Couple questions from CNC beginner

Hi there, I just finished putting the Altmill 4x4 together. I’m new to CNC and just have a few questions to get to know this machine better.

  1. I was expecting physical limit switches on both ends of each axis to prevent crashes - am I right in assuming that the closed-loop stepper controllers act as a limit switch here? In other words - in case of an error the machine would “crash” in to the rubber bumpers and trigger a stepper controller error when it can’t move any further? What about the Z axis (no rubber stops)? (I understand that homing on startup and correct max travel in firmware settings should usually prevent this)

  2. In the video tutorials, G-Sender’s firmware tool has descriptive names for all the $ settings (at least the ones they show in the video). But when I tried to change my default spindle, my $395 setting, and all the $ settings after 133 are all just called “Custom EEPROM field”. I did select Altmill 4x4 + Spindle as my profile. Could this be a bug? The spindle works but I’d like to really get to know this software and how it works.

The altmill has physical limit switches but I can not recall having seen a CNC setup where these switches actually directly interact with the motors/power in order to prevent an actual crash. They talk to the controller and it is the controller that acts on that input.
There are many scenarios where the controller raises an error condition and shuts down the motors. Hitting an obstruction (such as a bumper or maybe a fixture clamp) is one reason.
The physical zero position is slightly off from the rubber bumper. If everything works as it should, the rubber bumper would never be bumped. Alas, crap happens and that is why you have a bumper.
The z axis has the limit switch but you are right, there are no bumpers. Guessing on the reason, I would say the axis has very little mass and is relatively slow speed so a bumper would likely not be needed.
Regarding the second question - yes, it’s annoying that a field is labelled ‘custom eeprom field’. I wouldn’t call it a bug, it is done on purpose for some unknown reason. There might be documentation available for these entries but I am not aware of anything - ask Sienci tech support and maybe they can help or explain why there isn’t a better field description.

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Hello @and.kt and welcome to the group!

I can only chime in on part of question 1 as I own a LongMill without the SuperLongBoard.

That is why only one switch per axis is needed. Once the machine is homed it knows where zero is and that it can’t go beyond the max travel for that axis. Of course my machine does not have closed loop steppers so if something caused me to lose steps then my machine could still crash. That shouldn’t be a problem for you with the closed loop steppers on the AltMill.

Be safe, the AltMill is a beast compared to the little 3018 that I made my beginner mistakes on. Now I only have to worry about non-beginner mistakes. :zany_face:

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Thanks for your reply

You need to connect using the grblHAL firmware, not grbl. I can see in your screenshot you are using the wrong controller. That is why you don’t have proper descriptions. It’s not a bug, just user error.

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Perfect! Thanks for your help