hard anodizing, Machine-ability and thermal transfer?

[dnar]

From what I've heard the anodized black aluminum surface is much better than a mirror polished surface.

Craig

With Aluminum, black typically radiates heat in the order of 3-8% better than a natural finish.

[kitatit]

It chews off and cracks when you mill it. The effect is localized, and you can
hear the cutter complain, but you will not lose a cutter.

Steve

Thanks Steve,
yeah I was thinking of using hard anodising for its'd toughness plus it give a tough military look to.
Sounds like black has the most going for it though.

Kitatit,

In my experience mixedgas nailed it. You can hear it cutting, it sounds strange but a sharp tool can get through it. I use carbide for pretty much everything now days.

As for thermal I wouldn't worry too much about it. Remember anodizing is a Aluminum Oxide layer deposited on the aluminum base material, typically 5μm to 15μm thick. Black anodize is the same material, dyed then sealed, same with all colors.

Hard anodizing is usually the same process but much thicker, 12μm to 150μm. This gives it more wear resistance for extreme environments (your back pack isn't one of them) but will also provide much more of a thermal insulator because of thickness.

If it were my project I would just go with standard black and not worry about machining anything off after. The ~10μm thickness of Al2O3 is not going to make much difference in thermal performance. Everyday room temperature differences are going to do more to the thermal efficiency than a really thin layer of Al2O3.

$.02

By the way gorgeous little projector!!

chad

Cheers Chad, I'm pretty proud of how its turning out. The info from all you guys is invaluable for getting it right.

It's taken me ages to design it with little scraps of spare time but I'm not in a rush. It's the first time I've gotten to apply my skills to something I'm really passionate about.

I'm enjoying putting as much art as science into my builds. Kind of like building a show car for us late night, electro mechanical type people.

It's proving a very enjoyable outlet.

I'm getting pretty close to having the case detail finished. and wouldn't mind your input on a few details.

I don't have access to a mill in my current job so at this stage my friend who has a CNC mill at his work might do it for me.

I want to make it as easy for them as possible so they don't have to waste too much time helping me out.

My experience is all on manual mills so I could do with a few pointers regarding efficient fixture hold down for an NC also how thin I can make the case so it won't get too excited
and chatter when machining. At the moment, I've made the default thickness 3mm and will add some stiffeners where possible. I'd like to go thinner if i can with out making it too difficult to hold down when milling. I'll be adding quiet a few bosses to allow screwing to top and bottom case together which should allow some solid lands to clamp it down.

Without compromising the design to much,I'm making as many radii the same as possible to reduce tool changes as I know this job won't be cheap to machine.

Can I send you some SolidWorks parts when I'm finished so you can recommend any refinement to make it a more efficient machining process?

I have been thinking this might be sufficient. http://littlebirdelectronics.com/pro...er-control-kit

I'll get some in and try them out.

EDIT: I ordered 3 x MOSFET board kits. I will test with a GM20 next week when they arrive.

Hey Wayne thanks for that mate. I bought this 4way driver from Showlaser quiet a while ago. I can't remember if they sell single ones.

What do you think of this driver? I can't remember where the instructions for it are. what do you think the pots are for? Maybe I could make a single channel version of this if Showlaser don't offer it.

Does this look like a generic design or proprietary? I don't want to rip anyone off copying their stuff.