Author Topic: Powder coating advice  (Read 7273 times)

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Powder coating advice
« on: May 02, 2013, 04:56:01 PM »
Got a quote the other day from a local powder coating company about painting up some enclosures and was told the powder coating would be 2.50-5 a box which I thought was very reasonable. It was for 14 boxes, 2 in each colour. Got a proper quote from them, the colours I want is nearly 800, or to use the very limited colours they have in stock is 250. Now I know there is a fair bit of work involved but those prices are ridiculous!

So I've gone and bought myself a powder coating system and oven! Bought several colours to go with it, and just wondering if anyone else does it and can give any advice.

Sent from my thumbs using Tapatalk!

rullywowr

  • Electron Doctor
  • *****
  • Posts: 2390
  • Ben @ www.rullywow.com
    • View Profile
    • Rullywow Industries - PCB's, DIY projects, and more!
Re: Powder coating advice
« Reply #1 on: May 02, 2013, 05:17:48 PM »
Congratulations on getting the powder coating set up! You'll find it pretty easy to use. I use acetone to make sure there is no oils on the enclosure before powder coating, this is important.  Rubber gloves will help make sure you don't get oils on the enclosure.  I also would recommend getting some extra screws that fit in the bottom four holes of the enclosure. You can use the screws to the Raise enclosure up off of the plate when you put in the oven.  Keep in mind when you do powder coating that the decals or whatever you're going to do on top have to show through so usually lighter colors like white and similar work best if you're going to use a clear waterslide decal.  The most frustrating part about powder coating I have found is using clear. The clear powder tends to work well covering the decal and so forth except if you do not have your holes aligned it tends the crack off of the waterslide decal and ruin the whole thing When you drill the holes larger.  It is recommended to drill your holes first and make them a little larger so that you don't run into this problem. If you don't have some already you will need some galvanized wire which makes the ground connection for the powder coating pieces easier. No worries about hanging it with your hand on the ground about getting electrocuted it works just fine.


I would say the hardest part about powder coating is making sure you don't knock the dust off of the enclosure as you put it into the oven.  You can do multiple coats if needed I recommend doing a regular coat first and then after about 10 minutes to get out of the oven while it is still wet and hit it again with the spray if needed. Since the powdered instrumental liquid it will attract the new powder even without using the electricity ground.

Powder coating is very rewarding especially when you can powder coat an nclosure and be done with it and not have to worry about drying or any bad fumes.  Some of my favorite powder coating colors are the dormant colors. These spray on like a normal color but they pop really well when you use a clear over them and almost have kind of a candy sparkle, check them out.  

Lately I have been having lots of problems with the clear cracking over the waterslide decal so I am going to try spring regular lacquer over the final enclosure to avoid this issue.  Good luck and be sure to show us some pictures of your new powder coated pedals. If you need any other advice hit me up.
 
« Last Edit: May 02, 2013, 05:21:16 PM by rullywowr »



  DIY Guitar Pedal PCB projects!

jimmybjj

  • Electron Doctor
  • *****
  • Posts: 1071
  • Jim
    • View Profile
    • BeeJive Pedals
Re: Powder coating advice
« Reply #2 on: May 02, 2013, 07:40:48 PM »
Lately I have been having lots of problems with the clear cracking over the waterslide decal so I am going to try spring regular lacquer over the final enclosure to avoid this issue.
 

Too thick and cracks in clear can be caused by undercure. If the clear was delaminating from the base, then it would be a lack of crosslinking between topcoat & basecoat.

Did you partial cure (oppose to full cure) the base coat? Most 2 stage powders it is recommended before a full cure top coat for best intercoat adhesion, except for chromes they need full cure.

I'm not sure how much the decal would interfere with the crosslinking but i haven't had any issues with clears over waterslides or vinyl decals. I suspect it is more related to undercure.

Next time it happens, take a razor to the clear & see if any chips off while you drag the blade along. Try to get some off. Take the chips or shavings & put them on a piece of sheet metal & put them through a cure cycle. If they melt & flow then the powder was definitely undercured.
Pcbs no longer available

wgc

  • Electron Doctor
  • *****
  • Posts: 1747
  • Billy
    • View Profile
Re: Powder coating advice
« Reply #3 on: May 02, 2013, 08:17:34 PM »
All of the above is great advice.  Make sure your surface is clean and oil free.  Simple green or acetone work well to clean aluminum.  Prebake your parts to make sure the cast aluminum hasn't absorbed any moisture.  My coatings improved quite a bit once I started prebaking. 

