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CNC Soda Can cutting??
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CNC Soda Can cutting??

by Jacksonbrown on Wed Oct 10, 2018 8:01 pm

Hi all,

I had an idea but I'm not too sure how viable it is so I'm after some feed back.

Idea is to use soda cans as material for building RC planes using desktop CNC.

My approach is probably different to some of the google stuff I've found though. I want to design the thing more like a conventional airplane or old school balsa model.
I would design a 3D assembly with ribs etc. then CNC laser-cut the lot out of a flattened can (possibly I'll stick the sheet to something first) then fold the tabs and assemble, possibly gluing into place as I don't see rivets working.

I have the CAD skills, I have a bit of experience with industrial CADCAM but limited experience in this sphere.

Question the first, How many Watt laser to cleanly cut an aluminum can?

Also, any recommendations on a suitable unit with a roughly A5 platter size that I can feed G code into?

Jacksonbrown
 
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Re: CNC Soda Can cutting??

by adafruit_support_mike on Thu Oct 11, 2018 3:21 am

You might be able to make a laser work for thin sheet, but laser-cutting aluminum is generally difficult. The two major problems are reflection and heat transfer.

Aluminum is one of the more reflective metals, so just getting the laser to heat up a spot is the first challenge.. most of the energy bounces off instead of going into the metal. The second challenge is what's called 'flashback': reflection off the molten metal sending the laser beam where you don't want it to go.

Aluminum is also the third most heat-conductive metal, after silver and copper. You have to pump energy into the molten part faster than the energy can spread out to the surrounding metal.

Using a strong laser solves the problem of getting energy into aluminum, but it also makes flashback stronger.

In terms of laser strength, you'd probably need at least 150W to cut even thick foil. People with 40W lasers can usually etch a mark on metals, but not much more.

Industrially, companies that need to cut aluminum sheet tend to use either a plasma cutter or a waterjet. Plasma doesn't work well for thin sheets and isn't very good at producing fine detail, so it probably wouldn't work for you. Waterjets can do excellent detail in thin sheet, but they're kind of high-maintenance.

In terms of energy and complexity, you'd be better off using a lightweight milling machine. Aluminum is easy to cut mechanically, and much softer than tool steel. Even the least expensive cutters will last a long time. Shim stock doesn't require much force, so any of the CNC kits for woodworking will fly through it.

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Re: CNC Soda Can cutting??

by Jacksonbrown on Thu Oct 11, 2018 3:39 am

So there are good reasons why it isn't being done. Damn, that seems to be the case with all my 'good' ideas :)

From memory you guys sold some small CNC milling machines designed for pcb boards. If I can get the parts to lie flat it sounds like this might be the way forward?

Jacksonbrown
 
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Re: CNC Soda Can cutting??

by adafruit_support_bill on Thu Oct 11, 2018 6:20 am

We did carry the "OtherMill" for a while. There are still plenty of desk-top light-duty machines out there. Anything capable of PCB milling should be sufficient to handle thin aluminum too.

For milling thin sheet, I generally use hold-down-clamps and/or carpet tape to hold it to the bed. Vacuum tables are a more elegant (and more expensive) option.

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Re: CNC Soda Can cutting??

by adafruit_support_mike on Thu Oct 11, 2018 11:35 pm

You can also use shellac to hold small/thin parts in place. It's an almost ideal material for shop work.

Shellac is a thermoplastic that melts at about 80C, and also dissolves in alcohol. You can melt it directly onto a support plate, or make a solution, paint that on, then heat it to evaporate the alcohol and melt the thin film that remains. It sticks to almost anything, and holds well enough at room temperature to stand up to work on a lathe or a milling machine.

When you're ready to release the workpiece, a hot alcohol/water bath will lift the work free with zero force and clean the surfaces.

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Re: CNC Soda Can cutting??

by Jacksonbrown on Fri Oct 12, 2018 3:46 am

Oh man, my head is telling this is a dumb idea but that niggly little curiosity bug just keeps scratching away.

Do yourself or anyone else have any feedback on these guys or any other suggestions?

https://millrightcnc.com/buy-now/

Jacksonbrown
 
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Re: CNC Soda Can cutting??

by adafruit_support_bill on Fri Oct 12, 2018 6:01 am

I have not done any business with that company. But I have heard good things about them on some of the CNC forums. They seem to specialize in reasonably priced entry-level machines. A little more expensive, but better supported than the generic Chinese units you find on eBay.

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Please be positive and constructive with your questions and comments.