Unexpected move

(Honestly don’t know if this is a bug…)

I am seeing an unexpected movement when I start a NC program. I’m generating my G-code using Fusion. When I start a program, the machines moves to some “new position” and then prompts me whether I want to continue. I think it’s prompting me to do a tool change, if I need to. The issue is, I can’ predict where the machine will move to. Most of the time it goes up, and away, which is OK, but sometimes it plunges into my stock or my wasteboard, which is not OK.

When this starts happening, I pretty much have to power cycle my LongBoard. It’s like the place it’s going to move to is selected at startup, because if I don’t power cycle, it goes to the same bad place as the previous try.

What am I doing wrong?

Give this a try:

**To avoid potential issues with Fusion 360, we also recommend you make the following checks to your post-processor:

  • G28 Safe Retracts set as “Clearance Height”
  • Output M6 set as “No”
  • Output Tool Number set as “No”

I have just been previewing toolpaths while waiting for my machine. I have seen similar collisions in NC viewer and gsender preview paths.

I don’t know if this is related to your issue, but I found this video helpful in understanding how G28 and homing works in gcode. The comments he makes in here about the home resetting after a power cycle made me think of your description.

I suspect that is why Sienci suggests to use “Clearance Height” instead of G28 with fusion’s grbl post.

I wonder if my issue was about Safe Retracts … I have set it to clearance height and will see if my issue re-occurs. Thanks for your advice.