Lead-screw specifications
Hi everyone,
What are the exact specifications of the z-axis lead-screws?
Best wishes,
Martin
Re: Lead-screw specifications
Martin
8mm diameter, 8mm pitch, 4 threads
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Lead-screw specifications
Thank you very much, Peter.
Are there any documents regarding the mechanical specifications of the MK2 - e.g. stepper max current etc.?
Would make life easier.
I am planing some modifications regarding the motion parts, that I want to share later with the community.
Bye,
Martin
Re: Lead-screw specifications
Martin
I recall that I found the stepper specs by doing a google search on the part number (from the motor labels)
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Lead-screw specifications
I checked with PR support regarding specs for the stepper motors:
Motors used on X,Y,E axes:
2 phases
6.5 VDC Rated voltage
6.5 +- 10% Ohm Resistance
1A Rated Current per phase
13 +-20% mH Inductance per phase
>100 MOhm Insulation Resistance at 500V DC
Motors used on Z axis:
2 phases
8 VDC Rated voltage
8 +- 10% Ohm Resistance
1A Rated Current per phase
9.5 +-20% mH Inductance per phase
>100 MOhm Insulation Resistance at 500V DC
Very curious to hear about your upgrades/modifications. 🙂
Re: Lead-screw specifications
Hi all, just came across this post. I need to replace the (trapezoidal) black nylon lead screw nuts. Anyone have a source for brass ones or something more durable and better fit? Mine had a lot of slop straight out of the bag!
Re: Lead-screw specifications
Martin
8mm diameter, 8mm pitch, 4 threads
Peter
Don't you mean 8mm lead?
Pitch is the distance from one thread to the next regardless of the number of starts.
Lead is the distance traveled by the nut in one revolution.
Re: Lead-screw specifications
...
Don't you mean 8mm lead?
Pitch is the distance from one thread to the next regardless of the number of starts.
Lead is the distance traveled by the nut in one revolution.
of course you are right mate. the pitch should be 2mm !
----
but now a question related to the trapezoid nuts:
how severe is the tolerance/clearance of these nuts ?
i've got a pair of spare motors here (spindle only 300mm) that came with brass trapezoid nuts, but there i noticed a perceptible clearance (approx. 330um).
then i checked the nylon ones at my MK2 and they've had some clearance too (can't measure the amount right now, cause the printer is busy within the next 6 hours).
❓
is this a real problem, or does gravity work against it successfully ?
if it's a problem, wouldn't it be necessary to work with counter nuts ?
dem inscheniör is' nix zu schwör...
Re: Lead-screw specifications
Trust the gravity. 🙂
Or try these http://www.thingiverse.com/thing:1903200 😉
Re: Lead-screw specifications
I am giving those a go just to see!
So would they be 8mm 2mm pitch 4 thread?
Re: Lead-screw specifications
Yes, original MK2 nuts are Tr8x8 (4 threads).
Re: Lead-screw specifications
Trust the gravity. 🙂
Or try these http://www.thingiverse.com/thing:1903200 😉
hi david,
did you tried your lead-screws / trapezoid nuts yourself ?
i printed them in pla and petg (nylon failed so far), but i think the required torque to turn them at the steppers spindle is more than the stepper could provide, at least in "silent mode".
ususally i would try to mess around a little with x/y resizing... but then the whole nut won't fit into x-motor-end & x-idler-end.
dem inscheniör is' nix zu schwör...
Re: Lead-screw specifications
I use one pair of nuts in silent mode (I print in silent mode only) for about 3 months with no issues. Actually it is the very first pair printed, I never planned to use it for such long period, but I'm too lazy to put original ones back since printed ones still work. 😉
They are printed from PLA.
They were a bit tight at first time, they required a bit of run-in, so I turned them by hand on lead screw until smooth movement was achieved.
Basic prerequisite is perfectly calibrated printer. Most of i3 MK2 printers I ever seen make output a bit smaller than requested. Do some calibration prints, measure output and if needed, adjust steps/mm with M92 gcode command. Extruder usually needs calibration as well.
Re: Lead-screw specifications
...Basic prerequisite is perfectly calibrated printer...
😀 that's what we all intend ! 😀
from the dimensional point of view the printed trapezoid nuts are exactly 25.0mm in diameter (guess that's how it should be).... and i've no problem to screw tham at the spindle by hand... but they won't "run" down or upwards if i give them a quick twist (like the genuine and the brass one will).
guess you're right and they need a little "run in" time.
anyhow, it's a good idea to check the extruder calibration once more 😉 ...
dem inscheniör is' nix zu schwör...
Re: Lead-screw specifications
I printed these in ABS and they seemed to come out good but I haven't tried them yet. Anyone have a source for brass ones or something like that?
I was also checking this site out but hadn't gotten very far yet figuring out how to size and order the correct items. Thought it was interesting though.
Re: Lead-screw specifications
they won't "run" down or upwards if i give them a quick twist
They should never do that. If they do, there is too much play. It is most likely OK on vertical axis, gravity will do the job. But I like things as perfect as possible. 🙂
Anyway, source SCAD files are available on thingiverse and you are free to modify them and make customized version with a bit loose thread.
Re: Lead-screw specifications
There's no problem in having some play. New nuts on new leadscrews have play, or at least mine did. If you want to reduce play you have to use two nuts and a spring or an anti-backlash nut (on our X/Z configuration the spring and nut should be put above the default one, and that would reduce max Z height slightly and create some problems in the "hit the Z tops" phase in the calibrations). In fact some play may help reduce the wobble transfert from the leadscrews to the carriage, but that's just my opinion.
If you print the nuts, be sure that they have either some play (and run down freely by gravity) or have none at all: otherwise you may get backlash on z-hops.
The best thing imho is to have nuts with (slight) play and an anti-backlash mechanism, but it's difficult to achieve on this Prusa.
I've tried some brass nuts, they look nice but they leave metal debris on the leadscrew and need lubrification. I also think that they're more noisy. I don't recommend them.
I've used with success the printable nuts; for some reason, in PLA 0.20 is well tight, 0.15 is free running. I would recommend them to be tight as long as it's difficult to tell how much play is right. I've used them because one of the original nuts was broken, not because there was play; Prusa didn't have spares.
BTW, there seems to be no replacement nylon nuts available anywhere on the world.
Re: Lead-screw specifications
Interesting comments patrizio.b. I will try my printed nuts maybe this weekend when I redo the rods and bearings for the Z and X axis.
One of my lead screw nuts has slight play which must be fine but the other is very loose. Maybe it is ok but I can move the left side of the X axis up and down about 1-2mm.
Re: Lead-screw specifications
During a deep check of my MK2S to fix my wobble issue, I noticed that there is a gap between the lead-screw/trapezoid motor nut and the X-ends.
In the assembly guide there are absolutely not indications of how they have to be tighten.
Does they have to be well centered ? and how to do that ?
Does they have to be tighten or let loose to allow some lateral movements ?
Anyway, I think this could be a real root cause of the wobble issues.
What do you think about ?
Vincent from Elsass 😀