Are bearings or bushings best for 3D printers? And how can they be improved so that 3D printers can more quickly and reliably turn out parts of higher quality? Although increasing the quality and speed of 3D printers involves all the components used them, a good place to start are the bearings and bushings that make up the linear-motion subsystems critical to 3D printers.
Bushings and Bearings and Linear Motion
In most 3D printers, the build platform (including the extruder) slides over smooth rods as it moves back and forth. The polished rods support the components and guide the extruder along a precise linear path. Bearings or bushings are used on the straight steel rods to reduce friction and smooth out the motion so that it is a jerk-free.
Bushings, also known as a sleeve or plain bearings, are cylinders generally made of bronze, steel, or polymers. These materials reduce friction and the power needed to create linear or rotational motion, as well as to lower noise and wear. Bronze bushings are sometimes impregnated with oil so they are lube-free, or require external lubrication.
Bronze bushings tend to be less expensive than linear bearings. In addition, they can run on hardened or less expensive non-hardened shafts, so ancillary equipment can also be less expensive.
The downside of bronze bushings is that they can wear away at the shaft and sometimes need significant amounts of lubrication at regular intervals; this lubrication can form a gritty mixture that wears away at the shaft. In addition, bronze bushings can have a stick-slip problem, which results in jerky motion when printing-because, as the name implies, the bushings are prone to stick on the shaft (static friction), then slip over the shaft. They can also have large tolerances because many are not made to specification, and this makes them a poor fit for 3D printers.
Polymer bushings, another option for sleeve bearings, can be made from a range of materials. But they also suffer from slip-stick and overly large tolerances, especially if they are made from less expensive polymers or mass-produced. In addition, mass-produced polymer bearings are sometimes available in limited sizes and may not meet the needs of the 3D printer manufacturer.
High-end self-lubricating polymers will reduce the risks of slip-stick, especially when the coefficient of friction is low and the dynamic and the static coefficient of friction have similar values.
However, with more expensive polymer bushings, it may be possible to get exact tolerances and precise sizes.
Linear ball bearings
are the alternatives to bronze and polymer bushings. They can be tube-like, flanged, or pillow boxes, and all have ball bearings along their inside diameter where they run on a shaft. This results in rolling motion rather than sliding.
The cost of ball bearings varies significantly, depending on quality. Durable, name-brand ball bearings can be expensive compared to bushings. In addition, they should be used with hardened shafts so that the balls do not eat into the shaft. This makes the rods the bushings run on expensive. In addition, some believe linear ball bearings require more maintenance and regular lubrication to retain performance. Moreover, because dirt and dust can be attracted and mixed into the lubricant (usually grease), the balls eventually run louder and even jam if the grit-becomes significant.
The question of whether to use bearings or bushings seems to be more pronounced among those with RipRap printers. Those users (aka Makers) prize a high degree of innovation and many prefer to replace components or make the components themselves.
For those converting their machines or those committed to modifications, the debate as to whether to use bearings or bushings is particularly pertinent. There is always the option of including specified parts described in production catalogs. But for those who want to replace parts with similar-OEM ones, it is wise to investigate alternative brands. If they are also swopping bearings for bushings or vice versa, the alternative of making bushings or bearings can be important.
Vesconite Hilube Bushings
3D printer that uses bushings or bearings sometimes exhibits a phenomenon called dimpling and pimpling on finished parts. It occurs when the guide rod becomes nonuniform and is caused by the rod slightly lifting on one side and slightly tilting on the other as the extruder head moves from one side to the other. This is typically a result of wear on the rod. This phenomenon is eliminated when Vesconite Hilube bushings are used.
Vesconite Hilube is an advanced thermopolymer in the Vesconite range that is particularly well suited to operating in wet conditions, including pump and marine applications. It combines low friction and low wear, letting it perform well under difficult operating conditions.
The material is self-lubricating and requires no greasing, so bushings require little maintenance. Because there is no gritty grease that can get embedded in the rod's mating surface, wear caused by the constant movement of this contaminated mixture is eliminated. Wear caused by metal- on- metal contact also becomes a thing of the past because the hard-wearing polymer glides smoothly over the rods.
Hilube has an unlubricated coefficient of friction on the steel of 0.1, and can go as low as o.o8on polished steel. This makes bushing movement along the rod particularly smooth and eliminates the problem of the jerky motion (stick-slip) when the extruder on the 3D pointer moves to a new location. Hilube bushings can be made to specifications with appropriate tolerances and delivered globally via distributors or by courier, which simplifies logistics. And using bushings made to specifications and tolerances has also improved the quality of3D printed parts as bushing play can be minimized.
Original link: https://www.machinedesign.com/3d-printing/bushings-or-bearings-which-are-best-3d-printers