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G70 not retracting tool after finish pass.


Dec 18, 2023
Hi all. I'm trying to get an old CNC lathe up and running at my shop. We don't have any CNC machinists or programmers, so I'm relying on the manual and my basic knowledge from third year to stumble through this. It's an Ikegai TU30 with a Fanuc 18i-T controller. I'm trying to run a 2 line G71 for roughing my stock down to 5.5" from 6.5", since the controller doesn't seem to like the D operator for a single line. My problem is that while the G71 works perfectly, the G70 doesn't retract, and leaves me a nice candycane stripe across my part when it pulls back to the start. My assumption is that it's not reading the first G71 line, but I have no clue how to make it do that. Can I add the U operator into the G70 line as retract? Thanks in advance!

The relevant lines of code look like this:

M04 S300;
G00 X6.5 Z.1;
G71 U.125 R.01;
G71 P100 Q100 U.015 W.005 F.02;
N100 G00 X5.5;
N200 G01 Z-3.25;
G00 X12. Z12.
G00X5.5 Z.1;
G70 P100 Q100 F.005 S500;
In your rapid line before the G70 call, make sure you are rapiding above your stock size. Instead of G00 X5.5 Z.1, make it X6.75 Z.1. The machine always returns to its previous position before the G70 finishing cycle is called.
It’s really better to do a cut and paste from a download so the code we look at is the same as what is giving you trouble.

That’s not an option at the moment, or I would have. I coded it on the MDI panel as I don’t have a laptop on the shop floor yet, and the 18i-T unfortunately doesn’t have a built in web browser.
Yep, that did it. Thanks!
Always happy to help. Since you are new to programming get into a routine of programming the same every time. I always rapid .06" in front of the stock, and .120 (diameter) above when facing. When you are used to how you normally start, it makes it easy to spot errors in your setup when you miss a work offset or forget to touch a tool off.
I never use G70 myself at all. I always long code my finishes. But if you are going to use it or any other can cycle, Bigjon is right get into a standard way of doing your approaches and retracts and keep that format. It becomes second nature as you repeat it over and over and over and over..........