I'm ready to give up on machining aluminum kinda.... maybe?

I am trying to carefully word this. I mean no offense Just trying to establish realistic expectations on both sides. A large MPCNC machine can do what you are asking by all means…but you absolutely need to have perfect CAM to make that work. I am serious, absolutely perfect, not just picking random numbers and checking you will need to dial in everything. Your starting point is the numbers I suggested earlier. A 12"x12" machine is simple in comparison to run.

To put his in perspective Tormach does not even make a machine remotely clost to that envelope. starting at $19,000 and closer to high $20k you get, 11"x18". So yes, it is going to take some endmills to get dialed in, it would on that machine as well.

Is it 24" wide? If not do not make the machine that wide. Is it impossible, no, Barry machined aluminum on a machine with a 4’x4’ foot print, but not 0.5" deep.

My machine has a work area of about 12x7.5" (90 sq/in), you are trying to use 24x36 (864 sq/in). See the difference now?

My numbers will not work for sure. You are also using spindles few people around here use so we do not have much to go on here, but we are trying.

Not sure what this means, the minimum is about 3.25". If you are saying there is a 3/4" gap to the top of the material get rid of that. Start it as absolutely close to the gantry you can get. The machine basically doubles in rigidity each time you half the Z axis sickout length. 2" vs1", 1"vs 1/2" etc…3/4" is huge, especially in the giant machine you have.

It should not have any effect on price other than time. It will work without it you just need to have more perfect CAM settings. Just trying to get you going. Slotting is by far the hardest operation you can do with a CNC machine.

Work on one issue at a time. get the first pass as perfect as you can after that depth of cut comes into play and I suspect your spindle is out of tram. A crooked spindle will take progressively more uneven cuts as the sickout increases.

The 800W you have is probably the best bet as I can only imagine the 1.6kw one you have is significantly heavier and will only add to the issues you are having. Putting a V10 in a Honda Civic will actually make the car worse if that analogy helps. Power, size, weight are all balanced on this machine.

Some pictures of you build will help, and please tell me you have wood and plastic mastered and cutting perfectly? Wood meaning no scorch marks and very smooth surface finishes and plastic the same thing.

20" is the width of that current part.

3/4 is the travel I have from the top of the waste board, to when the z tubes are just about to come out of the lower bearings

My issue is consistency. I can cut an entire part with no issues, no chatter, clean cuts, take those “dialed in” settings to cut the next part and ibreak 5 bits on it.

I’ve trammed the spindle to the best of my ability. Im not sure at this point how to make it any better.

I will reduce the build area width and swe if thst makes a difference

If that is the case, look for cords or anything binding up a bit. The thing CNC’s do best is repeatability so now you are looking for outside influences. Loose work holding, hanging wires, dull bits, etc.

That’s why I’ve bought so much from you. I believe in the design. Just not sure what is going on

This cut fine, first try. No chatter, no issues. Tried to do the 2nd one and broke 4 bits and ruined my stock

You can see why I’m frustrated. It works 10% of the time for me for some reason.


Ok i took 11in out of the y axis.
I also welded 1/2in nuts to the tops of the support tubes and put a bolt up from the bottom of the table. Im hoping it helps with vibration in the gantry

I’ll see what happens after I rebuild it all

Your part looks great. It sounds like you are one variable away from success, which is pretty impressive.

I’ve been going through the same issues, but I’m using a LowRider so I have nothing to blame but myself. A part will cut beautifully for a while and then it will get the tiniest vibration in one little spot, and after a few more passes the little vibration turns into the bit burying itself. A little extra friction in one spot leads to heat in that spot leads to the metal softening and the end mill getting clogged. I do find that if I pause when things are getting sketch and let everything cool I can recover.

I wish you success!


Makes me wonder if it is as simple as adding some air. Something like this, https://amzn.to/38s2kuE. Not for coolant just air, get the chips out and keep it cool…

I have no idea why your user name never connects for me but you have cut tons and tons of aluminum. It has to be something stupid simple we are not thinking about. You do cut large pieces, and have had tons of success. To give an example The two different single flutes I carry, in MDF, one lasts hours on hours, the other goes dull in about 45 minutes. Temp differences when you are cutting, humidity…it is something small, and simple. Check your Grub screws.

I know, I guess I always get the same questions that I have to answer again. Its not like this is the first time with alum, just the first time on the new machine.

I have i back together. Im cutting the spoilboard again then I’ll try to tram the spindle…again…

This is where my spindle sits now in relation to the board. About 1" of usable cut depth which is all I need for aluminum so far. If I need more I can remove a spolboard layer.

I’m actually questioning my spindle right now. The 1.6 I have is the same weight so I’m going to swap it on and see. It almost looks like the shift is bent

Dam, from a Burly to a Primo it should be significantly easier. On all fronts, more square, more tram (easier to do so)…and a fresh build is always stronger, faster easier cutting. And shortest possible legs means good rigidity.

I hesitate to say this but make sure the tension bolts are tight enough…but if they are more than snug don’t bother.

Checking the spindle shaft is not easy without a dial indicator, but even a crappy one will work. Harbor Freight nearby?

Z axis straight and parallel not twisted or different distances apart top and bottom?

At this point something has to be overlooked.

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Are the circle you were cutting round? How accurate are they.

Pretty spot on. Within .01mm

If that is the case in all directions and to your specs that means you have very little run out and your machine is spot on. That leaves dull bit or add some air, or random stuff like hoses or cords snagging and pulling, leaning on the rails, whatever else there could be.

Same exact size as your burly build?

Watching that video it looks like you are using conventional milling. For aluminum I seem to remember reading a long time ago that Climb was recommended.

Conventional milling vs Climb milling.

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It was. I took 11in off the y axis today.

I put the other spindle on it. Theyre the same weight.

Climb vs conventional doesnt really apply to contour paths since it cuts both as it cuts.

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The pros where I work tell me 6000rpm 3 flute but, I can’t adjust rpm right now so I’m doing 24k with a single flute. Making pretty good progress.

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Wait, you don’t use an air blower to evacuate your chips (I don’t see any on your video, you’re recutting your chips again and again) ?
That’s really not optional, you need to add an air outlet blowing directly in the path of your bit. Evacuating the chips continuously is one of the most important things, especially the deeper you go.

So I’d start with this.

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Is anything holding your work down? It doesn’t look like you have anything securing the aluminum in your video.

Oh! It looks like you might have tape down. If that’s the case is it possible that the tape is just not doing the job? This would also make sense if you are using the same method to secure your work on both machines. If there is even a small amount of play that bit may grab and lift the plate. That’s a lot of weight on that tiny bit. This may be the cause of broken bits. :man_shrugging: Just spit balling.