ST-35 Tailstock wont zero

mikesparts · Jul 25, 2017

Hey guys we are having a problem with our 2015 ST-35, the tailstock will not zero out. When using "powerup/restart" or homing the B-axis alone the tailstock will move away from the chuck for a couple seconds then switch and move forward until it is all the way up in the jaws. The tailstock stays pressurized all the way forward and continues to think it's homing itself until reset is pressed. This is an ST-35 with the hydraulic tailstock and string encoder. We overnighted a new encoder thinking that was the problem but it didn't seem to fix anything.

Anybody had a problem like this before? Could it be a bad home switch or something?

Thanks,

Mike

thesidetalker · Jul 25, 2017

mikesparts said:
Hey guys we are having a problem with our 2015 ST-35, the tailstock will not zero out. When using "powerup/restart" or homing the B-axis alone the tailstock will move away from the chuck for a couple seconds then switch and move forward until it is all the way up in the jaws. The tailstock stays pressurized all the way forward and continues to think it's homing itself until reset is pressed. This is an ST-35 with the hydraulic tailstock and string encoder. We overnighted a new encoder thinking that was the problem but it didn't seem to fix anything.

Anybody had a problem like this before? Could it be a bad home switch or something?

Thanks,

Mike

While I don't have experience with that machine, my guess is it might be chips on the home position prox sensor.

The Y-axis way covers on our 2015 VF5SS are junk. They're the flat ones and tons of shit gets under them. Never been damaged or parts or tooling dropped on em. Just the way it came. As a result, a lot of chips get under there and so far we've had to clean off the home switch twice now.

When it gets gunked up it will either throw an alarm or when trying to home it will move away from the home switch, instead of towards it. Goes in Y+ until reset.

mikesparts · Jul 25, 2017

Thanks, have done more research since original post and there isn't a proxy switch for the hydraulic tailstock. It looks like it is based solely on encoder readings? I've played with the solenoids and they seem to be responding and actuating properly. This has got me thinking that the home position reading may have gotten lost or corrupted. The issue began at a startup, not something mid day or mid program or anything.

kustom1955 · Mar 30, 2020

mikesparts said:
Thanks, have done more research since original post and there isn't a proxy switch for the hydraulic tailstock. It looks like it is based solely on encoder readings? I've played with the solenoids and they seem to be responding and actuating properly. This has got me thinking that the home position reading may have gotten lost or corrupted. The issue began at a startup, not something mid day or mid program or anything.

Have you found the problem? I have a ST 30 that is responding the same way.

ChipSplitter · Mar 30, 2020

I would be really surprised if Haas didn't put a limit switch somewhere on the travel. We had a VF-2 do the same thing on the X axis. Opened the way covers and there was a chip on the sensor just as mentioned previously.

brianearle · Mar 5, 2024

mikesparts said:
Hey guys we are having a problem with our 2015 ST-35, the tailstock will not zero out. When using "powerup/restart" or homing the B-axis alone the tailstock will move away from the chuck for a couple seconds then switch and move forward until it is all the way up in the jaws. The tailstock stays pressurized all the way forward and continues to think it's homing itself until reset is pressed. This is an ST-35 with the hydraulic tailstock and string encoder. We overnighted a new encoder thinking that was the problem but it didn't seem to fix anything.

Anybody had a problem like this before? Could it be a bad home switch or something?

Thanks,

Mike

Having the same problem with an ST-20Y if anybody found any information

Orange Vise · Mar 5, 2024

The limit switch is covered in dried coolant and grease. It's a 10 dollar item that's replaceable, but a pain to get to.

If your tailstock keeps trying to move left, setting 53 that lets you jog without homing. You can use this to move the tailstock back home(ish) and try the homing routine again. It might take a few tries. Use caution when jogging.

If/when the machine finally homes to the tailstock, check your actual tailstock locations. It could be off by a full revolution or two of the ballscrew (1/4" per turn).

brianearle · Mar 6, 2024

Orange Vise said:
The limit switch is covered in dried coolant and grease. It's a 10 dollar item that's replaceable, but a pain to get to.

If your tailstock keeps trying to move left, setting 53 that lets you jog without homing. You can use this to move the tailstock back home(ish) and try the homing routine again. It might take a few tries. Use caution when jogging.

If/when the machine finally homes to the tailstock, check your actual tailstock locations. It could be off by a full revolution or two of the ballscrew (1/4" per turn).

Unfortunately mine, along with the 35 does not have a limit switch nor a ballscrew. However it does only ever want to go left because the axis value doesn't update

Donkey Hotey · Mar 6, 2024

brianearle said:
Unfortunately mine, along with the 35 does not have a limit switch nor a ballscrew. However it does only ever want to go left because the axis value doesn't update

Have you been through the troubleshooting or replacement steps for the string encoder?

Hydraulic Tailstock - Troubleshooting Guide

www.haascnc.com

ST-20/30 - Tailstock - String Encoder - Replacement - AD0227

www.haascnc.com

rjwalker1973 · Mar 7, 2024

Clean everything you can get to really well. Check pressure, too low of a hydraulic pressure on your tailstock can cause some funky shit to happen. B handjog and jog it back and check the machine position on your position screen and see what it tells you.

brianearle · Mar 7, 2024

rjwalker1973 said:
Clean everything you can get to really well. Check pressure, too low of a hydraulic pressure on your tailstock can cause some funky shit to happen. B handjog and jog it back and check the machine position on your position screen and see what it tells you.

Already have. The string encoder actually works as it updates the internal raw encoder value. But the machine position on the screen stays zero. It almost feels like a software bug or some parameter gone wrong.

Donkey Hotey · Mar 7, 2024

Wow, so the encoder shows updates on the diagnostics screen but, not on machine position? That's insane. Does it stop moving if you hit reset before it hits the limit? Can you jog the tailstock manually at that point?

brianearle · Mar 7, 2024

Donkey Hotey said:
Wow, so the encoder shows updates on the diagnostics screen but, not on machine position? That's insane. Does it stop moving if you hit reset before it hits the limit? Can you jog the tailstock manually at that point?

If the tailstock is too far left when it homes it gets stuck until I hit reset. If it's to the right of the home point it actually does finish the homing sequence. It will let me jog to the left, but not to the right because the axis is stuck at 0 and it doesn't want to go "positive" past the zero point. I've confirmed that it is actually reading the raw encoder value correctly though as it homes at the right value.

I can trick it into jogging to the right by repeatedly hitting the foot pedal and resetting the undershoot error. If I can find why it's not updating the axis that should fix everything.

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