We examined the technology options for use in linear drive trains being deployed on additive manufacturing or 3D printing systems in "Drive Train Technology Risks in Precision Linear Motion System Development." Now let’s look at available bearing technologies to determine which fits your application.
Crossed roller bearings (non-recirculating)
The main risk in this design comes from the removal of bearing play. Bearings may slip (referred to as “cage creep”) at higher accelerations or during high frequency moves. Eventually cage creep leads to a loss of movement in one direction. Anti-creep designs, which include features such as miniature rack and pinion designs or steel cables, are available. Another risk is the limitation of overall travel length, typically 16”-24” travel systems.
Square rail bearings (recirculating)
One of the more common bearing designs are also referred to as profiled rail bearings. Common risks include potentially damaging misalignment, along with contamination from powders, dusts, and debris. There is also a risk of vibration and noises, but these are likely only critical to high end additive manufacturing machines.
Glider style bushings
Sliding surfaces replace rolling elements in this, the most cost-effective of the choices. These bearings have a low friction plastic that is in contact with another surface and acts as the “lubrication” between the two moving surfaces. Key risks of this design include wear over time, poor handling moment or offset loads, and susceptibility to dust and debris.
A flexible design with many of the benefits of other designs, roller wheels have more forgiving installation procedures. The technology uses a roller wheel or V-style roller wheel on a bearing track or surface. The main risks with this design are loss of preload over time due to shock or vibration and off-axis loading.
These bearings are suited for high-end printing machines where mechanical vibration introduced from bearings prevents the proper build of parts. An air gap with pressurized air flowing between two surfaces is maintained and the bearing slides freely in any direction. Risks to this design are overloading susceptibility to contamination.
This is Part Two of a Three-Part Discussion. In our next blog post on this topic, we’ll look at available technologies for ensuring the proper positioning of production equipment components.
In the meantime, please check out the video presentation and download the white paper covering all three sections.
Ben Furnish, Market Development Manager, Parker Hannifin Corporation, Automation Group
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