Still new here and wondering what the pros think about the Rostock Delta design printers… Looks neat and specs are impressive. Build height seems easily extendable and the build platform doesn’t move ! Thoughts anyone ?
I don’t like the fact that the resolution, speed, and step-rate are not consistent throughout the build area. The machine is fundamentally capable of more detail and less speed near the center, and less speed and more detail the further you get from the center. If anything, you would want a machine with the opposite characteristics, on the assumption that the center of the platform is more likely to be used for infill.
It’s an interesting design, though, and I’m seriously considering using the 3 2-meter lengths of MakerSlide I have lying around to try it out.
@Whosa_whatsis the delta is actually capable of less resolution toward the inside, and more speed, with more resolution and less speed on the outside. I’ve got a nice pretty plot I posted on here a while back about it.
It’s a question of radial vs. angular speed/resolution (whether you are moving parallel or perpendicular to the radius). I’d love to see your plot, but I must have missed it, and a quick search of your posts wasn’t fruitful.
@Whosa_whatsis this is a graph I found on the delta google groups board that gives a good idea of how the resolution/build area of the delta bot appears: https://lh3.googleusercontent.com/-1p6cBfgiamQ/UI0gqJ1tioI/AAAAAAAAAKw/10McbTnzDco/s1600/resolution.jpg
Discussion about it is here: https://groups.google.com/d/topic/deltabot/5gyK1JSd0rI/discussion
And I now see what you’re talking about radial vs angular resolution. While angular resolution gets greater toward the outside, radial resolution tends to wane toward the center of the “wall”
Thanks, that’s a great visualization. Notice that when the head passes near the base of one of the arms (that arm becomes nearly vertical), the resolution on that arm gets extremely low, while the resolution (and thus the step rate required to maintain speed) gets very high on the other two. If you were trying to print a circle in the middle of the platform (which any slice of the average print will approximate), the steps/mm along the perimeter of the circle will increase as the radius increases, while the attainable precision of that radius decreases. That’s what I was getting at with my statement about resolutions.
Of course, this effect can be mitigated by lengthening the arms without increasing the radius to keep the entire volume in the relatively uniform center area, but this means that the machine must have more height in addition to the usable print height.
What magnitude of (half-step) resolution are we talking about?
I don’t know exactly, but in my experience, the margin between the resolution being too high to maintain step rates and too low for sufficient detail is well below an order of magnitude, and is getting smaller as both speed and quality demands increase. The move from microcontrollers running at 16-20 Mhz to ones running at hundreds of Mhz will, of course, make higher step rates possible (assuming torque and acceleration curves are adequate).
The step rates will be comparable to a cartesian bot for an arm that is near 45°, if that helps.