Re: Talk me out of (or into) a Delta
September 06, 2018 03:02AM
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Redemptioner
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scndctr
What's more, mine uses linear rails and not wheels, but I don't know if the rails are really significantly better.

Generally using linear rails on a delta it does not, assuming you are using polycarb wheels, improve the print quality. This is due to being unable to adjust pre-load on the linear bearings, something that is a critical element to be able to adjust in order to get perfect prints on a delta (fyi if your carriages and/or effector can move down the Z axis under their own weight you don't have appropriate levels of bearing pre-load).

We'll have to disagree about that. It is important that the sliders don't rotate when the belt stops pulling one way and starts pulling the other way. This does not necessarily mean that with the belts disconnected, the carriages don't drop under their own weight.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Talk me out of (or into) a Delta
September 06, 2018 03:36AM
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dc42
We'll have to disagree about that. It is important that the sliders don't rotate when the belt stops pulling one way and starts pulling the other way. This does not necessarily mean that with the belts disconnected, the carriages don't drop under their own weight.

Yes, but if the rails move freely without a load on the bearings the "majority" of them allow for some movement, this is because there is a gap between the casings that is allowing the "free" movement, sure it is a small gap but it is still a gap and also can allow the bearings to slide instead of rotating which generates additional noise/vibrations. Slide a linear rail up and down (ones with ball bearings, the other type are not worth talking about), the rails without the ability to adjust the bearing load you can feel the bearings moving around unevenly, compare to one you can adjust the pre-load and you will still feel the bearings but the feeling will be even and much smoother.

Now saying that, linear rails typically last much longer than polycarb wheels which is something to remember, but changing out wheels every few years on a printer continuously printing is not really that bad. Then you can look at what it takes to setup each type and one could argue wheels are much easier when you consider the choice and availability of quality extrusion for wheels but then again you can bolt a linear rail to anything as long as you take great pains to ensure they are installed square. Admittedly we are niggling over minute differences when comparing quality wheel setups vs quality linear rail setups, I am just saying the majority of people would not seen an improvement with linear rails over wheels, that and value for money you would be far more likely to get better print quality from the same money spent on a wheel setup compared to a linear rails setup be it on the cheap end or big end budget wise.
Re: Talk me out of (or into) a Delta
September 11, 2018 06:24AM
About guiding solutions:
For Zatsit, I used simple Delrin slides, gliding directly on MakerSlide profiles. I don't consider it to be a low-end solution, on the contrary:

The ultra-light Delrin slides practically do not contribute to the increase in moving masses. If carefully designed, used in a consistent mechanical architecture, and well tuned, they offer optimal performance for lightly loaded mechanisms, such as Delta printers. I even think they can reduce ringing, by providing a form of damping.

The architecture of the machine is more important than the guiding technology. For example, the lever for embedding the four slides of a trolley on Zatsit is 140x46mm. Therefore, a possible low mechanical gap in one of them can only have minimal consequences on the geometry of the mechanism as a whole.

Finally, the slides are silent, even when shaken at extreme speeds and accelerations. Have you seen this:

Zatsit so fast
Re: Talk me out of (or into) a Delta
September 14, 2018 04:20PM
So which igus slide do you use? I bought a small bit of their 27mm preloaded low profile slides & like the look but im not sure how good one rail would be against twisting forces because the preload can only handle 1n of force.
Re: Talk me out of (or into) a Delta
September 15, 2018 03:06AM
@warbunniex
I don't know if the question is for me, but for Zatsit, it's not an IGUS product, but simply slides machined from Delrin.
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