Designing Anodized Parts

[AdamHeard]

What precautions should be taken or features added to a part that is going to be anodized in comparison to a normal part? Do bearring holes need to be made slightly oversize? what about tapped holes?

[eshteyn]

when a part is anodized the thickness of the finish could be anywhere from 1/32 to 1/16 of an inch, i would suggest sending out a part to the anodizer and measuring it when it comes back

[Cory]

when a part is anodized the thickness of the finish could be anywhere from 1/32 to 1/16 of an inch, i would suggest sending out a part to the anodizer and measuring it when it comes back

30 to 60 thou over? :eek:

In our experience it's been more like 2-4 thou over.

[Jeremiah Johnson]

How much time should usually be allowed for anodizing parts?

[AdamHeard]

30 to 60 thou over? :eek:

In our experience it's been more like 2-4 thou over.

So, how do you compensate for that? Do you make all holes that much larger? or do the anodizers mask them off?

[sanddrag]

A machinist I know said for a traditional basic anodizing, the dimension added (outside the existing material) is so negligable .0002-.0003" that it doesn't need to be considered for most bearing press fits. If you are getting into hard anodizing, it is possible you could add a thou or two, and then it would need to be considered.

[Travis Covington]

Most colored (Type II sulfuric anodize, which is most common) should be anywhere from .0002 to .0008 thick.

Type I anodize (Chromic) is usually only .0001 and typically has no dye added.

Type III (hard anodize) is typically thicker than the above two.

[AdamHeard]

What I'm concerned with are; bearing holes, holes for shear pins and threaded holes.

So, if the anodizing is for cosmetic purposes (Type II- thanks for letting me know Travis), the effect is negligible?

[Travis Covington]

A machinist I know said for a traditional basic anodizing, the dimension added is so negligable .0002-.0003" that it doesn't need to evern be considered for most bearing press fits. If you are getting into hard anodizing, it is possible you could add a thou or two, and then it would need to be considered.

This is usually correct. Dont worry about it at all if you are just doing a regular colored ano. If you are doing a hard anodization, find out exactly which process you are using and contact the people themselves. They will tell you the thickness which will allow you to change your part dimensions accordingly. It should be noted, however, that "thickness" in the anodizing world refers to the total amount of material affected by the process, both penetrating and building. This means an anodize that is .0002 thick penetrates .0001 and builds .0001.

[Andy Baker]

What I'm concerned with are; bearing holes, holes for shear pins and threaded holes.

So, if the anodizing is for cosmetic purposes (Type I), the effect is negligible?

If your bearing hole is exactly how you want it to be, I would mask it so it does not get anodized.

Don't worry about the threaded holes and the holes for shear pins or roll pins.

Andy B.

[Travis Covington]

What I'm concerned with are; bearing holes, holes for shear pins and threaded holes.

So, if the anodizing is for cosmetic purposes (Type I), the effect is negligible?

No, Type II is what you want then. Type I is more functional than cosmetic, as it has no dye added.

[John Gutmann]

If your so worried about the bearing holes, why not just ream them out when you get the parts back? You cold mask them off or cork them.

-John

[Tim Baird]

In my experience, masking is the best bet if you already have the hole to the exact dimension and location that you want it. You can sometimes mess it up through reaming.

In terms of lead time, if you're friendly with the company and they don't mind working hard for you, it can be done fast. For the central mass teams, Dav-Tech plating in Marlboro is really good. I've dropped stuff off at 8am and picked it up at 4pm. However, a typically company, depending on the color and batch size, will take 2-4 days.

Also, if you're anodizing very small parts, make some spares. Tiny parts are known for getting lost in the tanks.

[Brandon Holley]

To really save some time and frustration, especially if you haven't worked with anodize before i'd suggest reaming holes out after you get anodize back. That is IF you are very concerned.

We used A LOT of anodized parts this year on our bot 125 in technicolor (http://www.chiefdelphi.com/media/photos/26803)

We left our dimensions the same and experienced no real huge problems with items not fitting. If your very concerned i'd go with cutting your holes slightly smaller than your actual dimension and then reaming them out after, it guarantees a correct fit regardless, and no one will see it.

[Cartwright]

If your so worried about the bearing holes, why not just ream them out when you get the parts back? You cold mask them off or cork them.

-John

Yeah...that is what we did, if the holes were too tight.


But anodizing is really great, it makes the overall appearance look way better and more professional. I'm almost positive that it played some small role in the success of numerous robots this year.

[Madison]

I'm curious how many teams that anodize their parts build their robot (or parts of it) first, then tear it down and send it off to be anodized.

I'd love to find the time and the resources to get our machines anodized, but usually I'll be hard pressed to take something apart once we've put it together and I'm a bit nervous about sending off parts that may not even fit together.

[Travis Covington]

I'm curious how many teams that anodize their parts build their robot (or parts of it) first, then tear it down and send it off to be anodized.

I'd love to find the time and the resources to get our machines anodized, but usually I'll be hard pressed to take something apart once we've put it together and I'm a bit nervous about sending off parts that may not even fit together.

We never assemble anything before powdercoating or anodize. We check dimensions and slip fits, but do not do any final assembly at all. There simply isn't enough time, as you said.

[Stephen Kowski]

I'd love to find the time and the resources to get our machines anodized, but usually I'll be hard pressed to take something apart once we've put it together and I'm a bit nervous about sending off parts that may not even fit together.

anodize everything if something doesn't fit make a new part and just polish it so it gets that lovely shine......chrome look goes with everything :)

[Brandon Holley]

I'm curious how many teams that anodize their parts build their robot (or parts of it) first, then tear it down and send it off to be anodized.

I'd love to find the time and the resources to get our machines anodized, but usually I'll be hard pressed to take something apart once we've put it together and I'm a bit nervous about sending off parts that may not even fit together.

Anodize/powder first, assemble 2nd...check your general dimensions, but there isn't time to go ahead and assemble and breakdown and assemble again.

[John Gutmann]

I love annodizing too, but doing it on such a time constraint is hard.

-John

[Kirk]

If you talk to an anodizing company they can usually control the buildup +/- .0004. You just have the bearing bores machined oversize by the amount that the anodize will build up and you are good to go. The buildup (growth) on a standard hard anodize is usually in the range of .002 - .005.

This is what we had to do with the teeth on the gears. When I hobbed the gears we cut them .002 undersized to allow for anodize buildup. In the end everything worked perfectly.

[Jeffrafa]

As far as timing, our team built up our practice robot, then got everything anodized on the final one before any assembly. Obviously this isn't always a viable option, as you must be building a 2nd to go this route, but it worked out well for us.

The anodizing company we used turned some parts around same day for us, since we were pushed - although a couple parts were next day. All was donated, which was nice, so additional expense due to turnaround time wasn't a problem.

I can't say much in the way of tolerance, our wheel bearing blocks didn't make it to anodizing. The tapered bearing blocks in our transmissions did get anodized, but the difference was negligible and didn't pose any problems.

- Jeff

[CraigHickman]

I'm looking at anodizing a bunch of parts next year, and time really isn't an issue with the guy we're going with. Will the bearing holes have any issues if we're going to press fit them anyway?

[DonRotolo]

If you really want/need to know just how much thicknedd a particular anodizing process adds to your parts, Travis Covington had the absolute best solution: Just ask the guys who are going to do it. THEY KNOW.

Alternative: Make a test coupon (a sample with some holes, slots, flats and stuff) and have it anodized, and measure ofr yourself what the difference is.

In the real world, if your vendor doesn't know his process, you find another vendor. If that's impossible, then you run some tests and measure.

Don