In a perfect world, every component would be manufactured exactly to specification. But perfection drives costs higher so it makes sense to accommodate variations — tolerances —as long as they do not compromise the finished assembly.
But there is a catch. If a device features four or five nested components, the components may be at the “worst case” limits of their design. Tight-fitting parts make assembly difficult and slow, and excessive friction can degrade the operation of the finished device. These accumulated “stacked tolerances” can be very difficult to resolve in manufacturing.
A cost-effective way to address stacked tolerances is to use a dry lubricant based on polytetrafluoroethylene (PTFE). PTFE is a powder and is mixed into a carrier fluid. The mixture is applied by dipping the parts into a liquid bath. The carrier fluid then evaporates away leaving a smooth, dry PTFE coating on the part.
Dry lubricants are versatile. They are compatible with most plastics and metals. They conform to virtually any surface; they readily penetrate into complex shapes and blind vias. Dry lubricants are safe, clean, non-migrating and are available with ISO 10993 certification. A brief heat-treating process can turn the coating into a hard, durable and attractive finish.
But most importantly, dry lubricants improve the performance of a finished device. They can instantly reduce the coefficient of friction on a treated part to as low as 0.06. This translates into a 25-30% reduction in actuation forces, greatly improving performance. Many medical devices would not be commercially viable without a dry lubricant.