Our team is looking to improve our robot aesthetics for the next season, and we are exploring the possibility of anodizing aluminum. Is the process something that can be done in-house? (We work out of a garage). Or are we better off trying to find a company that can anodize or try powder-coating?
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On our old team it was done one year with the parts taken home to a mentorâs garage. From my understanding the tanks they made from cut in half pvc pipe leaked and that was the end of that. They now do powder coating in house.
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Anodizing means youâre working with chemicals. Is it doable in-house? Well⌠yes⌠technicallyâŚ
But if you do it then you need to STUDY the SDS for the chemicals used, and take appropriate precautions.
Get a sponsor to do it, do powdercoating, or just rattle-can the robot (with proper prep work).
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The right answer for my team. There are several recent powder-coating threads on CD with pros and cons plus anodizing has more chemicals.
Summary:
- farm-out for surface treatment is really, really bad - kills your schedule waiting for others unless you pay for the service.
- powder coating is messy and you canât touch-up scratches very well but fun to try and may generate hazardous waste disposal problem.
- anodize coating has nasty chemicals and you canât touch-up scratches at all but fun to try and may generate hazardous waste disposal problem.
- spray can does a 99% beautiful job by any student and can be touched-up almost perfectly and is cheap.
None of these are as bad as âfumingâ which is pretty cool to treat the surface of many materials but can shorten your life.
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There is a less-nasty anodized process out there. I think Hack a day talked about it recently.
That said, itâs multiple baths, hot, and potentially messy. Plus disposal issues. My gut feel is ânoâ because you just wonât use it enough.
Powder coat is quick and pretty easy, plus no special issues with âI havenât used it in a weekâ like baths.
I havenât tried to patch powdercoat, but the key challenge is pulling it off the bot to bake it.
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This is not always true. Iâve found if you ask your vendor for free coatings your gunna wait 3-7 days. But if you actually pay them at least the normal lot charge, they will work with you to turn around them around much faster. All our anodize runs are dropped off first thing in the morning and picked up by the end of the day. Powder coating takes 1-2 full days for our vendor so we kept that at a single run early in the season.
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Iâd also suggest asking the vendor what you can do to save them time. This will vary for each vendor with what they typically run and how generous they are.
Things to save time might include sandblasting first, masking holes for them (which can be tricky) OR making it clear you donât care for them to be masked, being flexible with color choice, etcâŚ
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Consider using vinyl wrap. One of the teams I was judging at the District Champs had one of the most colourful robots at the event and it was done with a combination of vinyl wrap and coloured duct tape. They said it was pretty quick and easy to apply and one does not have to wait for it to dry. Damage to the finish is repaired by cutting a small patch and sticking it on. From arms-length, it was difficult to see the patches.
My guess is the shops that do the wrapping will have off-cuts and remnants of rolls that they may be willing to give your team in return for putting their logo on your sponsor panel.
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This is what we do. You need some powder. I recommend prismatic powders cheap and fast delivery. Need an approximately $100 harbor freight powder coating gun. And an old electric oven that you arenât going to use for cooking food anymore.
The process is super fast and easy. I often times can have a powder coated part put on a robot before I painted Part would dry.
This.
2386 made a makeshift powder coating setup back in ~2015 with a donated oven, and this powder coating gun provided from a sponsor (Iâd consider Princess Auto a similar vendor to what Harbor Freight is in the states). We could have a part prepped, sprayed and baked within about 30-45 minutes in a hurry.
A few years later they upgraded the setup to a more industrial oven that they (I think) still use to this day. But for starting out, an old unwanted oven will work wonders (as mentioned above though, please donât also use it for the team bake sale 
).
Any idea or educated guesses on a weight comparison between a powder coating and vinyl wrapping on an FRC sized robot? Anecdotally Iâve heard that wrapping is âtoo heavyâ, but Iâve never seen anything quantified.
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I wonder if @Alex_Cormier would have a better idea than most.
My team is lucky if weâre able to rattle-can every few yearsâŚ
Iâve looked into these things a bit, speaking in round numbers:
Expert powder coating is .002-.003in thick with a SG between 1 and 2
âNormalâ vinyl wrap is about .002in with a SG of 0.9
When done ânormallyâ vinyl wrap will be lighter per unit area (comparable-to-lower thickness, lower density).
If you get âthickâ vinyl wrap at .004in it can be heavier than PC. If you use a wrap that is not made from vinyl it may be .003in+ thick and denser.
If a non-expert is spraying PC, or the habit is to apply thicker coatings, PC can be up to 0.010in thick. Sometimes thicker for special cases or beginners.
Spray paint is usually .0005-.001in thick per coat with a cured density between 1.0-1.9SG kind of range. Thus spray paint is usually the lightest option because robot parts can be coated in the thinnest possible layer of material.
To crayola this out a little [units unimportant]:
PC:
1.5SG * .002 thk = .003 min
1.5SG * .010 thk = .015 max
Vinyl:
0.9SG * .002 thk = .002 min
1.5SG * .004 thk = .006 max
Paint:
1.0SG * .0005 = .0005 min (one thin coat)
1.5SG * .0015 =~ .002 (this is what we do, one very thick coat)
1.5SG * .002 = .003 max (two full coats)
FWIW anodizing adds in the range of .002-.005in thickness, about half of which is added to the part dimensionally. Aluminum oxide is DENSER (4 SG) than the aluminum it converts (2.7SG), plus the extra material growth. Aluminum oxide is denser than any other coating option. Likely anodizing is heavier than all but the heaviest of PC setups.
Edit:
tl;dr - There is a lot of overlap in all of the design spaces, so the many stories we hear that seemingly contradict each other may actually be true. I strongly recommend spray painting for a vast majority of teams. The bang/buck/weight/speed/safety tradeoff is phenomenal.
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I appreciate the detailed response. These are the type of numbers Iâve wanted to see laid out for a while.
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Oh no you ruined it for me. We have a vinyl cutter in the robot room and I was instantly fired up! But we are always removing some small stuff trying to get down to 125#.
Maybe we can get light weight material and still use the idea.
I am surprised to hear this. I think with many of the newer components (electrical system and brushless motors) itâs easier than ever to build under weight.
Granted, we arenât an elite team that does everything, but I think we do pretty decent and donât pay too close of attention to weight. A lot of our aluminum has even been 1/8 tube still for bases and such
Thanks for the tip. I thought most teams struggled with the weight limit; so our students havenât been making the most clever low-weight designs. Iâm looking at the CD thread about weight reduction.
And the weight of the surface treatment is important to us since the first competition we still had to fuss with making the flimsiest sponsor logo holder in the world after removing things like much of the climber, a vrm, etc.
This reminds me of the legend of a small boat owner painting his boat with epoxy paint and then it sunk from the weight.
You really donât want to be dealing with the chemicals involved in anodizing in the state of CA, when it comes to disposal.
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It is probably beneficial for your team to monitor the estimated weight as the robot is being designed and learn how to increase the accuracy of those estimates.
If you are having to worry about the weight of the surface treatment, you should also be concerned about keeping the sizes of the wires to the minimum allowed in the rules and minimizing the weight of the fasteners used by choosing smaller ones or choosing different fasteners. You may also want to consider alternative materials for lightly stressed components i.e. make sponsor panels and ball guides out of Coroplast.
Lastly, does every surface of every part of the robot need to receive the surface treatment? Can the surface treatment be only applied to the side of the parts that are most visible and not covered by other parts like sponsor panels?
Thanks. I wonder if foam board is similar, better, worse?