Fixed zero plate (magnetic)

[EricSchimel]

Hey everyone, I wanted to share this project with you. A lot of my cutting is done zeroing off of the table. I wanted a way to make this a little easier and more automatic. To that end I made a zero plate (and associated code) for my ShopBot. Basically the way it works is that I can zero off of a plate that is just outside of my cutting area by running a small script.

This lets run X Y and Z zeroing all in one routine (say when I come in first thing in the morning) or, during a job if I do a bit change I can send the tool over and tap the zero plate.

I am going to work on a way that the ShopBot could do this after a manual tool change during a job.

For now though, here's a video if it in action


https://youtu.be/DAfSdfw7DcE

I think I am going to modify this design a little bit. If there's interest I'd consider making a run of them. They are pretty simple to hook up, all you do is just wire a single wire to your "Input 1" on your ShopBot. You can keep your same existing zero plate if you still want to use that, and the code recognizes when you are zeroing from this plate VS your standard plate.

Let me know what you all think!

[bleeth]

Add this to the other "after market" zeroing plates that work well!
I would thread the bottom of the zeroing shaft and socket so when raising and lowering you could do it very easily in minute increments.
Also many of the machines do not have two steel rails close together to rest the plate on. A smaller rectangular base could be more universal.
An "add offset to z" variable would mean you could enter material thickness and then use it for top of material zeroing as well.
But all in all a very nice R&D project.
I like the LED's too.

Dave

[EricSchimel]

It's probably not clear in the video, but the entire shaft is threaded, and sticks down past the main block a lot so you can loosed the set screw and just turn the shaft a tiny bit to get it perfect.

The rails on my machine (PRS Standard circa 2008) are the stamped ones that are a bit "V" shaped. Don't most of the newer machines have those? (I know the old PRT machines had different tables)

That's a great idea about the offset too, that could be a prompt when you start the zeroing routine.

The lights are fun. I have that setup so it's blue when the machine is at rest, and pulsing red when it's in motion, that way I can see what it's doing from across the shop

[BoilermakerAndy]

On an older, non ShopBot CNC machine I had, we had a limit switch on the Z-axis. The sacrificial board was fairly stable, so after each skim, we would accurately measure the distance from the limit switch to the table surface, and - voila - zeroed in three dimensions via limit switches.

Granted, we used primarily one size bit to cut everything, so we created a fixture to replace bits accurately. Does anyone do something similar on a ShopBot?

[EricSchimel]

I've wondered about doing that on my ShopBot, I have a Z Prox switch. To make a script like that work I'd have to zero to the table first, then have it measure the distance from that position to the prox switch. That measurement would go out the window on a bit change so you'd have to do it over again... Basically sounds like the same amount of work as a Z zero plate. If you had a bit replacing fixture that would make a lot more sense.