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Topic: GRBL - how many stepper motors? (Read 231 times) previous topic - next topic

Robin2

I'm only asking this because I know there are a few people here who are familiar with GRBL.

My impression is that Grbl can only handle X Y and Z motors and cannot operate a separate 4th axis. The PCB that came with my CNC mill only has space for 3 stepper drivers and I think the same is true of the CNC shield. I have a Ramps shield for a Mega which does have space for 4 drivers.

Having found some simple software called DeskProto that can generate GCode for a 4-axis system I'm toying with adding a 4th axis to the CNC 3018 mill that I have for a year and have hardly ever used.

Assuming Grbl cannot control a 4th axis I believe, from some YouTube videos that Marlin can - as it is designed to operate X, Y Z and an extruder. However it seems that GCode for Grbl does not work properly with Marlin and therefore it would be nice to discover that Grbl can, in fact, control a 4th independent motor.

...R

PS ... while the multi-axis version of DeskProto costs money you can use it for free as long as you like if you don't object to it engraving a watermark on your project.

Two or three hours spent thinking and reading documentation solves most programming problems.

zwieblum

GRBL for Stm32 can handle 6 steppers regularly, 8 stepers if you sacrifice ISP. GRBL-mega can do 6 axis, too (ar least the copy I have here). but if you want to go beyond playing, use linuxcnc.

ballscrewbob

#2
Sep 17, 2020, 10:49 pm Last Edit: Sep 17, 2020, 10:50 pm by ballscrewbob
Most of the Arduino UNO based approaches can use a 4th axis but that is often just a mirror of another axis.
Mostly used for rotary type work.

Avoid grbl on a MEGA as the development has almost stopped in favour of the STM boards.
My ramps board has space for 6 drivers but 4 were enough for a 3d printer with a shared Z axis.


It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google (who would have thunk it ! ) or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

Robin2

My ramps board has space for 6 drivers but 4 were enough for a 3d printer with a shared Z axis.
I don't want a duplicate 4th motor, I want it completely independent of the other 3.

So I guess GRBL (on an Uno or Mega) is ruled out.

Thanks.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

zwieblum

Get a Stm32 BluePill, I can send you the code if you don't find it online.

Robin2

Get a Stm32 BluePill, I can send you the code if you don't find it online.
Not at this stage.

I want to build this as cheaply as possible with stuff I already have. This is something I might build and only use once or twice.

If I get really enthusiastic and if I find the Mega does not perform well enough then I might consider an STM32.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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