Problem- Buzzing while rigid tapping

[padobranac]

Machine - V.M.C. - KIA KV25
Control - Fanuc 0M

The problem came out suddenly, without any change on machine/control.

When machine starts to rigid tap, it immediately starts buzzing very loud.
It makes few threads (aprox. 3 out of 10 on one workpiece), and than feed and spindle stop (at R level i assume), but it is still buzzing. When I push Reset button, buzzing stops.

Buzzing is heard also when spindle doesn't rotate, between holes.
Buzzing can be described as on very bad bearings.
Buzzing is not heard when rotating with M3 at any speed.

Spindle motor is connected to spindle directly, with hard connection.
Rigid tapping, with same nc code (M29+G84) worked well before.

Now if I replace M29 with M3, it works OK (without buzzing), but it is not rigid (synchronised) tapping now.

[padobranac]

My coworker says that it used to happen also in past,
but just occasionally, with less intensity,
and much silently.
And it newer stopped before.

[underthetire]

Sounds like a built in sensor needs adjustment, thats if it uses one.

[ad64075]

What does your spindle load meter read when you head the buzzing sound?

[sinha_nsit]

Try lower rpm.

[padobranac]

Originally Posted by underthetire Sounds like a built in sensor needs adjustment, thats if it uses one.

That would be an sensor for reference of spindle?

Where this sensor should be, inside of the motor?

Manual adjustment (moving) or with parameters?

Originally Posted by ad64075 What does your spindle load meter read when you head the buzzing sound?

There is no spindle load meter on operator panel.
Maybe this could be seen in some parameter/diagnostic? 0M, I doubt.

Originally Posted by sinha_nsit Try lower rpm.

Tried, again same thing.
I tried lower and higher RPM,and also changed feed.
Buzzing is all the time the same.

[underthetire]

If it's the built in sensor, it should be on top of the spindle. It will have a fine pitch toothed wheel with a small pickup sensor. When those start to fail, or the adjustment gap is set wrong, the motor will buzz during rigid tap and orientation. Then you will start to get sensor alarms on the drive.

[padobranac]

Originally Posted by underthetire If it's the built in sensor, it should be on top of the spindle. It will have a fine pitch toothed wheel with a small pickup sensor. When those start to fail, or the adjustment gap is set wrong, the motor will buzz during rigid tap and orientation. Then you will start to get sensor alarms on the drive.

Thank you for your answer, BUT:
- I don't get any alarms, since now (may be in the future)
- during the orientation (M19), there is no buzzing heard

"the adjustment gap is set wrong"
That is in some parameter?

[pmrairokn]

Padobranac,

Have you found a solution to your problem? I have the same problem. Can you share?

Thanks

[padobranac]

I haven't solved my problem because I didn't had any needs to make taping for last few months. Now I need this function so I tried something...

I tried to adjust gap between sensor and toothed wheel.
I reduced it, before it was from 0.10 to 0.15 mm and now it is from 0.05 to 0.07 mm.
Nothing changed. I think it should not be less than that.
Maybe it should be more, or less?

Few notes:

- I checked connectors and wires, everything seems OK.

- Buzzing happens only in rigid tapping mode (M29 Sxxx + G84),
M3/M4 works just fine

- this start to happen suddenly, there were no problems with rigid tapping before some time (using the same program)

- There are no alarms at all.

- Mostly it does perform program (tapping)-ofcourse with buzzing,
only rarely it stops in the middle of cycle and buzzing continues,
and I have to push restart, but no alarms come out

- M19 spindle orientation works fine.

- Buzzing is heard also when spindle is stopped (at R level)

- Buzzing is worse with lower RPMs (below 1500).

- When I try with 2000 RPM or more there is no buzzing while tapping,
just when starting and stopping of spindle (at R and at bottom).

- when machine starts rigid tapping cycle and approaching R level,
spindle is stopped, buzzing is present, and it vibrates (making small movements left/right, I feel it when I put finger on the spindle)

- some time ago we have changed bearings of spindle


PULSE GENERATOR
A20B-9000-0500

AC SPINDLE MOTOR
MODEL 2S, 8000 RPM
A06B-0752-B190

SPINDLE PCB
A16B-2201-0440/05B


What to do next,
just buy new pulse coder,
or there is any way to check if it is bad?

Thanks in advance for any help!

[underthetire]

.004-.006" would be normal. Don't have a calculator here to convert. Sorry.

[padobranac]

Originally Posted by underthetire .004-.006" would be normal. Don't have a calculator here to convert. Sorry.

That is 0.10 - 0.15 mm, exactly as it was before my adjustment/reduction.

During this night I got another idea:
Maybe encoder of Z axis is bad - giving non-constant position,
and spindle tries to follow the Z axis....???