What's the difference between machine coordinates and work coordinates, and what do homing and soft limits do?

Two coordinate systems

1. Machine coordinates: the machine's own fixed frame, anchored at the home position (usually a corner with limit switches). It never changes.
2. Work coordinates (G54): YOUR origin, wherever you zeroed X/Y/Z on the stock. This is what the software's G-code uses.

Zeroing on the material simply records an offset between the two. The machine runs your file relative to the work zero.

Homing

Homing drives each axis to its limit switches to establish machine coordinates precisely. Why it matters:

• Repeatability: after homing, saved work offsets survive power cycles, so you can resume a job or re-run a file on a fixture without re-zeroing.
• Soft limits only work when homed (below).
• Machines without switches can skip homing, but lose all of the above, and every session starts from scratch.

Soft limits

With the machine homed, the controller knows where its physical travel ends and refuses moves beyond it (an alarm instead of a crash into the rails). A "soft limit alarm" when starting a job usually means: your job + its origin position needs more travel than the machine has. The design is too big for where you zeroed, or a rapid move (Z clearance, home-at-end) exceeds travel. Re-position the origin, shrink the job, or check the post's end-of-job move.

Pro tips

• Home at every power-up. It costs 20 seconds and makes everything else predictable.
• If a job dies mid-cut, homing + a saved work zero lets you restart accurately. Without switches you are realigning by eye.
• The job must physically fit: job size + datum position vs machine travel. The soft-limit alarm at job start is your friend telling you it does not.