What low friction coating to use?

[mil3k]

Hallo everybody!
My name is Kamil and this is my first post at this forum. I found it during googling after some cheap PTFE (type) coating and think that there is a lot of ppl who know about surface finish and may give me a hand with my problem.
The problem is how to coat internal surface of paintball barrel. Few days ago I had a small "flame war" about "does paintball barrels producers really coat they barrels with teflon or ceramics or they don't". My opinion was that it is possible to cover internal surface in barrel 0.683" dia. and 10" to 18" long, and my opponent say it is impossible becouse he can't imagine how to do it. As one of his arguments he use that he produce barrels (btw. according to experienced players word of mouth very good barrels) and what producers advertise as ceramic or teflon coating it is III anodising. So after few posts I have gave up trying to convince him, kicking with a horse is not my favorite fun, and I want to prove him that coating barrels with friction cating is possible even if he don't know how to do it. I'm going to buy few of his barrels and coat them.

So ladis and gentelman I want to ask you for help with choosing cost efficient coating which I could use.
Paintball barrels diameters are from 0.678 for reusable training rubber balls up to 0.683 - 0.695 for proper gelatine paint balls.
The material is aluminium PA6, type III anodising.
Barrels are coated to achive self cleaning effect after ball failure in the chamber and barrel. So the coating must prevent from stick gelatine shells and warer/starch based paint to walls. So the next few balls will push out of the barrel residue of broken ball.

I will appreciate if you can estimate the cost of such a coating. I live in the UK and will try to find workshop here.

best regards
Kamil

PS. English is not my first language so I appologize for my grammar.

[Gordon]

Hi Kamil

to the Surface Engineering Forum.

Being a long narrow bore with no line of sight access makes things difficult, but I won't say impossible to coat.

PTFE type coatings require application like paint products and then oven baked to cure. While giving excellent non-stick and low coefficient of fiction, they are relatively soft and will have a limited wear life.

Thinking outside the barrel might it not be worth considering applying a lubricant/release agent to the paint balls, something like a silicone oil/mould release fluid.

I will PM some contacts if you wish to take this further.

[mil3k]

(06-18-2010 01:36 AM)Gordon Wrote:  Hi Kamil

to the Surface Engineering Forum.

Thank you for warm greatings.

(06-18-2010 01:36 AM)Gordon Wrote:  Being a long narrow bore with no line of sight access makes things difficult, but I won't say impossible to coat.

Can you explain me a bit more why is it important to have a line of sight. Is it to control the thickness/depth of sprayed layer?

(06-18-2010 01:36 AM)Gordon Wrote:  PTFE type coatings require application like paint products and then oven baked to cure. While giving excellent non-stick and low coefficient of fiction, they are relatively soft and will have a limited wear life.

Thats why I thought to use PTFE. I don't want to pay extra just for logo teflon How baking in the oven will affect aluminium. It was one of strongest points of my opponent. He affirm that baking is in temperature highet than softening point of AL. I affirm that after hard anodizing the surface is not AL but aluminum oxide with higher softenning point.

(06-18-2010 01:36 AM)Gordon Wrote:  Thinking outside the barrel might it not be worth considering applying a lubricant/release agent to the paint balls, something like a silicone oil/mould release fluid.

It is impossible in the furry of spraing paint during speedball therw is no time to apply anything more then more paint to the hopper (balls container above marker) Paintballs are covered a bit with some oil which secure them from sucking moisture from the air. So there is a bit of lube.

(06-18-2010 01:36 AM)Gordon Wrote:  I will PM some contacts if you wish to take this further.

I will apriciate if you can send me those info.

Regards Kamil

[Gordon]

Hi Kamil

Quote:Can you explain me a bit more why is it important to have a line of sight. Is it to control the thickness/depth of sprayed layer?

Its more a case of the physical bulk of the spray equipment and minimum off-set or spray distance required which makes them impossible to use (fit into bore, hence no line of sight). The thickness/depth of sprayed layer is more a problem when considering say dip or brush application.

Quote:Thats why I thought to use PTFE. I don't want to pay extra just for logo teflon Wink How baking in the oven will affect aluminium. It was one of strongest points of my opponent. He affirm that baking is in temperature highet than softening point of AL. I affirm that after hard anodizing the surface is not AL but aluminum oxide with higher softenning point.

Depending on aluminium alloy and heat treatment history, baking temperatures could well alter properties away from what was originally intended. So this needs to be considered.

Quote:It is impossible Wink in the furry of spraing paint during speedball therw is no time to apply anything more then more paint to the hopper (balls container above marker) Smile Paintballs are covered a bit with some oil which secure them from sucking moisture from the air. So there is a bit of lube.

I'm only thinking that treating the paint balls may be an easier option than the barrel. Also, that a PTFE barrel coating probably would have limited life as the coatings are soft.