Large Delta speculation
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I am going to see if we can find an optimum width to height ratio. Please contribute your deltas specs here:
http://forums.reprap.org/read.php?178,806859,806943#msg-806943
or here if you prefer:
https://groups.google.com/forum/#!topic/deltabot/Gc2Ee9y3lrM
Lets see if there is an optimum.
Is there a way to do this by mathematics/simulation? If you know how please let me know (on one of the threads above).
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I really don't think there is an optimum ratio, but there are some design considerations:
- Taller vertical extrusions require thicker extrusions or cross bracing to maintain rigidity;
- A wider print area/larger delta radius needs longer arms, which may need thicker carbon fibre tubes to maintain arm rigidity;
- Taller and wider both increase the Bowden tube length if you use an extruder drive mounted on the frame. So for larger delta builds especially, consider a lightweight direct drive extruder mounted on the effector, or a remote direct drive extruder, or a flying extruder.
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I really don't think there is an optimum ratio, but there are some design considerations:
- Taller vertical extrusions require thicker extrusions or cross bracing to maintain rigidity;
- A wider print area/larger delta radius needs longer arms, which may need thicker carbon fibre tubes to maintain arm rigidity;
- Taller and wider both increase the Bowden tube length if you use an extruder drive mounted on the frame. So for larger delta builds especially, consider a lightweight direct drive extruder mounted on the effector, or a remote direct drive extruder, or a flying extruder.
For my 1.7m Delta the e3d titan extruder I had just couldn't push the filament without fairly constant problems, however swapping to the Bondtech and capricorn ptfe tube fixed a lot of issues with extruding and reducing the amount of retract that was needed, although my Bondtech has to run backwards as the bowden tube can only be gripped by the adapter rather than the built in fitting.
As for optimal dimensions I think that depends on what you want to make, if you want to 3d print lots of rockets, tall and and narrow is good, if you want to print lots of fossil skulls then wider and shorter is fine.
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There is a calculable ratio between all the horizontal elements of a Delta/Kossel printer. Meaning the horizontal extrusions, resulting bed size, etc. "Ratio" may not be the correct word because there are some fixed parts (the offsets in the 'corners' or 'brackets') and some variable parts (how long the horizontal extrusions are cut). Clearly "calculable".
Vertical? There are some lower ratios to horizontal that don't make much sense. Going upward is limited only by practicality of building, bracing, fitting into a home or other building, etc. Upward is (almost) unconstrained. Maybe eventually belts get too long, or homing takes forever or similar.
The diagonal rods fit mostly in the "calculate from the desired horizontal" category. They can have some constraints from a too-short vertical… ignoring that for a moment (because there are many other reasons not to be too short, like being able to print tall things!), then, mostly, diagonal rods are constrained by not wanting to be below 20 degrees angle at the maximum travel of the extruder (constraining angle will always be at the edge directly opposite any tower). Again, "calculable", either 'forward' or 'reverse'.
Back to the original question: No perfect 'ratio' between H and V. Maybe some lower limit on vertical, given a horizontal as a starting point.
There also needs to be some thought toward availability of given parts. As an example, there can be HUGE cost differences to get some of the components in 1.7 meter length vs. 1.5 or 2.0. This applies to many things that interact with each other, like the bed vs. the horizontals. Assuming a glass/aluminum/heater bed, my research indicates the glass is probably about the same cost in any diameter (per sq in or cm), the aluminum has HUGE step changes at various sizes (assuming cast plate, not sheet), and the heater has fewer step changes while still becoming quite expensive for anything beyond "standard hight volume sizes".
If we combine step changes in parts sizes, horizontal interactions that are calculable (and need the fixed offsets to precisely calculate a given build), verticals that are calculable, and a somewhat weak interaction between H and V... those are the thoughts that led me to create the calculator linked above.
Here is a repeat of the link:
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Some thoughts on google groups about this:
https://groups.google.com/forum/#!topic/deltabot/Gc2Ee9y3lrM -
Here is a example of my printers. They have a print height of about 1200mm. I have no issue what do ever printing tubes that highe, and powered by Duet's.
Im 6'3 tall
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Ok, I give up..
Are the drive belts running inside the slots of the extrusions?? -
I'm not the photo poster… but... if you enlarge the photo a bit and look carefully at the "closest, a bit to the right" motor in the photo, you can see the pulley. It appears the belt runs inside the "innermost" and "outermost" slots (as oriented to the triangle/circle) in the Extrusion.