Make sure you have a good ground connection.  Use a moisture filter in the air line to your gun, and you only need about 5-10 psi.  More than that and you blow the powder off the part as quickly as you apply it.

Powder is moisture sensitive and flammable so seal and store accordingly.

As for cracking clear coat over water slides, I've had the best results with laser printer decals, they withstand the heat better than ink jet.  Trim the edges as close to your print as possible and avoid large expanses of clear decal.  The powder coat clear builds quicker and thicker and you shouldn't have the witness lines at the edges like you get with lacquer.

Once you get some good parts, you'll be hooked.
always the beautiful answer who asks a more beautiful question.
e.e. cummings

rullywowr

  • Electron Doctor
  • *****
  • Posts: 2390
  • Ben @ www.rullywow.com
    • View Profile
    • Rullywow Industries - PCB's, DIY projects, and more!
Re: Powder coating advice
« Reply #4 on: May 02, 2013, 08:35:23 PM »
Great stuff.  The clear problems I have been having stem from them not sticking to the decal properly I think.  I haven't tried just putting the first coat on, letting it flow, stopping it immediately, cooling (before you can decal), apply decal and clear coating.

It happens most often when trying to enlarge a hole or scrape some coat off of the hole to insert a LED.  Since the LED typically has a small bezel it is hard to "hide" the bubble.  The clear tends to lift off the decal and cause a running "bubble" under between the decal and the clear.  When it works it is the best, hands down. When done right, the clear really seals in the decal and you can't see any seams - looks very factory.  At this point lately I have been really frustrated with the clear and I have redone the current pedal I am working on at least 4 times. :(  About ready to try just lacquer over it.

In my small toaster oven I use for curing I initially had issues with "browning" of the decal due to the close proximity of the upper heating coils and the decal.  I took the extra rack and wrapped it with aluminium foil and wedged it on the roof of the oven so the heat is indirect.  It really made a big difference and I find there are no problems with baking a decal.

With my small toaster oven I started out by using the wire rack to put my pedals on but found I prefer the solid pan.  The back of pedals I just gently lower by the grounding wire and put bottom up (inside resting on the pan).  For the main top shell I really find having extra screws (which you can reuse) works awesome for propping it up off the pan.  I have some metric for the NS enclosures and some 6/32 for the Hammond.






  DIY Guitar Pedal PCB projects!

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Re: Powder coating advice
« Reply #5 on: May 08, 2013, 09:10:20 AM »
Cheers for the advice guys!

Unfortunately I've had some things at home to deal with so only just managed to have a play on it today. I bought a small toaster oven, it should have been 40 but reduced to 30, and it works great! I got the powder coat system from Electrostatic Magic. It doesn't use a power supply to charge the powder, don't know how that works, especially as the earth cable connects to the gun, and works just on compressed air. I found that Boots and Tescos pharmacies sell Acetone to clean the boxes with. I found my best results have come from cleaning the box with Acetone, putting it in the oven for 10 mins, when it's cooled down, clean again with Acetone then spray it.

I'm not going to use decals, and instead use the transfer technique that davent posted about using acrylic medium. In the next day or two I'll do it on one of my test boxes and try clear powder coat gloss over it.

Here are the results, first one its blue candy, didn't have the right pressure in the airgun, but the blue base and blue sparkle were done with the correct pressure. The blue base plate isn't laquered yet, the blue sparkle box has a blue flake additive in the clear coat.






Sent from my thumbs using Tapatalk!

rullywowr

  • Electron Doctor
  • *****
  • Posts: 2390
  • Ben @ www.rullywow.com
    • View Profile
    • Rullywow Industries - PCB's, DIY projects, and more!
Re: Powder coating advice
« Reply #6 on: May 08, 2013, 12:16:54 PM »
Very nice!  It is strange that your gun doesn't have an electrode however.  In order to make the powder "stick" better I would suggest warming up the part to 400 or so before spraying.  You can give it a light dusting and then stick it back in the oven.  Once the powder flows out, you can hit it again and put it back to cure it.  When the powder flows it gets into a liquid state and will attract more powder even without any charge.

I would love to see the toner transfer decals!  Be sure to post some pics.  Welcome to the powder coating at home DIY club!  :)



  DIY Guitar Pedal PCB projects!

