Just another clamp...from aluminum

Got to hang out with @tgm022861 this morning for the express purpose of getting some aluminum cut. This was the first attempt on his lowrider 3. Boom. Granted, his LR3 is on the small side, but I don’t see anything about it that would make this perform significantly worse at a larger size. In fact, he had a loose belt and a loose motor when we cut this one (we found it later). He’s got some room to crank up the speed, even, but his firmware is set pretty conservatively for a machine this size. We ran into speed and acceleration limits pretty quickly.

Never mind the sound cutting in and out. I was just getting rid of some of our conversation.

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YES!

That was slick, and with a loosey goosey stepper, smiling right now.

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Nice! Very nice. Speeds, feeds, depth-of-cut, rapids, router, mods, lessons? Would be great to learn what’s possible, and what to aim/push for.

Horizontal belt mod looks interesting.

Cheers!

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Tom has written about that belt mod elsewhere. The idea is that he’s preempting a solution for belt stretch over a full sheet. For now, it’s small and he’s using it for development.

The adaptive is cutting at 30k RPM, 1mm DOC, 2mm stepover, 750mm/m feed.

The contour was 0.75mm DOC with a second rough pass of 2.5mm stepover (this helps clear the chips as the contour gets deeper).

We also use that helical pocket outside the part to make an entry for the slotting. I’ve plunged into aluminum before and it’s not bad at these depths. Ramping is slightly better. But this way is less stressful and doesnt take any longer.

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Thanks! Taking note of the details!

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Update coming soon…

While i was out riding minibikes with the kids, Tom was in his lab tweaking amd adjusting his firmware and toolpaths.
Here is the result:

And if it isn’t obvious from the video…HOLY COW!
For comparison, I sat down and reviewed the video of my 2x1 Primo cutting the same clamp. The videos don’t start from exactly the beginning and mine included the mid-job work-holding. Also, i thinned my clamp, Tom’s is full 1/4in, SO…
Using round-ish estimates (10s or so) i subtracted my rough pass for the thinning, the cleanup pass for the thinning, and two air-passes for the final contour (at least I’m pretty sure i subtracted that last one). I added back in the amount of time it took for a pass down the center slot to make up for the material I removed in that first step. The result is basically dead even. Within 10 seconds. So even if I’m off on the math because off rounding, I’m not off enough to change the verdict… LR3 ROCKS! I’ll update with the feed/speed/depths when I get them.

Now, I’m also not about to claim that i cut aluminum super fast on my primo or whatever, but I’ve gotten great feedback about where I’m at for a plastic cnc, and i do think I’m in the top quintile at the very least. And i have zero concerns about reliability with my feeds/speeds/strategy. Increasing the MRR for me leads to failures (the harder I push, the more common the failure). So for the LR3 to keep up, i think that’s saying something.

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What is the overall build size or usable area of his LR?

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It’s 24x by 20y (inches).

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I’ve written a bit about cutting aluminum on an LR2. Using a 1/4 in bit I bet you could cut the same part in half the time without troichoidal cutting.

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I have requests from two different suppliers about 1/4" aluminum bits. Can’t wait to try it!

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The trochoidal is definitely slower, but it’s included to have a more complete demo. It’s more of a test with a useful product than a means to get a clamp.

The feature is 1/4 in wide, so it could definitely be slotted like the outer contour. A 1/4in endmill wouldn’t have enough room for rough/finish but i guess a 6mm would do just as well.

Tom has a 1/4in endmill just to test aluminum, though, so maybe changing the feature to accomodate would be fun.

Do you have a link to your post or a keyword I can search? I’m missing it. It sounded to me like the makita was working pretty hard on the 1/8 at that DOC, so I’m curious how much you were able to get, and whether he’s going to have to take shorter passes to not murder his router. The Bauer already gave up earlier in the day.

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You are really making me wonder about the two machines. Dividing my attention between the LR and MPCNC takes, well, twice the time. The LR has some secrets built in that I no one has noticed yet and instead of revamping the MPCNC I could do a some tweaks on the LR.

MPCNC - kinda easier to build (except squaring), costs less mostly because of the LR linear rails, easier to source.

LR - kinda easier to use, removable from the table, might be able to make some design changes to beef it up a bit more possibly reduce cost, smaller footprint/usable area. This one does seem to have more fit and finish, and room for changes.

Maybe I should start a new discussion about this.

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I cut my aluminium for the boom arm with a 6mm two-flute, 900mm/min (edited!) trochoidal, 10mm DOC. The Primo did flex, but that’s what I wanted to see. If I build a lowrider will test with the same specs.

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Stepover?

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Oh sorry, it was 900mm/min, just checked the video (Cutting Aluminium - YouTube). Will tell you the exact settings after I am back from the in-laws. I think the stepover was sth. like 5-7%. Not sure though.

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This is getting better and better. Tom and i talked about why i prefer to trade doc for stepover amd speed, and well, he’s ripping.

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Okay that one is pretty good. Wonder if there is anything left in the tank. I would guess you are pretty close to a limit.

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He did buy a 1/4in endmill, so depending on how much AL he has left, he might do more testing. He has some specific projects for some of it though.

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