Issues with powdercoat masking 1

[kennedyqc]

We are currently machining aluminum and steel parts used in dental chair assemblies. After machining, many of the parts are sent to be powdercoated. My biggest problem is related to paint getting in the tapped holes. Our paint supplier has used various types of masking plugs with decent success, but are still getting paint in some of the holes. If there is paint in the holes, they are deemed "undersized" by our customer because the thread gage will not go (nor will the fastener used during assembly). If we chase the threads using a tap, the holes end up "oversized", not to mention the time it takes to check and attempt to fix each part. Does anyone have any suggestions in eliminating our issue?

 

[rhodie]

Is there any way you can place bolts into the threads while it is being powder coated?

 

[magic612]

Suggest to your powder coating supplier that they try using flangeless plugs. They are of a ribbed design, and they designed specifically for masking threaded holes for powder coating. That should eliminate the problem.

We carry them (see here:

http://www.viadon.com),

but most any other powder coating masking supplier should carry them also. Hope that helps.

 

[kennedyqc]

Alot of our problem is many of the holes are thru holes. Using the tapered plugs are ineffective since paint gets in on the back side. Do the flangeless plugs have much taper. We have tried to use the screws, but paint buildup at the corner of the screw and mating part is a problem. It is difficult to remove without damaging the part or making it ugly. The other issue with screws, if it is a thru hole, then you can only run the screw flush with the back side, otherwise you cannot get the screw out. If it is flush, paint still gets in the hole a little. It is such a fine line in getting the screw perfectly to depth. With the quantities we are running, the paint supplier cannot provide a consistant good part.

 

[magic612]

For the through holes, pull plugs might be a viable option as well, as long as the parts are not more than 1" thick (as most pull plugs are 1" long for handle, 1" masking area). Pull plugs may be oversized above the part diameter by up to 5%-7% - this is often the case in plating situations, where part is submerged. This may reduce getting small amounts of powder in the tops of the threads. (Typically powder coated parts only require a plug 2%-4% larger than the threads.)

As far as the flangeless plugs are concerned (for blind holes), they do have a very shallow taper. What helps is after the powder is cured is to rub the cured powder off the silicone mask; this prepares it for the next part (whether using standard tapered plugs, pull plugs or flangeless plugs).

Any other questions, feel free to ask - hope that helps. Check out our website that I listed in the previous post, you will find lots of options for masking that may give you some good ideas to help you out.

 

[masking]

Here is a link

http://www.echosupply.com/plugs.html

to check out different types of plugs that most masking companies usually carry. To meet some special needs, it is ususally more cost effective to use custom designed masks. There is a finishing industry newsletter that covers these types of issues. Subscribe at

http://www.echosupply.com