Thanks all.  To be practical the entire Mach3 directory should be backed up...

I upgraded to the latest lockdown version R3.043.022.  Upgrading was very simple.  The threading problem did not go away.  I did some tests and the behavior is repeatable. I was able, with three similar passes go over the same path.  The trick is that I had to offset each pass by 0.17mm.  I turned the control on and off and the behavior was the same. I am attaching the program file I used for testing.  Maybe I should ´downgrade´ to R3.042.033 which has been proven to work well with others.  I would like to know however if anyone can understand this behavior before reinstalling again.

Thanks,

Jorge

I turned the control on and off and the behavior was the same.
WHAT CONTROL?

Are you using the threading wizard to generate the code?
Do you have any backlash in the Z or X axis?
You should not need to do anything. Do a simple scribe test as that will tell you a lot.
RICH

By Control I mean turned off and then on the computer and repeated the test.

Installed V3.042.033 just to discard a Mach problem.

I just ran a test with code generated with the threading wizard and the problem remains.  The resulting thread has a fishbone shape.  As the tool penetrates more in each pass it is also displaced a small amount in Z, therefore this shape.

I may have backlash, but I am sure its neglegible compared to error the thread is showing.

This behavior makes me suspicious of my Z axis setup.  Will check that tomorrow.

Jorge

Jorge,
Your threading quality will only be as good as your lathe "system".
It's that simple. Do a scribe test.
 
RICH

Rich,

Here are some results from this morning.

Checked Z axis for backlash with a dial indicator: 0.03mm
Mach backlash compensation is disabled.

Check repeatibility precision of Z axis:  In 6mm its dead zero. Checked arrival point both with G1 and G32 and they behave exactly the same.

Then did a threading test (see attached).  Made three passes and they are off about 0.3 mm from each other.

I am attaching the photos of the test and the code used.

The spindle encoder is a Heindenhain that came with the machine.  The index signal is processed by a Machmotion B B board.  RPM reads well, and even RPM control with feedback is very accurate too.

Still cannot understand what is going on........

Thanks,

Jorge

Hi

Does your offsets change with pitch? So if you cut a 1mm thread then it's out by .3mm but when you cut a 2mm is it out by .6mm?

Jorge,
Post your xml file for the lathe that you are using.
RICH

Try the Dev version and see if it helps. Art found an issue recently that has been there since the start and has modified the driver, dont think the lockdown has that fix.
Hood

Hood,
Do you remember what the issue was?
RICH