Cheap 4th axis tear down and re-grinding
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- Опубликовано: 21 авг 2024
- I bought a cheap 4th axis from China, and combined it with a 1kW AC servo motor (also from China). The result is a super fast 4th axis, that can do precise positioning for 4-axis milling and indexing, and also reach 1000 RPM for turning operations. But how good is a $150 spindle mount? In this video I measure the run-out, and improve it by regrinding the mounting cone on the CNC mill.
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Very interesting analysis and repairs!
Love the ingenuity with the grinding!
Seeing the servo move back in forth leads me to believe the belt drive may be causing some of the tolerance issue.
that's a separate issue - the belt pulleys aren't perfectly centered either. The bearings are tight though, and I don't think that any wobble from the pulleys transfers to the axle. After re-grinding, it was almost perfect.
I have the 750w version of this motor, I'd love to see how you wired it up for step/dir control! I can't seem to get mine right but would love to have 3 of them on my CNC mill if I could figure it out. Subbed
The thing I worry about with these is rigidity; specifically in the belt drive. I think I’d be less concerned if it had a nice stiff cycloidial drive... also; I think I’d mount an encoder directly to the output of the drive for enhanced accuracy.
It's true that this setup is not going to be nearly as rigid as a proper rotary table with worm drive or harmonic drive. But with those, it wouldn't be able to go to 1000 RPM for turning. The idea was to keep things simple and cheap and do mill-turn operations. In plastic it's perfectly fine, and I also did some small pieces in aluminium. In combination with HSM and a 24kRPM spindle, the cutting forces are not that big and it copes reasonably well. Just don't compare it to a Hermle or something ;)
can you please share the exact links to the 4th axis and the AC servo or at least more specs? I would love to do the same. Thank you in advance
The spindle taper looked pretty good. Why couldn’t you just face off the front of the adapter plate?
Could have, but I guess it would have been a lot more grinding (bigger surface, more material to remove). Maybe it wasn't too clear in the video, but before grinding there was a few 1/100s on the taper and the face of the mounting cone, and after grinding it was essentially perfect (no visible movement of the 1/100 indicator). So it worked well. I didn't film enough footage of showing the final run-out...
@@codemakeshare What was the final runout?
Seems like with these cheap 4th axis and a AC servo you could build a pretty good rotary axis / CNC lathe.
Thanks for the video, very interesting to a newbie!
Would you be able to share the link to the 4th axis in this video?
whats the type and specs on the servo? nice vids, keep'em comming :-)
Hello do you have any idea what the bearing block is and are they available as a separate part? Seems they are using the same block on may arrangements though could not find details for the block itself..
no, unfortunately I don't... it's always very tricky to get any sort of documentation about AliExpress products.
The piece you need to take off is just screwed down
Very interested in the China servo motors-drives. Were you able to configure and tune the system using the Chinese docs? I have a conversion project and like the pricing of the China components, but I am shy that implementation might be lacking due to poor docs.
yeah, good point. I previously bought hybrid closed loop stepper servos for my Opti CNC machine, and those came with a fairly good english manual. But the AC servo on the 4th axis only came with a printed chinese manual. A friend of mine found an english PDF of a similar drive, and using both, I managed to make sense of it. The parameters seemed to be all the same, just the wiring was slightly different. The performance however is really awesome, and it was very affordable for what it can do. It's been a while ago, but maybe I can dig it up some day and try to write up the most important settings.
@@codemakeshare It would be awesome if you could make a video about the servo setup. There are no videos on RUclips that cover it.
@@codemakeshare Yes that will be really awesome. we are waiting patiently. kind regards from germany
can you share the aliexpress url? that you bought it.
Hello! Can this 4th axis be used to work with steel at a bigger machine?
Not sure, haven't tried yet. I've used it for aluminium and brass, and that works particularly well with my 24 kRPM high speed spindle (low tool pressure). In steel, the flex of the belt drive is probably too much, and steel likes lower cutting speed and higher tool pressure. Maybe small pieces of mild steel, with small cutters, might be ok, but it's certainly not going to hog into tool steel.
may I know where did you buy the timing belt and the pulleys ??
it all came as a complete set from AliExpress (search for CNC 4th axis or similar - this is the NEMA34 version)
@@codemakeshare ohhh thank you so much ! Good job