So I've had this happen a couple of times so far. When I start the run, the A axis plunges way down into the part. I quickly stop the program at that point, so I dont know what happens after that, but it is really odd. I've checked the g code, and it's not telling the machine to do that. I have a hypothesis, but I wondering if people here think it's a valid one. I'm using the Mill Right Mega V, and because it's new, I havent hooked up the limit switches yet. Because of this, my machine home is some random place that was randomly selected. Up to this point I've been homing it using a homing XYZ homing block, and I've been just fine without machine home being set. This cut was different. I had to start right at the very top of my z stroke. I still zeroed the work piece and all looked good to start the cut. Is there any validity to the hypothesis that Control thinks that my z axis is out of its machine limit, and it quickly moving the machine down to get into that limit before it starts the cut? Here are the first few lines of my g code in case someone sees something that I dont. I'm hoping that once I get these limit switches installed and "home" the machine, this will all go away. (T1 D=0.25 CR=0 - ZMIN=-1.6 - flat end mill) G90 G94 G17 G20 G28 G91 Z0 G90 (Face1) T1 S17000 M3 G54 G0 X5.3878 Y0.6708 Z0.6 G1 Z0.2 F40 Z-0.075 G18 G3 X5.3628 Z-0.1 I-0.025 K0 G1 X5.303 X0.947 X0.6653 G17 G2 X0.6653 Y0.9016 I0 J0.1154 G1 X5.5847 X5.7655
Use the OB fusion post here: docs:software:fusion360 [OpenBuilds Documentation] It uses G53 instead of G28. G53 is always machine home. G28 is a reference point that can be set (machine home if not set). If you dont have limit switches to home, grbl will set your machine home to the spot when you powered up your machine. When you say "my machine home is some random place" its because your spindle isnt in the same spot when you turn on the machine every time. So, make sure your Z is all the way up and your x and y are in the location you want (front left, back right) before starting Control. @David the swarfer has more info here: How to 'Fake the home'
Thanks for the help! Do you think the OB Fusion Post Process will be better for the Mega V as well since I dont have an OB machine?
The post is pretty generic and isn't machine specific. Where you may run into issues is with the controller. Some of those have their own way of doing things. What controller?
Then buyer beware I suppose. But why the questions on the OB forum and not theirs. Made me think that a blackbox was involved....
