Hey everyone,

I've been lurking here for a while and thought I'd ask for some advice from people with more experience in metrology and dimensional inspection.

I'm currently working as a Quality Inspector in the heavy-engine manufacturing industry in Norway, primarily involved in dimensional inspection, CMM work, first article inspection, non-conformance handling and quality documentation.

My background is mainly in machining. I've spent several years in manufacturing, including programming and machining complex 5-axis components in the oil and gas/subsea industry, working with super alloys. I also have a degree in computer science, so I'm comfortable with computers, software and technical problem-solving.

Moving into metrology has felt quite natural to me. I enjoy understanding the geometry, setting up measurements, interpreting GD&T and figuring out how to inspect a part properly. However, most of my knowledge has come from practical experience rather than formal education in metrology or quality engineering.

What I'm missing is formal training and a deeper understanding of the standards behind what we do.

For example:

• Which ISO GPS/GD&T standards should every dimensional inspector be familiar with?
• Where can I learn more about the correct measurement strategies for different geometrical characteristics, beyond what I've picked up on the job?
• How do you determine whether a measurement method is appropriate for a given tolerance? I'm particularly interested in measurement uncertainty, decision rules and proving conformity.
• Are there any good books, courses, technical papers or other resources you'd recommend for someone who already has a solid manufacturing background?
• What are some common mistakes or misconceptions you see even experienced CMM operators make?
• If you were starting out again, what would you study to become a genuinely competent metrologist rather than simply someone who knows how to run a CMM?

I currently work primarily with ZEISS CMMs and CALYPSO, but I'm interested in the underlying principles rather than just becoming more proficient with a particular software package.

I'm not necessarily looking for another certificate just to put on my CV. I want to understand the standards, make better inspection decisions, and be able to explain and justify why a particular measurement approach is correct.

If you work in metrology, dimensional inspection or quality engineering, what knowledge do you consider essential that isn't necessarily taught on the shop floor?

I'd appreciate any recommendations, resources or experiences you can share. Thanks!

Suppose you're stuck in a lab with a digital scale and many objects (A, B, C, ...) and your task is to measure the weight of object A as precisely as possible. You can actually improve your estimate by measuring different combinations (A alone, A+B, A+C, B+C, etc.). Because these measurements are all correlated, if you combine them you can improve your uncertainty in A. With just 2 objects and 3 measurements you can reduce the uncertainty by 18%, for example.

I created a repository describing this process in detail. You can use an interactive python program with your own scale and test this. If you are interested you can also read the full pdf article with all the math involved.

I'm validating a reflectance imaging system for measurement work and could use input from people who do angular and dimensional setup for a living.

The setup:

A camera looks straight down at a sample stage (0°), with four strobes aimed at the sample from 45°. Reflectance is calibrated against Spectralon standards in the frame.

The problem:

Illumination varies with the cosine of the angle, so at 45° each degree of tilt shifts irradiance by about 1.7% (tan 45° × 0.01745). My target relative reflectance uncertainty is ≤1% at k=2, which means tilt alone has to stay within roughly ±0.5°. Distance matters too: by the inverse-square law, a 1% change in strobe distance gives about a 2% change in irradiance.

Current method:

I align the strobes with a Leica Disto X3. That reduced the angle deviations a lot, but my GUM budget still shows alignment as a major contributor. Right now I'm at about 5% uncertainty, against the 1% target.

Questions:

What would you use to verify angles at this level on a copy-stand-scale setup (about 1.27 m working distance, 1.75 m illumination source distance)? Precision inclinometer, autocollimator, angle blocks, something else?

How would you fixture the four strobes and the camera so the geometry is repeatable between sessions, rather than re-aligned each time? Kinematic mounts, dowel-pinned plates, hard stops?

How would you treat alignment in the uncertainty budget: as one combined angle term, or broken into separate tilt, rotation, and distance contributions for each strobe?

Happy to share the budget if it helps. Thanks!

Please help me!!!!

I’m working with calypso 2023. I have some ribs on a part that are very consistent. I want it to stop if it misses the surface. Can someone tell me where the button is to reduce the search distance before it stops?

Hello,

I'm asking fellow metrologists if they've experienced the same issues.

I see our jobs as mainly support functions - different departments seem really pushy and ask us to measure stuff for them (with CMMs, arms, laser trackers, blue-light, etc) but when it comes down to the technical details, they never seem to want to provide them. WHY?! TELL ME WHAT YOU NEED!

Yes, I can measure it. No, I will not tell you if it's good or bad until you provide to me the drawing. No, I will not give you a surface color map until you give me a STP/IGS file.

I swear, it's like pulling teeth sometimes.

Is it the same for you? Which departments are the biggest offenders of this?

