Hi,
My Smoothieboard-driven OX Openbuilds CNC is coming along great.
I have connected proximity sensors to X&Y, allowing homing to work exactly as I want.
BUT, I just connected a floating Z-plate to allow me to home Z to the top of stock.
What you do is place the conductive plate on top of the material you are going to machine. The cutting tool grounds the plate, which is connected to Z-min making a Z-min endstop detection. This, combined with a Z-min offset of <the thickness of the plate> works great for setting the Zero point perfectly.
Unfortunately the home button G28 homes XY&Z when a Z switch is enabled. I absolutely cannot do that as the Z might crash through the stock, the fixings or even the table! I have to Home X&Y, and then manually position Z over the stock before homing. So what I want is:
G28 homes X&Y only
G28 Z homes Z only
Is this possible?
Imported from wikidot
…and 15 seconds more thought brings me to changing the javascript in my custom CNC web page to issue G28 X0Y0 instead of G28…
Feel free to ignore this.
Hi,
I’m making a CNC router based on the OX openbuilds platform too. Can I ask you a few questions? 
What spindle do you use on your machine? I see a lot of people go with the DeWalt 611, and I’m thinking of getting Makita RT0700 which is pretty similar. I’m still trying to figure how to control the spindle with G-code? Since the on-board mosfet only supplies limited current and voltage, it seems that it’s not possible to drive the 220V AC spindle. If I use the SSR, I can only switch on and off of the spindle, but no RPM control, correct. Or people actually just manually turn the spindle on and control the motion of the machine with G-code?
Also, do you use auto-levelling on your CNC? I plan to use aluminium extrusion as the milling table, so I can wire the table and the tool to create a circuit. I do have a smoothieboard based 3D printer with auto z-probing fearture and worked great, but it’s my first try on a CNC.
Thank you in advance.
Kaiyuan