New Inverted (Grounded) Delta Design October 27, 2016 02:03AM |
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Re: New Inverted (Grounded) Delta Design October 27, 2016 12:23PM |
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Re: New Inverted (Grounded) Delta Design October 27, 2016 01:51PM |
Registered: 7 years ago Posts: 143 |
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o_lampe
Pretty interesting design!
What steps/mm could you achieve with the 20/60 gears and a common 1.8°stepper?
Re: New Inverted (Grounded) Delta Design October 28, 2016 09:38AM |
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Re: New Inverted (Grounded) Delta Design October 28, 2016 10:27AM |
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Re: New Inverted (Grounded) Delta Design October 28, 2016 10:38AM |
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Re: New Inverted (Grounded) Delta Design October 28, 2016 10:33PM |
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o_lampe
What if you'd skip the parallelogram arms and use a leadscrew to move the upper vertical arm directly?
Don't know about the added complexity involved, but the resolution would be better.
Re: New Inverted (Grounded) Delta Design October 29, 2016 12:09AM |
Registered: 7 years ago Posts: 143 |
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MechaBits
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o_lampe
What if you'd skip the parallelogram arms and use a leadscrew to move the upper vertical arm directly?
Don't know about the added complexity involved, but the resolution would be better.
Yeah I was thinking of this for the scara, which is similar to the arms here if flipped 90 deg
Re: New Inverted (Grounded) Delta Design October 29, 2016 12:13AM |
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Re: New Inverted (Grounded) Delta Design October 29, 2016 03:00AM |
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Re: New Inverted (Grounded) Delta Design October 29, 2016 05:09AM |
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Re: New Inverted (Grounded) Delta Design October 29, 2016 11:25AM |
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Re: New Inverted (Grounded) Delta Design October 29, 2016 11:29AM |
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o_lampe
Maybe the cycloidal gearbox would be helpful here? You might end up with three NEMA14 pancakes like you wanted to in the beginning...
Re: New Inverted (Grounded) Delta Design October 29, 2016 07:16PM |
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Re: New Inverted (Grounded) Delta Design October 30, 2016 12:20AM |
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Re: New Inverted (Grounded) Delta Design October 30, 2016 01:18AM |
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Apsu
Please note that without endstops, I'm telling the IK where the arms are to start, but I'm manually positioning them to roughly that spot, which appears to account for the minor Z variations during X/Y moves visible in the video. That and the fact that these long, 20% infill Carbon Fiber PETG arms have a bit of flex to them, which might account even more for the variation as the arms are constantly pushing and pulling against each other during moves.
Re: New Inverted (Grounded) Delta Design October 30, 2016 09:13PM |
Registered: 7 years ago Posts: 143 |
Re: New Inverted (Grounded) Delta Design October 31, 2016 12:20PM |
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Re: New Inverted (Grounded) Delta Design October 31, 2016 04:48PM |
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Re: New Inverted (Grounded) Delta Design November 01, 2016 01:27AM |
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Re: New Inverted (Grounded) Delta Design November 01, 2016 06:19AM |
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Re: New Inverted (Grounded) Delta Design November 01, 2016 10:20AM |
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o_lampe
The last sketch is pretty simple and straight forward, but it also has a drawback:
Lengths of the hypotenuse of P_P triangle specifies the "gear ratio" and thereby accuracy, but it is very low when you print on the bed and the arms are almost folded completely. ( Jeez, I hope you got my point? )
Also the longer it is, the more inertia the motor will produce.
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With a ( planetary ) gearbox you can choose the ratio but keep the stepper as close as possible to the twist point.
I've printed some planetary gears in the past and they don't run very well. Milling the gears would be a nightmare, but the cycloid gears are pretty easy to mill.
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The drawback about cycloid gears you mentioned earlier are IMHO non relevant, like "the gears can't be driven backwards" actually is an advantage here. You might be able to idle the steppers between moves, which keeps drivers and motors happy.
The cycloid gears I linked comes with dual eccentric gears and I didn't feel any significant vibrations. ( They might reduce max. RPM though )
Re: New Inverted (Grounded) Delta Design November 01, 2016 11:41AM |
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Re: New Inverted (Grounded) Delta Design November 01, 2016 12:40PM |
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o_lampe
Thanks for taking the time to explain it to a limited german mind
But you mentioned the scissor lift which was actually what I had in mind too, when I wrote my last reply.
A car jack is similar to a scissor lift, right?
When you try to lift a heavy car ( and they are all overweight nowadays ) you feel it very difficult to turn the crank at the beginning. Later, when the jack is almost fully extended, you have to make several turns to achieve the same lift like before with only one turn. This is what made me think the "gear ratio " and thereby the accuracy is not constant in your design.
Re: New Inverted (Grounded) Delta Design November 01, 2016 01:33PM |
Registered: 7 years ago Posts: 143 |
Re: New Inverted (Grounded) Delta Design November 02, 2016 02:10AM |
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Re: New Inverted (Grounded) Delta Design November 02, 2016 03:37AM |
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Re: New Inverted (Grounded) Delta Design November 03, 2016 07:27PM |
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