User talk:Spiritdude

Hi Spiritdude, great work on the stiffness of our machine concepts. Looking at this is really overdue, thanks for doing this. Two missing points sprang into my eye:

1. The MendelMax is stiffer than the others, due to it's extra triangle at the top, that's right. But it isn't "fully" triangled at the top, the vertical bars can still buckle in X direction. If it were fully triangulated, this triangulation rod whould go down all to the bottom. OK, perhaps that's nitpicking.
2. The other one is, less nitpicking, triangulating frames is only one way to get them stiff. Another one is to use stiff bars. Like in single-lever motorcycles for the rear wheel, for example. So far, RepRaps make not really use of stiff bars, but it's thinkable for a Wallace-like design to be stiffer than a MendelMax. Look at ordinary milling machines and drill presses. They don't have triangulated frames, either.

--Traumflug 11:01, 1 August 2012 (UTC)

Thanks for the feedback, Traumflug!

1. fully triangulation at the top of MendelMax - let me check, yes, will correct it!
2. Can you describe more detailed what a "stiff bar" is, you mean just thicker? The point is, when you use vector-like (in regards of function) rods to stabilize a frame, like threaded rod based RepRaps foremost, the issue of vibration is obvious - the stiffer the bars and its connection to the other bars are, the less "vector-like" (one dimensional transfer of pull/push force) as also triangulation happens (a big footprint of an aluminium extrusion fixated for example). Whereas a threaded rod attached to a printed corner thingy won't function anything but just pull/push (vector-like). I assume, User:Prusajr: Prusa Mendel, and User:Whosawhatsis: Wallace, as well User:Emmanuel: FoldaRap look at where rods or bars do connect, I am not experienced with aluminium extrusions, but I'm very impressed of the photos of printed stuff by FoldaRap (on his flickr stream) and he describes also well how he achieved it (hotend temp recheck + fan to cool print while printing). Also, in one video of Printrbot maker [[User::Abdrumm]] states, that he is not pleased with the printing quality of his Printrbot (making pieces for Printrbots) and at that point I realized, just at looking at his videos, the z-rods where shaking/vibrating - which lead me to look at this issue of rigidity and vibration, first from a formal geometrical point of view, and second real world experiences (rigidity of stiff bars and such). I will follow Printrbots further to see if the lack of rigidity at higher Z is measurable:

I was thinking of a form (STL model) to print which reveals:

• skew of frame (e.g. Prusa Mendel frame at building time needs to be measured quite good, but I doubt one achieves 0.3mm exactment or so) - whereas Foldabot seems to do a good job avoiding skew with precise lengths bars (e.g. cut together, making margin very very small).
• vibrations (in particular at higher Z, when the printed item is moved Y)

Spiritdude 14:19, 1 August 2012 (UTC)