Modifications to GRBL files for safety reasons; when considering macros to send the unit to specific locations safety should be the first consideration. By default the GRBL files send the unit to X0Y0 at the end of the job, I discovered the hard way that going ‘home’ at the end is safer. Before I modified the GRBL file (both inches and mm) on the AltMill I ran a program that cut from left to right across the table. As the program was almost finished I reached (stupid) up to touch the left end of the piece and just as I did the file ended and the carriage moved back left to X0Y0 with lighting speed hitting my thumb which needed nine stitches to close. I suggest removing or remarking out the X0Y0 at the end of the GRBL file and replace with Home that way everything shuts down in an orderly and expected way moving to re-home itself.
Ouch! That hurts! Glad you didn’t lose the thumb but lesson learned (and shared). Be careful out there folks.
Hey Kimsey,
That must have been the biggest scare of a lifetime. You learned the lesson- we all need to learn- the hard way. Savety first. And it’s a good thing you found a way to change the behaviour of your machine to make it more safe, and maybe it is a good idea to have the home option for machines having sensors. And thats where the problem lies, gsender works with machines that have all kind of profiles, including ones that simply don’t have sensors to home on, or maybe don’t run a spindle to shut down.
Running a machine safe is to run it predictable. The most predictable way to run all these different profiles is to have it go to its starting point when it’s done.
Yes, your machine would prolly be more safe doing it your way, but it would be even more safe when there was a door to open before you could touch the machine bed. Even more safe would be if the machine stopped when that door was opened while running. If I remember correct, the slb has an io dedicated for a door switch.
I have been around industrial machines way more powerfull, way more speedy than even the Altmill that had more safety built in than a prison. The problem with that is that people tend to no longer see that there’s a wild animal in a cage. And then the beast doesn’t work smoothly, starts acting up and the quick fix is to open the cage (theres always a service key somewhere or something that will work as one.) A senior operator knows when he can reach in, looking at the screen to see if it’s feeding time or not and quickly fix the thing that’s wrong. Untill it’s normal to have the cage door unlocked to be able to meet production demands. And then the day comes that senior gets called away and the machine acts up. Junior, having seen senior working the machine opens up the machine not even realizing it’s not supposed to even keep working. Without glancing the screen to see if its feeding time he reaches in to do the quick fix thing, he seen done so often, and has his arm ripped off by the wild animal inside the cage.
The question that always gets asked is, what caused the accident. The answer should be, ignorance.
The solution is always another layer of safety on top of the ones already in place.
The thing that should be done is hanging a picture of the animal with the arm still in its jaws all around the shop.
Knowing your machine is what keeps you safe and I feel that the Altmill or even the longmill is as dangerous as an entry level “findoutasyougo” hobby machine can get.
I fear you wont be the last and not the worst victim of these wild beast, and I don’t think extra layers of safety will prevent that.
Your solution sounds logic for homing machines and maybe even for all. At the end of the programm, have it pause long enough to wind down before racing anywhere, being it home or xy0. Maybe even have a popup ask the operator to oke the return sequence.
I have personaly inmplemented the machine to pause right after I click start to prevent the machine flying of when start gets clicked by accident. My mouse is a cheap thing that goes to sleep after a few minutes. If the pointer hovered over start when it does, it can easely activate start when waking it up by clicking a button.
We learn as we go and sometimes the price of knowledge is too high.
Thank you for posting your story and your musings on how to make things more safe. It had me going on this tangent and while I seem to be all over the place, I do feel you have a point and are right that the ending sequence of g-sender can be, or even should be made safer.
I’m not sure about all the machines and code but the altMill GRBL does shut down the spindle to a stop at the finish before it moves back towards Home. With the finish set to X0Y0 the machine moves as the spindle is winding down.
OK, to begin with GRBL has nothing to do with your machine stopping the spindle and returning the spindle to X0Y0. You mentioned “by default the GRBL files send the unit to X0Y0 at the end of the job”. Your post processor included the command to return the spindle to X0Y0; that is not a “default” GRBL function. The commands to start/stop the spindle and move to a predetermined location is coded into your gcode file via your post-processor. If you want the spindle to return to a specific location, pause before moving, start/top the spindle, etc. you need to code these functions into your post-processor (or I guess you can hand code them into each individual gcode file which is the way tedious way to do it). For me, the safest way to operate a CNC machine is to fully understand all aspects of operation so you can have the machine do exactly what you intend for it to do. Learning how to construct and manage post-processors that meets your needs (and, in fact, preparing multiple post processors to meet specific tasks) is a critical skill to master for CNC work.
Indeed GRBL doesn’t have any default commands. I didn’t clarify that what I modified were the pre and post processor commands. Via the processor editing function in Vcarve Pro I modified several lines in the pre section and commented out the X0Y0 command in the post section and replaced it with Home. For my AltMill and control board X0Y0 moves immediately at the finish with spindle slowing down, with the HOME command the spindle comes to a complete stop and the Z axis retracts upward before moving to home.