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mtowara

Prusa Hephestos Lead Screw Mod

by mtowara Feb 3, 2016
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What is holding the top and bottom bolts against the X axis rails?

The screws cut their own thread.
If you don't trust that you could add some counter nuts, but probably then the screws need to be smaller for them to fit.

Hi,
I don't see anything missing, which part do you mean specifically?

http://www.thingiverse.com/download:2044777
http://www.thingiverse.com/download:2978150

the tensioner part for the bearing is unchanged from the original and can be reused (or downloaded from github)

Yes exactly that what i'm asking i did see this bearing part in the files, clould you link github link where, just to be sure what i'm printed.

What do you mean when you say that you loose a lot of resolution?

I'm about to make that change, but I need to have enough resolution to achieve the same layer height I get now (0.05mm), Will I be able to achieve that with a good result?

Thanks!

hey,
when I first made this I was worried that the lower steps per mm value of the leadscrews might be a problem. However I never had any problems with accuracy (+ the benefit of much higher homing speed).
If I calculate it correctly 0.05mm are still 20 microsteps (400*0.05), so you should be fine.

Cheers!

Cool! So I could even reach 0.025mm layer height? Right now with the default bars I tried 0.02 and the layers were practically not visible at all, so if with this leadscrews I could reach this resolution in a much more stable way (eliminating Z woble) it could be awesome, the Hephestos is turned into an incredible printer.

I´m also thinking in changing the X and the Y axis with one leadscrew each, it may be slower, but the precision may be increased to, am I right? What fo you thing?

Cheers and thanks for your fast answer!

wow, never tried to go that fine. But if it works with the threaded rods then it should also work with the leadscrew.
Not sure about the X and Y leadscrews, I think properly tightened belts are considered to be pretty accurate.

Be sure to post a make of your finished build whatever you go for :)

Hello , excuse me I delete my post, thank you for the reply and yes I use the firmware bq 1,4,2 , til would be possible to recover your firmware ??? I 'm not good at all this set myself sen to error thank you

( your response to my previous post )

All sets you posted should work.
HOMING_SLOW_FEEDRATE is just to the second probe slower the z - stop. Maybe your version of Marlin does not .

Could you please edit your comments , so that the police is not quite huge ? (Maybe that was triggered by the # in front of sets ) .

Comments deleted.

The set of defines you posted should work.
HOMING_SLOW_FEEDRATE is just for the second slower probe of the z-endstop. Maybe your version of Marlin doesn't do that.

Could you please edit your comment, so that the font is not all that huge? (maybe that was triggered by the # before the defines). thanks.

Hello,
i have anti-backlash nuts for my lead-screw, Can you give a version for the same?
Anti-backlash dimensions: https://dpbfm6h358sh7.cloudfront.net/images/2442119/257454653.jpg

Okay I had a look at it, that nut is HUGE. There is no way to fit it in into the existing design.
The only thing i could see working is to turn the nut around and put it ontop of the whole assembly. However this would look quite horrible and might also lead to other problems.

OK, Thanks for trying. Ordered regular brass nuts from ebay.

Don't you experience any backlash due to gravity on the Z?

Thanks again,

No, at least my nuts are machined to pretty good tolerance and don't have any noticeable backlash.

Looks doable. If you have basic CAD skills you can also try yourself, the onshape source link is in the description.

edit:
Looking at those dimensions I'm not sure if there is enough clearance for the z axis rod. You might need to file the nut down a bit. Will check tomorrow.

Hi,

Unfortunatly those things doesn't work with my hesphestos...
They printed well but it seems that holes for screws aren't aligned correctly with motor axes.
When I put right and left blocs without x axes mounted they're not facing each other, and when I mount the x axes there is to much tension on the screws and motors aren't able to move =(

There is something I have missed ?

--edit--
I also noticed a difference in the hephestos_x_axis_lead_screw_motor-end,
on my "factory" one I can push the x bars until the end of the bloc but not on yours.
I have checked this piece on hephestos github and it was like mine, perhaps this piece has been modified since you redesign it ?
(not sure if I'm fully understandable ^^)

Yes, I put those endstops in because in my original hephestos the rods where quite loose and tended to move to the left, thus leaving too little rod for the right part.

Hi there,
I'm not sure if I understand your problem correctly.
Are you having issues mounting the motor due to hole spacing? Or is someting wrong with the tensioner? The M6 screws are there to pre tune the tension, so that the tension on the belt is not too high.

Thanks for reply, I will try to be more precise.
It's not on the tensioner but on leadscrews hole spacing I guess (sorry for the confusion)
When all is assembled, leadscrews are not aligned with motor axes, I can force it a little with the coupler (leadscrew/motor joining part) but in doing that motors won't move anymore

Huh, thats strange. I'll double check if the hole center aligns with the original prusa part but it should be okay.
What material did you print with, maybe its a shrinkage/warp issue? Maybe something lifted from the printbed?

Have you had a notable improvement in the printing quality?

My z-axis was quite wobbly before, so it definitely improved in that regard.
Zapper97NY in his Make also says that he sees an improvement.

You lose quite a bit of resolution in the z-axis due to the much lower steps per revolution, but i haven't seen any problems in the prints even with auto bed leveling.

The printer now runs much quieter, especially the terrible whining noise during homing is gone and also homing is much faster now.

Thank you for your reply. Yesterday I had some time and I printed the tensioner mod. I've saw great improvement with this only. I will try to get some lead screws for the final touch though.

so great that you made this model! i was looking for a model like this for almost a month,

You're welcome, let me know how it performs!

ive orderd the parts for the leadscrew, but they are out of stock. so it will take a while before i can upgraide mine printer.