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Re: Re: Powder coating advice
« Reply #7 on: May 13, 2013, 06:55:29 AM »
rullywowr - I don't have any problems with getting the powder to stick to the boxes. There is an earth cable that goes from the gun to the bit I'm coating and the instructions say to hold the gun with bare hands, I'm guessing for the ground. On the website of where I got the gun, the used to sell one with the separate power pack, but changed the design of it now. There is now only the compressor airline to the gun, then the earth cable from the gun to the part. Less wires to tangle up I suppose. Also, on their website, it also shows how you can coat glass, ceramics and wood! I'm tempted to try powder coating one of my glass demi johns for wine making!

The toner transfer decals unfortunately didn't work. Seems the acrylic medium melts in the over when curing the clear powder coat and makes an absolute mess of the box. It was worth a try as is would have been a ridiculously cheap and easy way of doing graphics on the boxes. The other option, is to use a normal spray paint laquer, bit then that would defeat the hole point of having a powder coat system and the extra durability it gives over spray paint.

I've now ordered some water slide decals, and got a couple of questions. Do I need to do full face decals? Or can I cut the decal sheet into parts for different parts of the pedal? For example, tone and volume knob labeling, can I use 2 separate small labels just slightly bigger then the writing? Thinking a decal sheet would last a lot longer that way. Also, I've got both laser and inject printers, so I ordered the sheets for laser printer. Am I right in saying that they don't need to be clear coated before putting them into water and they are less likely to go brown when curing the clear coat?

One last thing, I powder coated a couple of boxes yesterday, and the paint it's thicker in some parts more then others. Is that normal?

Sent from my thumbs using Tapatalk!

jimmybjj

  • Electron Doctor
  • *****
  • Posts: 1071
  • Jim
    • View Profile
    • BeeJive Pedals
Re: Re: Re: Powder coating advice
« Reply #8 on: May 13, 2013, 10:38:07 AM »
One last thing, I powder coated a couple of boxes yesterday, and the paint it's thicker in some parts more then others. Is that normal?

That is most likely a result of "hot flocking" (heating the box and then applying powder) when hot flocking the powder melts on contact, applying powder in the way is prone to build up. You will get much more consistent results(where thickness is concerned) if you can avoid hot flocking. It is really hard to get good results with tinted powders (i.e. candies) hot flocking, it usually ends up "framing".

All that being said there is nothing wrong with hot flocking it's just harder to get consistent results. There really is no reason to hot flock the base coat. It might be nessesary to hot flock the second coat if you don't have adjustable kv's or you don't have a grounding rod.
Pcbs no longer available

rullywowr

  • Electron Doctor
  • *****
  • Posts: 2390
  • Ben @ www.rullywow.com
    • View Profile
    • Rullywow Industries - PCB's, DIY projects, and more!
Re: Powder coating advice
« Reply #9 on: May 13, 2013, 10:51:48 AM »
Good stuff.  If you are using a Laser (this is important) Waterslide Clear decal you do not have to apply anything.  Just powder coat the enclosure, place the decal and let dry FULLY.  It is really important you wait (24hrs+ is good) because any moisture that is left under the decal will make your clear coat cloudy and/or have bubbles.  I don't mess with inkjets because the ink runs and it is just a PITA.  I found my HP Color LaserJet1600 on craigslist for $60.  Replacement toner set was like $60 from amazon and I am good for over 2000 pages of awesome color.

As long as your heat is around 375F or so, you shouldn't have a problem with toasting the decal.  In my small toaster oven I wrapped the extra grate with alum foil so to keep the heat from the top coil from directly scorching my decal.

As far as cutting out different size waterslide (just for the control labels) etc, there are pros and cons to each.

1. Cutting out smaller decals for just labels:
Pros:  Saves on paper
Cons:  Harder to position, may result in more visible edges being shown, more likely to mess up during application, easy to skew or get off center

2.  Cutting out a full face decal:
Pros:  Easy to position, if you use regular paper to drill the template and place knobs it will be exactly like you see in the picture.  Also makes for less seen edges and the ability to have more concise artwork.
Cons: uses slightly more paper (but worth it IMO).

If you want to save a bit on decal paper, just print your decal out on regular paper and then trim a slightly oversized piece of decal paper to fit over it and attach it on the sides (vertically) with tape.  Feed that paper back through and it will print only on the area you covered.

