Lubrication-free lead screws fit the bill for feed mechanism IVD machine
Tasked with the design and build of a fully automated in vitro diagnostics (IVD) bottling plant, an engineering firm specializing in the development of analytical medical equipment found itself presented with a unique challenge.
Part of a lab-diagnostic test kit designed to test blood cells and bodily fluids—including joint, spinal and brain fluids—the IVD equipment had to accurately fill reaction vessels with lab-diagnostic reagents in volumes of only a few microliters. The reaction vessels then had to be completely sealed and placed in Styrofoam™ trays that would also serve as packaging. (See Figure 1)
Automating this task was no easy task. A vibratory feeder needed to bulk feed the reaction vessels to the handling plant, before placing them at a pick-off point in an orderly row. Grippers then needed to gently pick up the fragile vessels before taking them to be bottled and brought to the sealing station. After being sealed, the gripper would open to drop the vessel gently into the correct tray.
Priding itself on the precision and reliability of its designs, the engineering firm only wanted to use components that had been proven in the medical industry over time. (See Figure 2)
They chose a self-lubricating DryLin® trapezoidal lead screw nut from igus® to facilitate the feed mechanism and stroke movement—converting rotary movement into linear motion. The nut is made from high-performance plastics, which means it is wear resistant and offers a long service life—without the need for any external lubricant.
Corrosion-resistant miniature linear guides are used in the stroke movement of the gripper. The linear guides are also lubrication-free, making them similarly ideal for the sterile environment, as well as being robust and cost-effective.
If problems ever do arise, as they can occasionally, components should be quick and easy to replace. This was an important feature. After all, nobody can afford the costs resulting from long plant or machinery shutdowns. How ever, the engineering firm says it has had nothing but the best experience to date, with no history of failures in any area.
The fact that these mechanical components are lightweight is an added benefit that has a favorable impact on the overall weight of the bottling plant. Although speed plays only a minor role, precision when feeding the reaction vessels is also extremely important.
It took about nine months from the development of the IVD plant until it was commissioned for the strict cleanroom conditions. Dust was the customer’s greatest enemy, one that could interfere with test results, so it had to be avoided at all costs during the handling process. The custom-built bottling plant guarantees this one-hundred percent. The fully automated IVD bottling plant has been in routine operation and running without fail since April 2011.
This article was written by Matt Mowry, Product Manager, DryLin Linear Bearings, igus Inc., East Providence, RI. For more information, visit http://info.hotims.com/45605-165.