Recently I am working on a CNC conversion for a Grizzly G0602 lathe.
It is currently a bit tacky (ex: the mounting hardware for the stepper motors is made out of wood).
Probably one of the worse CNC conversions around, but basically works.
Don't currently have any suitable pieces of aluminum, the plan is eventually to redo these parts in aluminum.
Some other people seem to have gone far more elaborate (such as replacing the leadscrews, ...), but for now I am being conservative and wanted to preferably avoid any irreversible permanent modifications (also, trying to do things on a budget where possible).
A little bit of it can be seen here:
And, previously:
Since then, I switched to a smaller piece of tool steel for testing and set the compound to ~ 7 degrees, so slightly less absurd now. I have some lathe tools with inserts, but inserts break easily and I still don't entirely trust this setup. I was also testing with a piece of metal which was already basically ruined.
I also changed some other small things, like now sampling RPM off the spindle (as opposed to the black plastic gear). This is basically done via a small cardboard holder with an IR LED and a photodiode, with reflective areas bouncing light from the LED to the photodiode. Internally, there is a divider, and parts are strategically blackened with a sharpie to limit internal reflection. ( Though I have since discovered that blue Dykem apparently absorbs more IR than sharpie ink does. ).
Control is via a Raspberry Pi 2, with CNC control software that is custom written (still implementing features and debugging it).
The control program is written in C, currently does basic stuff (G0 and G1 moves, homing, work offsets, ...).
G2 and G3 modes don't work correctly yet, nor are any canned cycles implemented.
Some things are planned to be somewhat redesigned, but I haven't gotten around to it.
A also plan to mount a secondary (largish NEMA34 stepper, 1805 oz-in 8.8A/ph) motor to use as an indexing-capable C axis, but this will probably need to wait until after I can start redoing parts in aluminum (bought the motor and driver already).
However, the AC induction motor would be kept for things like turning and similar.
A stepper isn't really an ideal choice for turning (lots of torque but not a lot of RPM).
Despite my efforts (reading and comparing stuff online, ...), the stepper wasn't nearly as fast as I had originally hoped.
Decided to get a big stepper mostly because a 1kW BLDC Servo (or similar) would have cost almost as much as the lathe itself.
The stepper was, in comparison, significantly cheaper, and many things I want to do would need indexing.
Previously, also did a CNC conversion of a G0704, but used a FlashCut kit for this.
Ended up needing to use external motor drivers as the internal drivers in the box provided with the kit were a a bit "weak" and kept losing steps (and its power brick ran disturbingly hot). After switching to external motor drivers, there was seemingly more torque (with the motors also running cooler and quieter), and the step-loss issue went away.
The result of some of this experience was that I decided to go full custom on the lathe, since it didn't really seem like a huge step up on the complexity front (and also I could do it a lot cheaper by using a RasPi).
Update, made an adapter plate and mounted the alternate spindle motor (an 1805 oz-in NEMA34):
Adapter plate is 1/8" steel (from a piece of 2x4 steel tubing), and the pulley was salvaged off an old car alternator. Had to make another adapter to extend the motor shaft and also connect from the 1/2" of the motor shaft to the ~ 11/16" of the pulley. Held on with a 3/4" nut, as I don't have an 11/16-20 die, and didn't want to turn the end-section down to 5/8 to use a 5/8" nut. The threads are a little flat, but "good enough".
I am not sure what alloy the tubing wall is made of (it is harder than mild steel but softer than 4140, and rusts readily; probably a carbon steel of some sort). Had sanded and spray-painted it to limit the spread of rustiness.
It is capable of indexing to positions (C axis), as well as spinning as a spindle (using M3/M4/M5).
Motor is currently set at 5.5A and is wired as bipolar-parallel.
Maximum RPM's achieved are ~ 400-500 (~ 800-1000 on the motor), but speeds over around 300 RPM are fairly unstable (unable to turn steel and motor is prone to stall). It is capable of turning steel at 200-250 RPM, and has a lot more torque at low RPMs. It is geared down mostly as its main purpose is more for indexing than for turning (I still have the main AC motor for turning).
I am well aware that a BLDC Servo or similar would be better for this (or a 3-phase induction motor + VFD for variable-speed turning), but these were a lot more expensive than a stepper.
New here, G0602 Lathe CNC Conversion
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