Unreliable safe height

After getting my meticulous z-axis up and running (thank you @MeticulousMaynard for all the work you put into that) I’ve noticed that Groundcontrol seems pretty inconsistent in retracting to its safe height before traversing. In my experience, the ‘go to home’ function is reliably preceded by the z-axis retracting to its safe height. However, it doesn’t seem to automatically raise before the ‘go to here’ function, or if using the navigation arrows. Do others have this issue? Is there a solution?

Not a problem. I’m happy to give back! :smiley:

I’m not sure about the “go to here” function, as I’ve never used it, but jogging the sled around with the arrows has only ever moved the sled around without affecting Z-height. If you look at the code that Ground Control sends to the Maslow, it says:

Which translates to:
G91 = Incremental programming
G00 = Go to specified coordinates (The X and Y variables) as fast as you can go (rapid move)
G90 = Absolute programming

So in layman’s terms, that code means “move 100 mm incrementally in the X direction as fast as possible, then return to absolute programming”

While running my machine, this has been very useful to me. I can set my Z to 1mm, and then jog to the edge of the sheet. This is easier than doing that at the Maslow’s safe height of 5mm, because I can see more easily where my tool is.

An easy fix for you would be to set one of your macro buttons to a safe retract. The code would look like (assuming you’re working in mm):

You could set the macro text to read “Safe Retract” or something like that. At least that saves you from having to go to the Z-axis menu.

That makes sense; I can see how keeping the bit low could be useful. Setting that macro sounds like a good idea. G code is a whole new world for me; I guess I didn’t really appreciate that parsing the g code could answer my question. Thanks for your fast and thorough reply!

I’ve been learning on a Shopbot PRSAlpha at a local maker space. I can confirm that it also does not adjust the Z-axis before jogging to the X-Y you set. I know this because I dragged a drill bit about 8 inches across a beautiful piece of 1" thick baltic birch I am cutting a work bench out of :(. I was surprised it doesn’t warn or anything if the current position is below the safe height when you hit the jog command. I would have thought a warn prompt if in the unsafe area would be a logical thing here…


Wow, 1mm? You are able to get stock and position it on the frame so accuractely that there isn’t 1mm of variance in the stock? Nice!

I was dismayed to discover (while cutting simple 1mm thick text in to the workbench I mentioned above) using the makerspace shopbot that the Z was off by ~4mm resulting in 5mm deep text in the area I was cutting. Talking to some experienced members later on they said so many people use the machine and the spoilboard gets cut up so quickly that it is almost impossible to guarantee a level surface, let alone variances in material thicknesses and warping of the stock.


how are you using the safe height setting? I’m not aware of anything in ground
control that lets you move to the safe height with a button press, and I don’t
know of anything in g-code to move to a safe height.

David Lang

I’ve found that, in many cases, my Maslow handles warped material better than some of the gantry machines I’ve run. Because the sled moves along the surface of the material, it follows the curve, so you can get more consistency in your cut depth (ignoring, of course, all the backlash in the stock Z-axis). I also nail my work piece down so it’s sitting nice and flat on my spoilboard. Of course, a machine with a good vacuum table can make warpage a moot point.

I think that they’re refering to the first command sent to the controller when you press the “home” button. If I remember right, that first commands the Z axis to 5mm, then moves in X and Y to get to the saved home position, and finally lowers the Z to 0.

Otherwise, “safe height” would be something set in CAM.

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@dlang I was referring to the Shopbot in ref to the safe height.