[subnoize]

Forgive my noobness!

So I have a Sieg X3 with the deluxe CNCFusion.com kit. I added the A2ZCNC.com tooling plate that allowed my to mount a Sherline 3700 rotary table as the A axis around the X axis. I use LinuxCNC as my controller software.

This is my first CNC machine and I've never been a machinist so I've only been cutting machinable wax and learning that way. The concept of homing with 3 axis was pretty straight forwards and so I never gave 4 axis homing any thought until I had it all mounted and was looking at it.

I assume that I would redo my setup in LinuxCNC where the Y axis 0 is dead center of the A axis rotation. The Z axis 0 would be the very top of the stock at the Y axis 0 position. Hopefully you can see it in your head what I'm talking about!

So, if somebody with more experience can chime in here and give me some pointers it would be great! Links and such would be great for further reading on what I'm getting into here.

[109jb]

You can really do it any way you see fit, but IMO, X,Y,Z home is no different than for a 3 axis machine. Home is just to tell the machine where it is at and how far it can go in each direction to define the travel limits of the machine. This is the G53 coordinate system. Now your part zero (G54, G55, G56, etc) makes sense to have Y zero on the axis, but that is not the home position.

To put it in perspective, when I was working as a CNC machinist for a living on semi-large vertical machining centers we had many jobs where we would mount a 4th axis to the table. We didn't go disassembling the machine to move the home switches when we did that. We just set the

[moriboy1]

I'm not quite sure, but I think you are asking where to set Z0 as it relates to the A axis??

[subnoize]

I'm not quite sure, but I think you are asking where to set Z0 as it relates to the A axis??

Well, I actually made up a 4th axis file and loaded it into LinuxCNC just to see where it lined up. The dead center of rotation of the A axis is Z axis 0 and Y axis 0. So I set everything up to use this and started my first cuts which worked great in general operation but now I have to figure out why it drives the A axis so slowly. I think the degrees to IPM thing is set wrong.

The best part is I'm starting to know where to look for my own answers. It didn't really occur to me until I woke up this morning after dreaming about CNC machines all night to load a file and see how LinuxCNC displayed it in relation to the A axis.

Thanks for your concern though! Its nice to have a place to go and ask questions like this!

[rlockwood]

You'll have a much better time if you learn to program your Z offset at the centerline of the 4th axis. Setting Z off of the top of stock in centerline 4th axis work is a terrible idea, it will inevitably cause inaccuracies. Really, the best thing to do is establish the Z centerline distance from your table, enter this as a Z fixture offset. Then touch all tools off on the table.

Rotary axis is always in DPM, and you need to calculate the effective IPM based on the diameter of the workpiece.

And like someone else said earlier, you really shouldnt have to alter your configuration much at all, except to add the a-axis into your setup. Then you'd simply set your work offset up based on the location of the 4th axis, and go from there. Your configuration and home position are independant of your workpiece location-- those should be set based on where your limit/home switches are and are really only for establishing an initial reference point at startup, and establishing where the machines travels begin and end.