Forgive me if you already know all this (which you proably do) but I use Inkscape and the pedal vector pack. I find it great to mockup a pedal with knobs and small circles for drillpoints all and then when its time to print the decal just hide the "knobs" layer and you will have a ready to go decal.  I export to PDF and then print from the PDF "actual size).  The "alignment" tools in Inkscape are awesome, lets you get all your knobs exactly correct.  You can double click on the knob or item you want after you import it and then put a select box around the item.  Press CTRL+G to group it and you now have a knob you can easily move into your pedal.  
« Last Edit: May 13, 2013, 10:53:53 AM by rullywowr »



  DIY Guitar Pedal PCB projects!

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Re: Re: Powder coating advice
« Reply #10 on: May 14, 2013, 03:50:10 AM »
jimmybjj - I don't hot flock as such. What I mean is I clean the box with acetone, heat it up in the oven, then when it's cooled right down I cleaning with acetone again then I spray it with powder. By the time I spray it with powder the box is back to room temperature again, and it was the same technique that I used on the blue sparkle box (which didn't have this problem). That was a 1590A box though, and the problem happened on a 1590BB box (on both of them).


rullywowr - thanks for the advice on the decals. I've got a couple of tester boxes that I sprayed up, so I'll try both techniques (big decals and small, individual ones) on the them. Just googled the temp for the 'C conversion, and it's 10'C higher then what the oven is so hopefully it will be ok with the decal browning.

I've never used Inkscape, is it easy to learn the basics so I can do the pedal art?
That is a bargain for the printer! I managed to get a Samsung CLP-325W colour laser for 55 and it was end of line, last one in the store and ex display (it should have been 180). At the time I was only looking at getting a cheap Samsung black and white printer for PCB artwork!

Sent from my thumbs using Tapatalk!

jimmybjj

  • Electron Doctor
  • *****
  • Posts: 1071
  • Jim
    • View Profile
    • BeeJive Pedals
Re: Powder coating advice
« Reply #11 on: May 14, 2013, 04:48:04 AM »
can you post a pic of the box in question? I might be able to tell whats happening by visual inspection. I've made almost all possible mistakes and continue to make some of them :) Why do you heat the box between acetone applications?
Pcbs no longer available

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Re: Powder coating advice
« Reply #12 on: May 15, 2013, 06:23:16 PM »
Cheers for the offer. Ill post some pictures in the morning. I've got another 12 boxes I want to coat but I want to solve this problem first!

Sent from my thumbs using Tapatalk!

stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Powder coating advice
« Reply #13 on: May 28, 2013, 11:47:58 AM »
been waiting for some good weather to arrive, as I'm spraying in my shed and have the toaster oven in the garden. Not ideal, but when i get a chance I'll be cleaning out the shed, cutting a hole in one of the walls and installing a small fan with a spraying bench under it, with the oven on the other side.

First 2 pictures are of the enclosures that had what looks like a dip in the paint and a dodgy look down one side. I've had the same problem down the side of another box, and I think it's due to a lack of powder thickness maybe.

The rest of the pictures are of the enclosures I've done so far, with a couple of mock ups of the parts. I'm in the process of learning Inkscape and designing the water slide decals for them. The blue 1590A boxes and the white 1590B boxes will have blue sparkle flakes in the clear coat.












stevie1556

  • Electron Doctor
  • *****
  • Posts: 1064
    • View Profile
Re: Powder coating advice
« Reply #14 on: June 18, 2013, 11:53:11 AM »
Just an update, I've played around with the powder coating kit more and I'm getting some great results! The compressor I'm using doesn't have a pressure gauge, but just a knob that you turn to set the pressure, which isn't ideal. I plan on either getting a pressure gauge or a silent air compressor sometime in the future. The instruction manual says to operate it at around 50 PSI, so I was definitely not running enough air pressure previously, which seemed to cause almost all my problems.

I've been learning how to use Inkscape following the tutorial on here and finding my own way of doing things and getting the hang on it. On my SWAW box (white) and my Sparkle Boost box (blue) you can see where the decals have yellowed. I did turn the temp down for one of them but without any luck. However, the acrylic medium technique that I was told about I've got working now, and it works great. the picture below on the purple box on the left hand side shows it, although as it was an old test box I did scrap half the lettering off. But it works well and you can't see the acrylic medium, and you can't see the edge of the water slide decals either (even when I cut one up and randomly placed them on the box). I'm very tempted to use the acrylic medium technique though, as it works out massively cheaper then the water slide decals, and no risk of air bubbles!

I'm really beginning to love the candy green and candy yellow colours though!