IN DEVELOPMENT Switching the LM8LUU to IGUS drylin®

Today, Tom weighed in on the issue:

 

Which IGUS bearings did you order / how did they go?

 

@JesperJuul , may we know the result of the IGUS and which ones did you order ? Thanks

 

I've been trying to work out the correct IGUS bearings, and this is the advice I've had from an IGUS distributor in the context of "what is the best replacement for the LM8LUU in a 3D printer"

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The closest would be the RJZM-01-08. However the overall length of the LM8LUU is 45mm and the Igus is only 25mm.

For accuracy on a 3D Printer you are probably best to stay with a recirculating ball bearing style, rather than the liner style of the Igus range as the friction factor is more with liners.

If you do want to try the Igus range perhaps you could put two RJZM-01-08’s in place of the LM8LUU, or maybe even try only one of the RJZM-01-08’s.​

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The RJZM-01-08 bearings cost around USD$20 each, so you'd need 16 RJZM-01-08 replace the 8 existing LM8LUU bearings, which would cost around USD$320. For now I'm going to hold fire on this upgrade, unless someone as some more insight on better ways to do it!

 

I did do it, and for a lot less. Got the RJ4JP-01-08 from a shop in England. I think I paid something like 36 Euros for 12.
Overall they work. I am not sure if I have any loss of quality because of them, but I will be changing them out to see if there is a difference. One thing I can say is that if the rods aren't really parallel, they bind quickly. But they are quiet.
I am back and forth about changing the rods to the anodized aluminum ones to see if that makes a difference.

 

There are places on the BB where two smaller bearings - that have been spaced as widely as possible - might do a better job.

As Tom points out in his video, IGUS bearings that are not sold in a metal jacket are supposed to be inserted in a finely toleranced structure (H7, I think). It's that hole which squeezes the plastic bearing to it's final inner diameter (it arrives too big). There's no way of 3D printing at that tolerance, and even if you could it probably wouldn't be rigid enough. Folks who can machine metal might have a go at machining holders for the cheaper IGUS bearings without a jacket. But you'd have to think that fun to want to do it!

I think I'd go with Misumis for the Z axis for sure.

Then pick small metal jacketed Misumi's for the X and Y. 25mm times 2 (per LM8LUU) is probably too much, so perhaps more like 10mm times two (which should cost less). By spacing them as far as possible there might be performance improvements. And as Tom says, such friction as these bearings impose won't stop the stepper from doing their job but it may help impede ringing (or somesuch artefacts).

 

I said this before as a means of overcoming rod deflection but also good for the Z axis as its main weakness is the length of the bushes allowing less effective parallel motion but there is not much room to do it. I would suggest that @Tom De Bie thinks about this with his tall BB.

 

@mike01hu don't you think there's a danger that if used on the Z axis the extra friction of the Igus will mean that the bed doesn't descend with every step? Consequence banding.

 

Really I meant that each bush should be replaced with two shorter ones but much further apart.

 

That's actually not a bad idea. Although I'm not convinced that the Misumi bearings are worth the the money. I have so many Chinese bearings lying around there should be at least one or two I can match to each smooth rod.
For the Y axis I'm going to use the 10mm smooth rods because of the weight whats going to be resting on them. Even if it's only a bowden setup (kraken).

 

I feel misumi makes a difference, especially in noise and maintenance.

For reducing flexing, we could also consider Linda's rails mounted transversal in order to reduce flexing. I wonder if that would help.

 

That would most definitely help, but it would take a complete redesign of ten entire Y-axis. Something I'm not going to be doing for the moment as I already opened up the holes in the Y brackets to accept 10mm smooth rods. Maybe you could do it for us

 

I did enough changes, and have some fun mods to finish once I am back home like my iron man like electronic cover and either a end stop on the bed or change the firmware to home with the current sensor on white paper in one of the corners.
After that and after profiling all materials I have, it is direct Titan of chase! Or maybe linear rails (not Linda rails, damn iOS), even if I have a I3 mkii to mount and calibrate also. And work

 

Tom, did you find room in the carriages to handle the 4mm increase in the OD of the 10mm bushings?