Building a delta. Push rod length question.
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I am getting ready to purchase the smart effector and another duetwifi. I am using 2040 extrusions for the uprights as I am going to have a 1m high tower. I have a hotbed that is 220mm in diameter and want to know the minimum length the pushrods need to be to cover that and no waste height. I am having a really hard time finding info to build on the internet. All I can find is 80% the length of the bed but that doesn't sound right an mathematically would leave you short of the edge. I might also extend the bed out to 300mm with an aluminum plate as a heat conductor.
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I'd recommend if you want a meter high to use the great recipe DC42 put together here - https://miscsolutions.wordpress.com/2015/06/01/building-a-large-delta-printer/
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The updated version is described at https://miscsolutions.wordpress.com/dc42s-large-kossel-build/.
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the normal advice is that the rods should not go below the 20 degrees to the bed angle I would err on the side of caution and say 25 degrees is a good measure. The 80% refers I think to the length of the horizontals not the bed.
DC's build has been copied many times over now and is a well tried and tested design.
Doug
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For a printer the same as DC's (and mine which followed it), 360mm magball type arms are very much long enough, even to print on an oversized bed (mine is 300mm). Initially, various simulators and calculators came up with 330mm which was too short. Deltas do not lack z height, and the issues caused by too short rods are much more problematic than too long rods.
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Indeed simon hence my suggestion to go longer my bed is 360 Diam and arms are 450 long (Which may be to long) and with 1 mtr verts and 495 horizontals with the Robotdigg 20x40 corners I get 400 mm build height at the centre
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Thanks guys for the info. I will take a look at DC42's delta.