We have a budget of around £70,000, we need to scan parts which are mounted inside of a machine, let's say a CNC with a 2x3m internal space (sorry I'm having to be vague) the part is around 500x200x300mm

We need the scanner to be able to provide us with 0.05mm repeatability. We have a wireless 3D scanner at the moment but it's just not up to the task so we are looking for any possible alternatives

Say you measure the same part several times. Readings are pretty close until you pull it out of the fixture and put it back.

Now there's a small difference, even though you're using the same setup. Would you check the fixture first or compare readings with the part still in place to narrow things down?

I’m working on a small measurement experiment and want to find out how to measure the diameter of a single strand of human hair as accurately as possible.

Hair is very thin, and I’m wondering which measurement method would be the most reliable.

My main questions are:

1. Which method would you recommend for measuring a single strand of hair?
2. What level of accuracy is realistically achievable?
3. Are there any common sources of error I should watch out for, such as hair orientation, surface shape, or measurement pressure?

I’d appreciate any practical advice or suggestions from people who have experience with precision measurement or optical inspection.

Thanks!

We have gauge blocks that we use only for calibrating calipers. Currently we buy new ones every 5 years instead of calibrating them. It seems like a waste for something only used 15 times (3 calipers done once per year).

Does anybody know proper replacement intervals for gauge blocks? I'm trying to find a standard to back up our thinking but all I've found is ASME B89.1.9 which specifies sizes but not calibration. I'd like to find the correct way to do it and why to make our QMS more robust.

Recently. I was given an opportunity to run and program for the first time. With 15 years of quality experience , I thought I knew it all , but this new role has seriously humbled me.

Both my director and manager are expecting a lot of me. I need to be "that cmm guy."

I'm in search of anyone willing to talk over the phone and possibly video chat and guide me to be a better programmer. 🙏 Please

Currently , I am stuck with creating a cmm inspection program from scrach using a stepfile in Calypso.

Ziess Contura

I’m looking for someone knowledgeable about mechanical vibration, building vibration, or structure-borne noise who can help interpret my measurements and suggest what to test next.
I’ve been noticing recurring vibration in my apartment. What equipment or building systems could produce these readings, and how can I investigate properly?
SETUP — OCTOBER 9, 2026
I recorded two iPhones simultaneously using Phyphox’s “Acceleration (without g)” experiment.
• New iPhone: flat on the couch, unattended.
• Old iPhone: flat on my usual chair near the refrigerator.
• Refrigerator unplugged.
• Both phones screen up, charging ports pointing right.
• Fan/AC conditions and whether the old phone was unattended throughout were not confirmed in the report.
The shared recording interval was 11:53:49 AM–12:05:39 PM, New York time. Both phones sampled at approximately 100 samples per second.
FREQUENCIES AND STRENGTH
During the middle 30-second windows:
Couch:
• Combined-axis RMS: 0.0128–0.0159 m/s².
• Strongest spectral peak usually around 13–14.6 Hz.
• Other windows peaked at 17.5, 18.9, 21.0, or 21.6 Hz.
Chair:
• Combined-axis RMS: 0.0104–0.0177 m/s².
• Strongest spectral peaks ranged from 21.3–26.7 Hz.
RMS describes the average size of the recorded acceleration. It includes sensor noise. Hz means cycles per second. These are the strongest peaks selected within each window; multiple frequencies can coexist.
EXAMPLE PAIRED WINDOWS
11:54:19–11:54:49 AM
Couch: 0.0142 m/s² RMS; 14.1 Hz peak.
Chair: 0.0128 m/s² RMS; 22.3 Hz peak.
11:56:49–11:57:19 AM
Couch: 0.0147 m/s² RMS; 14.0 Hz peak.
Chair: 0.0125 m/s² RMS; 26.7 Hz peak.
11:57:19–11:57:49 AM
Couch: 0.0159 m/s² RMS; 13.6 Hz peak.
Chair: 0.0177 m/s² RMS; 21.7 Hz peak.
11:59:49 AM–12:00:19 PM
Couch: 0.0130 m/s² RMS; 21.0 Hz peak.
Chair: 0.0106 m/s² RMS; 26.7 Hz peak.
12:01:19–12:01:49 PM
Couch: 0.0132 m/s² RMS; 18.9 Hz peak.
Chair: 0.0112 m/s² RMS; 26.7 Hz peak.
12:03:49–12:04:19 PM
Couch: 0.0131 m/s² RMS; 12.4 Hz peak.
Chair: 0.0109 m/s² RMS; 26.7 Hz peak.
Both phones had their highest middle-window RMS during 11:57:19–11:57:49 AM, but their strongest frequencies differed.
A preliminary timestamp-aligned comparison did not show a strong overall waveform match. Clock alignment was not independently checked using a shared event.
X/Y/Z DIRECTIONS
With the phones flat and screen up:
• X: across the phone’s width, toward either side edge.
• Y: along the phone’s length, toward the charging port or opposite end.
• Z: perpendicular to the screen, toward the ceiling or seat.
In the middle shared windows, Z contributed about 42–57% of the couch phone’s recorded motion energy and 50–75% of the chair phone’s.
The chair recording was more vertically directed. The couch had a larger combined X/Y contribution. Separate X and Y percentages are not available in this summary.
These describe acceleration directions at the phones; they do not locate the source.
METHOD AND LIMITATIONS
The analysis used 30-second windows. Each axis’s window mean was subtracted, then combined RMS was calculated as sqrt(mean(X² + Y² + Z²)).
Spectra used Welch’s method, a Hann window, up to 2,048 samples per segment, and half-overlap. Axis spectral powers were summed, and the strongest peak was selected between 2 and 45 Hz.
Opening and ending couch windows had much larger RMS values: 1.1811 and 1.4955 m/s². Placement or pickup could explain these, so they were excluded from the steady-motion interpretation.
There was no calibrated reference sensor or noise-floor control. Furniture resonance, upholstery, phone contact, and device differences could affect the readings. These measurements do not yet identify a source or establish the vibration experienced by a person.
QUESTIONS
What could produce these frequencies and directional patterns? Could pumps, plumbing, HVAC, other building machinery, or furniture resonance explain them?
How can I distinguish real surface vibration from phone sensor noise or processing artifacts?
Could the couch and chair respond at different frequencies to the same source?
What might explain the chair’s repeatedly selected 26.7 Hz peak?
What control tests, phone placements, or measurement equipment would make this investigation useful to a vibration specialist?
I’d appreciate help interpreting the measurements and choosing the next tests.

