I use GRBL on a Uno for my X axis power feed. Also has a Bluetooth interface and is controlled by GRBL Controller from my phone.

https://www.model-engineer.co.uk/albums/member_album.asp?a=53829

4 axis arduino project

This isn't "4 axis" as such – the board allows cloning of one of the axes for gantry machines and, while the "4th axis" step & direction outputs can be brought out separately, it is noted that GRBL can only control 3 axes. The GRBL developer has said that a 4 axis version of GRBL won't fit on an Arduino Uno due to lack of memory. Protoneer also has a version that fits to a Raspberry Pi, giving a "stand alone" controller where the Pi replaces the PC.

There is a branch of GRBL for the Mega 2560 board here though this too is 3 axis.

A true 5/6 axis capable branch that runs on the Mega is available here though I have been unable to compile this – I get something that reports as GRBL1.1P onto the 2560, but it doesn't appear to have compiled as 5/6/ axis, just 3 when I check the parameters. I think this may be due to having previously compiled the 3 axis Uno version of GRBL on the same laptop – during compiling of the %x version in "verbose" mode I get references to using "previously compiled" modules. Not investigated further yet, though.

Grbl Gru is supposed capable of driving either the 3 or 5 axis versions of GRBL. Universal Gcode Sender will apparently send 4/5 axis commands to the Mega-5X version, though it can only display 3 axes.

Another Arduino option would appear to be through Estlcam, which I was unaware of until it was mentioned in the thread about Joe Noci's CNC lathe. The CNC part of Estlcam is not charged for & will work without limitation independently of the chargeable CAM part.

nema17 with a 100/1 gearbox

Will see if it has enough grunt to move a lathe or shaper or mill table

I would guess that speed will be your main issue. GRBL will output pulses upto 30KHz. Assuming 800 steps/rev, your motor will require 800 x 100 pulses per output shaft revolution = 80,000 pulses per rev. I make that 22.5 revs per minute at the output shaft at 30KHz – so a low feedrate when attached to a leadscrew. Going to full steps( 200 steps / rev) would up that to 90 rpm, but even with a 5mm pitch screw that is only 450 mm / min. Always assuming that your motor will provide meaningful torque at 30KHz ?

Nigel B.

Thanks for that, Ronald … I was not aware of bCNC, but have found several videos that look quite useful:

**LINK**

https://www.youtube.com/channel/UC6duiWL-qeoP1a7QbmSbpDw/videos

MichaelG.

I have both Universal Gcode Sender and bCNC available to use on the Raspberry Pi but use bCNC because it will show the toolpath. UGS would show it too on a more powerful computer.

You may have noticed that I have not completed the power connection to the Raspberry Pi yet but that will be done soon using the buck converter mounted on the board near the power supply to drop the 24 volts to the 5 volts that the Pi needs. My connection that I use now does not supply enough current to the Pi.

I also have a Arduino Mega 2560 set up with Marlin instead of GRBL but I haven't taken the time to do more than verify that it will turn the stepper motors with the commands.

If you connect power to the A4988 without the motor attached it instantly burns out the A4988. It took burning out 3 of them before I found the information on that. It was documented but not real well.

Right! Not the A4988 then. In my mill power feed I use a DRV8825 on a Pololu carrier board. This is a much more up to date driver with better performance than the 4988 and is happy for the ref voltage to be adjusted without the motor connected –

**LINK**

I've also used the 8834 which is useful for low power motors and low voltages – will run happily on 5V, use two in my Arduinome clock, one for the gravity arm reset and the other for the dial.

If you think GRBL is complicated you should try Mach 3! I got GRBL driving a simple stepper from a UNO very quickly from the serial monitor, the main complication was interfacing to GRBL Controller on my phone via Bluetooth.

GRBL would be interesting for a lathe except that it lacks threading, and a G Code sender adapted for lathe work (as far as I know). A UNO or similar running GRBL is similar in concept to a motion control board, so it ought to be possible to interface say Mach 3 to it if there was a suitable plugin.

As I think more about it I may have been leading you and others astray. I had used a CNC driver board monuted atop my Arduino Uno and had the higher voltage hooked to it for that. Thinking it would be better for the stepper motor driver module I tried to adjust the reference voltage to set the maximum current without the stepper motor hooked up. That was the mistake. That was a year ago and I'm not certain which stepper motor driver I fried. I may have fried both the A4988 and the DRV8825 trying that. I wish the person who wrote the instruction that mentioned not to do that had made it in bold and bright red. One sentence in a page that mentioned not to do that.

I can definitely say that neither the 8825 or 8834 mind having the reference voltage adjusted without the stepper connected. What is NOT a good idea is connecting or disconnecting the motor when the unit is powered up!

I'll chip in my setup…

Proxxon MF70 with home made stepper mounts and NEMA 17 motors

Arduino Mega 2560 running Marlin with Protoneer (ish) CNC shield carrying A4988 stepper drivers

Universal G Code Sender from a branch with Marlin support

G Code either done manually or using dxf2gcode

The NEMA 17s drive through flexi couplings to cups which fit over the handwheels. I think the flexi couplings are important for avoiding missed steps with NEMA 17s. Other folks have resorted to NEMA 23s.

I wanted hacklash compensation which sent me down the Mega route. GRBL on the Mega can do backlash compensation but can't be configured to drive the IO pin permutation required by the CNC shield. Marlin can. It's a bit odd for milling but it does the job.

Dxf2gcode is OK for profiling around 2d shapes but lacks sophistication beyond that. The main branch lacks pocket milling capability but there is an experimental branch for this (which I have not tried).

There is some interesting looking newer stuff around that can use for example the Teensy board instead of Arduino. I haven't got past reading about it yet because basically my setup does what I need most of the time, the occasional shortfall being mainly in the CAM department rather than the CNC controller.

Regards, Andy