Anybody tried these? Looks like they might work nicely.
http://www.8020.net/PDF/Fractional%20Section%209.pdf

Dave

The general consensus is that they won't work well for cnc. Too much play and too easy to bind. A lot of people ask about them, but I've never seen anyone use them.

Darn...seemed too good to be true.

The general consensus is that they won't work well for cnc. Too much play and too easy to bind. A lot of people ask about them, but I've never seen anyone use them.


That's kinda what I thought when looking at them too.
Even though I think the play could be adjusted out some, I am not sure that enough could be completley removed for good accuracy when working with alum or steel.

Then you do have to wonder about the binding too (even though I had not thought about that.)

But if anyone has made them work w/ accuracy w/o binding, I'd like to hear about it too.

Hi All,

First post here – but long time CNC fan. I built a small machine a few years ago – it didn’t work too well, but I learned a lot. I’m now ready to build a new one.

I just spoke with an engineer at 80/20 and at my local 80/20 distributor - they both agreed that their bearings should work if I am not looking for super high tolerances – which I’m not. I mainly just want to cut out wood & foam for projects.

My next step is to send a sketch of what I want to the engineer, he’ll spec out the parts needed and price it. As long as this isn’t too expensive, I’ll probably build a small (~30x20x6) table in this fashion and see how it goes. I’ll post my findings.

If anyone has any suggestions, please jump in.

Thanks!
-Ed

I am thinking the unibearings would be allot better. as you can take two peices of say 1515 and put in another say 8" 1515 inbetween using the unibearings this would allow the whole binding issues and allow you to tighten it up.

Hello all -

I am new here, but not to the hobby or the industry.

YES - I have used these for two designs - both were manually positioned motion platforms with less than 5 pounds. The arrangements were extremely simple (single 80X80 beams) and the requirements were extremely minimal and they failed to satisfy me or my customer. I will likely never use them again. They DO bind - unless they are left extremely loose. They don't slide all that great, either. At first, I figured it was something I had done incorrectly, but after a couple attempts by first myself, then a collegue, then the customer to come up with a happy medium, we gave up in agreement that they were just not worth the results we were getting.

Personally - I would NOT recommend them for a machine. I will use something like Redi-Rails (www.pacific-bearing.com), which are the cheapest guiding I have found (?). I would likely even use cam followers on Cold Rolled before I used these things again. Sorry, 80/20. I will continue to buy your other products - just not these things.

Scott

The flange bearings will not work for motion applications that require accurate postioning. In order to take out the slop you have to use the included blue u-shape shims....this also will make the bearing have more friction...delrin against anodizied aluminum. Far better and cheaper to go with rails or shafts.
The 1020 series bearing will cost you close to 50 bucks.
I use them all the time but only for manually moving fixtures into place and then locking them down with the brake kit.
If you are set on using them I have some I'll sell ya ...cheaper then what you could buy em' for...I have a few dozen laying around..

Good input, thanks for the warnings.

Maybe I'll just use 80/20 for the frame and find another rail bearing system to attach.

Thanks,
-Ed

Currently using these linear bearings on my y axis. Only carries about 10 pounds (the plasma torch). After spraying with silicon spray mine slides and zips around OK. Nothing like a precision bearing but I do think these are servicable for some applications. Also...mine are from T Slots so they might actually work better.

jr

For a full range of profile extrusion visit; http://www.marchantdice.com/linear/retrosystem.pdf
Send your enquiries to admin@marchantdice.com

I actually tried those linear bearing on a small router that I was building. As mentioned in these posts there was binding when I tried to decrease the clearance.
Definetly not useable for cnc.

Dan Mauch





That's kinda what I thought when looking at them too.
Even though I think the play could be adjusted out some, I am not sure that enough could be completley removed for good accuracy when working with alum or steel.

Then you do have to wonder about the binding too (even though I had not thought about that.)

But if anyone has made them work w/ accuracy w/o binding, I'd like to hear about it too.

