Optimising Aluminium Machining Speed

I need to make a lot of thin sheet aluminium parts, 1.2mm thick. We currently have a jig that uses 18 bolts to bolt down the stock so the machine can make them


. The bolts are a very slow method!
Does anyone have any super fast methods of holding down thin plate to machine as quickly as possible?

Just looking in from the outside, I’d say what you are doing is the best method. It may not be fast, but there is no way the metal plate will move. That’s what you want. Just chalk it up to production time.

Looks like your already using a supplemental spoil board. Why not make a bigger one with shallow pockets for a couple sheets of aluminum and use the blue tape and CA glue method to hold the aluminum down. That would also allow you to use smaller tabs.

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Or to tag off @Ed.E , Create multiple supplemental spoil boards, (jigs) that you change out as the part finishes, empty, and load as the cut goes.

I think multiple jigs/spoil boards could be the way to go. Then a larger jig to hold the interchangeable jigs. When the job finishes, I could just slide out the interchangeable jig and slide in the new one, all loaded and good to go.
Still not super fast, but would ensure the machines downtime is minimal. Currently takes 5-10 mins to change out the stock between jobs!

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Here’s what we’re making for reference

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This may be antithetical to what most people on a CNC machining forum would say, but have you considered having these laser cut? If there’s a particularly critical dimension, you could make a fixture to do some secondary machining and clean up the edges. Would need to do a bit of a cost analysis to see how much time it would save vs how much you value your own time.

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Thanks for the reply Winston - I’ve been watching your videos for years!
The problem is that I machine a small recess for the thread inserts, making it a 3D part. I also do a light chamfer on the top edge.
I could redesign it to be 2D for manufacture by laser, although I don’t think the end product would be as high quality. I wonder if it’s possible to laser cut, then do the recess and chamfer afterwards?

I know rigidity is important in all parts being cut. If I am looking at your picture right, it looks like you have a middle cross brace that spans the length of your plate, correct? If this is so, then you really could do less in hold down. A middle holding plate with “I” beam looking ends would be sufficient. What thickness of material are you cutting? And is your holding plates the same material with the same thickness?

The biggest issue that anyone cutting aluminum needs to worry about it load up, or build up of cut material. This is when the material isn’t being removed fast enough and starts causing the aluminum to get hot and start to actually melt onto the endmill, which in-turn, causes the finished edge to build up and look crappy.

With your setup though, you have a really thin piece of aluminum running along the front, middle, and back of your fixture. If you increased the thickness of those pieces to 3/16" or even 1/4", then you would be surprised at just how good they would be held down with less bolts. This also would allow you to remove the two side pieces for good. With a little thicker holding piece, you could put 3 bolts on each end and the single bracer down the middle with 2 bolts holding that down.

If your machining toolpaths don’t move across the ends of your fixture, you could replace those 6 bolts with wing bolts. This way you can quickly screw in those bolts and tighten them by hand. If you don’t understand what I’m explaining then I could draw something up for you and post it here for you to understand it better.

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Expanding on the above, what about using studs and wing nuts? Then you drop it on, spin the nuts and go. Less fussy than bolts perhaps?

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Excellent suggestion, and note that there are nylon wing nuts available, which are pretty inexpensive in bags of 100 (check w/ Grainger/Fastenal), so no worries about alignment/hitting them.

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