In the medical device industry, surface texture has become an important aspect of product design. It not only provides the means to refine the physical appearance of an item, but also increases an item’s surface grip qualities. And through surface texturing, manufacturers can create medical tools that pick up less fluid and debris, mark implants for tracking, and add textures that aid in implant acceptance. So it is of no surprise that these medical manufacturers are increasingly seeking ways to improve the level of control exerted in surface texturing. Laser texturing is often the technology of choice and is now applied to many medical parts.
In addition to helping manufacturers create better implants and medical tools, laser texturing can also can be used in the production of molds and dies for medical components. These applications have benefitted from recent developments in laser texturing, including the introduction of femto lasers and dual laser systems (see Figure 1).
Femto lasers are the latest laser technology available on the market. These cold lasers create perfectly sharp corners and edges because they generate completely burr-free surfaces (see Figure 2). Burrs are even undetectable when the cutting surface is viewed under a microscope at 200x magnification. This new class of laser opens up a variety of new materials, including ceramics, gems (e.g., sapphire), various polymers, and glass, for medical applications.
Femto lasers are able to cut more intricate patterns than previous laser technologies because the laser beams are smaller and thus can create smaller details in parts. Such intricate cutting capabilities enable laser texturing to be used for even the smallest medical applications.
With femto lasers, it is also possible to generate very fine microstructures that can be measured in nanometers. These microstructures create colors — through a naturally occurring phenomenon — within the finished piece that are visible when held to a light source (see Figure 3).
In addition to the development of femto lasers, the other significant technological breakthrough in laser texturing is the development of five-axis dual-laser systems. A dual-laser system is one that can automatically change its laser source from one type to another within seconds. This allows manufacturers to machine a wider variety of materials on a single machine than with single-laser systems. Such increased versatility means that manufacturers can perform more work from one laser texturing machine than was previously possible.
With single laser systems, operators can manipulate the laser’s strength by changing the laser power settings, which gives a certain degree of control, but the ability to change to a different type of laser entirely enables greater control over the laser texturing process. Fast changes between laser sources are especially important for those medical manufacturers that experience frequent shifts in part demands and designs. Those shops depend on flexible equipment to quickly respond to the needs of their customers.
As the use of laser texturing continues to grow, advances such as five-axis machine movement have further improved it. With five-axis capability, manufacturers increase their productivity because this machining process dramatically reduces the need to manually manipulate workpieces during the part production cycle. Laser texturing technology also undercuts round shapes, meaning that the underside of a sphere can be machined without turning the part over. The reduction in necessary setups also eliminates stacked errors from finished parts.
A current limitation to laser texturing is the size of the laser field, which is only as wide as the lens of the laser. Once texturing is complete within that field, the machine must readjust to place an untexturized surface under the lens. However, new technology in automated laser positioning is on the horizon that will eliminate this barrier. Advances in the technology will enable lasers to follow along a machining surface without having to stop and reposition. Automatic adjustments could make the laser texturing process up to 20–30 percent faster than it is currently.
Automation further enhances the productivity of laser texturing. Process automation makes laser texturing a more viable machining process for high-production environments because the automation increases the production capacity of the machine. Additionally, modular work holding systems easily integrate laser texturing with other processes that a manufacturer may already use. Production parts can mount on pallets with a reference system that transfers across multiple machining processes and eliminates the need to re-reference parts between steps, which drastically reduces setup times.
Traditionally, one of two technologies has been employed to provide mold texturing. Moldmakers with five-axis machining capabilities often use them to create textures in addition to general machining. This can be an acceptable alternative if the shop has excess five-axis machine capacity or only a relatively small percentage of jobs that require texturing. Otherwise, the opportunity costs quickly accumulate, as the equipment could be more productively utilized with roughing and finishing operations than with time-consuming texturing. Additionally, texturing in this manner requires very small, specialized tools, which increases the cost of the process.
In those situations, moldmakers may turn to chemical etching. Compared with five-axis machining, this method offers substantial time and cost savings. Unfortunately, it also requires sacrifices in the areas of consistency and quality due to the impossibility of precisely controlling the texture produced. Chemical etching also carries with it environmental issues that must be addressed.
As an alternative to chemical etching, the laser texturing process entails using a laser to sublimate material, or turn it directly from solid to gas (see Figure 4). Laser texturing centers can be equipped with pulsed, fiber-optic lasers of varying strengths and a variety of lenses with different focal lengths to maximize productivity. The process promises several key advantages to mold making shops and other part manufacturers requiring surface texturing.
Laser texturing offers far more precision and accuracy than can be achieved via chemical etching. Regardless of how much care is taken during etching, it is impossible to eliminate variation that results, even if it results in only slight differences between workpieces. Laser texturing machines produce textures directly from digital files, allowing the creation of any number of identical components (see Figure 5). While variation is acceptable between components in some applications, it becomes a much more apparent issue for critical tight-tolerance, high-precision medical components where differences could affect part performance. Laser texturing ensures accurate, high-quality, and completely repeatable surface finishes.
Unlike chemical etching, laser texturing has no environmental impact. Because of the nature of the chemicals used for etching, U.S. companies using it must comply with a host of regulations that substantially increase process costs. Often as an alternative, these manufacturers will farm out their chemical etching work to suppliers in countries with little or no environmental regulation. Unfortunately, doing so substantially increases lead times and restricts production flexibility when it comes to responding to urgent customer needs. In short, laser texturing is typically more cost-effective and/or faster than chemical etching, depending on whether viewed in terms of domestic or international alternatives.
In addition to adherence to strict government regulations, chemical etching is quite labor intensive, and each part undergoing the process must be carefully prepared to ensure that the chemicals only access the features to be textured. Exposing other areas of the part to these chemicals can result in the entire piece being scrapped. Additionally, the process requires preparing chemical baths into which the parts are submerged and cleaned and disposing of the chemicals, all steps that involve a lot of labor. In contrast, laser texturing consumes minimal labor. An operator sets the part in the machine, loads the program, pushes the start button, and walks away until the texturing is complete. Although the actual process time required for laser texturing substantially exceeds that of chemical etching, laser etching requires considerably less labor. Laser texturing technology reproduces a 3D surface texturing within a few microns of accuracy.
Laser texturing machines increase productivity of the manufacturing process because they can replace several other machining steps. A five-axis laser texturing system can machine a part on all five sides without manual intervention of an operator, which saves up to 80 percent on setup time. A laser texturizer can machine grooves and corners as well as etch a workpiece, all in a single setup.
On the design side of manufacturing, laser texturing provides for greater legal protection of innovative and proprietary textures and patterns. The inability of chemical etching to produce repeatable results renders the process incapable of creating textures that could be submitted for patent protection. Laser texturing overcomes this obstacle, allowing manufacturers to create and legally protect surfaces that result in a truly unique appearance and feel in the final product.
Laser texturing can be used to protect against counterfeit parts. Through the part program, a user can create a unique texture code on a nanoscale. Industry experts predict that nanosized textures will eventually be used in medical component traceability. In these instances, a manufacturer would create a unique pattern, invisible to the naked eye, to mark parts to uniquely identify those they produced.
With today’s increasing demands for product differentiation, laser texturing machines provide medical manufacturers with a means to meet and exceed their customers’ needs, whether it’s surfaces with intricate patterns and textures, precisely sharp corners, or resistance to debris. By incorporating previously unattainable levels of quality and repeatability, a medical shop utilizing laser texturing will quickly stand out in the sea of competition.
This article was written by Gisbert Ledvon, Director of Business Development, GF Machining Solutions, Lincolnshire, IL. For more information, Click Here .