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OpenBuild vs linear bearings

Posted: Wed Jul 26, 2017 5:11 am
by mark.moorcroft
I'm interested to hear opinions on the comparison between OpenBuild rollers and actual linear bearings. I would think the rollers would be good at reducing vibration. Could one generalize.. small build platform, small parts = linear bearings. Larger parts, 300 x 300 platform with larger nozzle = OpenBuild rollers? I'm a total newb who has never had a 3D printer. I'm zeroing in slowly on my first design. In the end there is no avoiding mistakes and lessons learned ;-)

Re: OpenBuild vs linear bearings

Posted: Fri Jul 28, 2017 1:13 am
by Tomasz Stawarz
As far as I knew - if they would be good with vibration reduction they would lose in precision department. Only two options to reduce vibration ( that are available when building 3D machine and also walls ;) ) are: increase mass of vibrating things (they will be harder to move therefor will vibrate less) or absorb vibrations (add something that will be able to change kinetic energy of vibrations into some other form of energy - in case of drywall with mineral wool inside its heat). But absorbing is connected with deformation of structure (like spring being compressed). There is ideal material for kinetic energy absorption and it is any non Newtonian fluid, there is also solid substance with similar behavior to it that is sold under brand D3O. But you wouldn't like to use it as rollers material ;)
I think that OpenBuild rollers are used in big projects because their price and ease of use in such projects and not any other reasons.

Re: OpenBuild vs linear bearings

Posted: Sat Jul 29, 2017 8:38 am
by Bekroogle
Tomasz Stawarz wrote:
Fri Jul 28, 2017 1:13 am
There is ideal material for kinetic energy absorption and it is any non Newtonian fluid...
Wouldn't that only work with fluids that gain in viscosity as shearing increases, as opposed to non-Newtonian fluids like coffee which tends to jump out of a mug at the slightest provocation?

Just curious.

Re: OpenBuild vs linear bearings

Posted: Tue Aug 01, 2017 1:00 pm
by Tomasz Stawarz
Bekroogle wrote:
Sat Jul 29, 2017 8:38 am
Tomasz Stawarz wrote:
Fri Jul 28, 2017 1:13 am
There is ideal material for kinetic energy absorption and it is any non Newtonian fluid...
Wouldn't that only work with fluids that gain in viscosity as shearing increases, as opposed to non-Newtonian fluids like coffee which tends to jump out of a mug at the slightest provocation?

Just curious.
Hi,
I rechecked it on Wikipedia - coffee is Newtonian as water and tea and so on in normal, every day conditions. https://en.wikipedia.org/wiki/Viscosity#Definition . And non-Newtonian https://en.wikipedia.org/wiki/Non-Newtonian_fluid i was thinking about is exactly of Shear thickening (dilatant) type - most common example is mixture of 1:1,25 corn starch and water https://www.youtube.com/watch?v=JGfynrsdaV0. Have nice time watching - its really nice video :) . If you would like to check my idea of vibration absorption you can also check this video https://youtu.be/bLiNHqwgWaQ?t=42s

Re: OpenBuild vs linear bearings

Posted: Wed Aug 02, 2017 9:15 am
by Bekroogle
Right on. Abstracting away everything else, that you're speaking specifically of shear thickening fluids answers the heart of my question.

W.R.T. coffee, https://www.google.com/url?sa=t&source= ... g_1tTsjyoA from MIT has done casual research showing a correlation between "quality" of "coffee" and The degree to which it is shear thinning. Though, upon closer inspection, by coffee, she means espresso. I believe it has something to do with the emulsification of oils in the brew (something you probably don't get f so much from American brewing methods).

Any thoughts on how vibration dampening using shear thickening fluids could actually be implemented for 3D printing?

Re: OpenBuild vs linear bearings

Posted: Tue Aug 22, 2017 4:02 am
by Tomasz Stawarz
Hmmm... First of all we would need some fluid that doesn't age ( e.g. water would evaporate from water+corn starch mixture, and you wouldn't like to have a year old mixture in a printer). But assuming we would have a suitable fluid I think that I would be able to find some way to use it. If You will be interested in this thing we can open new topic.
On the other side there is solution to deal with vibration - and that is to increase mass. Im planing to pour a concrete into aluminium extrusions or something like that ( make a lid for my printer from reinforced concrete ).
And according espresso - it's more like oil than water ;)

Re: OpenBuild vs linear bearings

Posted: Thu Aug 24, 2017 4:44 am
by ronka
zheez.. how abouth getting off topic i think tomasz, newton and bekroogle should get a room.. :lol:
lets go back to mark's original question wich is something more people (me) like to know:
OpenBuild vs linear bearings... thougts anyone???

Re: OpenBuild vs linear bearings

Posted: Mon Sep 11, 2017 3:05 am
by Trakyan
There isn't much to say more.
Cost wise you'll find it easier and cheaper to get long extrusions than to get long smooth rods. That and the extrusions can double up as your frame whereas smooth rods will usually want something else to give them stiffness. And since rollers on extrusions don't need to completely surround the extrusion, you can bolt one side of the extrusion to a frame to make it fully supported rather than just end supported, that's something you can't do with smooth rods.

Another thing you might care about is noise, linear bearings on smooth rods, especially the cheap ones, are rather noisy, rollers on extrusions are noticeably less so. Something to keep in mind if you want the printer running at night or in a room that gets used.

Linear bearings are also relatively sensitive to dust and dirt on the smooth rods which get under the cheap and poorly made seals/wipers on the linear bearing. Rollers on extrusions usually have sealed bearings, and the dust isn't as likely to find it's way into the bearings, and the rubber rollers themselves probably couldn't care less if the extrusion was dusty. That being said don't go dumping a bag of sand on either of these options.

Downsides are that the rubber wheels will have some give which could lower your repeatability, though I don't think this is an issue on desktop machines. Another downside is that aluminium extrusions aren't necessarily made for linear motion and may not be as straight as smooth rods which are intended for linear motion. I guess they add more parts and require a bit more assembly I guess.

Re: OpenBuild vs linear bearings

Posted: Mon Sep 11, 2017 4:16 pm
by MikeOToole
I build on a budget but would use linear rails if they were superior enough to v-wheels with aluminium extrusions (my current choice) at an affordable price... (I know v-wheels cost more than roller bearing + rods but...)

Decision Process:
  1. First I had to decide what to build the printer frame with... Aluminium extrusions won hands down...
  2. Next, do I use roller bearings (or any other bearing) and rods or v-wheels? v-Wheels won out for several reasons...
    • Already have the extrusions so I don't need rods...
    • v-wheels generate much less noise...
    • precision, I could remove virtually all erratic movement using eccentric nuts...
  3. Existing builds and the quality they produced (basically the CR-10 was producing pretty damn flawless prints and not a roller bearing in site)...
Research:
I read lots of reviews and watched a lot of videos on new and existing designs and for the most part my initial decision was confirmed.

Whether you choose one or the other makes very little difference at least at 0.1mm resolution, but as I'm aiming for 0.01mm I might eventually go the linear rail direction but not for now... ;)

Re: OpenBuild vs linear bearings

Posted: Thu Sep 21, 2017 10:33 pm
by Jim JKla
Maglev anyone ;)