Switching to lead screws?
So I have a z rod with a pretty awful bend in it, and I've thought that instead of just replacing it with another 5mm rod that I'd get a couple of lead screws online and some 5mm to 8mm motor couplers. Is there anything I should look out for? Any weirdness with couplers and those lead screws? I know I probably won't see much if any improvement in z resolution, but if it needs repair I might as well upgrade (if it is in fact one haha).
Thank you!
Re: Switching to lead screws?
Are you seeing an impact on prints due to the warped rods?
The nice things about the 5mm rods is they have a little give to them and the printer can operate just fine with it. On one of my printers one of the rods is slightly warped, but the prints still come out perfect.
Re: Switching to lead screws?
For the most part prints come out looking fantastic, but sometimes my taller longer prints get a bit of uneven z banding.
Re: Switching to lead screws?
Hi guys
Unless you buy threaded rods made from stainless steel, they will be somewhat bent. One reason why Josef supplies 5mm threaded rods is because they can be straightened more easily.
I have invested in steppers with 4 x 8mm lead screws. They are also bent and the play in the nut is significantly more than that in the 5mm rods.
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: Switching to lead screws?
It doesn't seem like there's any disadvantage to going with a leadscrew, nor does there appear to be any distinct advantages. This is kind of what I thought, I guess my biggest concern was the z motor couplers interfering in any way.
Re: Switching to lead screws?
Also another thought for the more knowledgeable here. Would I have to make any changes to the firmware if i did decide to go this route?
Re: Switching to lead screws?
Yes, but its quite easy thing to do. You need to adjust steps per mm for Z axis in configuration.h.
You can use on-line calculator http://prusaprinters.org/calculator/ .
Re: Switching to lead screws?
In the latest firmware, the file is Configuration_prusa.h and the line to change is:
// Steps per unit {X,Y,Z,E}
#define DEFAULT_AXIS_STEPS_PER_UNIT {100,100,3200/0.8,179}
You simply replace the old thread pitch (0.8) with the new pitch.
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: Switching to lead screws?
Thank you all for the help! I've never done any firmware tinkering but I'm quite eager to learn more in case I ever have to get in there for any reason. I do think may go with a couple lengths of 8mm leadscrew just for experimentation sake. If it doesn't work out I can easily get some more 5mm rod .
Re: Switching to lead screws?
Another thought came to mind , a good compromise between leadscrews and threaded rod might be to take a threaded rod like we all already have in our printer ( albeit straighter) and give them a polish to make the movement of the nut over the rod itself smoother which would might not be a huge improvement , but it is still something. Another thought is to add some sort of anti backlash mechanism in there, and there are plenty to be found online. I may go this route instead now , again mostly for the sake of experimentation and trying something a little bit different.
Re: Switching to lead screws?
Lubricating the threaded rod is definitely a good idea. Even for lead screws, you should lubricate. Lubrication will reduce any friction that is preventing smooth travel.
With regards to anti-backlash nuts, I don't believe they are necessary. There shouldn't be any backlash when moving upward because the weight of the X axis keeps the nut pressed against the top of the thread. You might see backlash if there is any up and down movement in the Z axis, such as using " Z Hop" in Cura, but I wouldn't recommend using that. The direct drive extruder on the Prusa is excellent and so the retractions work more than well enough to prevent any scarring on travel moves.
Re: Switching to lead screws?
I do agree with you that the anti backlash should be somewhat unnecessary when moving in a normal way on the z axis due to the weight and gravity keeping constant pressure on the screw threads itself. I think that benefit is had more so with lead screws and the nut they use as they move more freely and smoothly. Something to perhaps mention is that a bit more play between the nut and rod( lead screw) should not have much of an effect on the z resolution so long as that play is linear and not perpendicular to the motion.
Re: Switching to lead screws?
Jack
Z-Lift is present in some slicers without even activating it. Take, for example, KISS. When printing supports, they are printed at a different height (except for the first layer) than the main print. Z-lift is employed when moving from one support to another.
If there is any backlash in the Z axis, the tightness of the X belt can generate sufficient opposition to gravity to cause print issues (Z axis not lowering at the correct time).
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: Switching to lead screws?
Peter,
Oh I wasn't aware of that. I only use Slic3r and Cura. But that is something to note.
This is why I try not to change Z directions. Do you use a slicer that frequently changes Z direction?
Jack
Re: Switching to lead screws?
Jack
KISSlicer does this with supports. I didn't realise until recently when I was watching a print with supports.
The first layer is printed (for example) at 0.2mm. If the slicer is set for support Z gap to be 0.05mm, the next layer prints the supports at 0.35mm and the model at 0.4mm. This continues throughout the print. However when moving from one section of support to the other, the extruder is lifted by the support gap, moved and lowered again. I haven't worked out the logic of Z-lift on support moves as yet, but I guess it's because not all support is printed before the model.
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: Switching to lead screws?
Peter
That is bizarre. Can't figure out any reason for that, but I will make sure to avoid KISSlicer haha.
Jack
Re: Switching to lead screws?
Jack
Actually, I get the best results from KISSlicer. So, if you don't want to see good quality prints, then avious it... 😉
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: Switching to lead screws?
Is there a reason, I am not aware of, that the online calculators for calculating Steps per mm have NOT been updated to include the latest 32-bit Stepper motor drivers that run at 1/256 Driver microstepping??
Do I just use the calculator as is and set 1/16 driver micro stepping and then multiple my calculated results by 16??
So if I have a 1/256 Trinamic 2208 stepper driver micro stepping on my axis and my lead screw is TR8x2 and my stepper motor angle is 0.9 is my steps per mm = 51,200??
I set the following in the calculator:
Motor a Step angle : 0.9
Driver micro stepping: 1/16
Lead screw pitch: 2mm
Pitch presets: M8
Gear ratio: 1:16
Is this how to use the calculator to compensate for the fact that it does NOT have the 1/256 micro stepping option for Trinamic 2208 drivers???
https://drive.google.com/file/d/1GyGbrCIUOACyQ7JbGSiyapcALmLJeKSb/view?usp=drivesdk
https://drive.google.com/file/d/1vovxE_MUnbRFj7jBhBvyru7ipo1OvXEV/view?usp=drivesdk