below are answers
On 19 August 2017 at 12:52, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
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On Sat, Aug 19, 2017 at 11:38 AM, Hrvoje Lasic lasich@gmail.com wrote:
Ok, so correct me if I am wrong but you are asking some mechanical questions.
mechanical / physics, yes.
so, I speak in general now and if you have question ask deeper.
Force needed to drive whatever you want to drive will be exactly the same at the end part of system.
on the print-head yes. but because of the doubled speed, the DRIVE end *NO*, the force is NOT the same.
so, if on the print head-side force is the same then it is on the drive side same as well (work can not be missing somewhere). However, if you are doubling the speeds, then overall work required will be some higher value so, correct would be to say that because of double speed you are having more force on print head needed and as result drive will also have to work more, losses will be bigger etc.
anyway, that is all theoretical. Real value would be to find out force you need to have on print head then do some sort of calculation back to the drive. I guess you don't know that but maybe you can see what has been done on system that have other drive and then try to extrapolate what you will need. We can also assume here that someone has already put some reserve on what is now there, so possibly you can leave same motor or if you have problem increase force at disposal assuming you can do that on same motor size (nema 17 or so)
I think backlash here will be your biggest problem here. Backlash is in fact inertia of the system. So, for example when you run you want to stop you cant do it right away, you need some time/distance. Or comparing to electrical engineering you can compare it to inductance. Inductance is resistance plus reactance.
You said that you expect lesser backlash on pulley system. If that is the case (I am not sure why or why not this statement would be truth) you will be able to increase speed up to certain point but you will have to test where is that point. Basically you will have to do a lot of testing.
But efficiency of belt system could be slightly different then efficiency of `non` pulley system (whatever it is). But again, efficiency could be neglected for sake of easy of calculation or
you
can put around some value that (guess) could be 80-90%.
i'm assuming that there are no significant losses around pulley bearings.
What you will be looking is gear ratio on pulley that could alter force/speed ratio and same thing on other system.
the gear ratio on a single pulley system is 2:1.
also, you will be looking on backlash.
*thinks*... backlash should be reduced (halved) due to the better effectiveness of the pulleys - assuming that there is no "play" in the bearings (we can assume decent bearings / idlers).
l.
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