Why might this carve in aluminum be so rough?

I’ve tried twice now to carve this aluminum and both times it has cut super rough. The first time I’m pretty sure I damaged the bit when I tried probing the surface of the metal and jammed the bit into the metal…whoops. This second time was smoother with a new bit, but still quite rough.

Feed speed: 100 in/min
DoC: 0.011"
Bit: 1/8th Fishtail Upcut (Teal from the starter bits)

The 100 in/min seems fast but I saw it recommended here on the forums that going fast with a shallow DoC to keep the chip load higher, about 0.003. The machine cuts wood, mdf and acrylic very well.

The chowdered aluminum (I tried with two bits, that’s why it has cuts in different directions.)

The toolpath.


First of all - have you trammed your spindle?
Tramming = making sure the end mill is truly peependicular (straight up) to the X/Y plane.

0.011" may be a bit deep if your system is out of tram / soft.
Try 70ipm/ 0.004" DoC at 16k RPM and see if that improve things.

I dont have expereience with the fish tail bit, I mainly use 1F/2F bits intended for alu myself.

I don’t work aluminum, but that seems to have the hallmarks of an off-axis mill, because you’re getting hills/valleys. Have you confirmed that your tram is true (as Haldor mentioned) and that your all squared up? Are you squaring the surface with a flat-bottom bit before carving (or is that what you’re trying to do here?)

I have trammed the machine, and double checked it. Made sure all the v-wheels are nice and snug and all that. I was running the dewalt at about 1.5

I thought so too, but I’ve checked everything I can think to. Though I haven’t flattened my waste board yet as my machine doesn’t have a permanent home yet. Would that be able to cause this kind of result though? Wouldn’t the result just be out of square?

Since making this post I tried doing a run at 0.005 DOC and 50ipm and it was nearly as bad.

I would try a bit better suited for aluminum…a single flute endmill is what I normally use. It depends of what you are trying to achieve…are you just facing the aluminum?

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My ultimate goal is to make a corner finder block. I have some of these https://www.inventables.com/technologies/solid-carbide-single-flute-upcut-end-mill …would it possibly work better?

Some things I have figured out for cleaner cuts in non-ferrous metals:

  1. Lube is your friend. I use WD40 in the aerosol can. Light sprays right on the part. No need to flood the thing, just a light mist.

  2. Get the chips out. I keep a constant airflow at the point where the bit is cutting of about 15psi.

  3. Shallow depth of cut AND thin cut at the side of tool. For a 3.175mm bit, my stepover would be 1mm or less. For a 1.578mm bit, step over is .5mm.

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Try an end mill like this one…

Looks like you’re causing the aluminum to gum up when you cut. A better end mill will help.

Okay good :slight_smile:

If your Z axis have any flex in tilt or elevation (even minute) the bit will end up being tilted and wanting to dig in. This isnt a good combination. A poor bit for the job may also compound to this.

I do a bit of aluminium (but not on Xcarve) and for a 1/8" 2F bit on a unknown system I would start with:
35ipm @ 17k RPM
DoC 0.004" (Increase this value if previous work out okay)
WoC 80%

My first DIY CNC I would have no problem going 0.004" at 20IPM per tooth but 0.008" would cause issues do to lack of rigidity on my Z axis. I have the same machine today but its upgraded with stiffer gantry, mass damping and a very stiff Z-slider and I can now go way beyond my initial capacity.

I have a couple of these on the way, you think they might work out? They were cheap so I couldn’t pass it up when I bought a couple 1/4" straight flute bits for wood. https://www.kodiakcuttingtools.com/viewproducts/carbide-end-mills-2-flute-double-end-stub&parttohighlight=995435188

I’ll give 35ipm, DoC 0.004 a try. By WoC you mean stepover? I was running 40% stepover before.

Well, dang. I was updating my toolpaths and noticed my third attempt was at 0.080 DoC…not 0.008 … that could be why it was so bad.