O/T - Dry Film Lubrication - application to small bores

We are looking at how we can best apply a light coating of dry film lubricant to inside diameter of a small cylindrical housings on a production machine doing about 10 parts a minute without making a mess.

Cylindrical housings have inner dimensions of 0.05 - 0.38 inches in diameter x 0.15 - 0.63 inches long and need a uniform coating of lubricant.

We can capture the part and seal it between two flanges using right sized o-rings . . . but how do we atomize? aerosolize? the dry film lube and blow through the cylinder with any excess being reclaimed and recirculated through the system? Is this a good application for electrostatic coating?

I have never done anything like this before but want to include this feature in a machine that is manufacturing and assembling these components for a customer. Anyone here with experiencing with automatic application of film coatings of lubricant? The parts will be heated and dried right after application of the lube.

Whatever you do, you will need very good thickness control, so as not to compromise the fit with the inner member.

Through bore or blind hole?

While I don't have direct experience with your problem you might look at ultrasonic spray heads to atomize the lubricant . Bill

You might also have to think about part orientation to minimize gravitational buildup or meniscus effects.

If you've got a specific coating in mind, contact the vendor for that product. They should have application engineers that have dealt with these issues before.

CarbideBob said:

Through bore or blind hole?

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Through bore . . .

I've done something similar with a fluoropolymer coating on an aluminum bore before, but that material would only bond directly to the aluminum substrate in a single molecular layer--with any extra simply blowing away--so control of dispense volume and layer thickness wasn't important (other than cost of wasted material).

For that process I used a spray nozzle that we developed by modifying a glue dispense needle to have little radial holes and a capped end. Air and the coating material were mixed in the right ratio via conventional Nordsen spray valves and then piped to the applicator needle.

For consistency you might need to spin/translate the needle, otherwise you'll get thick spots near the needle openings.

Nordsen might even have a product that does this these days. I'd start with them.

If the size and shape of the part is amenable, you might be able to use a gang of brushes or swabs on a platter to push through the bores, just touch a reservoir of lube and then pull back out through the bores. Would a dry powder work? Moly, graphite or similar? Is the purpose of the lube to ease subsequent assembly? Something else? What is your part made from? What are the parts that fit these holes made from?

motion guru said:

Through bore . . .

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Where I used to work for a while we had to apply loctite to each through bore at a similar production rate.
From the bottom of the fixture up came a rotating spray head that would coat the bore and then retract so the bearing could be pressed in from above.
Basically a hollow capped shaft with a tapered side hole, air actuated up/down, DC motor rotation, and PLC controled.
I was impressed with how well and fast it worked. It was crazy repeatable.
Pretty slick but not sure about your min hole size. Maybe such with differing heads for your bore variation?
Bob

Not the answer you asked for, but this works well. We have built lightly loaded mechanisms with less than .0002 running clearance on small journals. Oil lubrication was not feasible. Did use Dicronite with great success.

I have seen through hole stuff done for silicone chips (research lab stuff i can't discuss any more than that, yes i know normally chips don't have holes) get coated by sealing both sides but unlike how you describe, they used a rubber sealing pad as wanted 100% no top -bottom coverage, just hole wall, then pumping a slug of the desired coating through it pneumatically. Was a pretty complex but beautifully simple afair, a peristaltic pump pumped a dose of liquid from the bottom collection vessel through filtration (disposable inline syringe filters!) into a simply bottom of a U tube, the part bore was on one side, other side then got a slug of nitrogen to blow product through coating hole sides as it went, Key was getting system setup so the slug of fluid had the right velocity to get the correct even coating + duration of post blow to remove excess, hence qty and nitrogen pressure apparently mattered, also how the plate sealed to the hole also did in that the hole had to have enough of a restriction bellow it to ensure fluid made contact all around.

Inspection of the results was there biggest issue though. In there case the failed coating would also be caught later in production, but in yours errors in coating may get missed and presumably cause in the field type issues, so you might want to also be adding some kinda automated coating QC check to confirm the 100% coverage is met?

Adama, was there a reason Nitrogen was used rather than compressed air?

motion guru said:

Adama, was there a reason Nitrogen was used rather than compressed air?

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I'll venture a guess that was because it can be purchased "dry pumped" with essentially ZERO particulates, contaminants, moisture, or oil in it.

I could not produce that grade nor pressure, (3300 PSIG, IIRC) either one off the A1 or A2, not sure Bien Hoa AFB Base Fuels could do off their DELON-500M, either, though "very damned close".

It had to be flown into First Log. Was used to re-pressurize the equilabrators on large tube artillery.

Honestly i don't know, i was only there for a short time, and whilst i could kinda ask questions, that was not one of them. I was there because of parts i was making for a friend who was involved in designs of the equipment to do the next step to the parts. He was some kinda problem solver for these kinda projects and do to my electrical and mechanical abilities and the capabilities of looking at a problem late on a Friday and having a working solution Monday morning with out all the usual university politics holding shit up i kinda filled a useful niche. Often a lot of the process fixes we brought to the table were straight out simplifications of complex shit they were doing in the kinda strange ways people who are too clever get caught in.

The advantage for you going with something like nitrogen if its available might be in keeping the substance uncured, so you can keep passing it through till depletion. All depends if you can simply coat things well enough by just blowing a slug of liquid through the bore, or if you need to spray on a more controlled thickness, in which case carbide bobs approach is a neat and simple way to go.

Why is a bit of particle contamination a issue in a artillery piece? I don't get that, sure i get you don't want it full of water, but surely std industrial grade nitrogen is plenty good enough to lob shells at a opponent?

adama said:

Why is a bit of particle contamination a issue in a artillery piece? I don't get that, sure i get you don't want it full of water, but surely std industrial grade nitrogen is plenty good enough to lob shells at a opponent?

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It probably was. But the "dry pumped" Nitrogen is stored in the heavier-walled 3AA cylinder, marked with three white ring bands on grey body, at the higher pressure that cylinder allows.

Recharge - these are shock-absorbers on steroids, lineal descendants of the concept Maurice Houdaille made his bones with for the old "French 75"- involved pointing the tube up at a high elevation, "and some other stuff", and done in the field.

Pressure out of the bottle drops rather a lot as the gas goes into the size of "shock absorber" used on a 175 mm & 185 mm gun or 8" SP HOW. My expectation would be that the higher pressure source gas made it all faster and easier so any given tube was fire-mission-ready again sooner, rather than later.

They didn't need all that much of it in a whole year, 3rd & 4th Corps Tactical Zones I supported, so somebody must have used good seals,'coz the tubes didn't long sit idle.

One of them cost me an 85 dB down "notch loss" in my hearing - the one that has several times given me a class call with Leyland Titan Motorbus'en I cannot hear on London's silencer course of asphalt.

The tube I was passing too close to APPEARED to be doing a recharge to my overly tired glance as it was pointed at the moon. Not so. Tet '68, and Charlie had gotten right up close to the Long Binh wire. The fire mission that ruined their last-ever day used a "gun" (direct-fire weapon) in Howitzer or even a mortar (indirect fire weapons) tasking to lob a 175 mm projectile many miles up into the stratosphere and drop it less that 2 klicks away from the gun.

Fire for effect, first round, only round. As usual.

It was rear element, Div Arty, 101st Airborne Division. Their gunners knew the historical necessity of making every round count, and count double, even triple if they could make it so.