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A Sharper Focus on Metrology for Medical Manufacturing

Ilene Wolff
By Ilene Wolff Contributing Editor, SME Media
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Alicona’s metrology solutions can measure form and texture in one step.

Metrology technology companies have two key reasons to innovate in the medical device arena. One is to keep up with changing standards for medical manufacturing from ISO, PTB (Germany’s national standards laboratory), NIST and the FDA. The other is to make their products compatible with new manufacturing methods being adopted by device makers, such as additive manufacturing (AM).

Also, metrology companies are keeping their sights set on the future by refining hardware to operate faster and be tough enough to work in a shop environment, either in-line or in-process, and by tweaking software to do more automatically while providing useful information from the shop floor to the C-suite. They’re also innovating more detailed metrology and offering technologies to facilitate global operations.

For example, in the past year alone Jenoptik AG (Jena, Germany) introduced two new optical technologies, the IPS 100 3D, an internal test sensor that enables automatic inspection of the internal surfaces of cylinder bores with a 360° view of the bore hole, and the IPS F400, which performs optical inspection of machined surfaces.

Whatever the standards, it’s critical for medical manufacturers to use metrology technology they can trust to comply with current good manufacturing practices and other requirements.

“The FDA requires that you go through software validation, and by that I mean you have to make sure that a circle [command] creates a circle when you press the button, so there are a lot of rigorous efforts by our partners to go through the software validation to ensure that when they sign their name to a report they can stand behind it,” said Don Demetrakeas, applications manager, central region, Hexagon Manufacturing Intelligence (Wixom, MI). “We help our customers with that.”

Other metrology companies that work with medical manufacturers help, too.

Vary Your Focus to Measure Hills and Valleys

Alicona Imaging GmbH (Graz, Austria; Chicago) offers metrology solutions for surface texture, which is covered by clauses in ISO 25178 (Geometrical product specifications—Surface texture: Areal), parts of which were enacted from 2010 to 2016. The company’s head of R&D sits on one of the committees that helped draft surface texture clauses.

It may seem counterintuitive, but not all devices to be implanted in the human body need to be completely smooth, making ISO 25178 that much more important.

With some joint replacements, bone ideally grows into the textured surface of the prosthetic, and some metal orthopedic screws have functionally textured surfaces as well.

“If implants are to heal well, the surface of the implant needs to be of a certain texture—sometimes wrongly called ‘roughness’,” said Stefan Scherer, Alicona’s CEO. “Areal surface metrology technologies, such as Focus-Variation, allow the fast, robust and repeatable measurement of those surfaces and the assessment of areal surface texture parameters such as core material volume [see Alicona graphs] defined in the new ISO standards.”

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Alicona’s Focus-Variation allows an operator to assess areal surface texture parameters such as core material volume defined in new ISO standards.

The company’s Focus-Variation technology combines the small depth of focus of an optical system with vertical scanning to provide topographic and color information from the variation of focus. In one step, it can measure form and texture, with surface texture measured in typical depths of 10–25 mm (0.39–0.98″) depending on what objective the user selects. The highest vertical resolution is 10 nanometers.

The suite of Alicona products serves various markets and can operate in general laboratory-type settings as well as in shop floor production operations. As a result, the devices must not only be accurate but also tough. “From the beginning, we designed our instruments such that they fit into an automated environment,” Scherer said.

The CEO promises quarterly advances in Alicona’s hardware and/or software.

“The most recent advancement in the software was the Edgemaster [which measure edges regardless of type, size, material or surface finish of the tool],” he said. “And the most recent improvement in our hardware was a speedup for the sensor of a factor of 3 to 4.”

Merge Scanning, Analysis and Reports with Software

With growing use of alternative manufacturing methods like AM and the adoption of mixed materials in the medical industry, industrial CT scanners like the Metrotom from Zeiss may be more important than ever for performing nondestructive metrology on parts’ complex geometries and layered construction.

“As [AM] technology grows, particularly in the 3D world, CT is a perfect fit,” said Raghu Bhogaraju, CT applications specialist at Carl Zeiss Industrial Metrology (Brighton, MI). “Just like the layer-by-layer [way] you actually make the part, I can take the data and slice it layer by layer after the CT scan is done, so that I can show you how good of a construction you have on your machine [with resolution of just over 5 µm].”

If the company’s hardware makes metrology on 3D parts possible, its Calypso software is making it more convenient and helping medical manufacturers comply with FDA and ISO design control guidance. PiWeb, a new Calypso add-on, automatically does the “handshaking” among any kind of scanning, analysis and reports; the software also has a new model-based definition feature.

CT scanning of mixed materials—for instance, a titanium layer over a PEEK core—has always been challenging, said Bhogaraju.

“The challenge there is that they’re so far apart on the density spectrum that I need to be able to get a good definition of both the PEEK and the titanium together,” he said. “So, in order to do that I need to be able to come up with algorithms that can refine the edge detection between those two materials. And that’s what we’re good at—taking a plastic part with metal pins in it or a metal part that is over-molded with a plastic sleeve, scanning it, and getting a good definition between the plastic and the metal.”

The secret’s in the software, he said.

“Calypso is the first true metrology package that has the capability to do mixed materials,” Bhogaraju said. “It’s a big improvement for a lot of our customers who have been asking for this.”

Those customers include makers of USB connectors, syringes, surgical instruments, and titanium orthopedic knee joints that want to see whether bone tissue has successfully grown into the device, and more.

While the marriage between AM and CT metrology seems a match made in heaven, the Calypso add-on software Piweb works with any of Zeiss’ metrology machines.

“All those different instruments have their own advantages: Maybe it’s a larger part that doesn’t fit within the volume of the CT, so you go to a traditional CMM,” said Scott Lowen, software product manager. “But regardless of the instrument that’s measuring it, the results of the measurement are coming into a collective software report.”

