Powder coating a Shoptask Bridgemill

[erwin66]

I have been thinking about powder coating my Bridgemill. It would be heated up to 350-400 degrees to cure the powder. Anybody think this would warp the unit? What other options do I have for a coating that wouldn't just peel off the first time it got coolant or cutting fluid on it?

Thanks
Erwin

[Bloy2004]

Here's what I did. So far the paint holds up pretty well. Some areas I just roughed up the original paint and it has chipped where tools make agressive contact...such as the stand lip/tray.

....shoptask 3/1 lathe/mill assembly and mods

I don't think I would powder coat the machine in an assembled state....assuming you've removed all the materials that would be affected by the heat, all fitting parts and joints will need to be somehow parted to disassemble if coated while still partially asembled. I don't recommend powdercoating a machine such as this......but, others may have done it.

[erwin66]

I will be totaly dissassembling it and removing the present paint as well as masking the parts I don't want coated. Just seams to me that heating it to 400 degrees would warp it. I have tried painting a few parts but the cutting fluid softens it and it comes right off. I havn't tried Rustoleum on it yet, might give it a try.

Thanks
Erwin

[LeeWay]

I have powder coated some parts in the past. I did a minilathe tailstock, the headstock on my lathe along with a couple other parts on it. A steel router mount for my mill.
I did all these @ 400 degrees for about 25 minutes.

The trouble with PCing cast iron isn't warpage, but letting the entire part get heated up first. It takes really a much longer time to do this right, especially on larger parts.
The headstock parts were left in the oven for 30 minutes. I also used it like a kiln in that I left the parts in the oven and let them slowly cool down. Didn't open the door. Removed the the next morning.

You will need a powder that has some overcurring protection. The semigloss black powder I use has this, but some of my other powders don't.
I have let this black cook for nearly an hour before with no ill effects.
Other colors like red and orange turn brown at 22 minutes.

You also don't need to cook them at 400. You can cure many of today's powders at 250 degrees, just takes longer in the oven.Most powder dealers will tell you how long to leave a low cure in the oven for different types of parts.

[sharpshooter90]

I will be totaly dissassembling it and removing the present paint as well as masking the parts I don't want coated. Just seams to me that heating it to 400 degrees would warp it. I have tried painting a few parts but the cutting fluid softens it and it comes right off. I havn't tried Rustoleum on it yet, might give it a try.

Thanks
Erwin

The original Patriot machines that were assembled in USA were fully powder coated. JT told me that the process was very costly because the heavy castings took a long time to reach the proper temperature and also a long time to cool down. The powder coater would only do his parts as a special batch so they could occupy the oven for 12 hours. As far as warpage is concerned, I don't think its an issue. The beauty of cast iron is that it becomes stable after a reasonable curing time- after that the final machining is done. Raising it to 400 degreees would not be enough to cause the molecules to re-align themselves.

[erwin66]

Thanks Guy's!! I feel alot better about coating my machine now. I am going to see if I can find some lower temp powder. If not I am going to give Rustoleum a try.

Erwin

[digitalmdj]

Powder coating is cured at 350 degrees. Once the casting is at that temp they spray on the powder coat using an electrical charge which attracts the urethane powder. And then it is cured at 350 degrees until the coating melted to the surface and then cooled slowly. The problem with powder coating is it cannot be reapplied after the process without being totally removed or it will not stick. Even paint wont stick to it very well after that.

[LeeWay]

Not quite true on your descriptions.

Not necessary to preheat parts unless it's cast stuff that may be prone to outgassing. Cast aluminum has done this a time or two on me. Cast iron hasn't.

Powder coating can be removed by sand blasting. It isn't necessary to remove old powder coating to respray it depending on the type of powder and finish needed. You can apply multiple coats of powders. Some powders require at least two coats. Sometimes three.
Chrome first, candy apple colors and then perhaps clear coat.

Most of todays powders can be cured at lower temps. Some can even be used on MDF and some plastics. These are the real low cure powders, but typical powders can be cured @250 degrees. Much quicker to get parts to that temp, though it does need to cure awhile longer.


Here is a link where I get some of my powders.
They don't mention the lower temp curing on this page, but good info about PCing.
http://store.columbiacoatings.com/cg...?display=about

Here are a few words from Caswell's site

Cure Time Dependencies

The total curing time of the film is dependent on several factors: substrate material, gauge or mass of the substrate, the shape of the substrate, i.e. sheet, tube, hollow objects. Large articles will take longer to heat up before curing commences. The color of the coating may also affect the cure schedule slightly, as some pigments absorb heat more effectively than others. Large articles may be susceptible to non-uniform curing if a temperature gradient exists across the oven. Changes in the cross-section of the articles themselves can also result in temperature differences and incomplete cure on parts of the coating.


Required Temperature & Curing

It is important to remember that the effective curing time commences when the object has reached the required temperature. This process allows for the flowing out and chemical reaction necessary to complete the cycle. Recommended baking times are always quoted after the substrate has reached the said temperature.

[digitalmdj]

Preheating is the only way to go if you want a durable finish . After you put the machine into service and you want to redo the powder coat later down the line you will need to remove all of the powder coating. Also it is expensive to do in the first place so make sure of the color. Trying to sandblast the casting after the process is finished is time intensive and costly. That why people have things powder coated its durable and hard to remove.

[diycnc]

you dont need to sand blast the part to recoat it. you do need to blast a painted part to powder coat it though.

we used to redo powder coat here some times when the finish wasnt great and all we did was hit it with a da with 80 grit and repaint it. as long as you rough up the suface it will stick just fine..

Preheating is the only way to go if you want a durable finish . After you put the machine into service and you want to redo the powder coat later down the line you will need to remove all of the powder coating. Also it is expensive to do in the first place so make sure of the color. Trying to sandblast the casting after the process is finished is time intensive and costly. That why people have things powder coated its durable and hard to remove.

[digitalmdj]

Remember paint wont stick to powder coat. Touch up will be hard. As I said powder coat is expensive and re coating costs just about the same so their is no benefit as far as price. I have one question how much will it cost to do a complete machine?

[sharpshooter90]

you dont need to sand blast the part to recoat it. you do need to blast a painted part to powder coat it though.

we used to redo powder coat here some times when the finish wasnt great and all we did was hit it with a da with 80 grit and repaint it. as long as you rough up the suface it will stick just fine..

JT told me the first one they did cost the powder coater some money because he based his quote on the size of the parts, not the thickness of the castings. The heat up-cure and cool down time took so long that his oven was out of service for a full day. After that the price was about 750.00 including the sand blasting, cleaning and taping of machined surfaces if done in batches of 5 or more. If done properly the powder coating is practically indestructable and will last the lifetime of the machine. Any chips would result from some major crashes and can be touched up with a good epoxy based paint. Matching colors is no problem as long as you stick with the basics like red, blue, black etc.