This may have been asked before, I have looked through the forum, but may be using the wrong search terms. I apologize if already asked and answered. My question…Is there a stop switch or something that will stop the Z axis from going down too low. I messed up a couple of time and made the Z go too low and had to use the E Stop button to stop my machine and fix my mistakes. They are my mistakes, but was wondering if someone has rigged something like this up. I would love something like this on mine if you have, I would even pay you for it. I sometimes get absent minded (old age), and do stupid things, and having something to help watch out for my incompetence would be great. Thanks for your help, and, in finishing…I LOVE THIS MACHINE, more fun than I have had in a long time.
I can’t say that I have seen a lower limit switch setup on the X-Carve. On an unmodified machine, I would think the collet of the router/spindle would hit the wast-board before the Z axis carriage comes off of the rails…
but that doesn’t mean someone hasn’t thought of it.
Soft Limits is the solution to your problem.
With homing and properly defined travel limits, it greatly reduces/almost eliminates jogging too low (or high) in the Z axis.
I will search how to do this. I never knew you could do soft limits. I am completely new to this, so I am slow at learning, as there is a lot to all of this. One of these days, just look out, I will know what I’m doing and things will be much simpler for me then. Thanks for your reply.
Thanks for your reply. I will google for x-carve modifications and see what I find.
Here are the basics concerning homing switches and limits, summarized.
Soft limits only work if the command (distance) exceed the soft limit range. If Z loose steps (drop) or something comes loose soft limit offer no safety factor.
Yeah, they’re pretty useless if the screws fall out.
okay. This is getting pretty interesting. Do you think that if I ordered another z limit switch and put on this, and then figured out how to make the unit stop if it hits the z limit down switch, that this would be possible?
This is kind of making sense to me. I get the concept of the switches. I know the best solution is for me to not move the thing too low, but, knowing me, I don’t think that is a viable solution. I think I’m going to order another limit switch and experiment with this idea. If it works, I will put up how I figured it out. I hope I’m not the only person out here that is dumb enough to go too low. Once I did it thinking the homing was set correctly, but somehow it got out of whack and I wasn’t in the shop with the machine when this happened. Thank goodness I was using a buffer waste board, as it basically destroyed the top waste board, the project, and I was scared too death I messed my machine up, but it didn’t. Those stepper motors are pretty strong when you get down to it. Thanks so much for the link above, and for replying to my post.
Where does that statement say it completely 100% fixes ANY failure mode? It says it greatly reduces/almost eliminates jogging too low/high.
The original problem statement seemed to indicate an incorrect jogging NOT complete mechanical failure. To help solve the originally stated problem, Soft Limits are the easiest thing to implement and, in my opinion, the best solution for the stated problem. I feel my recommendation is spot on.
I wasn’t taking into account complete mechanical failure because in a complete mechanical failure (which, lost steps is a complete mechanical failure), you can’t predict anything…
But yes, you are 100% correct, in a mechanical failure scenario, soft limits won’t help.
You can do it. If you want to go to the effort to make it work. Many people that have started doing this decided it wasn’t worth the hassle.
I know that there are times one just has to prove something to them selves. So, have at it.
I used a lower Z limit switch on my S02 a while back, but only for a brief time. It was a hindrance, IMHO, and did not protect from mishaps. YMMV.
If you implement one, I think you will find that it needs to be adjustable up and down the Z axis so it can be reset for bit length changes.
I posted only to provide additional information - not to correct yours. As you suggest, soft limits will prevent exceeding the machine threshold as long as it in sync / physically intact.
Many of us have not gained much experience, start off with little knowledge and getting a hint of “there is no free lunch” may serve a purpose for all others that read the thread 
You all were correct on the z axis limit switch. I sucked at implementing this. I still had to try just for the principle of it. Anyway, my solution was to put a webcam looking at the machine, that way when I leave it running, I can pull it up on my iphone or ipad and watch without having to stay in the shop, or if it is running late at night. I do appreciate all of your input, as by reading what you said, it gave me enough insight to know I couldn’t get this to work perfectly, and I stopped instead of spending the next 3 years on it. When I start something, I don’t know why, but I sometimes just can’t let go until it works. Again, thanks to everyone, I do appreciate this forum and all of your help. Maybe someday I will be good enough at this to help someone. I am very good with computers if anybody has questions about that.
Thanks