?? Z Axis Crashed ??

I have a Sharp 2412 with a fanuc control. It spends most of it's time offline. I had the PSU in the combo drive repaired last year. After about 3 months of the machine being off, I powered it up normally and did a zero reference return (full rapid) and while the Z axis was moving up it felt like it crashed (could feel it in the concrete under my feet) but when I checked it's position it wasn't beyond the home reference position marker. Well the PSU had blown again (overvolting) so I figured it sent an abnormal current to the servo during the zero return and then it went into some kind of failover mode that e-stopped the axis.

So anyways I had to send the PSU back out for repair again, while that's being done I decided to do a full service on the machine. While I'm up on the Z axis replacing the oil metering units, I notice a loose chunk of steel I immediately think "oh great, something did break after all" I fished it out of there with a magnet and it looks like a physical stop for the z axis?!? I dont see a part for this on the Sharp parts book. My software AND limit switch failed? This is kinda crazy that it appears my Z axis almost shot off the rails... Is this what happened? I can't think of any other scenario. It looks like it was ripped out of the casting of the Z axis servo housing and sheared one of the bolts off... so it was definitely some extreme force. How could this happen? Did my limit switch fail?

See pictures below:

No physical stop like this in parts diagram (previous owner added them in?)...

I just climbed up top of my 2412- nothing like that on my machine.

No holes drilled in the casting either.

I have a 2005 2412 and that block IS on my machine.
Why do these machines have limit switches with absolute encoders. Is the limit switch just there for extra safety.
Now I wonder if they even work.

Kallam said:

I have a 2005 2412 and that block IS on my machine.
Why do these machines have limit switches with absolute encoders. Is the limit switch just there for extra safety.
Now I wonder if they even work.

Click to expand...

That's interesting. Mine is a 2005 also. Oi-Mate MB, without absolute encoders.

I'm wondering if the block is to help set the Z limit, and OP's machine lost the APC batteries when it was sitting idle.

Do you have the APC option on your 2412?

Do you have the APC option on your 2412?

yes 6 volt battery backup

Kallam said:

Do you have the APC option on your 2412?

yes 6 volt battery backup

Click to expand...

Just a guess, but I think the purpose of the block is to set the G28 position. One person at the control, one up top with a feeler gage...

Kallam said:

Do you have the APC option on your 2412?

yes 6 volt battery backup

Click to expand...

Yes APC's, battery was replaced about 5 months ago with reference positions re-established.

Kallam said:

I have a 2005 2412 and that block IS on my machine.
Why do these machines have limit switches with absolute encoders. Is the limit switch just there for extra safety.
Now I wonder if they even work.

Click to expand...

I'm starting to think it failed. The Sharp parts book has it listed as a "popular" replacement part (with a red star next to it)

Update, Sharp says the limit switch likely failed. Going to replace it. Just thought the other sharp owners would want to know.

@Kallam @jancollc do you guys have a picture of your z limit switches? I just pulled the cover plate off of where it's supposedly located in the parts diagram and there's nothing there...

Can you get a picture of the part number and brand name, etc? I called Sharp and they don't have it in stock so I have to try and find it somewhere else.