Igus Drylin Linear Rails

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JUMBO_walrus
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Igus Drylin Linear Rails

Post by JUMBO_walrus »

Has anyone installed Igus Drylin Linear Rails on their HevORT? Or does anyone have any experience with them on other machines? They look like a nice alternative to ball rails. And the pricing looks to be decent as well. I'm planning on running dual rails for my X, so I would think the weight capacity shouldn't be an issue.

-Keegan

mavmav
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Re: Igus Drylin Linear Rails

Post by mavmav »

I have and the results unfortunately where not too good.
They looked like great alternatives - lightweight, really quiet and somewhat less expensive.

Did a bit of research before purchasing but the only way to find out turned out to be by trying them.
So I spent a lot of time modifying the wobble wing parts and XY mounts and putting things together.

I used Igus N Guide Rails - 27mm on the Z axis and build plate slides.
They looked good and moved well.
The problem is too much play with the sliders and the bed would wobble around while printing.
Especially at speed. About 1mm, just enough to screw up the print.

I installed the same N Guide Rails - 27 mm in parallel along the Y axis.
That jammed repeatly.
Same issue, the sliders had too much play and the X axis would skew and bind.
No amount of adjusting and belt tensioning I tried would make it work reliably.

For the X axis I used an Igus 12mm T Linear guide rail.
Its their equivalent to a regular linear rail.
This I had high hopes for due to its extreme lightness - its aluminium.
Nope, not with a 388g Hemera bolted onto its side.
It cant take any type of side load and will bind.

The problem is none of the rails could take any type of side or twisting force.

Metal linear rails obviously have much higher tolerances and the strength to handle the side stresses.
There is more of that going on than I first realized.

Live and learn.

JUMBO_walrus
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Re: Igus Drylin Linear Rails

Post by JUMBO_walrus »

mavmav wrote:
Wed Apr 14, 2021 12:17 am

Live and learn.
Thank you for sharing your experience! I was hoping that I could run these with my dual rail setup because they would be considerably lighter than 2 steel rails. But, alas, 'twas not meant to be.

- Keegan

toni1982
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Re: Igus Drylin Linear Rails

Post by toni1982 »

@mavmav There are sliders with an adjustable play within the Igus linear rail series. And also - only one slider/bearing per axis is meant to be free of play.
The other requires a little clearance to prevent jamming. Imagine a very wide and heavy 3D printer bed, of the moving type, gliding over five linear rails/shafts side by side. If now all of the sliders have a little play to the sides, the whole bed will have some play to the sides. But you require to remove it from only one of the sliders to remove it from the whole bed since they are all sitting side by side. (in a row) You can't "stack" a limitation. Zero play times one is the same as zero play times ten. Putting it more than once into the same row doesn't improve anything while making movement much more difficult.

The play-free slider/bearing is called the "fixed" bearing, and the others are the "loose" or "floating" bearings. The fixed one is the spot that dictates the precision. The floating one/ones should have as much clearance as possible without introducing tilt or wobble. If you have a play-free (fixed) slider on both sides, it means you are allowing zero deviation (like a few microns) for the straightness, shape, and parallelism of the rails over their whole length, which is technically virtually impossible to achieve. If a setup with parallel zero-play sliders runs smoothly, then it's most likely because it's being forced through by slightly bending the structure of the printer. It doesn't require to be much and doesn't have to affect the print quality, but it will increase wear.

Most people don't realize how even a massive metal structure can still flex a little from medium or low loads. It's just very little. You might pull on a heavy steel bar and consider it impossible to cause even the slightest effect on it by hand force. But if you measure it, you may find that it's actually flexing by some tenths or hundredths of a mm.
I was baffled too when learning about this in my education. Things bend more than one would assume, on a small scale. That's why milling machines have their frames made of massive blocks of cast iron weighing tons. If there was even the tiniest amount of flex, it would introduce vibrations, damaging the blade of the milling tool or even making it break.
Preventing flex in a range as low as some hundredths of a mm requires a much stronger and stiffer construction than one might think. Just as a side note.
I'm about to start with my high-temp printer build using Igus W rails and I'm pretty confident about it. I also have some ideas in mind regarding the arrangement of the sliders and the angles in which the play is removed from each spot to increase the coverage.

Btw. higher precision means "lower" tolerances, not higher. Tolerance is the allowed deviation from the "perfect" state.
A higher tolerance means lower precision because you're "tolerating larger deviations".

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