Light Marks the Spot on Medical Implants

A custom, flexible laser marking system marks medical devices, checks quality, and connects to front- and back-office production and inventory systems.

Although laser marking may seem a straightforward task when compared, for instance, to developing wrist implants or artificial hips, poor marking systems can introduce pinch points in the manufacturing process or even stop the line entirely in the event of failure.

When Wright Medical Technologies (Arlington, TN) went looking for a new production-level technology to mark their reconstructive joint devices and biologics, they needed a system that offered flexibility, reliability, ease-of-use, and connectivity with production tracking software and systems. Working in concert with the laser-marking firm Telesis Technologies Inc. (Circleville, OH), the combined engineering team was able to develop a robust, portable system that satisfied these requirements.

Marking In Vivo Medical Devices

The Telesis system facilitates marking using a step and repeat function.

Implantable medical devices like artificial ankles or plates and screws must be manufactured to ultra-tight tolerances. Artificial joints with excessive surface roughness, for example, can cause patients pain. And because the devices are embedded in tissue, the devices must be made from non-toxic materials that resist corrosion and wear. To top it off, implantable devices must function without fail, whether the operating lifetime is years or decades. "The name of this game is to build a minimally invasive product that limits patient recuperation time and provides them with a stable joint that is designed to last for many years," says Joe Moody, senior process engineer at Wright Medical.

Indelible marking allows manufacturers to comply with ISO specifications and the US FDA's proposed unique device identification (UDI) rule that will soon mandate scannable 2-D matrix codes on every implant. The UDI is a system used to mark and identify medical devices within the healthcare supply chain. The proposed rule by the FDA will establish a UDI system that will require manufacturers to include both a plain-text version of the identifying data and a version encoded using automatic identification data capture (AIDC) technology such as linear and two dimensional bar codes. According to Ralph Villiotti, east regional sales manager at Telesis, "marking also gives medical device manufacturers an important process control tool that helps ensure the highest levels of production quality. Specifically what manufacturers are looking to achieve is complete traceability of the part from 'cradle to grave,' he says. "The laser marked implant can be traced back to the day it was manufactured, the machine that it was made on, and the person responsible for quality control and marking--all through the addition of the laser mark and the software included with the Telesis system to log each mark complete with date and time stamp."

For many years, chemical etching was the go-to technology for marking. The process is not only time-consuming, but also involves toxic chemicals. Laser marking provides a chemical-free alternative that can permanently mark a product in a few seconds. In laser marking, the galvo-steered laser beam anneals the surface to create a black, indelible mark by inducing carbon migration toward the surface of the material. It does not involve ablation, nor does it damage it or change the material metallurgically. This is important for medical devices that must operate over extended lifetimes. "You don't want to etch the surface," says Moody. "You don't want to compromise the substrate because that can cause stress microfractures that weaken the bulk material."


The team started with a modular platform consisting of a 20- to 30-W, Q-switched ytterbium-doped galvo-steered fiber laser marking system controlled by the Telesis Merlin II LS laser marking software running on a PC connected to the plant network. Working with input from Joe Moody and Wright Medical Process Engineering Manager, Tim Smith, Telesis also developed a 36-in. wide CDRH certified Class I enclosure to accommodate the full range of parts and handling fixtures.

The marking system can accurately position with repeatable high tolerance parts over four degrees of freedom: x, y, z, and ?. To enhance x-y stage repeatability, the workstation is built on a heavy machine base with Blanchard ground top. The addition of the rotary stage, with its 360° of motion, simplifies the marking of rotationally symmetric parts. The command sequences for the marking are generated off-line. Using those files, the Merlin LS software drives four axes of positioning in a programmable mode to ensure that the beam waist of the laser output corresponds to the surface of the part, optimizing the quality of the marks.

Joe Moody of Wright Medical running a Telesis fully integrated class I ProMed laser marking workstation.

Wright Medical and Telesis worked together to customize the automated machine interface (AMI) for the Merlin software that links the marking machines to the plant network server. As a result, any one marking system can upload data or a marking pattern to the network file server, where it can be accessed by any other laser system. The Merlin AMI is identical for every marking machine on the network. This enables operators to move seamlessly from machine to machine. It also allows mobile machines to be moved from one location to another and one task to another without impacting usability.

The Merlin software validates each step in the marking process and speeds changeover. If a product line has seven different components, the system can rapidly change from one to another. To do so, the operator scans his or her badge and the barcode on the traveler that accompanies the part The AMI displays a picture of the part and the mark so that the operator can confirm the operation and initiate marking. Combining the barcode with a process interface allows the system to maintain a history of each component during fabrication. In the event of a problem, operators and maintenance can trace back the error to the source, whether that is a hardware problem, an operator issue, or an anomaly like a power outage.

Ultimately, the effort grew beyond just a one-time project--Telesis now offers the capabilities in a customizable platform called the Promed. "Medical device manufacturers must have traceability on their products," says Villiotti. "With UDI, they'll soon have to add 2-D matrix codes. Through the input from different groups, we developed a modular marking platform that can adapt to different parts and fixturing to meet these unique requirements. Our standard became a standard for this industry because we wanted to address the needs of the medical device manufacturer."

Medical device manufacturers need to focus their time and energy on developing quality components, not production infrastructure like laser marking systems. "What it comes down to is the ability of your technical staff to adjust the laser marking product to your needs at a cost that's feasible," says Moody.

Merrill Apter is the vice President of sales at Telesis Technologies (Fremont, CA). Julie Tracy is the senior vice president and chief communications officer, Wright Medical Group, Inc. (Tracy, CA).

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