inside. He just used the standard masking tape painters use for windows.
 
I find scraping paint afterwards to be tedious and time consuming. Imo if you are going to paint a case it's worth the extra cost in the beginning to mask what you need.
 
In the metal fabricating field generally these masking plugs are used. They can be re-used a number of times until the paint build up on them becomes impractical.

http://deeh10136.de.plus.compute.ihost.com/en-gb/caps-plugs/push-fit-plugs/masking-plugs/masking-pull-plugs
 
What about screwing a nut through wherever you are planning on mounting the chassis connection prior to coating.  Use a washer, if you need more coverage.

It probably wont break off [the coating surface] perfectly clean afterward, so you wouldn't want it in a visible position, but somewhere inside the case would, I'm sure, be acceptable.

If you go with a method like this, make sure that the thread that the nut goes onto is shorter than the nut itself - so the nut shields the thread from the coating, and you don't have bother when you come to unscrew it.


(yep, i know its an odd post for my #1, but, hey...! : )
 
JAY X said:
Hi All!

I just finished a prototype of my summing mixer,  https://groupdiy.com/index.php?topic=63515.0
and I painted the case myself. I just painted the case and the cover by the outer side, so inside there is no painting, to provide galvanic conection to connectors.

But now, if i want to make a small run, and have the cases painted professionally (powder coating), the cheapest option is to paint every thing... inside and outside.... and maybe loss the galvanic connection.... :p  it is a dilemma!!...


Jay x

I would think that ordinary automotive paint would be a better choice for this application. Everything is easier that way. Powder coating is generally thicker than most paint, so then you may run into a fitment problem as well.
 
dirkwright said:
I would think that ordinary automotive paint would be a better choice for this application. Everything is easier that way. Powder coating is generally thicker than most paint, so then you may run into a fitment problem as well.

Nah.

With ordinary automotive paint, you always get a thicker paint job, because you have to start with a primer coat followed by a base coat, color coat, and a protective clear coat.
 
metalb00b00 said:
Nah.

With ordinary automotive paint, you always get a thicker paint job, because you have to start with a primer coat followed by a base coat, color coat, and a protective clear coat.
In the end, both solutions end up with not too dissimilar thickness. Automotive paint is much more work, gives a potentially nicer finish, but also not as scratch-and-ding resistant as powder. OTOH, automotive paint is DIY'able.
 
This may, or may not be pedantic, but pretty much no cars are painted in "diy-able" paint any more.

(by "diy-able" i mean just walk into a shop, buy some stuff,  go home, and use it)

Cars are painted in 2k which is not a home job, unless you really know what youre doing, and have the breathing kit.  But it is way stronger than anything out of a rattle can.

..but then powder coat is not really home work either.

For me, powder coat is for garden tools, but that's just my subjective opinion! : )

 
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