Lowen explained how Calypso and PiWeb are convenient for collecting, analyzing and reporting on data for medical manufacturing that’s becoming increasingly globalized, and for pushing data and reports up from the shop floor to management. That’s because they create a central database with a user interface for anyone in manufacturing to access the information they collect and analyze, and subsequently fix any problems detected.

“For example, Scott could have a CMM in Michigan and his subsidiary office down in Mexico could have a CT machine, and they could be measuring the same part using Calypso,” said Bhogaraju. “But with this database the management can pretty much tie up both results in one location to actually keep track.”

Without PiWeb, inspection results are usually held locally, Lowen said, not only to the instrument but also to the quality department.

“And there were just typical communication barriers of trying to get those results to manufacturing or process engineers or the teams involved with making adjustments to make better parts,” he said.

For security purposes, PiWeb resides on a medical manufacturer’s server.

Just as PiWeb makes detecting problems wherever they occur more convenient, Calypso now accepts CAD models with model-based definitions—embedded dimensions vs. parametric designs—that make life easier for metrology technicians.

“The user just needs to import the CAD file rather than sit down and create this big program that has all the measurements he needs,” said Bhogaraju. “With a parametric CAD file, I need to bring it into the software and then say OK, give me a plane-to-plane distance, or in the CAD file, if I have a few bores or cylinders, give me a diameter true position color, whatever it is.”

Dimensional information can also be imported into the PiWeb software.

“It’s reducing programming time, or setup time,” said Lowen. “It creates a more consistent program because you have less chances for operators and their influences or specific training or knowledge [to affect the process], so it’s creating a more standardized method to create the measurement plan.”

Automotive Regulations Were Good Training

The name of Jenoptik Automotive (Rochester Hills, MI) can be misleading. The company works with medical manufacturers, too, and brings some relevant experience from the vehicle industry as well.

“With some joint replacements, bone ideally grows into the textured surface of the prosthetic, and some metal orthopedic screws have functionally textured surfaces as well.”

“When you talk about regulations and standards, as they become ever-more restrictive I would say we have a good head start because when you look at global manufacturing and restrictions and documentation and everything that goes with them, the automotive industry provides us with a significant amount of guidance,” said Andreas Blind, vice president of sales, services and marketing. “What I see in the medical industry is that it’s just starting with full-blown 100% inspection of parts, with traceability of parts.”

As recently as 20 years ago, when an automotive OEM or supplier produced a part, it was impossible to trace that part’s history back to its point of origin, according to Jenoptik. There would be no part data, no measurement data, no way to tell what machine it was manufactured on. Consequently, automotive manufacturers started holding suppliers accountable for warranty costs related to failed parts.

As a result, the entire automotive industry started adopting technology that would allow each piece manufactured by a facility to be completely and transparently traced back to its point of origin, including any manufacturing data, such as date and time of manufacture, the machine it was manufactured on, part measurement data, and more.

“In the medical field, for the longest time you had manufacturers that had a cradle-to-grave approach,” said Blind. “So, you had a DePuy or somebody that made everything in-house. But they’re getting away from that.”

As medical manufacturers become more global, traceability has become just as important to them as it is to automotive manufacturers. And when you have the capability of 100% parts inspection, manufacturers can completely control their manufacturing processes. Jenoptik delivers part data that allows manufacturers to adjust their manufacturing processes to reduce or eliminate bad parts, adjust part sizes on the fly, and determine why a certain batch of parts failed.

Also as in the auto industry, Blind predicts metrology will become more automated in medical manufacturing.

“What I see as a coming trend is more and more automation of visual inspection,” he said. “It is driven by several factors: cameras have become way better, computing power has become better, and the understanding of those parameters has become way, way better.”

Measure Small Parts Even in Tough Environments

Like Zeiss’ technology, that offered by Capture 3D Inc.(Santa Ana, CA), the exclusive North American partner for GOM (Braunschweig, Germany), helps medical manufacturers comply with design control requirements from the FDA and ISO.

“Blue light 3D scanning technology, also known as optical metrology and structured light, is used by the medical manufacturing industry to ensure parts, molds, tools and dies meet design intent and are within dimensional tolerance,” said Matt Bosley, sales engineer at Capture 3D’s facility in Huntersville, NC.

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The new ATOS Capsule features an encapsulated housing for industrial environments.

GOM’s technology is used for manufacturing orthopedic implants, dental implants, and tools and guides for surgery. It has even been used in cadaver labs to help develop new surgical instruments and procedures.

Earlier this year, GOM introduced the ATOS Capsule, an optical precision measuring machine featuring high-resolution cameras. The device is targeted to small parts applications in the medical and aerospace industries.

True to its name, the Capsule features an encapsulated housing for industrial environments and includes parametric inspection analysis, GD&T, trend analysis, surface defect mapping and optical tracking.

ATOS 3D scanners engineered by GOM are used throughout the manufacturing process because they can produce 3D mesh data for product development, provide adaptive machining capability, and enable quality control for near-line and in-line production applications, Bosley explained. The precise 3D mesh contains crucial measurement information for instant feedback, dimensional verification and corrective action, if needed.

Sensors in ATOS units can also be paired with a robot to increase process throughput, repeatability and reproducibility.

In addition to their full inspection software capabilities, ATOS 3D scanners contain process checking traceability features and are certified through NIST and PTB, placing them in Class 1 with the smallest deviations. This allows them to meet medical manufacturing requirements.

ATOS and GOM inspection software imports data from CT and MRI scanners for a complete external and internal analysis.

With the ATOS ScanBox series of off-the-shelf automated solutions, medical companies can automate quality control processes with intelligent offline and online measurement programming.

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