Y rails for H-Bot etc??

Hi,

I'm working out how to build either a H-Bot style or X Y Carriage style (e.g. Makerbot style), Reprap.

From my understanding of H Bots the Y rails are quite important.

Can anyone advise about whether rails like these advertised on eBay look OK [www.ebay.com.au]

They seem to be chrome plated steel mated to aluminium base.

Or these

[www.ebay.com.au]

Which appear to be the same, but don't specify materials.

Thanks

I'd suggest contacting the second seller and see about the materials. They appear to be the same stuff. Of course, you could build a lot more stuff out of the second lot of parts.

Is either one is accurate enough to do the job - it's China, who knows ....

Thanks Uncle_bob

I've actually decided to initially try conventional 10mm round rods and SC10 linear bearings. I've ordered a pack of 10 bearings, from a supplier on eBay but they won't arrive for several weeks.

I'm going to try to source the rods locally, but I can't get hold of H6 tolerance, so I'll have to make do with H9, or possibly use hardened non-stainless rods instead.

If there is too much flexing etc, I will probably have to buy those rails, but I won't know until I try

I think the rails are a cute idea. I have not tried using them, but they look pretty rigid. I'd hope they are fairly straight as well ....

I wish I had supported rails on the Y axis of the MendelMax 1.5 that I built. Even though I used 10mm rods, it still flexes quite a bit, though in my case these rods are 520mm long. The original design called for 8mm, and since I was building a bigger one, I figured 10mm would be fine. I probably should have used supported rods, or 12 or 16mm ones instead.

Mounting one of these supported rods on something like a 20x20mm T-slot extrusion, would probably make them quite stiff.

I found many of the cheap bearings from China to be of rather poor quality. The ones I got had a bunch of crud in them (mostly rust), so I cleaned them in varsol in an ultrasonic cleaner, and that helped quite a bit. Check each of them by running them on a rod before putting everything together. You should be able to tell if they move smoothly or not. I ended up ordering some Japanese ones from Misumi instead, and they have worked well, though I never did see how long the Chinese ones would last. I didn't throw Chinese rods into the mix though, as mine are from Misumi as well.

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Mike Anton
[manton.ca]
[laserlight.wikidot.com]

One way to clean that stuff up - put it in a jar of motor oil and just let it sit for a week. Then do the solvent clean in the ultrasonic. There's stuff in modern oil that will nuke rust and some sorts of solvent resistant crud.

Good idea, I never thought of that. My thinking went more along the line of if there is rust in them, then I'm not sure that I actually want to use them, unless their operation is smooth, and often even after cleaning it wasn't, as the balls were rough from the rust. I took one apart, and it certainly is not what you would call a bearing in the state that it was in.

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Mike Anton
[manton.ca]
[laserlight.wikidot.com]

One possibility is that there are metal particles in the bearing, who knows where from. The oil will help get them out of there. If the rust has taken out the ball bearings, there's no hope. You have a paperweight.

Crazy I know, but sort of back to the start of the thread (and totally / shamelessly hijacking it):

If you were going to make an I3 like beast with a *long* Y axis, could you just mount a pair of those linear bearings to a plate? Support the Z off of the plate rather than off of the rails. More or less a plywood I3 with a base plate. The plate could be a chunk of aluminum. It could be a thick chunk of plywood.

I don't see why not. My Y axis is done with 4 similar linear bearings mounted to the bed. But, I think you mean "could you just mount the rails to a plate?", which would be more like an I3.

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Mike Anton
[manton.ca]
[laserlight.wikidot.com]

Yes, more or less re-do the base of an I3.