Will Linear Rails and Blocks Fail Quickly?

For the past year and a half I have been working on designing and building a cartesian style printer using linear rails for all three axes. The frame is built and the rails are in place just about to be squared. Now I read the excellent article, 'BUILD A 3D PRINTER WORKHORSE, NOT AN AMAZING DISAPPOINTMENT MACHINE' (https://hackaday.com/2016/07/06/build-a-3d-printer-workhorse/) wherein the writer says not to use linear rails on X and Y because "... they won’t last for long." The reason given being, "printed plastic debris and even fragments of their own assembly will sooner or later cause them to block."

My first printer (a commercial Up!Plus) had linear rails for all axes and because print quality was so good with it I decided that was the way to go with my home brew machine but reading the warning above gives me pause. Have I made a big mistake? Will the longevity of the linear rails be as poor as the article says? This machine is past the point of a redesign going and back to smooth rods.

If the only issue with using linear rails is them getting bits of plastic into them, this doesn't seem to be an insurmountable challenge.

As for getting bits of their own mechanism into them eventually, this doesn't seem logical since the only part this could refer to is the little wiper on either end of the block that runs into the rails groove to keep it clean. I don't see how it could wear enough to cause debris sufficient to jam the balls. Perhaps the ball re-circulation part on either end of the block could wear out too and cause jamming? But would not these two problems mean that linear rails in themselves are a bad design and unworthy of use in any machine?

Can anyone with experience with linear rails and their longevity please comment?

---

New browser from the creator of Opera: [vivaldi.com]

I don't know what your definition of "quickly" is, but I have have been using linear guides in my printer's X and Y axes for 2 years of daily printing with no signs of wear at all. If you did get bits of plastic into the rails, unlike getting bits of steel into them, they may get a little rough, but they won't be damaged. You can always take them apart, clean them out, and relube. Many come with plastic seals that closely follow the contours of the the rail to keep debris out.

I think the author of the article is wrong.

Lifetime of linear guides is measured in distance traveled and is a function of applied load. End of life is defined by some reduced performance, such as movement out of spec, etc. The mechanical forces applied to linear guides in a 3D printer are pretty small compared to their rated loads, so lifetime should be quite long.

Edited 2 time(s). Last edit at 09/28/2016 06:59AM by the_digital_dentist.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I was hoping that if I oil the rails/blocks periodically they would run indefinitely. On my Mendel90 I do just that; add a few drops of Vactra 2 once and a while and there is no problems with the smooth rods. I assumed the linear rails would be the same since it's also steel balls running in a steel track. Pretty few parts to go wrong.

Since the wipers on my cheaper set of rails don't fit the rail grove perfectly I have I thought of making better wipers. I'll give that a go if I experience problems with the factory wipers. All in all, the rails and blocks just seem like a robust solution that should stand up to serious use.

---

New browser from the creator of Opera: [vivaldi.com]

I guess the way to achieve movement out of spec would be to wear the balls down (make them smaller) or wear the tracks out (make them bigger). Both require metal wear which I agree should take a long time on a 3D printer. As long as crud doesn't build up in the blocks there should be no trouble.

---

New browser from the creator of Opera: [vivaldi.com]

Sounds unlikely to me. A 3d printer is a rather benign environment for linear rails compared to many industrial uses. Why would you get much in the way of "plastic debris" on the rails? And why would that be a problem for linear carriages anyway? The carriage ends do a pretty good job of wiping away debris from the ball tracks. I've just been salvaging a linear rail from a silicon wafer handling machine that I believe was used for washing the wafers. I suspect that was a much harsher environment than a printer will ever be, and looking at the layout and weight of the mechanism (basically a 4 dof robot arm) the loads would have been a lot higher too. I had to remove some corrosion from the rail, but the carriages still run smoothly and without detectable play.

I just looked at the original article- he wasn't talking about linear guides. He was saying that linear bearings- i.e. ball bushings- are the parts that don't last, and goes on to say that plastic bushings are the way to go. Hmmmm. I still disagree completely, and I suspect the author doesn't even know what a linear guide is...

The article isn't about building a reliable work-horse. It's about spraying perfume on a POS to make it stink less.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

It seems I mis-read the author badly but now I can disagree with him on this point based on my own experience. I have had two machines and never once had a bearing failure on a linear rail or smooth rod, much less ever even had a piece of plastic try to get into a linear bearing. I can't see it happening as long as one pays the littlest attention to the machine. I've had wisps of plastic try to wrap around a z rod but not try to get into a linear bearing.

---

New browser from the creator of Opera: [vivaldi.com]