4th axis on RAMBO using motor extensions

[Legolor (Caleb)]

Thank you for the quick reply!

@jeffeb3

Ryan and others are saying that it isn’t easy when you are already using all 5 internal drivers. “dual endstop” is what we call the firmware that uses 5 motors and dual endstops for auto squaring. The serial firmware uses only 3 motors, and endstops are pretty pointless, since they don’t do any squaring.

Yeah, I am running 5 motors and I use the “dual endstops” for homing/squaring. I was a bit confused especially by this comment just about if it was in fact possible to keep my current setup while adding a motor extension.

@jeffeb3

I don’t think any of the pins are shared. There are some non-obvious limitations. For example, the step pin may need to be a PWM capable pin, for example.

I see, these are the sort of things that I was worried about and keep me up at night . I’m hoping that the dedicated motor extension pins on the RAMBO 1.4a were well designed and will work.

1. Thank you. I will look more into the firmware side. I’m not too familiar with Marlin and I’m a little nervous to reflash my board when the time comes. Besides mapping pins and defining an A axis is there anything else that I really need to do? What file would I edit to add an option to manual move the new axis from my LCD display?
2. Yeah I was thinking using other unused pins as worst case thing, I could even drop the enable pin on the stepper I think if I need. Is there any reason why I would need to scavenge for pins or unplug the LCD though? The motor extensions should work?
3. I have been working on CAM since that seems to be the slightly harder part. So far I have done the schorchworks method, I have also made my own method using blender and fusion (without the expensive 4-axis machining extension) for more complicated objects like what my picture in post #1 shows. I also want to try to use HSMworks in solidworks. I hope to put out an instructable or something showing these methods off.
   These methods are still mainly focused 3-axis gcode but remapped to the rotary axis. I hope that I can either manually add rotational 4th axis commands into the gcode or get hsmworks running. To be honest I mainly want to enable the 4th axis just to not have to switch the pins each time I want to change from conventional 3-axis to rotary 3-axis. It would also be nice to have the y-axis motors engaged during cutting so they don’t move around (currently I have to unplug them).

@jeffeb3

Don’t forget to tune the current limiting potentiometer on your a4498. They aren’t tuned at the factory.

Haha I have burnt out 4 of these already. Good thing they’re cheap!

I am still mainly surprised at the lack of documentation and user posts about these MX pins on the RAMBO. It makes me think something may be wrong Any more thoughts or concerns would be greatly appreciated!