Looking for brainstorm help. Shameless begging really.

[lendaddy]

We make a plunger here from screw machine stock. It's a 1/2" diameter spring loaded pin that you can pull back on and retract it into a "body". I hope that makes sense, think of it as a piston that travels inside a jug, but can actually protrude 1/2" outside the jug when released (or pulled back, aginst spring tension, inside the jug).

Anyway we weld these little suckers to a tubular assembly and have the whole business e-coated. Ecoating is a dip coating process. The parts are polarized as is the paint in the dip(opposite polarity). This causes the adhesion. Anyway we would LOVE to find some coating(or any other idea) that when applied to the pin would prevent it from being coated. They are currently Zinc coated which helps a tiny bit, but still allows enough paint to adhere to cause stiction in the "jug" which we have to work out before packing. Silicone is OUT! They would kill me if they got their system contaminated with it.

I was wondering about telflon or ceramic, but am not sure. If anyone has any ideas or experience in e-coating you would be my hero.

We spend hours and hours each week just freeing these up.

I figured what the heck, people in here know all kinds of weird stuff. Thanks again.

[id10t]

Well, since it is done via electrical charge, could you insulate whatever parts you don't want coated and flip their polarity to match the paint to reverse the normal process? Or can you change the material the pin is made of so it won't take a charge? (ceramics?)

[Simon S]

is plating pior to assembly an option?

likely not cost effective(?)

[turbo6bar]

lenmommy, I've used Techline's ceramic barrier coating on a set of pistons. I ran the engine for roughly 5000 miles and tore it down (low oil pressure, mismatched engine case, really long story). Anyway, the pistons came out very nice. I was able to scrub off the built up carbon with a little degreaser and brush. It's possible this might work, if the ceramic coating creates a "charge barrier?" between metal and coating.

I also used a thermal dispersant (also from Techline). The coated cylinders were super-duper slippery. Don't know if this would work, but it sounds like some testing is warranted.
jurgen

[qikcpa]

could you wrap it pre dipping...duct tape/tiny condom comes to mind.

how bout a picture?

[KevinP73]

How about applying a length of shrink tubing before ecoating and then remove it after?

[dad911]

Wax?

[lendaddy]

Good ideas guys, thanks. I just did a quick scan of your ideas, but they look good! The wax, and other dissolving type coatings wont work as the parts go through a pretty intense wash before dip to remove greases, oils, etc..

I don't have time right now, but I'll really look into these in a couple hours. Thanks again guys!!!!!!

[project935]

Teflon is a fairly standard coating used in automotive fasteners to keep the e-coat buildup off of threads. The Teflon usually holds up well on weld nuts as they are being attached and also helps to prevent weld spatter build up too.

[RickM]

Can you make the plunger out of plastic.

[lendaddy]

Just for a little interesting info, this does have some Porsche content The company we make these for is a Porsche supplier. They designed and manufactured the retractable tail system for the 993. I'm not sure if they do the current version them now though. Small world.

I am working an a reply to all the questions/suggestions now. Once again I just want to say thanks!

[lendaddy]

could you insulate whatever parts you don't want coated?

No, The parts are pressed together then the plunger is welded to the assembly. There is no way to isolate the polarity of one piece.


Or can you change the material the pin is made of so it won't take a charge? (ceramics?)

Gave that some thought too. The problem is that the pin needs to be rugged. It's a safety device that stops a "falling load" incase of failure. I fear ceramics would be too brittle. Also, it would require a months long design change approval/testing/BS process.


is plating pior to assembly an option?

Yes, we currently have them bright zinc plated before coating. The Zinc is a little tougher for the E-coat to bond to so it helps some.


jurgen: Various

You have some good ideas there on a coating. I do not believe we would be able to "isolate" the polarization, but a slippery non-stick coating may really help.

could you wrap it pre dipping...duct tape/tiny condom comes to mind.?How about applying a length of shrink tubing before ecoating and then remove it after?

Another good idea. The clearances are very small so you would have to be quite creative but is is definitely food for thought.


Teflon is a fairly standard coating used in automotive fasteners to keep the e-coat buildup off of threads.

That was my initial thought. There is however one problem. The other end of the pin gets pressed into a knob so the operator can activate the plunger. The end of the knob needs to accept the e-coat to maintain proper appearance. There may be a way around this though.


Wax?

The problem here is that the parts get a high heat solvent bath before coating (so their pool does not get contaminated with oils, etc..) otherwise it would be great!

Can you make the plunger out of plastic.?

No, for the same reasons stated above regarding ceramics.


You guys have some great ideas! I will post a pic too, thanks again!!!!!!!!!!!!!!

P.S. One of these days I'll figure out how to do bold and color changes etc.. so my reply posts will be easier to read

[project935]

Teflon coating - I'm sure the end could be masked prior to Teflon application. The weld nuts I've seen just have the coating in the threads (brush/swabbed in?) - the rest of the nut accepts the e-coat just fine.

www.alphatechcoatings.com
www.metcoat.com
www.precisioncoating.com
www.crestcoating.com

[lendaddy]

Here are some pics, should clear things up.

[ubiquity0]

Is that a bong??!

[project935]

LOL ... I thought the same thing. Precision carburator.

[lendaddy]

Originally posted by ubiquity0
Is that a bong??!

lol, We get that all the time. Infact when someone has a stupid idea around here we grab one of these and hand it to them, as in "here take another hit"

935, thanks for the links, I'll look into that.

Thanks again!

[KevinP73]

Is the inside of the tube e-coated? If not how about installing a thin fibre washer at the intersetcion of the plunger and the knob. This can serve as a seal or a gasket to prevent any solutiion from entering the assembly. Then during the e-coat process if you can plug the main body (the big tube) with a cork or perhaps high temp rubber plug (as in powder coating) to prevent any solution from entering from the inside.
Hard to describe but I think you get the jist of it.

[lendaddy]

Originally posted by KevinP73
Is the inside of the tube e-coated? If not how about installing a thin fibre washer at the intersetcion of the plunger and the knob. This can serve as a seal or a gasket to prevent any solutiion from entering the assembly. Then during the e-coat process if you can plug the main body (the big tube) with a cork or perhaps high temp rubber plug (as in powder coating) to prevent any solution from entering from the inside.
Hard to describe but I think you get the jist of it.

Yes, the inside does get coated, otherwise that would work great. The tube itself is simple DOM steel so it's a corrosion issue.

Thanks.

[qikcpa]

can you do the coating in stages...inside first. then assemble and then outside.