Hi all,

I've got a couple riding on the 1515 extrusion. I can torque one by itself by hand and get movement. If I bolt two together some of that goes away, but the drag increases. For the price I know that round shafting and linear slides can be found on eBay (two 8020 bearings are nearly $100) that would work an order of magnitude better. So know we need to come up with uses for these puppies so they don't go to waste, right? Any ideas? :o

Lance

Why not use linear round bearings / bushings complete with housings. Worldwide shipping is OK! if the combined weight is less than 2kg (4.4 LB)
visit http://http://www.marchantdice.com/linear/pricelist.pdf

i see someone built a router using these slides works great from what i see.. check it out

Why not use linear round bearings / bushings complete with housings. Worldwide shipping is OK! if the combined weight is less than 2kg (4.4 LB)
visit http://http://www.marchantdice.com/linear/pricelist.pdf

Bad link, too many http

yup just remove one.

im starting to build a cnc mill with 80/20 for the x and y slide rails. ill let you know how it works. if it doesnt work too well, it wont be hard to switch to something else.

I am able to shim and adjust 8020 linear bearings to get very little play and can not make them bind up. Is it because I have a clean invironment? or is there something lurking in the closet?

My biggest peeve is the large difference between the static and dynamic coefficients of friction. The instantaneous force to start a load moving is up to 13 times greater than the force required to keep it moving. Fortunately, it is instantaneous.

This adjustment technicue introduces some side loads on the bearing pads and thus upon the little screw that mounts the pads to the linear bearing extrusion. That violates 8020s rule that bearing pads are supposed to be under compression, only. I've had no problems, but I don't move with heavy things.

PROCESS TO ADJUST 8020 Linear Bearings

1. remove the top bearing pad from the slide.
2. center the side bearing pads in the t-slot rail
3. shim as required to get > 4 oz of drag from compression only
4, install the top bearing pad, centered in the t-slot rail
5. adjust both side bearing pads up until the the top of the t-slot is held tight against the top bearing pad (you may have to shim the top bearing pad down first) and the drag is > 6 oz from compression only
6. adjust the top bearing pad until it touches one side of the slot in the rail and the drag is > 8 oz
7. check that all the bearing pads are tight against the correct rail edges and surfaces.

To measure the drag, I have a small electronic scale that can measure up to 5 pounds in tenths of ounces. I place the rail only on the scale and zero the scale. I then install the slide on the rail, stand it up vertically on the scale and gently push down on the slide until the slide starts to move. Push down on the slide with enough force to just barely keep it moving and read the value on the scale. My target is between 6 and 16 ounces of dynamic drag with most of it from compression.

When I get one adjusted, I tighten (probably over tighten) the screws. That pulls a little bearing pad material into the hole around the mounting screw, helping to keep the bearing pads in place. If you have to re-adjust the bearing pad, you may have to take a razor and cut this material off. Adjust a bearing pad too many times and you won't have any material left for the screw to engage.

I have a human-controlled router setup using 80/20 rails with these bearings:

http://www.mcmaster.com/ (catalog page 1073)

http://architectural-prototypes.com/pic/pr-5105-a.jpg

The router trolley is smooth, but the other axis is prone to racking. I'm debating whether to cnc this rig with slaved steppers on the cross-slide or to build a new system that doesn't rack. That said, I have no experience with cnc; I'm gearing up to get a cnc Taig and use that experience to inform my decision regarding the router project.

archproto,

There are links here that show how to reduce racking of the gantry by using pulleys.

Racking seems to be the biggest concern on the 8020 bearings. (Ie misaglinment between the "normally" Parallel - dual X axis rails, Y axis, etc.)

I have built - yet to try in motion (other than chucked in a drill ;) )- a (4 axis, X1, X2;Y1,Y2) hot wire foam cutter. In manual testing, it seems like the bearings will be ok with little binding. In this application they are driven through their motion axis/center. It may be possible for them to bind as they travel due to the height of the Y axis. X is 48 inches, Y is 18 inches. Note:" The Pics attached don't show the bearing surface material installed.-- sorry 'bout that.

Will tell more late May-June when I return to the shop and see if it works or not!
--Details will Follow-- Most likely in the Foam cutting/Hot Wire section of the forum.

:cheers: Jim

Waynehill,

My setup has gone through a series of changes, usually right in the middle of a project with an impending deadline, and I disassemble it between jobs. At one point I added a pulley system cobbled from a Mayline parallel drafting rule; I didn't have any steel cable in the shop so I used (insert snicker here) upholstery thread. In the next iteration I used steel cable; less stretch but still not perfect. Since it is still a human-powered motion control, the moment stress on the rails and bearings is not equal throughout the travel. I'm guessing that the cnc modification (I plan on using a separate stepper/lead screw on each side of the gantry) will even things out and solve the racking issue.