Engraving works fine so far. But as soon as I try to cut trough the wood (12mm Multiplex/plywood) the spindle starts rumbeling after some time and I have to stop the machine. It seems that the spindle gets shifted (and than tries to cut too much material at once).
I was able to cut a small rectangle, but with a heart it always fails.
I already tried:
Tightening the grub screws + Belts
Tightening the screws from the core (was a little loose)
Increasing the stepper voltage (before it was 0,63, but seems that 0,68-0,72 doesn`t help)
Do you’re trying to cut 1.5mm depth at 500mm/min?
That’s pretty slow. How big is your machine? What endmills are you using?
I cut 3.25mm depth at 1800mm/min. That works very well with the 1/8" single flutes that Ryan sells in the V1 shop.
By the stepper voltage, I assume you mean the vRef on the stepper drivers. That actually should be setting current. For most drivers, 0.7V is close to 1.4A. How warm do your motors get?
12mm depth of cut with a 1.5mm bit? Unless you are stepping down on that, it is way too much for the bit to handle on plywood. If your model can afford the extra radius, maybe use a larger bit. Alternatively you can rough with a larger bit, do a tool change and finish any corners with a smaller bit.
Cutting the whole 12mm all at once, yeah, you’re SO much better off doing that in multiple passes. That’s the beauty of a CNC is that it can absolutely repeat the same path more than once. Reduce the depth of cut so that you’re doing it in many passes, and you’ll find that you can move faster, too. As I said above, with my 1/8" single flute, I’m cutting down by 3.25mm each pass (So a bit over 1/8") which means 4 passes to get through 12mm (or 1/2") plywood.
Yes, this is one of the important things to learn about Cnc work. You will find a lot of good advice on stepovers and feed rates, but the depth of cut will be very dependent on the machine itself. Even among mpcnc builds, some can handle more doc than others all other things equal. On a new mpcnc a safe doc to start with would be around the diameter of your tool. So for a 1.5mm bit, start with a 1.5mm step down. Once you have stepover and feed rates good, then try going deeper until it starts to get ugly.
First of all, thank you for all the replys.
So “d” means diameter and the overall depth is 12 mm. The “Z+”… is the depth with each step (I took the naming from Estlcam).
So I took 0.2 mm with each step and after the 4th-6th round the spindle starts rumbeling around.
I also had the same issue with a 2 mm bit.
Build volume is 600 x 300 mm, Motor temp I haven`t checked so far.
600X300mm is a reasonable sized machine. You shouldn’t be having rigidity issues with that, even if you’re using EMT conduit.
So maybe it’s the spindle? Many of the Chinese spindles have a lot of runout, which will cause trouble. Several are also underpowered which doesn’t make things better either. I have a 3018 with a Chinese spindle that can’t be convinced to cut through wood, even though the machine is otherwise good. It does engraving just fine, and can do PCBs though, which is all I ask of it.
I suspect the spindle or the spindle mount may be loose. But it is really hard to tell from here. 0.2mm is very thin in wood. If you are having trouble going deeper in one pass, then something is wrong. And then when you are 11mm deep, one teeny tiny mistake will take a big bite and you’re cutting at 11mm instead of 0.2mm.
Are the bits meant for cnc? Or maybe they are dull? The ones from the V1 shop are good for a reference to know if a bit is really wrong.
I choose the China spindle to have less noise. Normally I would say it is running smooth.
I also have a Dremel 4300 here which I could use to check if it is the spindle, but that one is really loud.
I think I can also try to cut deeper with a larger bit.
I brought the " VHM-Fräser-Set Uncle Phil approved 1" kit from Sorotec.
Bits Included:
1 x 1,0 mm Diamantverzahnt Best. Nr. LDV.0100
1 x 1,5 mm Diamantverzahnt Best. Nr: LDV.0150
1 x 2,0 mm Diamantverzahnt Best. Nr: LDV.0200
1 x 2,5 mm Diamantverzahnt Best. Nr: LDV.0250
1 x 3,0 mm Diamantverzahnt Best. Nr. LDV.0300
1 x 3,0 mm Einschneider Best. Nr: L1S.0300
1 x 3,0 mm Zweischneider Best. Nr: L2S.0300
1 x 3,0 mm Zweischneider ALU Best. Nr: L2SA.0300
1 x Frässtichel 90° Best. Nr: LGS.0090
1 x Gravierstichel 60° 0,3 mm Best. Nr: LGS.3175.60.03
Could it be stepper drivers overheating and switching off momentarily? That’s what I think is what made my first runs very bad. Makes the whole thing a bit sour - “skipping steps” --> more current --> more heat --> more problems. And it’s intermittent as change in room temperature and/or any occasional breeze would affect it if it’s on the brink.
Seems that I am not allowed to upload pictures as a New Member here…
So the Setup is on the Balcony right now and will be moved to the cellar at some point.
I also have some original stepper drivers from my 3D Printer here. (A4988- They should also work with the NEMA17 Motor) So maybe I will give them a try.
In my experience, over temp results in 30s or so of off. You may have been fighting something else, like intermittent wiring or contacts coming loose when they heated up.
As others said, it sounds like runout or maybe tramming. If the spindle is not well trimmed to the cutting surface than each pass could ad more load on the bit and cause issues as well.