I think that’s going to solve your problem. With the zip ties you have to pull that belt REALLY tight to stretch the zip tie loops enough to prevent them from moving under load - if they’re not flexing when you move the gantry then the belt is probably pulled WAY too tight. Pluck one of the belts… if it sounds like a guitar string then it’s way way way too tight. If it sounds like a bass string tuned down a step or two then it’s closer to where it should be.
I think you’re right - but I never had a successful cut in metal with zip ties. It’s moot really - you solved that problem in the primo. honestly that’s a big reason I’m upgrading.
The zip ties can be pretty rigid if you keep the loop short. At least one end should be a tight loop.
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That was likely my problem - the loop being too long.
Cutting force is not the issue here, it seems to be vibration induced.
Cam pathing .014 depth 300mm/min. Spindle around 20k rpms
I’ve gone down to 50mm/min and up to 700. No change in the vibration behavior.
I’ve gone down to 10k rpms and up to 24k rpms. No change in vibration behavior.
As you can see in this video, that movement is from 1 finger.
I’ve watched your vids on aluminum. I cant come close to speeds or depths that you show. I’ve tried cutting with a 1/16 endmill down to .05mm depth cut and it does 1 pass then vibrates into oblivion.
I’m not trying to be argumentative here, but I should be able to cut deeper than .14mm/pass without the bit eventually playing ping pong and destroying itself. Ive even gone so far as to do 2 roughing cuts to open the channel up wider if it does do thst. It didn’t work.
I’ve added multiple air nozzles thinking it was chips, and have added oil to the mix as well.
one is all the way tight. The other is about 1/2in if that.
Nether am I. Something else is wrong as I am saying. My videos are a bone stock as recommended build. should be achievable for anyone with a build my size or smaller very easily. This is exactly why I am not easily letting this go.
Your video looks to be fine, if the belts are moving perhaps you over tightened them and broke the fibers.
Also, as it says in the milling basics, there is such a things as too small a bite. 0.3mm DOC is very small and you could be work hardening your material, or just have a dead cutter from only using a single surface.
I would let this go if you were close to my build size and close to my speeds and depth of cut but you are not even close to being near the ballpark. Trust me, something else is wrong. As designed you should be able to achieve anything in my videos worst case, at least get close.
Why don’t you show a full build picture and some close ups of your zip ties. (your tension on the belts is the most worrisome for me as the fibers can be broken). They should not make a sound when plucked.
Well the whole point in the 2nd machine is to start fresh and not worry about these issues, which Is why I haven’t really tried to fix it at all.
I’ve tried to cut deeper, turns into immediate bit breakage
Single flute made for aluminum 1/8" upcut, new, bits?
Well this escalated quickly 
I kid… I think we are all trying to get to the bottom of the issue.
One other problem that I found I had was play in the Z axis - I didn’t have the tension bolts tight enough to keep the spindle perpendicular during cuts - when you hit the material at an angle you’re back to changing the amount of material that’s contacting your cutting edge, thus changing your optimal spindle speed and feed rates - this is why the first pass goes fine and the following passes end catastrophically. There isn’t much you can do except stop the cuts - sometimes a speed or feed rate adjustment can even it out but eventually it’s going to go south as successive passes magnify the problem. Something is out of square, or being pushed out of square during the cut. Wether that’s a belt problem or insufficient bearing to rail contact somewhere, I dunno.
first thought, is problems with the bit. If your using 1/8" you should be using a single flute. If you are, then after trying a short cut, stop and remove bit and look closely at the end, if you see any aluminum fixed on the end. then you know it is work harding. Caused by dull bit. Or Your bit ‘skating’. This can be caused if your Z axis is out of tram or perhaps a little loose . As for the belt tightness. I made the mistake of moving the tool and watching the belts, thinking that they were to loose. Try thinking the other way. Watch the tool and flex the belt. The tool will not move enough to see. The cutting forces are not nearly as high as pushing with a finger on the tool.
I relaxed the pressure on my belts and cuts were much better. Just my two cents, been there often myself
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I’m using 3 flutes because I have a spindle with a VFD. I run it somewhere around 12000rpms for aluminum.
I tried a single flute and the vibration was much worse.
If i flex the belts, the tool will indeed move.
Its not a matter of the first pass being ok, or the end pass not. If I try to cut beyond .14mm on the first pass, it’ll happen right away. You can watch the spindle start bouncing around in the cut.
All new bits. I bought a box of 30.
We run at about 20K and a two flute is far too much. At 10k you might get away with a two flute but slowing down with a single flute is still probably best. I suggest trying again with a single flute and letting us help you get dialed in. An 1/8" three flute does not have large enough flutes to clear a large enough chip to take the heat away with it. A three flute has to turn at 1/3 the speed of a single flute…and usually needs flood coolant to help wash away the chips and keep it cool. A single flute gets large chips out in less than a full revolution so heat and chip re-cutting should not be an issue.
Another way to think of it is at the same RPM a three flute cutter has 3x the cutting forces actually “flexing” the belts more. All depending on your perspective and constant variables. Most small motors do not have enough torque at low speeds to run a 2/3/4 flute. Another perspective is a three flute needs to have 3X the feedrate to keep it fed and we operate slow feedrate machines.
When I make the same cuts with a 2 or single flute, it vibrates more with each flute removed.
I will say that I updated from the zip ties to the belt adjusters and I’m cutting 2x faster with wood than I was before. Even with wood I would get a noticeable vibration at the spindle. Maybe this was the issue.
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There have been many times that I’ve found reducing spindle speed helped smooth out my cuts. It’s counter intuitive - when things start going sideways the instinct is “more power!” When actually a less aggressive approach is in order. Glad the mods helped! I’ve had more success with single flute small diameter bits (significantly less velocity at the cutting surface) than with large multi-flute bits. It’s actually been more of a problem for me to get the spindle slow enough than the other way around.
What I found was the sslower I made the spindle speed, the worse the issue got. I don’t think it had to do with that though, I think there was another issue going on. I won’t know about aluminum for a while though I have 2 projects to get through this weekend first.
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I’ve heard that chatter is often just hitting the harmonic frequency a lot of times so higher or lower can sometimes fix it. In practice, I haven’t been able to really see that. But I don’t cut aluminum.
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I think it has something to do with the mini rambo board. It slows down and gets choppy when doing a curve or a circle. The new machine I’m building with the SKR board with the same Gcode does not do this. I’m thinking that stuttering behavior is causing the spindle to bounce between the walls of the cut
It may be having trouble computing the arcs. There are some versions of the firmware that have trouble. Around the 415 version mark.
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I turned off arcs on both gcodes per the recommendation. I haven’t updated the firmware on it in a while though.