What is the most UP-to-date Prusa design

Hello all,

I'm about to endeavor to print my first copy of a Prusa. I know there are so many designs, especially the derivatives from thingiverse: [www.thingiverse.com]

So heres the question: What would you include in your next Prusa build to make it more efficient? Which extruder design would you use? Please keep it a plastic discussion.

I personally don't like the z-axis motors with the couplings, just the idea of the print bed hanging from something is asking for trouble.

So what do you think?

I also dislike the standard coupling design. There is an extremely fine line between being too slack to grip the threaded rod properly, or too tight to avoid fracturing the plastic. New couplings are certainly high on my list of things to do. Some people seem to have devised interesting alternative designs – like this one: [www.thingiverse.com].

Well I was thinking of getting rid of the couplings all together and introduce the Z axis model from the Mendel/huxley. I have that right now and there is no problem thus far. Here is what im referring to, the drive cogs on the bottom: [www.reprap.org]

This version of the coupling solves all the problems: [www.thingiverse.com]. Josef tells me he is putting it in his repository.

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[www.hydraraptor.blogspot.com]

The 10 prusa machines built at the Bath masterclass last weekend all had Nophead's new z coupler and it works really well. Its also easy to install in any new or older machines.

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[richrap.blogspot.com]

awesome.

So Im assuming that this two motor thing has a reason to it right? I currently have 1 motor on the huxley using the gear cog system to lift the Z's
What led to this two motor on top deal?

Thanks for any more input. Keep it coming.

owism8 Wrote:
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> What led to this two motor on top deal?

No need for a belt for the z-axis, simplifies things somewhat at a cost of needing an additional motor.

Belts are cheaper than motors though. But i guess you get rid of two 3 gears which take some nicer calibration to print out.

ok so goal was simplification.

owism8 Wrote:
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> awesome.
>
> So Im assuming that this two motor thing has a
> reason to it right? I currently have 1 motor on
> the huxley using the gear cog system to lift the
> Z's
> What led to this two motor on top deal?
>
> Thanks for any more input. Keep it coming.


Getting everything aligned is hard enough, adding the belt/pulley combos just makes it more so. I've found the dual motor setup works pretty well, but adjusting the current properly was a little tricky. It works great during prints, but sometime pauses while given large (10mm) step changes using repsnapper. Honestly I prefer buying an extra motor and not having to worry about one more belted axis to tune regularly.

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Germanicus

Sorry I don't understand the problem with griping the threaded rod
Just cross drill it and the coupling and insert carter key or roll pin?
Now the motor shaft that's a different thing it's much smaller and has that flat side it seems to be slick with not much purchase.
But from what I can see no one is having a great deal of problems with it.
So if I am going to cross drill my threaded shafts I would clock the thread index* and remove one element for error.
(*That is try and drill in the same way both shafts and couplings.)
In olden times there were Two kinds of errors. Compensating error and cumulative error.
I hope that two motors will compensate for each others errors.
I have spent way too much money and time/gas. on my threaded rod finding a very straight chunk to cut two or three peices from.
So I picture the rod running true but a roll pin or carter key will allow some wobble in a not too tight clamp and not drop out.
"Henry" would have used many(hundreds in a "T".) carter keys and castellated nuts all over the thing.
and some would safety wire most every hot or moving part.
Any who that's my opinion or two cents worth..

i lathed a 5mm hole in my threaded rod slightly less than the motor shaft and tapped it on only gently with a hammer... only problem is now it's there for ever.

edit: by 'slightly less' i mean the drill bit way maybe .1 of a mm less or maybe they were the same.

Edited 1 time(s). Last edit at 07/07/2011 12:11AM by mlagana.

thanks all

How about your choice of X carriage for the hot tip to ride on?

Which extruder design do you prefer?

Which electronics do you prefer? (and where can I order the best cheapest one)

Thanks again.

Frame legs with foot or without foot?

Foot is good. There are derivative works that introduce a leveling mech into the foot.

Thanks!

How about the x axis holders? I saw this one: [www.thingiverse.com]

Any thoughts?

Nophead's new clamp (linked above in his post) solves most of the problems by using a 1/4" PVC tubing (available in pet shops/aquarium supplies) as a sleeve on the motor shaft. I can testify that this stuff grabs the 5mm motor shaft like a demon; I've built a MrKim 1X2 repstrap that uses this method to attach the Z axis threaded rods [www.thingiverse.com] . In fact, it uses two bits of tubing, as it connects the PVC sleeved motor shaft to the 8mm rod with a 3/8" tube. I've had no problems with slipping. BUT my motors are at the bottom on my 1X2, so the weight of the X-axis is not trying to pull them apart, so I would advise using the 1/4" sleeving and nophead's clamp for a normal Prusa with the motors at the top.

As an aside, I'm starting to print a Prusa, and it's going to have LM8UU bearings running on 8mm linear rod, which I've found very smooth and accurate on my 1X2. There are Prusa part variations on Github and thingiverse to mount bearings rather than the PLA bushes. But I don't like the motors at the top design of the Prusa - despite nophead's new coupler, I would prefer the motors at the bottom. I think this could be easily achieved by adding an extra rod at the bottom, moving the motor mounts from the top to the bottom, and using the Huxley top clamp for the Z rods. This would eliminate what I see reported as the biggest problem of the Prusa.
Anyone built a Prusa like this, or can think of any problems? To the original poster, as you can see, the most up-to-date Prusa is only limited by your imagination!

Yes Thank you . I see that there is no limit into what can be designed into prusa. Just wanted to get feedback from experienced users since I dont want to recreate the wheel.

Well keep your feedback coming. More questions below:

How about your choice of X carriage for the hot tip to ride on?

Which extruder design do you prefer?

Which electronics do you prefer? (and where can I order the best cheapest one)

What x axis holders do you use? I saw this on thingiverse: [www.thingiverse.com]

Thanks again.

"Which extruder design do you prefer?""owism8 " Wade's at first thence print out the hinged accessible ones you like.
but i found that the instructions are not to my liking the hobbed bolt i got was hobbed on the threads but if i reverse the bolt
and hob the shoulder my printed parts fit much better motor mount screws clear the big gear much better and drive gear meshes nicely
i like my big head hot end as it fit my printed part first try. like its made for a Wade extruder .