Monthly Archives: October 2014
Motion Control Application – LM76’s FDA/USDA Compliant Linear Bearings
E. Longmeadow, MA – Motion Control Application – What do you do when you’re linear actuator bearings are including cheese debris? Particularly when your cheese slicing system requires FDA/caustic washdown compliance and FDA inspectors are on site reviewing all process operations for included debris which can propagate harmful bacteria.
“THE” Application
- Repeated Impact with Dense, Malleable Product
- FDA Compliant Materials
- Caustic Washdown
- Self-Lubricating
- No Product Inclusion
“THE” Issues
Originally, our customer specified LM76’s standard stainless, FDA/PTFE linear bearings in their linear actuator. This bearing met all the fundamental requirements: FDA/Caustic Washdown compliance, self-lubricating and no catastrophic (mechanical) failure mode. Initially, we felt the standard running clearance between bearing ID and shaft (.001 overall, .0005” either side) would be sufficient to clear debris. Not so. Thus, we needed a seal that would be FDA compliant, have a low “K” or wear factor and low coefficient of friction so drive torque wouldn’t be negatively affected. Since standard industry nitrile and buna seals were never in contention, we had to design a “scraper seal” from scratch.
“THE” Solution
John Tarbell (President and Internationally regarded Plain Bearing Expert) reviewed several materials and selected Ertalyte® PET-P because it met all criteria relative to FDA/Washdown compliancy, “K” (wear) factor, coefficient of friction, machinablilty and thermal expansion/contraction. The ETX seals were designed for a slight interference between bearing ID and shaft. In addition, a “spring area groove” was designed behind the scraper lip to allow for proper spring-flex action and to accommodate thermal expansion during operation. Lastly, undercuts were machined at both ends of the bearing shell to anchor the snap-in ETX scraper seals. Since the scraper lips are zero-clearance on the shaft, the interference fit prevents cheese residue from migrating beneath the seal as it scrapes the shaft surface.
Founded in 1976, LM76 has been a leading designer/manufacturer of motion control linear bearings, slides and linear motion systems. LM76 is renowned for its industry leading Minuteman Teflon® Composite linear bearings. LM76 is a leading supplier of precision linear shafting: RC60, 300 Series Stainless Steel, and ceramic-coated aluminum shafting. LM76 also offers several FDA/USDA compliant linear bearings and slides for the food processing, pharmaceutical, medical, and packaging industries.
For additional information contact Mike Quinn at: LM76, 140 Industrial Dr., E. Longmeadow, MA 01028; Telephone: 
413-525-4166, Fax: 413-525-3735 or E-Mail: mquinn@lm76.com or visit the website at http://www.lm76.com
