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Ball Bearing Slide for 2020 or 1" Extrusions

by LoboCNC Jun 22, 2019
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I'm thinking of upsizing slightly and maybe running on teflon tape, also known as anti chaffing tape. Not sure of the accuracy yet. I'd agree, first hand knowledge that the steel surface bearing on the aluminum extrusion will see very quick wear. They don't like each other. Wonder if PEI Tape would be enough; certainly thin and easily replaceable. ExoSlide sells sleeves that fit over their bearings. Wonder if they are readily available? Love their product, but wasn't ready for the price. All things considered in the end, their price is actually not too bad........., but looking forward to helping make this work.

Getting some 6mm ID PVC Round End Caps. May not be overly accurate in thickness. Will be easy to slip the bearings in and trim. Maybe tack with a bit of CA glue. 6mm ID hose is hard to find in the common Ebay / Amazon places. We'll see what happens.

Maybe print some single wall roller sleeves.

What about bearings such as these, will they last? https://s.click.aliexpress.com/e/bEFysAfe
Nylon bearing with glass balls, should be pretty strong. Will need a remix though, for 603 or 604

Nylon race bearings have only about 1/10th the load rating of steel bearings, so you could only handle very light loads.

Would it be fine for a delta printer or for z axis on Cartesian? As I understand, load in these cases is mostly on lead screw or a belt, and the slide acts only as a guide

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Bought some. There are really interesting. Very smooth. With the POM plastic as the bearing material no lube is required. Load capability is Load rating (stat) 3 Kgf (6.6lbs)
Load rating (dyn) 4 Kgf (8.81lbs)
Speed Limit 3,000 rpm

I like these discussions for this very reason, learn something new everyday.

Assuming you stay light in the preload (the adjustment screw to take up tolerance) and you have 3 of them equally loaded you can carry something that is 19.8 lbs per bearing sleeve. They are a little more expensive. Personally I think they would work well for this application. Watch for a remix if someone want's to give it a try. A remix is required because they are slightly bigger for the smallest size.

Well, I'm very new to 3D printing, and these numbers don't tell me much.
I tried to do the math, I'm gonna be doing it in SI though. So, let's take something like Z axis slide for i3 style printer, such as Ender 3. Static load for 3 bearings combined is 9 kgf, or roughly 90N, we have two slides, that means we have to apply 180N of force to break the bearings. Default acceleration in Cura is 2000 mm/s^2, as far as I remember, or 2 m/s^2. To apply 180N of force at acceleration of 2 m/s, mass of the moving part (carriage) should be 45 kg. That's 99 pounds in imperial units.
So... it's one of three things. Either I suck at math, or the bearings actually insanely strong, or you really don't need that much durability on 3d printer. Of course, I didn't take into account preload or gravitational force that affects other axis, but still as far as I can tell there is just no way those bearings would break under normal 3D printer usage. Am I right in my assumptions?

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The bearings are not seeing the load of the acceleration unless the belts are pulling down on the bearings, which with proper alignment should not be the case. If you have something tall riding on the bearings that can unbalance the load sharing during acceleration and case some additional loading. Again we try and keep our loads centered to reduce ringing in our prints. The other way the bearings will see a load from the acceleration is on a ramp, which is not the case in our 3d printers. The main load is going to be gravity or the weight of the device being carried. The load from acceleration is carried by the belts and stepper motor imposing the acceleration / movement and its mounting.

BTW, the data sheet for the POM bearing surfaces with Stainless Steel balls is the same so the Glass balls are not the issue with the load.

I was thinking about load on Z axis slides, vertical ones, when I did the math. I just got surprised by the fact that the expected load on 3D printer is an order of magnitude lower than those bearings can support, even considering the fact that they are not as good as metal ones

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Calculating the actual loads for a linear bearing is usually pretty difficult because the overhang moments are much more critical than the normal loads. Of course, if you are using multiple linear bearings, you can avoid the overhang loads, but that kind of defeats the purpose of using a linear bearing that can take loads and moments in all directions. All that said, you are correct that 3D printers don't usually come anywhere close to stressing the bearings that tend to get used in them. Bearing issues people see usually have more to do with using the wrong materials or with misalignment.

Would be good for a CoreXY also where the bed is moving up and down. The X & Y are relatively light. I like the idea. I have all the parts to build the original and will try using kapton tape as a protector on the 20x20 Al rail. I order a set of the nylon 603s from amazon to have a look and play with them.

I suspect your caps or Teflon tape will be too soft for the small diameter steel bearings, and they'll take a compression set. PEI or Kapton tape would be much better as they are both pretty hard - about the same hardness as the ExoSlide polycarbonate tires. Note you can also use square steel tube, although most people, I suspect, prefer using the 2020 extrusions.

I agree with the softness. Can use square steel tube, but most purchased printers already use 2020 extrusion and those annoying creap plastic wheels and poor quality bearings. Looking to upgrade the current hardware on the existing frame; a TronXY x5s for me. Kind of silly that we purchase these cheap printers and then spend a lifetime swapping out parts to make it better. I still have the same frame :-) .....

nice proof of concept, I can see some potential issues with metal bearing wearing down extrusion frame as most are made with soft type metal such as aluminum.

Adding wipers to keep most of the grit out will help a lot and replacement of the tubes shouldn't be a terrible proposition. Seems like this would be an excellent method of producing a large format laser engraver/cutter or 3D printer.

Adding wipers is a good idea - I'll try to sort that out.

There's a reason the pro machines have them. Grit and dust are the biggest contributors to bearing surface wear. Other than going Ninjaflex or just cutting them from rubbery sheet I'm not certain how easily it will be accomplished.

I was thinking of something more akin to felt wipers, maybe using a thick cotton string.

oOOOoooo,I like it!

Yeah, steel bearings running on aluminum is not great, unless you can get the aluminum hard anodized. The 1" versions however, will run nicely on square steel tube.