Repair: Vast XT Sensor

[[Me...]]

Hello all,

I have a request for you and this may be a huge no-no but we have a Vast XT (G) that is in need of repairs. due to budget cuts and unknown 3rd party repairs, I am tasked with the repair of this sensor. I have no experience in repairing of these sensor heads but it sounds fixable. what I mean by that is a spring may have disconnected inside. I'm not sure if that is it but Z Direction probing causes clicking noises (And cannot calibrate) as if the internals are bumping something.

We have talked with Zeiss and the toll to cross that bridge is $10,500. My question (And I'm going to use this thread as a log) is does anyone have experience and suggestions on what I should and shouldn't do? (I already know I shouldn't be doing this but its this or the bin.)

I have some photos of the sensor shown at an angle appearing as if it had a terrible crash in the -Y direction.

XTSensor.xlsx

[[No...]]

Ask yourself: What goal are you trying to achieve?
In the end you want to have a sensor that can measure accurate results, don't you?

I'm quite certain that Zeiss did not offer you a repair but a refurbished sensor, becaue a new VAST XT is around twice as much.

Let me tell you that there is a lot more to a VAST sensor than meets the eye. For example there's a vibration damping system inside, which suppresses oscillations caused by movements. Without this it can't take reliable measurements. This system can only take a certain amount of force before it wears out and has to be replaced. This is or was especially an issue with the XT sensors, as their deflection range is smaller than that of a big VAST sensor, so a crash does more damage to the damping system. I was told the new gold types are less prone to that kind of damage, but the two we bought some time ago are still too fresh to tell. But in the past we had a lot of the old XT types replaced because of this problem, that's for sure. I doubt that you can repair this on your own.

The other thing is that there's a lot of electronic adjustment work to be done to a VAST XT head before it is ready for use.
One example is the linearity of the position measurement system, as its mechanical movements are not linear and have to be compensated electronically.

All these delicate adjustments are probably out of tune at your head, so it's very doubtfult that a simple mechanical repair will do.

[[Me...]]

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Your right, A major electrical failure may not be easy to replace and if I did know, I probably work at Zeiss, but alas, I don't. I did however open the case up with the help of a Zeiss Technician. once we opened the case, it was clear at least one issue mechanically had failed. A leaf-spring like connector had broken away. In total 4 of them (See photos). From when the technician tried to calibrate the sensor, the X & Y probing directions where ok so this makes sense as to why the Z probing would always fail.

I'm going to take a good one off and measure that part. I'm going this route since I don't think I can find a replacement easily.

Vast XT gold (SmallerSize).pptx

[[No...]]

Thanks for the images. I never saw the inner workings before.

[[To...]]

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I'd like to see deeper into it....

[[No...]]

Me too!
Teardown! Teardown! 🤣

[[Me...]]

So I've went to go take measurements and was greeted by another broken piece. looks like a plunger shaft. It has a plastic top and a metal bottom. so that was glued back together with super glue. It may not be ideal but I think it looks good. It is easy to access so if my fix for that doesn't work, I can easily swap it out. I also measured those leaf springs and did a rough draft drawing.

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I hear ya, I would like to see them as well and I will try to get a complete teardown but work still wants me to do layouts. My plate is full but I will try to get that soon! It may be a video for youtube though.

Leaf Spring Drawing & Plunger.xlsx

[[To...]]

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Is that a leaf spring or a strain gage?

[[No...]]

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Don't hurry, I was only joking 😉
But I would like to see what's inside. You never know when you might need it.

[[Me...]]

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I'm calling it a "leaf spring", I'm unsure the technical name but its no gauge. I've attached a photo of one. Their is quite a few of these that are used to hold it all together. This allows the sensor head to freely float. more details on "tuning" in the attachment.

I'm a little afraid to open the sensor head as of right now. reason being is I'm not sure how long I am staying with the company due too labor cuts. I don't want to leave a puzzle for the next person.

I've talked with the design and tooling department, we are going to make these springs ourselves, It may take a couple weeks but they think its do-able.

Springs.xlsx

[[Me...]]

Update: The springs are made, they were just sent out for heat treating and should be back in two weeks.

[[Me...]]

We received in the newly made leaf springs. They are a little shoddy but work for this case.

With the springs and plunger shaft assembled back into the case, we attached our XT sensor to our Contura CMM (Not the CMM we use this sensor with but we know the Contura is in good shape). Once we powered the CMM on we heard a humming noise. The sensor is pulling the plate in the +Z direction and seems to be holding it there, hinting at an electrical issue.

My understanding is something that senses deflection is outputting NG signal saying its taking a probing point and needs to zero the deflection to complete the probing point. Their is not a whole lot of electrical components so I'll open this back up and start testing. Any suggestion of where to start will be helpful.

New LeafSprings.xlsx

[[Me...]]

Ok, I found the issue, The broken shaft that I glued back together was missing a piece. It was supposed to be a 30mm long shaft and I found the rest of the shaft stuck in one of the coils (Z - Direction). This cause a little bit of damage to the coil (See attached) but it still functions as its supposed to.

I fixed up the shaft and reassembled the sensor head together, and now its time for testing. I've put the sensor head on our Accura machine and It was able to balance the master probe, however, during this, it took an unusual long time to balance the probe but the probe is 7 to 7 so far, no fails yet. After this I ran the probe through probe qual. This ran successfully and even passed the master probes spec (ر0.5µm, Sigma >0.5µm).

With this information I deem the sensor head fixed although temporary until I can get a replacement shaft that is not superglued together and the sensor tuned by Zeiss (Management does not want to do this until next calibration, Oct 2022).

So their you go, the insides of the Vast XT-G head.

Fixed Plunger Shaft.xlsx

[[Mo...]]

Would anyone be able to tell me how you opened the sensor?
We have a broken one that we did not send back for repair by exchange and would like to open it up and take a look inside.
How did you remove the cover? There are 4 screws on one size, but that just loosened the insides.
How do you remove the cover?