Design engineers in the food packaging, bottling, pharmaceuticals or similar industries are continually faced with challenges to minimize unwanted bacteria in linear motion components. These challenges are found in processing, packaging, handling, and automation equipment in washdown environments. Here are the top four design tips you should know for minimizing bacteria buildup, keeping your operation running clean:
Two-piece, open-ended bearings with grooves or inserts should be avoided in washdown environments. Microscopic bacteria have the tendency to hide in the crevices, grooves, and plastic bearing inserts, increasing the chances of spreading disease. The same principle is true for recirculating ball bearing type products that require grease lubrication to be used due to the metal-to-metal contact. The lubrication picks up material from food items being processed, becoming trapped inside the multiple crevices and cavities around the balls in the raceways of the bearing, creating a breeding ground for unwanted bacteria.
One-piece bonded bearings are recommended for these types of washdown applications because there are no grooves, crevices, or space between the liner and bearing shell where residue can become lodged allowing bacteria to grow. They are also PTFE based, self-lubricating, with bonded linear material, and require no external lubrication that can potentially collect contaminated materials or bacteria.
When it comes to multiple component sub-assemblies, bacteria can build up around the connectors and joints. Newer technology that incorporates dual rail load capacities and functionality into a single rail design can eliminate potential areas of contamination collection.
It's best to minimize component assembly as much as possible in washdown environments. Traditional methods for linear assemblies include various connection points that create crevices, joints, or cracks where liquid can penetrate, or bacteria can begin to accumulate.
Two-piece slide systems are ideal for washdown environments because they reduce the amount of connections points that come with multiple component assemblies, and they are designed with smooth, curved edges that do not have recesses where buildup can occur.
Washdown applications should get special attention when mounting linear rails. In these settings, it’s a good practice to use standoffs to keep operation running clean around your linear motion system, especially where contamination and bacteria buildup are a concern.
To the right is an exaggerated example of good practice when mounting with standoffs.
The location of fasteners and linear components is important to consider for washdown environments. Fasteners can protrude creating another area for contamination to accumulate, especially when mounted on the washdown side.
Bringing the fastener up through the bottom of the rail to be mounted can help eliminate these areas. For fasteners that enter the washdown area, use a dome nut (or similar) for easier cleaning.
For components that are not FDA compliant or that don't meet other regulations for food contact, it is recommended to cover those components with stainless steel shields or covers that have been radius on all corners.
For more information on PBC Linear solutions for washdown environments read: Linear Motion Design for Washdown Environments.
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