r/Metrology

I’m building a Michelson interferometer with a HeNe laser to measure the interferogram on a single Si photodiode. The only lens in the setup is placed after the beam splitter, in the detection arm. With my current alignment, the interference pattern on a screen is a set of straight, parallel fringes, and the photodiode sits in that field to record intensity as I scan one arm.

For a quantitative measurement (i.e., determining the laser wavelength), is there any advantage to having a circular fringe pattern instead of straight fringes?

My understanding is that, as long as the photodiode is small compared to the local fringe spacing and sees a clean modulation from bright to dark as I scan the path length, the global shape of the fringes (circular vs straight) shouldn’t matter.

I am new to polylworks (using 2025) and was wondering when you construct a line from two features, say the center points of two circles for example. What determines the direction of the line? Is it the order you select the two features or their order in the tree. Sorry if this is a dumb question. Thank you!

Hey guys, so I am a welding engineer that recently got in charge of metrology lab on my company as a quick fix until we got the production numbers to justify having a metrology engineer in charge of the lab. I have a little problem, the lab is being used for multiple purposes and not solely to measure so with this brief context my issue is that i need a measuring table that can travel though shopfloor to be stored in another place and be moved to the lab once it needs to be used. I am already buying a plate fixed to the floor of 2.5 x 2.5 meters (100 x 100 inches), this plate is going to have holes spaced every 10 cm (4 inches) to fix any kind of fixtures for the different kind of parts that i need to measure (this is the plan for big parts). the problem comes with little parts as i would need to create larger fixtures for the parts to be "floating" on a ideal height for the guy who is going to be measuring. the measurements of parts that the table would be intended for would be around a cube with 60cm (24in aprox) on each of its dimensions. my issue is that i want it to be sturdy enough to be fixed once it needs to be used on the lab, but easy enough to move around the lab and the place where it is going to be stored.

*i am measuring the parts with a romer arm, and a leica laser tracker for bigger parts

do you guys have any idea or recommendation? anyone has dealt with something like this ?

*sorry if there is any grammatical errors, english aint my first language,

I just started a job in a new field in the inspection department of a machine shop. My mentor has been here for 40 years and he can be very no-nonsense but has a funny bone in him. I was thinking about bringing in a tape measure and starting to “inspect” items and then ask him for advice when “something doesn’t look right”. Anything along the lines of that if you guys have any ideas.

I believe GD&T is one of the key topics in a CMM job interview. However, in the two interviews I attended earlier this year, the conversations were usually led by HR or the GM, and they tended to focus mostly on general questions—like the most challenging time in my career or what I’ve learned from difficult situations.

I’m curious—what kind of GD&T questions have you been asked?

I have an offline program that was written from a 3rd party offsite. It was unfinished and I added more features, alignments, report pages and finalized the program in real world series 6 scanbox.

We have csv files that export when we approve a report in Kiosk mode that gets uploaded to our CM4D which populates the data into trend charts.

On this program, only 10 edge points with the dT value are exporting to the csv while the rest of the features are not there. The features that are not exporting are a mix of ones that I created along with the 3rd party. I am at a loss of what could be causing this. It has never happened and the only thing I can think of is some weird obecure setting that got carried over fron someone elses setup? AI isnt much help....as usual its taking me to menu items that don't exist. Zeiss forum is dead these days and your lucky to get one response. I know we have a guru or two here....

Note...all features have xyz and normal checks and tolerances and are populated in the overview table.

Hi everyone, longtime reader first time asker. I am working on a supplier verification project with designing gauges for incoming lineals. I have 20 years of experience in a manufacturing adjacent role but just transitioned into a quality engineering role. I was wondering what kind of gauges you all use to verify incoming lineals. Looking at twist/bowing, height, etc. the more creative and effective the better. Also, if anyone has any good resources on gauge design I would love recommendations!

Bonjour,

j'ai régulièrement des problème de CRASH PCDMIS et je ne sais pas d'où cela peut venir .

Le Soft est sur le disque C

Mes programme sont sur le disque D

Ma configuration :

Processeur Intel(R) Core(TM) i5-8600K CPU @ 3.60GHz (3.60 GHz)

Mémoire RAM installée 24.0 Go (23.9 Go utilisable)

https://preview.redd.it/5e4oih257eah1.png?width=506&format=png&auto=webp&s=ad3d52c82a9302d894cdd07c1101bf8ad5599576

Si vous pouvez m'apporter quelques pistes ..

Merci

Bonjour,

je fais appel a vous car je suis un peu perdu avec la configuration de mes palpeurs.

Depuis quelques jours (épisode de grosse chaleur) j'ai plus rien de cohérents entre mes palpeurs.