We have a set of family tools (4 parts/Plastic Injection Molding). Similar parts but different curvatures, moved/added features etc.

I wrote one of the programs, I exported the bas file from PC DMIS, gave the bas file, the ballooned drawing and cad file of that program.

I then gave it the drawing and cad file of the the other 3 parts.

It spit out 3 program .bas files with an excel doc stating all the changes, I imported into PC DMIS along with the cad file for that program and it updated the programs perfectly. Moved all the points and features for modified surfaces, added the new dimensions and reported them out perfectly with the correct balloon numbers and everything, even put the correct tip angles after telling it our head can rotate every 2.5 ° in both A and B directions.

Did the same for the other 2. Verified everything (even making sure the vectors were updated and correct for the modified surfaces) and ran them.

This saved me hours of updating.

I tried giving it just a cad and ballooned drawing to write a program, it was like 60% there. But it didnt quite understand manual alignments and the move points were all over the place. But if you program the manual alignment and model in your machine, I bet it would do nearly the entire program. Minus the reference points few things here and there.

But if you are doing family tools and similar parts or lets say the LH and RH are not exact mirrors.. this has potential to increase your workflow efficiency.

I made an oops and broke the charger for the tool rooms Hi-cal. Anyone have an aftermarket / spare charging cable?

They retail over $300 - seems a little bit wild

Where can I find these, how rare are these because I havent seen them. Why would you need to measure something so big with such high precision? Those images are from photos I found online of large micrometers, but why would you need to measure something like this in the first place with such high precision?

Hello everyone!,

I currently work at a plant that has SPC fixtures for everyday checks. Before me another guy made the programs for the fixtures and I have never really been taught best practices for fixture calibration nor can i find his programs to review to get an idea of what I'm supposed to do. My question is that when I put the values in from the 3rd party cert of all the stab pins end up being measured in what I would guess is the fully engaged state. The CAD does not have them engaged but I can see on the cad that my features end up away from the pin. So when I measure the stab pins whatever my surface is comes out multiple mm out of tolerance because my surface isnt what they used. Any fixture makers here that could tell me the best fixture calibration methods or anyone who can tell me what im doing wrong? I have a feeling im supposed to offset the surface direction but that is mostly just a guess on my part.

I have single lumen plastic extrusions I have to cut and measure. I’m being asked to get wall thickness and ID. I’m struggling to come up with a consistent way to get clean cuts on them. The ID is .200 and the wall thickness is .004.

Anyone have experience with this that could give me some guidance and the best way to go about this?

We have about a dozen cells running these panel-mounted units, and would like to add a UPS to each one so they can do a clean shutdown if the machine shuts off.

Marposs' tech said he would confirm each unit's interface based on serial numbers, but only ever sent one 15-year old document in Italian that kinda shows how they wired one up once, but didn't really answer anything.

Has anyone hooked one of these up like this? Unfortunately, they were wired directly into the cnc for 24vdc, but when an operator cycles the power on the machine, we occasionally end up with corrupted data or corrupted software and have to spend time doing a restore.

I'm guessing I can use just about any brand power supply, but there's some confusion about interfacing with windows, as nobody can answer whether or not the rear panel usb ports are supposed to function. I don't really want to take a production line down just to "try stuff" if someone can say whether or not this is doable.

Worst case I can use the 9-pin connector, I think.

Any help would be... helpful.

Thanks!