Thread: DIY powder coating.

count me in as well
Pete

C'mon Pete, woof yer tea down, jump back on the forum, and answer your admirers.

Ken

Ok ok, standby. I was about to do a part and take photos of the process but the kids screaming upstairs suggested I should probably put it on hold until after dinner. Bob will be pleased to know I'm taking a better camera down with me ... as much as I know he appreciates the artistic bent of Pete's "expressionist era", guessing what the photo is actually of probably isn't in the spirit of the board. Should have them up later tonight.

Pete

Pete,

We do not want pictures of screaming kids, we want to know how you powder coat bits and pieces, then cure them.

There's no doubt that powder coating is a great process, but is probably not ideal for applying to machined surfaces that engage with other machined surfaces. For example, dovetails, table tops etc.

Dinner is over Pete, now back to work.

Ken

Right, here we go. This is the part we're doing, it a fixture to hold my Proxxon drill on the QCTP. Nothing fancy but it will hopefully work ok. I think I can only post 4 images per post right? Multi-post entry then.

After TIG welding the part need to be cleaned again, I use scotchbrite belts on my linisher for this.



An auto paint shop will be able to sell you some wax and grease remover. Powder coating is really no different to other painting processes; it's all in the prep. However because it's baked at 200C it CANNOT go over the top of other painted surfaces, so it MUST be bare metal only.



Hanging in the "booth" ready for coating. The powder is like talc but the good thing is overspray really doesn't matter, just blow it off/sweep it up/etc. However you absolutely cannot touch the powder once it's on the part. The good thing is if you do, just blow off the powder and start again. The metal wire it's hanging from is important as the part is grounded and a static charge is applied to the powder, thus attracting it to the part. After I took this photo I actually hung it from a fishing line swivel so it could rotate fully.



Sieve the powder to break up any lumps. The only reason I wear gloves is simply habit, and also to keep greasy fingerprints off the clean part. As I mentioned, it's really not that different to other painting processes, but I figure why half do something, hence why I use wax and grease remover and wear gloves.

This is the gun that's used. VERY little air is used and the powder just wafts out of the end of the gun. The box behind it is the power supply which imparts a static charge to the powder, the amount depends on the gun, but anywhere from 25 to 100 thousand volts. The higher the voltage the better it's attracted.



I couldn't take photos while applying the powder as you need to also push a button shown below to energise the gun, but this is about the distance the gun will be from the part. It's actually quite bizarre seeing the powder waft out and seemingly magically get attracted just to the part. Done carefully there's not a lot of overspray.



The part and the button I mentioned, the part is now coated and ready to be moved to the oven. It's generally a good idea to do a dummy run of how you will do this because at this stage nothing can touch the powder.



In the oven set to just over 200C, you CANNOT use the kitchen oven, so this is just a little toaster oven from K-mart. Apparently the powder gives off a very slight toxic product when curing, hence why you can't use a food prep oven. Toaster ovens are very cheap though. When I get time I will build a much larger oen to take big projects.

Pete,

Is it possible to apply the powder without a gun. For example, is it possible to chuck the part in a bag with some powder, shake it up, and wallah?

Roughly, what sort of buildup is produced on the part, ie. how thick is the coating, are we talking 0.1mm or less?

Ken

Originally Posted by neksmerj

Pete,

Is it possible to apply the powder without a gun. For example, is it possible to chuck the part in a bag with some powder, shake it up, and wallah?

Roughly, what sort of buildup is produced on the part, ie. how thick is the coating, are we talking 0.1mm or less?

Ken

No the paint powder is attracted by the static charge. You may be thinking of plastic coating, I did that at school but the process is completely different. The gun is the heart of the process I'm afraid, but they're not that expensive in the US, more on that later.

I use a cheap digital thermometer to measure the PART temperature, as that's what really matters, not the oven temp. It takes around 15 minutes to bake, but that depends on powder manufacturers and effects.



This is the part about half way through the bake. It may not show too well in the photograph, indeed it's not all that obvious in the flesh unless you know what to look for, however there's a definite "orange peel" effect still there as the paint flows out (BTW I may refer to it as paint or powder in these posts. The powder is simply specially ground paint, just without solvents, that flows under heat and cures.



Finished curing, now simply open the oven door, let the part cool and it's good to go.



Cooled and ready to be fitted.

Ken to give you a better understanding do a search for Electrostatic Spray Painting.

Originally Posted by pipeclay

Ken to give you a better understanding do a search for Electrostatic Spray Painting.

Well yes and no. I believe BIG users of paints (ie cars manufacturers) electrostatically charge their systems to reduce overspray, but conventional solvent based paints are used. If you're looking for more information Google, unremarkably, "Powder Coating".

This is what I was coating, the finished part installed on the QCTP

Pete,

That's great. You have done well to answer many questions under pressure, now you can put the kids to bed, unless they are on fridge duty.

Ken

The whole process took MUCH longer to write up than to actually do it, the best thing is that cleanup means blowing the gun etc out with compressed air; simply blow the dust off! MUCH nicer than stinking solvents and sucking through a respirator for hours. It's a one coat process, so no primer to worry about, and we probably all know how durable the finish is.

This is something similar to the kit I use.
Elite HotCoat Powder Coating Kit - Stainless Steel Wire - Powder Coating Handbook - Eastwood
A friend bought that kit back from the US for me so I'm not sure how their shipping rates go. However when I was after more colours of powders they didn't seem too interested, nevertheless that was a while back so maybe things have changed. Have a scrounge through their site and it should be possible to find a list of powders they sell. They're not expensive, there's very little overspray so they last a while, and won't go off. Another source of powders is Columbia Coatings ColumbiaCoatings.com - Best Powders - Best Service - Best Price! They are cheaper and have a better range than Eastwood. It's also possible to get effects such as crinkle etc etc, indeed the motor cover in another post I did in black crinkle and it came out extremely well. The black we used tonight was a standard gloss black, there's another gloss level above that called mirror black. In this case had I not been doing this for the board I would have done it in satin as the part wasn't especially well prepped in terms of buffing the imperfections etc out, and the higher the gloss the more they'll show. I didn't think satin would photograph very well so used gloss. Since it's just a tool it really doesn't matter.

Hopefully that's enough to get started in the search. There's a stack of information on the net if you search under powder coating. Eastwood do a book that comes in that kit which also explains things quite well.

Pete

Thank you Pete.

That was extremely informative. Now that you have made your drill support bracket, what are you intending doing with the drill? Have you devised a means of indexing the headstock spindle?

Bob.


p.s. The clarity of the photos is appreciated but I was warming to the evocative soft focus shots.

Another question Pete, How old is the Model C? I notice that it has plain spindle bearings and a late model cross slide.