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looking at the photos. Oh wow that is some NASTY heat build up. Heat is a real problem with aluminum because it melts at so low a temp. It looks like you are melting the chips?
My best guess is “rubbing”. The speed the cutting edge moves across the material is a combo of the RPM and feed rate. If one of them is off (RPM too high, feed rate too low) the cutting edge will make multiple passes over the same spot after it is cut. So the edge rubs against it, causing friction and heat. In wood this causes charring.
One way to fix this it to increase your feed fate or to drop your RPMs.
Increasing your feed rate can be a problem because it puts more load in the system, causing flex and chatter and missed steps. (a stiffening mod will help reduce this) You can compensate for this by reducing the depth of cut.
So for aluminum you want to cut fast and shallow with lower RPMS
Again looking at this photo I would say check your depth of cut and feed rates. Also check your Z zero height. Make sure it is not too low so you are taking a deeper bite during your first pass.
What kind of spindle do you have? The Dewalt? Do you have something blocking the down draft from the router. If so try taking it off, that bit of air blowing the shavings around may make a difference.
It would be a good idea to invest in a coated bit, it helps.
Another big trick I found was to set it up so that it is cutting a channel wider than the bit. With the thicker aluminum runout in my spindle (wobble) was causing the bit to bind in the channel and break.
I changed my cut file so the deeper cuts were actual done with 2 passes 40% apart. (offset the curve and made it a pocket operation instead of a profile) It made a huge difference.
That last part is what I think (a big part of) my problem was. It was cutting great until the bit started getting down deep into the channel it was creating. Maybe I’ll try doing what you suggested and giving it a little more room to wobble without hitting the sides.
I have the DeWalt and was running it at 5 ( as Robert Reike said above), but I’m guessing that was far too fast. I’ll adjust some of the settings and report back. Thanks y’all.
And if you’re in a metric country and can’t get .1875" steel, then shims are a necessary thing. My choice is either 4mm or 5mm so either a shim or trimming down the v-wheel spacer. Goes a long way to explaining why I still don’t have the X-axis mod done yet.
No aluminium so far but I’d like to give it a try. I usually cut aluminium on my manual mill as it can take quite an aggressive cut which makes it a lot quicker but is limited in cutting complex shapes. Cheaper to beef up the X-Carve than to CNC the mill.
Just went to have a quick look at the X-Carve and there are actually no spacers on the x-carriage.v-wheels, my mistake. There are just washers (1mm I think) between the v-wheel and the x-carriage extrusion.
I calculate .1875" as 4.76mm so a 5mm bar means I need to use washers that are .3mm thinner than the current ones. I can’t get .7mm washers but I do have some .3mm ones. Two of those would give an error or .1mm (0.004" for the imperially inclined). Too much? I’ve been over this a while back, don’t know how I forgot about it. Oh that’s right, old age…
If I go with a 4mm bar then I need to add a .75mm spacer (washers) instead. Not sure if one way is better than the other.
I did look at the 40x40 extrusion from Makerstore, I can get 1 metre o that locally for a reasonable price, but I can’t get the Openrail locally. Getting the necessary 4 metres of Openrail shipped from the US would be about $US90.
I did the stiffening mod with a bar of 4mm steel. that 4mm steel is never 4mm because it has a rough surface.
It ended up PERFECT thickness, no extra padding or shimming required.
pretty good. I mean I didn’t measure it all around before the fix, but after sandwiching itin between the makeslides, it had a pretty consistent distance between V-profiles.
The carriage had a perfect travel smoothness as fas as I could tell.
Here are my results from today engraving aluminum. Not sure of the grade, as it was a drop from the local metal supply. The text was created in Inkscape and then imported in to Easel as a .svg. The depth was set to 0.001 in.
The estimated engrave time from Easel was 1 hr and 14 min and it probably took around that long, I didn’t time it. The piece was then cut out on the band saw and a hole drilled in it to finish it off. One tip I would add would be to check belt tightness. I had a problem with the x-axis slacking and once I got the belt tensioned properly, I had zero problems. I should also mention that I have the 500mm machine with zero stiffening mods or such.
0.001 in, there were a couple areas that it said it couldn’t carve, but they didn’t show up in red. It was probably in the text on the bottom, those letters are pretty tiny.