Quand je fais une prise de mesure avec un seul palpeur, pas de problème de dimensions ou d'épaisseur tôle par rapport à mon 3D.

Mais si je fais un programme qui fait intervenir plusieurs Ø différents c'est l'anarchie.

j'ai un décalage en X de 0.2 entre le Ø5 et le Ø0.5 (pas de soucis en Y ou en Z). Un décalage de 0.4 en X, 0.3 en Y et 1 en Z entre la bille de Ø3 et la bille de 0.05 ...

J'ai beau qualifié et requalifier .... je n'arrive à rien

Résultat de la sphère bille Ø5 : X: 393.49 / Y: 1262.76 / Z :-647.08

Résultat de la sphère bille Ø3 : X: 393.90 / Y: 1262.61 / Z :-648.16

Résultat de la sphère bille Ø0.5 : X: 393.43 / Y: 1262.81/ Z :-647.00

Est-ce que çà joue?

Merci de votre aide

Version PC DMIS 2024.1

https://preview.redd.it/tacxsvd8c7ah1.png?width=545&format=png&auto=webp&s=36d164832a9d400e18f38e873619602312045031

https://preview.redd.it/fi8j8ivca7ah1.png?width=1188&format=png&auto=webp&s=ab4e35ae2a345953413b20c9e451a38c6e8bb171

This should be simple; Plane-Hole-Slot datum structure, slot width constrains rotation, and customer calls out separate single-axis position dimensions for width and for length each with MMC, (but not the slot as a feature). BUT, here's the twist: The slots are diagonal from the B-datum axis origins.

My take is that, while you can dimension a width or a length with MMC because they are toleranced and a bonus can be calculated. However, you can not use MMC on a skewed width/length because that tolerance zone is reduced due to the angle from the axis.

As has been discussed to death here, you can not use MMC on a slot because it is not a single feature, rather it's an amalgamation of 3 features; 2 matching radii and a length. So, you dimension a to the center-point of the slot at RFS condition.

So, the program engineer at "huge aerospace company that everybody knows the name of" doesn't believe me! Am I missing something? Am I not explaining things correctly? Or is this VERY EXPERIENCED program manager just a dunderhead?

I'm dreading Monday morning and having to do a Teams meeting with this doosh and my manager. I haven't told him that I'm an engineer myself, but if he's intractable, that probably wouldn't matter. Oh, the joys of aerospace companies, where the "Peter Principle" seems to still be alive and thriving...

I have a certificate in CNC machining and now I do CMM inspection and programming. Are there jobs out there that involve CMM's and programming that aren't aerospace or defense related. I love my job and find what I do super cool and I'm constantly learning but I think I'm burning out due to the poor work life balance. I'm in Massachusetts and a large majority of the shops near or around here are all aerospace. Are there other routes or similar jobs out there? I'm unsure if I'm looking with the correct words or not.

Hi guys. I'm running a Zeiss Eclipse on Calypso 2016 (I know... Old 😢) and I've noticed that calibrating with the sphere is... Not good. All of the angular rotations are off by several thousandths from each other after calibrating on the sphere (say 0,0 orientation is Z0, 90,90 is .008" different when measuring the same plane). To combat this, for the past year or so I've gone to manually calibrating using a precision ring, and checking the diameter, X, Y, and concentricity against the ring as measured with the master probe. I try to keep as much of my programming as possible in the 0,0 orientation for this reason. Sometimes I do need to articulate the head, and in those cases I do the same calibration with the ring on its side, except I don't use the master probe, I just adjust the two angles of the probe to match each other.

My question is... Why is the sphere calibration off by so much? The machine is very well maintained and calibrated by Zeiss approved techs. It holds it's calibration fine once it's set, but I cannot get accurate measurements relying solely on the sphere. Is there a better way to combat this issue? Is it well known? Or is there perhaps wear somewhere that I'm not thinking of?

Additionally, I recently replaced the TP20 Body, as most of my modules have been "clicking". Most of the modules are about a year old or less. Unfortunately, whenever someone else runs the machine, it tends to get crashed and I'm left trying to salvage the modules by adjusting the pins (pushing them back in after crashes. I actually learned that on this sub). I'm having seriously diminishing returns on the pin adjusting helping the modules stay connected though (as in, not clicking during a run. It's the same click that a crash produces). Is there anything else I can do to help this issue?

New cmm is a non starter. Trust me, I'd KILL for a new one, but it's not even worth the argument. "it doesn't make chips so it doesn't make money".

Thanks all.

Calypso 7.6

So the machine will pick up probe from rack /Tree move to a safe area index to the required angle then instead of heading for the sphere it will go Z+ and hit the hard stop.

But it's only happening to one probe all the others work. Any ideas would be appreciated.

thanks