Different spindle speed between M3 and M4 Fanuc 0T-B

[Diri19]

Dear all,
I have got an old lathe Fanuc 0T-B controlled. Last days I noticed a strage working on spindle speed rotation . When I command in MDI or Auto mode G97S200M3, spindle starts running correctly at 200rpm; instead when I command G97S200M4, spindle runs at 180rpm.
At every speed commanded in M4 direction, spindle rotation is lower about 20rpm then commanded speed.
Do you have some ideas about this trouble?

Similar Threads:

• Fanuc AC Spindle Drive speed does not match S-code speed
• Fanuc Oi-MC Spindle Speed Issues
• Fanuc 6T spindle speed
• Problem- Fanuc 5T Spindle Drive Speed
• Fanuc 0M Spindle Speed Problem

[machinehop5]

Dear all,
I have got an old lathe Fanuc 0T-B controlled. Last days I noticed a strage working on spindle speed rotation . When I command in MDI or Auto mode G97S200M3, spindle starts running correctly at 200rpm; instead when I command G97S200M4, spindle runs at 180rpm.
At every speed commanded in M4 direction, spindle rotation is lower about 20rpm then commanded speed.
Do you have some ideas about this trouble?

..what happens when trying Spindle speed zero ? does it drift ? If yes, which direction M3 and M4

[lshingleton]

For Spindle direction on the electrical drawing does it have a different relay in the electrical cabinet ? or done through the spindle drive ?
Old machines have different systems for sure sometimes --------If it has a relay change check for condition

[drdos]

I am going to assume that you have a Fanuc spindle amplifier as you didn’t specify otherwise. That being the case then you will have two variable resistors labeled RV9 and RV11. How to adjust is you run your spindle to 1000 rpm’s and adjust RV9 (M03) to achieve 1000 rpm’s. You do the same for M04 but adjust RV11. If you don’t have a Fanuc spindle amplifier then you will have to find the manual for that drive.