Aluminum workholding

I have a 12x12" piece of thin aluminum (~1/16") that I am cutting (trying to cut :slight_smile: ). I have tried a couple of things and my results have been predictably awful. The bits I was using worked hard and some of the cuts were clean, but where the piece was not firmly kept down all kinds of nasty things occurred.

The material is thin and because of it’s size I can’t get it to stay flat on the spoilboard with clamps. I put some thin plywood under it and that improved things a little. I think I need to try a thick plywood base and use tape and CA glue next. Would the work-holding wax be better?

My other attempts at aluminum went better because I was working with thicker pieces that have more rigidity.

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It depends on where you are cutting on the 12 x 12" piece. You could cover the entire surface or just around the edges and where you are going to cut.

This is a prime candidate for blue tape and CA glue.

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I second the tape and glue method. I cut a lot of thin aluminum sheet and have found its really the only way to go. Doesn’t take long to set up and your stock isn’t going to move on you .

In addition to blue tape-CA, you might consider sandwiching the aluminum between two pieces of plywood or mdf to keep the thin aluminum from vibrating and ruining the cut. Pocketing a recess the thickness of the aluminum with a tight x-y fit will provide lateral holding power beyond clamping force between the two boards holding the aluminum.

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First off, I see that I should be using the blue tape and CA combo. I will definitely do that.

Regarding Mitch’s suggestion to sandwich the piece with two pieces of plywood or MDF: The top sheet will have to be pretty thin since I don’t have a lot of working depth on the bit.

I’ve attached the file. I also think that the cuts themselves are a problem. The pockets (holes) cut really nicely. It’s the long narrow channels that are an issue. I know that this is not generally recommended. I am thinking I need make these pockets somehow. My son designed this one and I was worried a bit about it. I decided to see if I could cut it anyway. The bits I am using took a lot of abuse. This is definitely user error.

Thanks all for the help

120 aluminum w notches.c2d (28.3 KB)

Hmm, first thought is… what is the finished product? I have a thin piece of brass I will need to machine for a sign. It will end up attached to a MDF or PVC backing board in the finished product, so I will bond it to that before doing the detail machining to give it stability.

Your part looks like a flat-pattern that will be bent/folded into a box of sorts. If I were doing a lot of these I might consider a small vacuum table. Otherwise, tape / tape & CA might be the ticket.

Tod,
It is intended to hold a fan and you are correct that it will be folded into a box. After cutting it, that will be the next challenge… Figuring out how to fold it. I haven’t been ready to ask about that until I at least managed to successfully cut one. I’ll have to go with tape and glue because a vacuum table isn’t something I will be getting anytime soon.

I’ll give it a try in a day or two to see how it goes cutting it with it attached to the waste board.

Thanks for all the great comments. I really appreciate this forum.

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Mitch, Interesting!

I will have to try that when needed. It would allow you to cut it. But I don’t see how you could engrave.

@Zman I didn’t realize you were trying to engrave. Totally would not work for that!

Mitch,
I was commenting on your idea. The OP did not say if he was engraving that I can see.

I will have to try it some day though

I will have the same challenge. Really thin brass on top of a MDF/PVC substrate. I know a few roofers that have sheet metal ‘breaks’ for bending aluminum, but I don’t think they are at the level of precision we’re looking for. I’m thinking with some hardwood or aluminum scraps I could make something.
Side view…

Clamp each side then bend the 45° edges together.

That is a cool idea. I’ll have to give it a try. I have to get the piece cut successfully first though.

You could also use a contact cement spray can to glue it onto a flat backer board. Contact cement will hold the metal firmly and evenly. To remove just heat and slide a knife under or open a slight gap from the backer board, turn it on its side and get a little solvent in there and it will melt off. The metal once off can be cleaned with more solvent. This method will result in less bending of the metal when separating it from the backer.

Cool suggestion. I have to try the contact cement idea. Is there one that you would recommend?

I did manage to get the piece cut. There were significant enough variations in surface height that I had rezero the Z axis and run the job again. I am thinking that the contact cement idea might make a difference. There was a huge improvement in the quality of the cuts this time. I wasn’t using coolant (my spray bottle quit spraying early on) but the bit and the work piece kept cool. I take that as a sign that I had reasonable Feeds and speeds. I even bumped it up a notch and it seemed to cut as well or better.

Aluminum is a significant step up in fussiness. I wasn’t going to really try it just yet but I had requests that took me there. The thicker stuff was actually a lot easier to work with. That was counter intuitive to me. Then again don’t have a well developed intuition for this. I am new to CNC and learning something with every job.

One of the next things I need to sort out is getting the machines tuned up a bit more. I get pretty prominent variations in surface heights in pockets which I assume are a sign that I haven’t tramed the machine well enough ( it is pretty well dialed in for wood though). Am I right about that? Or should I be looking elsewhere to solve this issue?

Once again, I am deeply appreciative of the community here and the carbide 3d folks who are so willing to lend a hand. I hope I can return the favor some day.

@Dennyboy Which product did you use? I’d like to give that a try myself.

You can google spray can contact cement. There are many brands but be sure to get actual contact cement which is non repositioning meaning you stick the two pieces together and there is no moving them. They will be flammable but you only need very little and a can goes a long way. Using contact cement allows you to use a very smooth backer such as metal, plexiglass or even plate glass.

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I use 3M 77 contact adhesive in the shop a lot. Locktite makes 3 levels of bonding with 3 different products. The 3M 77 is a permanent adhesion with the right materials. I use it mostly to bond paper to wood for scrolling. If you take a rag wet with mineral spirits and wet the adhered paper and let it soak the paper peels right off. Then you must wipe down the surface with mineral spirits to get the residue off. I only spray the paper side and not both sides. If you spray both sides it is very hard to get the paper off. Plus I spray the adhesive and immediately stick it together. If you spray both sides ad allow the adhesive to dry it is permanent or at least very hard to get off.

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You could use a box brake for shaping your piece after it has been cut. I have been using a Grizzly G0556 - 12" Pan and Box Brake that works pretty well for small pieces 12" and less.

John

Hi John,
I’ll take a look at that. My piece is less than 12" so this could be an option for me.

Thanks