FAQ

Here are some quick answers to frequently asked questions:

I get an 'error' message about the WCS is not selected and the default will be used:

This is not an error, it is a warning. It means you have not selected a WCS in the Setup|Post tab.
Set it to '1' then click the ... to the right of the edit box and select 'set as default' so that all future Setups have WCS 1 (G54) set as default.

I am trying to generate code for a plasma cutter but I keep getting error messages:

In order for good gcode to be produced you have to set up your CAM operations correctly. Please follow the instructions.

When my job starts the tool scrapes across the surface of the work, or even gouges the work on a rapid move:

Everyone needs to know where home is and have a suitable sense of self (-: For a CNC machine this is 'home' and the Machine Coordinate System 'MCS'. Industry standard for CNC home is the positive ends of tool travel. For a LEAD, this means X right, Y back, Z up.

Always 'home' after turn on or reset, always always always. If you have any doubts about the machine state, then home it again. You may need to jog to clear clamps before this, the machine does not know where the clamps are, YOU do, so you must do the thinking.

Now that we have a home we can go travelling into Work Coordinate System (WCS) territory. GRBL has 6 WCS systems though using only the first default one, G54, is the most common. The 'setZero' buttons tell the controller where 0 is on the raw material, the origin point that you set in Fusion360. This is stored as an offset from home in the controller. This offset is stored and will survive a power cycle,so if the power goes off during a cut, your part 0,0,0 is still known, but only after homing, which is why homing is so important.

With this home we can now do safe moves at the start and end of a job. The job does not know where the tool is so the first movement to the starting cut might hit a clamp or whatever is in the way. The correct thing to do is raise the tool as high as it will go, (almost) guaranteed to miss all clamps, before moving. This is done by telling it to move in Machine coordinates (the default is the current WCS) so you will see a line like G53 G0 Z-10 (Z-0.39 if you are in inch mode) in the Gcode. This tells Z to raise to 10mm below the Z home position. The 10mm is the default, it is sure to clear the limit switch. If it goes to Z0 it will trigger an alarm, so we need some clearance below it. You can change the option to 1mm if that is enough to clear the switch reliably.

Having raised Z to a safe height, the machine can move anywhere safely (unless you have some weird job setup that is pushing the limits of what your machine can do) before it lowers to begin the cut.

At the end of the job it raises again, this gives us clearance to jog it out of the way so we can unload the part, or clearance for a tool change. The post also has an option for moving X and Y at the end of a job. You can use that if you want it.