Newbie- 4th axis/Rotary Table setup. Please help!

[TheProCreator]

Okay, I'm very new to CNC. I recently purchased a "hobby" 3 axis 24"x40"chinese-made machine with an add-on 4 axis rotary table. All axis' are calibrated and working great in Mach3. I will be using this machine to make small 3d model parts out of wax, foam, or plaster. Tool paths are being generated with DeskPronto.

Here is what I need help with... Axis A needs to be mounted to to table. Right now my home location for XY and Z is set in one of the back corners of the table.

Do I need a new home location after I mount the 4th axis?

Also, what is the best way to calibrate Z depth and start position for 4 axis milling?

Do I need to dig deeper into Mach 3?

Any help, suggestions, links or reading info would be very much appreciated!

[awerby]

[QUOTE=TheProCreator;849665]Okay, I'm very new to CNC. I recently purchased a "hobby" 3 axis 24"x40"chinese-made machine with an add-on 4 axis rotary table. All axis' are calibrated and working great in Mach3. I will be using this machine to make small 3d model parts out of wax, foam, or plaster. Tool paths are being generated with DeskPronto.

Here is what I need help with... Axis A needs to be mounted to to table. Right now my home location for XY and Z is set in one of the back corners of the table.

Do I need a new home location after I mount the 4th axis?

[No, "Home" is just a reference point. You can set your floating zero points in relationship to your home position if it's accurate enough, but that depends on the type of switches used.]

Also, what is the best way to calibrate Z depth and start position for 4 axis milling?

[You generally want your Z and Y zero points to be set at the center of the rotary axis. One way to do that is to mount an accurate ground cylinder in the A axis chuck (preferably a 4-jaw, so you can dial it in with a dial indicator to make sure it's concentric) and touch off to the top of it with your tool. If you add the radius of the cylinder, that's the center of the axis. Similarly, if you touch off the side of your tool (or an accurate cylinder or edgefinder in your spindle) to the side of the mounted cylinder in your chuck and subtract the radius of the tool plus the radius of the cylinder, you've got the Y=zero location. Once you've done all this, you can make a reference block with accurate places indicated to zero to, so you don't have to do it each time. These don't have to be at the actual zero points, but can be a measured distance from them, so you don't have to dismount your part to rezero.]

Do I need to dig deeper into Mach 3?

[It certainly wouldn't hurt...]

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[Torsten]

Originally Posted by TheProCreator Okay, I'm very new to CNC. I recently purchased a "hobby" 3 axis 24"x40"chinese-made machine with an add-on 4 axis rotary table. All axis' are calibrated and working great in Mach3. I will be using this machine to make small 3d model parts out of wax, foam, or plaster. Tool paths are being generated with DeskPronto. Here is what I need help with... Axis A needs to be mounted to to table. Right now my home location for XY and Z is set in one of the back corners of the table. Do I need a new home location after I mount the 4th axis? Also, what is the best way to calibrate Z depth and start position for 4 axis milling? Do I need to dig deeper into Mach 3? Any help, suggestions, links or reading info would be very much appreciated!

Assuming your Machine requires physical Homing to find its Reference Position then yes if the Rotary Table gets in the way of the slides moving to the Home Position it would make sense to move the Home switch location so you would be able to Reference the machine.
After all the purpose of a Homing switch is so you dont have to redial everything in every time you restart the machine.
Once the Workoffset of the Rotary Table is setup you simply Home and start your Job.

[TheProCreator]

Thanks, this really helps.

I am also following threads here in CNCZone to make my Z touch plate. I was thinking to use a conductive cylinder held in place by the rotary table. This should work as well right??

[neilw20]

Why move the homing switch?
Just move the Z axis clear, and manually reference X and Y axis from the diagnostics page.
Then move to some clear spot if needed and reference Z.
If the Z axis is above the 4th axis, there should be no problem.