Hi everyone, hopefully I can get a simple explanation to this question. I have a piece of wood 6"x12" setup on the bed of my machine, this is basically to see if everything is going to cut where it needs to be cut and not elsewhere like it did in the past on other projects. Two nights ago I had the machine drill 4 holes into the wood maybe an 1/8", the next night I came back and wanted to get the holes drilled a little deeper. This was to verify that everything was setup correctly and I could get repeatable positioning. After zeroing X, Y, Z on the wood I sent the machine to drill the same 4 holes a little deeper and with a thicker drill bit. Well, when the machine went to the first hole it was about 1mm to the right of the hole, I expected it to be right on top of the hole but it wasn't. This verified that when I do get ready to cut into the plexiglass that I will be using for my project, if I don't do everything the same day I will have issues. Getting to the point, how do you get your exact positioning on the machine so you can repeat that exact position the next day. What numbers am I looking for so I can just move to the positions and then zero X, Y to those numbers. I am using the OpenBuilds software with the BlackBox etc. I recently had to tear apart my machine and totally square it up and finally add my new more powerful steppers etc. So far i am very pleased but i really would like to get this figured out for future reference. Appreciate the help and thanks to everyone.
Homing sorts this for you. Homing sets the machine home, everything else is an offset from machine home, so if home is correct and consistent, then all existing offsets are also correct. GRBL in the Blackbox stores the offsets in EEPROM, which means they survive power cycles. I have done many jobs where it got late and I went to bed having turned the machine off. Next day, turn on, home (1), and check WCS and find it is exactly where it was set for the start of the job, as it should be. Just continue with the next cut (which must of course be referenced off the same 0,0,0 as the first op). Since you saw an offset after you reset your WCS ..... Remember that you are setting the centerline of the tool, so if you changed the tool diameter and then setZero with the tool against the edge of the work, it is now offset by the difference in radii of the 1st and 2nd tools. (1) on my machine I use the 'fake the home' method but I see limit switches on your machine so you don't need to worry, homing should be all you need. When to home? after machine power on after any bump, crash, interruption, software glitch, ie anything that can cause a loss of position certainty. Note that GRBL resets home when power on reset GUI connects on USB So you must home after any of those events as well.
Awesome. Thank you very much for the help. Sometimes I don't home, I just square up my material and then move to the position of the material and then set my X, Y, Z, axis. /* Since you saw an offset after you reset your WCS ..... Remember that you are setting the centerline of the tool, so if you changed the tool diameter and then setZero with the tool against the edge of the work, it is now offset by the difference in radii of the 1st and 2nd tools. */ I see what you are saying here, it makes sense now.
