Z axis assembly smashing into top of carriage

OSX Mojave (10.14.2)
Carbide Motion 4.0.412
Shapeoko 3 XL
Fusion 360 2.0.5331

BLUF: Z axis assembly smashing into top of carriage after Z origin in Fusion 360 CAM incorrectly set.

Background: I had previously posted about the potential of issues with Motion not correctly setting axis limits or utilizing soft limits, now it seems I found a problem. After inadvertently extruding a shape above it’s Z origin in Fusion 360, I made a rookie mistake of not adjusting the origin within CAM. At least this is what I think caused the issue.

Observation: After loading a new program into Motion and zeroizing X/Y/Z, I experienced a violent smashing of the Z axis into its upper limits after the program started running. For a 2 week old machine this was a worrying experience to hear it grinding and slipping through the belt.

I don’t understand why the limit switches or soft axis limits are not being utilized, these are expensive parts to leave up to the g-code to protect. Another thing I noticed is the retract height moving from the homing point to start a job is NOT configurable in Motion. Since Fusion’s g-code started its first plunge at X/Y center, it was up to Motion to move to the start point, where it drug an endmill smoking straight through a workpiece. Normally I click the run button directly above the X/Y center, however this was after a tool change and Motion had returned the tool to home.

The Machine is awesome, and the accuracy for a system under 2k is remarkable. The software however, both Motion and Create have a long way to go in my opinion. Any advice, explanations, or workarounds would be excellent. This community seems to have an excellent group of people, really looking forward to getting the most of this machine!

EDIT Something else I just noticed that may compound this problem is that the January 9th release of Fusion seems to have gotten rid the Machine Setup portion with CAM. This is where machine Axis limits were entered and would alert if something you were trying to do was outside the parameters of the machine.

My previous related post-

Thanks! - John

Hi John

What post processor are you using in fusion? I had a similar issue when using the wrong one…


Hey there Luke,
I’m using most recent Carbide 3D one, provided with Fusion (just double checked to make sure it was not the older version). I’ve confirmed that it was my mistake with the stock origin within Fusion, confirming that Motion will drive the motors beyond the machines limits if the gcode tells it to. You’d think this should/could display a warning in Motion once you load a program that conflicts with the machine’s limits.

I imagine with your beefed-up Z axis this could end up worse than a slipped belt…?


You can have soft limits enabled, that will stop any crashing but you must home and reset zero on startup…

Otherwise you can plunge a 6mm bit very deep into your work. Don’t ask me how I know…