I feel like something isn’t quite right with my Z axis values. With my SKR I got from Ryan when I home my LR3 it thinks its at z =200. Without disabling soft travel limits I am only able to go down to 100. Are these two values stored in the LR firmware or is it possible to change the soft limit or Z value after homing with a g code command? I am also curious why these values are the starting point? For me after homing Z should be around 300.
I’m not a Lowrider owner, so I’m confused by why you are the first post that has complained about this issue. I’m sure I’m missing something. Is your build taller than the default?
You can reset the Z to anything you want by executing G92. So, you can send:
G92 Z300
And the current Z position of the router becomes 300.
As for the 200, it appears to be set in configuration.h around line 1700:
#define Z_MAX_POS 200
Modify this define to whatever height you want for your Z.
Note that softstops are almost useless for the way most people use their machines.
The Z=200 is not a big deal. You want to set the Z=0 based on your work piece and bit.
The LR3 firmware homes up, and it sets a value of 200 (which is wrong for every machine).
But the Z probe will look for the touch plate as it goes down. You will need a short script to use G38.2 and G92 to set the Z based off of your bit and your work piece.
The scripts are talked about often here, and I don’t have it handy. I believe it is also in the shop page for the touch plate and the docs.
I believe the Z=200 is a legacy from the community developed firmware from the LR2. I know with my LR2 the 200 value happened to be pretty close to right.
For my firmware, I changed it to 128mm, which is right for my machine. 78 is probably close for an as-designed LR3.
However, that value is next to meaningless the instant that you put material underneath the tool. Well, unless you have a bit setter and zero off of the spoil board. If you are doing that, its a small amount of extra work to recompile the firmware with the correct Z offset.
It could home Z upwards and set it to 0, but I think Marlin limits the Z travel to whatever you define the max as, so 200 is a value that guarantees that you will get to the Z switches.
I think I figured out why I was so confused. I believe I have the wrong screw on my Z. I’m not used to thinking in mm and didn’t put it together that 300 mm couldn’t possibly be the correct number for z travel. My screw is 2mm per rev rather than the recommended 8mm per rev. If I switched to the correct screw then I think all the default numbers would match up much better.
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There are Lowriders built with the 1-start lead screws (2mm per turn). It helps with the Z axis dropping when the steppers are powered off, and it supplies more Z torque. The downside is that the maximum Z feedrate is lower (roughly 4X).
If you have not already, you do need to adjust the steps per mm for the Z axis. It can be done from the display, from g-code, and directly in the firmware. If you’ve previously used the display or g-code to adjust the steps per mm, then direct firmware changes of this setting are ignored. This behavior is so that settings are not lost when firmware is upgraded.
I believe the Z steps per mm will change from 800 to 3200. If doing the task from g-code, M92 can be used. An M500 must be used to save the setting.
I think it is just the default size in Marlin.
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