High Cycle Linear Bearings

[kolias]

I’m designing my second CNC Router and I wonder if anyone has built one using the 8020 “High Cycle Double or Single Flange Linear Bearings”

I just got a sample (Single Flange) to experiment with it and feels just right for a CNC

Your ideas?

[RomanLini]

What's the slider material?

If it's just a plain plastic they will probably be only good for low speeds.

[kolias]

Originally Posted by RomanLini What's the slider material? If it's just a plain plastic they will probably be only good for low speeds.

Its called UHMW and I know about this stuff, very good but seems expensive.

For 6 bearings (enough for 3 axis machine) about CAD$500.00

[ger21]

Not a good choice. You'll find they bind rather easily.

There is a machine on here using those, though.
http://www.cnczone.com/forums/diy-cn..._bearings.html

[svanommen]

I too considered those linear bearings and as you've pointed out they get pretty expensive pretty quick.

To me it seems quite counter productive for the following reasons: Cost - CNCrouter parts bearing blocks are not expensive at all.
Wear - the plastic can only wear to lubricate itself. As we all know accuracy is key. So once the plastic bearings have broken in, it's a steady decline of accuracy over use.
... I had a 3rd but the above 2 are more than enough for me.

If you do go this route I would be curious to hear how it runs though. =)

[mlabruyere]

If you have a shop that sells 80/20 near you go there and ask for a demo table setup with the bearings. You'll find that it takes little lateral force to cause it to bind. The small sample you have there won't alow you to place any real force on the bearing material. They are great for creating movable members in a shop but not really great for CNC work. I looked at these too....

I did buy the bearings from cncrouterparts for my first machine. My second one is getting "real" linear rails and bearing trucks.

[Benonymous]

I can see the attraction, these are a purpose made part to go with the extrusion. However, I agree with the other posters that these will wear quickly. You can do much better for the money

[kolias]

Originally Posted by ger21 Not a good choice. You'll find they bind rather easily. There is a machine on here using those, though. http://www.cnczone.com/forums/diy-cn..._bearings.html

Thank you Ger21 for the link, very interesting

[kolias]

I’m afraid that I will have to disagree with you guys about the UHMW slides.

As you can see from the attached photos, I made my own UHMW slides for my present CNC machine and after 1 year of operation I can’t say enough good words for them. Although the way I installed them was very primitive because it started as an experiment, they turned out to work very well, silently and very efficiently.

I bought the UHMW material from LeeValley.com and cut them with my table saw or scroll saw for the small pieces and it was fun to work with them. If the 8020 slides were not as expensive I would definitely have gone with them.

I’m not saying they are the best but to my opinion they are an excellent alternative

[RomanLini]

There's plenty of better plastic choices than UHMWPE for that job. Delrin would be a big step up being slipperier harder and higher melt temperatures. There are also plenty of specialty bearing plastics that have lube etc built in and are not that much dearer than UHMW.

Having said that, I do like plastic bearings, my machine uses IGUS brand Drylin bearings, they are excellent as a 3 part composite with teflon for slip, plastic as a binder and a high stiffness component for anti-creep. They sell them as sliders too to go direct onto round rails either supported or non supported.

Kolias- Nice setup!