chuck limit switches

OVER HIGH LIMIT · Oct 5, 2017

We have an okuma crown cnc lathe in our shop that I love but the open/ close prox switches drive me crazy when im flipping matl. anyone know how I can override or wire around this issue? thanks

brian.pallas · Oct 5, 2017

I personally wouldn't run a machine with the chuck sensors disabled. If it's causing you problems sounds like the sebsors need to be adjusted?

Booze Daily · Oct 5, 2017

I usually just run all 1st op. then set up and run all 2nd op.
A flip op. is asking for trouble IMO. I've had guys load a new blank when they were supposed to flip it.
It didn't crash the machine, but still..

mkd · Oct 5, 2017

Make sure to run it with the doors open also.

Ox · Oct 5, 2017

Heck, I have one machine that tosses a collet switch alarm now and again ... and doesn't even have such a switch! :eek:

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Ox

ewlsey · Oct 5, 2017

The only thing you can do is cut your jaws so that the chuck closes to the same general spot on both ops.

I hate those stupid switches. We used to share jaws between machines, so you could never count on the chucks closing to the same spot. We were constantly adjusting them. I wish they just had a pressure switch like other builders.

One time I was adjusting the switches and my coworker turned the spindle on with my hands 2" from the drive belts. Scared the crap out of me. If I wasn't so stunned I would have laid him out. He knew I was working inside the covers.

Ox · Oct 5, 2017

Guess that's why the came up with "Lock-out - Tag-out" eh?

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Ox

gregormarwick · Oct 5, 2017

ewlsey said:
The only thing you can do is cut your jaws so that the chuck closes to the same general spot on both ops.

I hate those stupid switches. We used to share jaws between machines, so you could never count on the chucks closing to the same spot. We were constantly adjusting them. I wish they just had a pressure switch like other builders.

Drawtube proxes are set and forget, not adjust as required. Seems it's incredibly common for people to not understand how they work, and be constantly messing with them.

They are NOT there to tell the control that the chuck is clamped in exactly the right position of travel.

They work in conjunction with a pressure switch.

The pressure switch tells the control the chuck is closed. The prox switch tells the control the jaws are not bottomed out in the chuck body - if they are set correctly.

Once set correctly, the only reason they should ever need adjusted is if the drawtube nut backs off - which is also a good indicator of if the drawtube nut has backed off...

ewlsey · Oct 5, 2017

That's a great example of how stupid LOTO is. You can't adjust those switches without the machine powered on. Even if you eyeball them to the right spot, often they are too far away axially or right on the edge of where you want them.

I solved the problem. I now work alone.

ewlsey · Oct 5, 2017

gregormarwick said:
Drawtube proxes are set and forget, not adjust as required. Seems it's incredibly common for people to not understand how they work, and be constantly messing with them.

They are NOT there to tell the control that the chuck is clamped in exactly the right position of travel.

They work in conjunction with a pressure switch.

The pressure switch tells the control the chuck is closed. The prox switch tells the control the jaws are not bottomed out in the chuck body - if they are set correctly.

Once set correctly, the only reason they should ever need adjusted is if the drawtube nut backs off - which is also a good indicator of if the drawtube nut has backed off...

Have you ever used an Okuma or are you just making this shit up?

Any time you switch from ID clamping to OD clamping, the prox switches have to be swapped. In my old job, almost all first ops were ID clamping. Almost all second ops were OD. The operators could expect to change the switches several times each day.

gregormarwick · Oct 5, 2017

ewlsey said:
Have you ever used an Okuma or are you just making this shit up?

Any time you switch from ID clamping to OD clamping, the prox switches have to be swapped. In my old job, almost all first ops were ID clamping. Almost all second ops were OD. The operators could expect to change the switches several times each day.

No I have never used an Okuma. I apologise if I spoke out of turn but If that's actually the way they work then it's a joke. Surely they're not still like that??

All the lathes I have used work the way I described.

ewlsey · Oct 5, 2017

Every Okuma I have ever seen has prox switches that have to be dicked with. I think most people are just used to it. It's one of the Okuma quirks that you have to live with. There are others.

NiCu2829 · May 28, 2019

Is there a proper technique/method to setting the proximity sensors? One of the sensors on our chuck has moved and needs to be set properly. I attempted to reset it, but it's still alarming out. Thanks in advance!

Ox · May 28, 2019

Did you check for a small pc of Schidt on the surface of the prox?

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Ox

NiCu2829 · May 28, 2019

Ox said:
Did you check for a small pc of Schidt on the surface of the prox?

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Ox

Indeed I did. The sensors are clean. There appears to be a large range for the sensors, I'm looking for a technique to get them set at nominal so to speak. Or is it a trial and error thing?

Thank you for your time!

Ox · May 28, 2019

Many different switches and applications (coming in from the side, strait on from the end, etc) that unless your MAINT manual lists the proceedure for THAT prox in THAT app, it's likely just going to be trial and error.

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Think Snow Eh!
Ox

ewlsey · May 28, 2019

All the Okumas I ever ran required the prox switches to be adjusted for each job, depending on how far the drawtube moves to clamp the chuck. I can't recall ever seeing another brand of machines setup the same way.

One a Mori Seiki or something, they typically monitor chuck pressure or use a prox switch that tell the control the chuck has moved from fully open or fully closed. The Okuma is more picky.

gregormarwick · May 28, 2019

ewlsey said:
All the Okumas I ever ran required the prox switches to be adjusted for each job, depending on how far the drawtube moves to clamp the chuck. I can't recall ever seeing another brand of machines setup the same way.

One a Mori Seiki or something, they typically monitor chuck pressure or use a prox switch that tell the control the chuck has moved from fully open or fully closed. The Okuma is more picky.

Ewlsey, now that this thread has popped up again, do you know if this is still a thing with new Okumas?

Okuma are on the table for us right now for a new mill turn purchase, and it will see frequent setups for new jobs. If this is going to be a thing I'd have to deal with, it's a huge black mark against Okuma for me.

ewlsey · May 28, 2019

I have not seen a new Okuma in 6 years, but it was true then. I know some guys get around it by cutting their soft jaws in the same draw tube location for every part. That was no an option for us because we moved jaws between several machines.

That said, it just takes a few seconds to set the switches.

RC Mech · Jul 8, 2019

Draw Tube Prox Sensors

Bringing this thread up as it's relevant to my Taiwanese/Fanuc lathe.

Would swapping out the prox sensors to a larger dia sensor allow for greater 'throw' so to speak? Getting tired of adjusting these switches. Automation Direct has 18 mm dia inductive prox's for $20. Current style is about 8 mm dia.

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