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Bushings or Bearings: Which are Best for 3D Printers?

June 13, 2018
The goal is smooth, jerk-free motion, long-life, durability, and low cost to improve the quality or parts made by 3D printers.

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 in 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 jerk-free.

Bushings, also known as 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.

Vesconite Hilube bearings or bushings come in a variety of types and sizes and are well suited to providing smooth motion for 3D printer components.

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 coefficients 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 runs 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.

Hilube bushings (white) mounted in a 3D printer on a smooth guide rod.

3D Printers

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 catalogues. But for those who want to replace parts with similar non-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.

Here’s a close-up of the Vesconite Hilube bearings used on a 3D printer.

Vesconite Hilube Bushings

3D printer that use bushings or bearings sometimes exhibit 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 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 steel of 0.1, and can go as low as 0.08 on 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 printer 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 of 3D printed parts as bushing play can be minimized.

The Hilube bushing for 3D printers is self-lubricating, wear resistant, and has a low coefficient of friction.

Here are some case studies of successful use of Hilube bushings in 3D printers:

Norway: Norwegian innovator Kent Thoresen is using Hilube sleeve bushings in his project to build a more reliable and less-noisy 3D printer. About eight years ago, he started 3D printing various parts for other projects and became aware of some clear weaknesses in open-source 3D printer designs. So, he started redesigning and refining his own 3D printer. Friends began to request his designs, as well as friends of friends; he continued to refine his designs, eventually building more than 200 printers for his network of acquaintances.

His current printer assembly is stiff and dependable, an improvement over many of the low-cost, flimsy designs that are available. It is tough and technically solid, and does not require calibration if the plates are moved, unlike many of the less-sturdy, commercially-available designs.

“The current design has been tested for almost 4,000 hours,” says Thoresen. “I will test it for 5,000 hours and, if I am comfortable with its performance, the design will be released to the open-source community.

 “After 2,500 hours, we also tested the bushings and there was no indication of wear,” he continues. The bushings, along with the other printer components, are currently undergoing their final leg of testing and, if they prove themselves, will be part of the final design.

“We want to create a printer that is cheap, dependable, and will eliminate worries about wear,” Thoresen notes. “Print jobs can take two to four days and I want to ensure that users can print continuously without having to worry about equipment failing or cost of the print time and the material used should there be a failure.”

South Africa: A company that sells South African computer components and accessories chose Vesconite Hilube bushings when the brass bushings on one of the owner’s 3D printers needed to be replaced. The owner, Deon Eksteen, has three 3D printers he uses to make components for local businesses and factories, as well as toys he sells.

When one of his printers’ bronze bushings wore out from a combination of use and the abrasive paste of lubricant and particles which formed between it and the shaft, he searched for a polymer bushing replacement for his XYZ Da Vinci 1.0A printer.

This was difficult in South Africa, where 3D printing is still establishing itself and where 3D printing stores and filament importers do not supply replacement components for that printer due to a lack of demand and support from 3D printer distributors.

Other parts, components, such as wear parts and bearing, can be made of Vesconite Hilube.

Eksteen sought in vain through an online shopping app known for supplying the latest electronics, fashion, phone accessories, computer electronics and toys, but did not find replacement brass bushings of the correct size. Approaching various brass bushings suppliers was also unsuccessful as he was asked to place orders for more than 1,000 units.

Armed with the dimensions supplied by a globally-recognized blog specializing in 3D printer conversions, Eksteen approached Vesconite Bearings and ordered 8mm-long bushings with the correct specification.

Within five days of finalizing the order and verifying that Vesconite Hilube was appropriate for his needs, a courier dropped off the bushings, which were exactly made to specification. Eksteen’s 3D printer was fitted with the bushings and, so far, has printed for 7,253 hours with no signs of wear on the bushings and the rods are still “super-smooth.” His previous bronze bushings had a life of 2,000 hours.

He also appreciates that the new bushings run quietly, unlike printers with linear bearings that, with linear movements at 120 mm/., are extremely noisy due to friction between the ball bearings and linear rods. The wear-resistant bushings are also not as prone to the uneven wear of bronze bushings, so there is no “dimpling and pimpling” and finished parts have a quality finish.

If you have any questions Vesconite Hilube bushings, please feel free to call the company.

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