Program eratic after a tool change Lathe <resolved. CSS was too high>

[cnckeith]

I had to simulate the tool changer. I did have the a-axis turned on and working but I didn't have a physical tool changer durig the test. On Monday I'll have the tech support guys run it on our in-house lathe to see if we can shed some light on your issue

[cncsnw]

Philip,

Try running a copy of the program, with all of the feedrates changed to comparable time-based (mm/min) rates (G98 mode).

There are different accel/decel rules in play with feed-per-minute vs. feed-per-revolution. Running the same part in feed-per-minute may show you whether it is dropping steps due to inability to keep up with the accel/decel ramps.

Your G99 feedrate amounts seem conservative enough, but 1000 meters/min seems like a pretty aggressive surface speed. What material are you cutting?

I assume your spindle is maxed out at 3200 RPM throughout this cut, since -- at 40mm diameter -- that would give you a little over 400 meters/minute on the surface speed.

[PhilipTrueman]

Problem solved.
Fixed the cnc lathe.
In the spindle setup wizard the setting was set to G98 as default instead of G99 feed per rev.
I have just run a quick facing and turning program with 4 tool changes then run the program 3 times without re homing.
And it run perfectly.
I changed the setting in the spindle setup back to G98 and it still ran perfectly.
All i can think is that the motor drivers are maybe getting warm They have fans on the heatsinks.
I tried keeping the spindle and coolant running in between tool changes but that doen't make the problem re appear.
It seems to be a mystery why it happened over 2 days.
One thing that doesn't happen is that the spindle doesn't change speed as the tool goes to a smaller diameter.
Thanks for eveybody's help on this problem.

[tblough]

One thing that doesn't happen is that the spindle doesn't change speed as the tool goes to a smaller diameter.

Marc already explained this. At 1000 meters/min, you are already at your max rpm at the stock diameter. There is no way for the spindle to increase any more when the part gets smaller.

[PhilipTrueman]

One thing that doesn't happen is that the spindle doesn't change speed as the tool goes to a smaller diameter.

Marc already explained this. At 1000 meters/min, you are already at your max rpm at the stock diameter. There is no way for the spindle to increase any more when the part gets smaller.

Thanks

[PhilipTrueman]

The problem was that the CSS was too high and it was throwing an error because it couldn't achieve the speed.
Back to work making some parts. Thealuminium is 6082 T6 the large diameter is 90mm and the bottom of the groove with 2mm radius in the corners is 50mm. All dimensions were within 0.01mm Only another 23 parts to go. Then turn the part around and machine features on the other side.

[cnckeith]

thanks for reporting back! glad you got it solved. thanks for posting the photos.