What Is Metrology and Why Is It Needed?

What is Metrology and Why is it Needed?

Metrology is the scientific study of measurement. This field of study defines measurements under a common understanding, applies these measurements in practice, and uses them in analysis across industries. Because of its broad applicability, metrology is used worldwide to establish accuracy and precision in many critical fields.

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Using Transformation Matrices with Point Clouds

When working with large point clouds, particularly those from our FARO Focus S 350 long range scanner, it is often necessary to modify the existing point cloud to align or organize the data. For example, scans from the long range scanner are translated and rotated in all six degrees of freedom to align to one another and create a contiguous point cloud. To do this, a transformation matrix is applied to the data.

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Is There a Difference In: Accreditation, Compliance and Competence?

Who do you trust to tell you what your parts measure and how the parts compare to the standards of 3D CAD / 2D drawing specifications?

How do you know that you can trust them in the first place?

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What are my Part Digitizing Options? Buy a Scanner or Use a Service

Most companies that have a need to digitize parts ask the “Make/Buy” question.  Do I purchase part scanning equipment and train staff (Make) or do I find a good service provider (Buy)?  Or are there levels in between this?

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Basics of Metrology – Gage Repeatability and Reproducibility

Everything in life has a certain amount of risk associated with it. For the consumer of a product or process the risk is also tied to cost. The measurement results that any accredited metrology laboratory provides you will ultimately be used as either evidence that your product or process is within bounds, or outside of bounds. If it’s within the boundaries of acceptability then the cost associated here is the cost of the third party inspection. However if the inspection shows the product or process is out, then the costs become a bit more complicated, as you will need to review the product and process and possibly adjust it one way or another.

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What are Casting datums?

We have all seen prints with many datum reference frames on them. The fact that there are multiple sets of datum’s is not an issue and is put in place for functional design reasons. There can be so many that they look like an alphabet soup. But what about raw castings? Generally the functional part datum reference frame(s) have not yet been cut into the parts yet.  This where casting datums come into play.  They are typically designated as X-Y-Z or Z-Y-X.

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Can you Measure a Gap in CT that is Smaller than the Voxel Size of the Scan?

A common question that we are asked is: what is the resolution of a CT scan for determining gaps or voids or true surface locations?  We are also asked:  How can you measure a gap between two parts that may be closer than 1 voxel in size?  The answer lies in sub-voxel surface determination and in the number of voxels that are involved and continuous surfaces as detailed below.

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Using a Hybrid Approach to Additive Manufacturing Metrology – CT – CMM

Modern Additive Manufacturing (AM) methods often employ subtractive machining to achieve precise dimensional and surface finish characteristics.  This is due to current AM limitations in build precision and surface quality.  These hybrid AM / subtractive components also demand a hybrid approach to measurement.  Internal features on AM parts are difficult or impossible to non-destructively measure using solely traditional metrology methods and so industrial computed tomography (CT) must also be employed.  CT scanning not only allows for precise measurements using metrology CT, but allows for detection of internal defects that are not otherwise able to be seen.  However, well machined portions are best served through other measurement methods due to precision requirements and data characteristics. This can necessitate a hybrid measurement approach.  However, traditional CT scanning and service providers are not trained as metrologists and do not follow particular standards related to metrology – especially ISO17025. Also complicating measurement is the design and datum reference frames used for additive parts that typically follow a traditional machined component print layout.  A layout method following best practices from the casting industry is suggested here. This article explores the methods (GD&T), issues, limitations and current solutions associated with good metrology practices for AM and hybrid AM components.

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How to Handle Quality and Inspection Requirements in Uncertain Times

COVID 19 has literally shut down a majority of the world’s production. As we have talked with our customers over this time, we have found that many have reduced their workforce or have implemented rolling furloughs. The problem is that once you let that skilled person go, they may actually find other work before you can hire them back. So, all of the training that was invested in them is gone. This seems especially true of Quality staff. During each normal business cycle and when things get tight, the quality staff is the first to be reduced. A new staff is then later brought on once the cycle has completed with the requisite experience or they are slowly trained up to a proficient level. This is logically the case as production requirements are lower during these cycles and removing production personnel would immediately and directly hamper the ability to generate revenue.

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Ensuring Accuracy of Gages and Fixtures Through Accredited Calibrations

If we lived in a perfect world the parts you manufacture and the gages used to check them would both be exactly to nominal specifications. At that point a gage would be obsolete and so too would be the metrologist, but we all know that this world is far from perfect and that the best we can ever do in the study of measurements is to provide our best estimate of where the actual value lies along with a provision of uncertainty of measurement that can be traced all the way back to the international system of units.

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