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How to Overcome Repeatability Issues when Laser Marking Medical Instruments
Brian Buntz
May 30, 2013
3 Min Read
.svg?width=850&auto=webp&quality=95&format=jpg&disable=upscale "How to Overcome Repeatability Issues when Laser Marking Medical Instruments")
A major concern when purchasing a laser marking system for medical instrument marking is securing the repeatability needed to hold the tight tolerances expected in banding or very small characters to be seen during arthroscopic surgery. As we know, the standard laser marking is an "annealed" mark that lends great legibility due to its high contrast surface mark typically completed with a fiber laser such as the Telesis Technologies FQ20 laser. Although it is important to make sure that the laser mark survives passivation/sterilization, the main issue is holding the tolerance. For example, a medical instrument maker might need to hold 0.002-in. on the incremental banding out the full 24 inches of marking a surgical drill. Here is a brief check list of hardware items to ensure that the laser system can hold this type of tight tolerance.
Just as starting the build process of any structure, the laser marking system must use a solid base that is as flat as possible. For example, the machine base used on the Telesis "ProMed" system (pictured here) uses an Inter-Lakes steel structure with a Blanchard ground top and bottom to 0.002-in.-per-ft. flatness. Nothing is more important than having a flat, solid structure to bolt your xy stages in place and overcome any issues with repeatability.
The xy stage is a necessary part of the ProMed system since the long surgical drills typically are much longer than a standard marking window. A servo driven stage like the Nutec or Aerotech is typically used to again hold the .002" tolerance needed out the full travel of the slide sometimes 900 mm in travel. The slides will also be rated heavy enough to hold the rotary device necessary for turning the drills for banding and incrementing.
The rotary chosen to insure repeatability must be a direct drive unit like the Velmex rotary used on the Telesis ProMed system. Adding a pneumatic collet chuck to the programmable theta makes operations more manageable and helps insure repeatable placement of the instrument each time.
Sometimes overlooked is the post used to hold the laser while marking. Any vibration to the system, even though on a solid structure, could cause the laser to move slightly effecting band repeatability. The Telesis ProMed system utilizes a dual rail HD THK rail programmable type tool post with gusseted laser mounting bracket to insure there is zero movement or vibration to the laser.
Along with the above mentioned hardware items, it is extremely important that the laser marking system utilizes a software package, much like the Telesis Merlin LS software. It is important that it has four axis of programmable controls to handle the xyz and Theta device programming all inside a common interface and easy for the operator to control the complete system --lending the ability to hold the tight tolerances necessary while expanding tools like "step and repeat," banding, UDI-2D matrix, and flat field programming to make use of the system very user friendly.
Contributing author Ralph Villiotti is the medical device market manager at Telesis Technologies Inc. (Circleville, OH).
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