Small motion innovation cuts cost and saves space for analytical labs

Waters Corporation is a manufacturer of liquid chromatography instruments, mass spectrometers, thermal analyzers, and rheology instruments, supplying analytical laboratories with the equipment needed to operate efficiently. Waters recent release of ACQUITY Ultra Performance Liquid Chromatography (UPLC) represents further development in the field of liquid chromatographic analysis. The UPLC provides a significant improvement over High Performance Liquid Chromatography (HPLC), in that it offers increased resolution, sensitivity, and speed. UPLC also improves upon productivity, providing scientists more information in a single run than previously possible. While performance of the ACQUITY system was at the forefront for the Waters engineers,it was not their sole consideration when designing the system. Waters envisioned a machine that not only would out-perform its competitors, but would be a more economical and ergonomic choice as well. The new system was to sport a smaller footprint than traditional HPLC units, ensuring it would consume less of a laboratory's valuable bench space. This compact design would also guarantee that users could more easily stack, organize, and arrange the various models. The design-engineers envisioned a basic system that would consist of a sample manager, one of several UPLC detectors, and a high- pressure pump. Upgrades would also be available, including a high capacity sample organizer. Meeting these tight requirements would entail the use of smaller internal components in both the main unit and the optional module, which holds an additional 21 sample plates. Waters' initial efforts to create the required parts did not yield the desired results, according to Ken Plant, a principal engineer on the Waters UPLC project. " We initially attempted to devise a homemade solution, an adaptation of a mechanism we had developed about eight years ago," he explained. "That mechanism created an XYZ movement to replace our traditional Z/Rotational movement and had served us quite well in our older models. However, this system of off-theshelf pulleys and belts simply could not be squeezed into the smaller footprint we were looking for. If it was going to happen, we knew it would require some ‘out of the box' thinking. More to the point, it became clear that in our effort to produce this compact mechanism, we could benefit from the use of specialized outside resources." A colleague of Plant's had worked with Kerk Motion Products, and felt Kerk might be able to offer the optimal combination of reliability and miniaturization for this mechanism. After consulting with Waters' engineers, Kerk presented the company with components that would allow the engineers to produce a sample manager—the heart of the UPLC system—that would meet the company's reduced size requirements and produce the increased speed and performance that was so vital to the UPLC concept. "While other vendors were selling off-the-shelf commodity items, Kerk's products allowed for customization and flexibility to react to our customer needs," said Plant. "We were impressed that Kerk was willing to work with our engineers to customize their components and ensure that they would mesh into our system." Kerk quickly realized the opportunity available to them working on such a specific, detailed application, and was interested to see if a solution could be created that met all Waters' goals. "Waters has effectively utilized our products and resources and has achieved a truly remarkable solution to a difficult design challenge," says Kerk applications engineer, Bob Hawkins. Within the sample manager, the Kerk components are incorporated to drive the robotic XYZ mechanism holding the needle that draws liquid samples from each sample plate. To achieve the X and Y movements, the ACQUITY arm incorporates one Kerk ¼ in. lead screw and two specially adapted Kerk nuts, while the Z motion is accomplished through two Kerk spline shafts and splined bushings. In the optional sample organizer, a ½ in. lead screw and anti-backlash nut is employed to produce the Zaxis motion, allowing the robotic machine to shuttle as many as 21 sample plates back and forth to the sample manager. The spline shafts, which run parallel to each other, feature splined bushings, providing a driving mechanism for two axes of motion. The assembly utilizes lightweight alloy steel spline shafts treated with Kerk's proprietary low friction Kerkote TFE coating mated with Kerkite composite polymer bushings. "It wasn't performance or size that made Kerk components desirable. Kerk's products offer long wear-life," Plant said. "This was a critical consideration, as our chromatography systems need to operate at a very high level of reliability. Continuous uptime is very important to our customers." The launch of the UPLC has been a success, with praise from many customers. "The ACQUITY UPLC will soon become the choice for the development of fast LC methods in the pharmaceutical industry," said Dr. Anton D. Jerkovich of Novartis Pharmaceuticals Corporation. The success of the ACQUITY system is also reflected in the sales figures, as Waters has sold 1,000 of the core units, and expects to more than double that number in 2006. TMD Kerk Motion Products Hollis, NH kerkmotion.com