lathe zero X & Z

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lathe zero X & Z

Postby Robertspark » Sat Oct 28, 2017 6:32 am

being a bit thick here, in need of some guidance from cnc turners....

How do you zero the X and Z dro's on a lathe relative to the material you are turning?

Do you normally carry out a facing operation to zero the Z, and a turning operation to zero the X?

Or is it done by eye? (one or both axis)

Or do you use two touchoff plates (given you may have a finishing tool with a bull / rounded nose) {yes the tool tip naming is probably wrong, but you get the idea visually}

The reason why I ask is I've been looking at some lathe macros, and some of them have an axis zeroing procedure, hence I'm trying to figure out when, where and how this is done, given if you set a facing macro to run, would it run from the current co-ordinates (i.e. and previous g-code or manual jogging or MDI entry would get it to the right location) and then the facing operation would begin or would you programme the start point as part of the macro (and or axis zeroing routine)?

Looking at both wizards and macrocodes to run the various operations:
grooving / parting
external taper
internal taper
external + internal fillet
internal + external arcs

Open to suggestions and any operations i missed.
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Re: lathe zero X & Z

Postby Derek » Sat Oct 28, 2017 10:34 am

My lathe is a converted manual machine with ball screws on the X and Z. Servo driven.

On the X axis I turn a section and measure. I have found with my lathe that simply touching off does not give an accurate cut. If I'm really trying to hit the mark I'll run a few roughing passes then the finish pass all oversized and then measure. There are a ton of variables when turning as compared to milling. Lots of potential deflection. The same applies to the Z axis but not quite as bad. Just a change in RPM on the final cut is enough to change the OD.

I initially set the tools with a brass shim to get them close. If I'm doing a production run I'll plan on sacrificing a few parts for setup. If it's a one off or small run I'll sneak up on the first one and tweak as I go. It holds tight when you get all the variables settled. This all changes for every different material I cut.

I use the built in wizards in Mach turn for most of the operations. Anything that is complicated and needing multiple ops I'll use CAM. My plan if we had diameter mode and threading was to use Mach in demo mode to generate the code via wizard and then save it to UCCNC to run.

Here is what I'm working on right now. Gun drilled S7 tool steel cams. ID thread on the ends. Turning with a 4mm round insert cutting in both directions. Grooving with a .125" carbide. Lots of steady rest work. I used CAM for programing not Mach.

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Re: lathe zero X & Z

Postby Robertspark » Sat Oct 28, 2017 10:41 am

Thanks Derek

I am looking at making some wizards very similar to mach3. Which will generate the tap files too
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