Mk 3.9 with MK4 Z Axis motors.  

RE: Mk 3.9 with MK4 Z Axis motors.

Jeep 

RE: Mk 3.9 with MK4 Z Axis motors.

Nice print!

Printed Solid has this LDO.  1.68A, .9 and a hair more holding torque.  Otherwise looks like the one you are using.

https://www.printedsolid.com/products/ldo-nema-17-motor-power-ldo-42sth40-1684

RE: Mk 3.9 with MK4 Z Axis motors.

Posted by: @lino77

Jeep 

 714466bc-screenshot_20231031-203401.png

Can I ask is that signed by Josef himself.

RE: Mk 3.9 with MK4 Z Axis motors.

LDO-42STH40-1684MAC worked great.  Printer detected as MK4, speed is great, printing is silent, and input shaper works perfectly.

I think this is the motor PRUSA uses on teh MK4.

RE: Mk 3.9 with MK4 Z Axis motors.

i have the same signed printer 

RE: Mk 3.9 with MK4 Z Axis motors.

Did you have to change any of the wires?  I noticed the colors were in a different order - I know colors don't always mean anything but since it's the same manufacturer (LDO)...

Posted by: @category-5

LDO-42STH40-1684MAC worked great.  Printer detected as MK4, speed is great, printing is silent, and input shaper works perfectly.

I think this is the motor PRUSA uses on teh MK4.

RE:

Yes.  here is a photo of the working wires.  Just use a pin to lift the tabs on the connectors and you can pull the wires out to re-order them on both sides.   I trimmed mine down and then re-crimped the DuPont side (black).   If you haven't done it before it’s a pain in the butt. I ordered some molex click-mate wired connectors to make some native buddy board-to-stepper wires, but for no reason other than because I can.  Wire them like the picture and use PRUSA's adapters and the printer auto-detects that it is a MK4.

RE: Mk 3.9 with MK4 Z Axis motors.

Thanks a lot!  Very helpful.

 Yeah i was considering shortening the wires- at least there's plenty of length for mistakes but I think I can handle that.

RE: Mk 3.9 with MK4 Z Axis motors.

Finally got the upgrade finished using the 42STH40-1684MA as @category-5 suggested.  I noticed that you really don't have to change wiring at all if you don't mind the color matching (and don't mind the very long length of the cables that ship with them).

 Honestly, considering the compatible motors are $34 for a pair from Printed Solid (out of stock now though!), unless there's some disadvantage to the .9 steppers, it hardly seems like the 3.9 needs to exist.  I wonder if anyone has been able to do a comparison.

Photo of the maiden voyage... Print quality with the pre-sliced spatula looks perfect.

RE: Mk 3.9 with MK4 Z Axis motors.

Yeah.  I got my stepper from eBay so the wiring may have been changed from stock, but they surely wouldn’t have worked as received.  Glad to hear they ship with the correct wiring. 

I hope printed solid gets them back in stock.  My theory is that the LDO branded motors were used internally at PRUSA and when they finalized the spec and ordered branded ones, the leftovers went to printed solid.  

I don’t see them available anywhere else right now so hopefully they come back in stock.  

agreed.  No need for 3.9 if these can be ordered.  Also no reason to order full 4.0 kit.  

RE: Mk 3.9 with MK4 Z Axis motors.

As (it sounds) most folks following along here, I got the 3.5->3.9 upgrade bump. I was about to take the printer apart and was wondering about upgrading the stepper motors at the same time. I see only the Z axis ones are available at Prusa--with the new wiring connector is all.

SO I'm going to swap 0.9 LDO one's in. And it happens that if you look for the newer part number (LDO-42STH40-1684MAC), there's a pack of them for the Railcore builds on clearance for the same price as getting 2 shipped elsewhere. Never hurts to have spares to play with 😉 https://www.filastruder.com/collections/ldo/products/ldo-stepper-motor-set-for-railcore-ii-300zl-zlt

Since somewhat shorter pre-cut cables are available too, I'll get a couple so I can also have spares of them to practice with or tinker.

RE: Mk 3.9 with MK4 Z Axis motors.

Has anyone seen an reduction of VFAs with the Ldo 0.9 stepper? Any comparison photos? 

RE: Mk 3.9 with MK4 Z Axis motors.

Posted by: @kenzo42

Has anyone seen an reduction of VFAs with the Ldo 0.9 stepper? Any comparison photos? 

I'll be hopefully rebuilding my mk4 this weekend and swapping in the new LDO motors, can show some results if I can get it all done (ah family plans taking priority over hobbies)

RE: Mk 3.9 with MK4 Z Axis motors.

Posted by: @kenzo42

Has anyone seen an reduction of VFAs with the Ldo 0.9 stepper? Any comparison photos? 

I did a comparison between my MK4 and my new MK3.9 - see the photos in this post.

RE: Mk 3.9 with MK4 Z Axis motors.

I had some 0.9° stepper motors delivered today: LDO-42STH40-1684MAC.  I've fitted them to my MK3.9.  I wired them using dupont sockets as per the above discussions (so only the blue and green wires are swapped with respect to the MK3.9 adapters).

(You'll need to click on this photo to see all the connectors)

My printer now self-identifies as a MK4.  🙂 

Unfortunately it doesn't behave like one.  I printed another test piece to check that the VFAs, which were more visible on the MK3.9 than the MK4, had been improved by the new motors.  And they haven't 🙁 .

The photo below shows a stack of test pieces - from top to bottom:

• MK3.9 printer with new 0.9° steppers, model sliced for MK4
• MK4 printer, model sliced for MK4
• MK4 printer, model sliced for MK3.9
• MK3.9 printer with old 1.8° steppers, model sliced for MK4
• MK3.9 printer with old 1.8° steppers, model sliced for MK3.9

Unfortunately, it's quite clear that the new stepper motors (top print) haven't improved the VFAs compared to the old ones (bottom two prints).

I can't immediately think why this might be the case.  Could the wire positions have an effect?  I did try swapping the red and blue wires, so that all the colours matched the adapter, but all that did was reverse the Y-axis motion.

I'm curious whether anyone else has done a before-and-after comparison and been able to see an improvement in the VFAs.

RE:

If anyone wants to provide another data point in the VFA comparison, my test piece is attached.  I printed it in the supplied orientation, so that the curved face is towards the front of the plate.

RE: Mk 3.9 with MK4 Z Axis motors.

Did you try re-running the setup?  Could be the printer calibration is still advancing the motor 1.8 degrees per step, even though the steppers can do better.  

RE: Mk 3.9 with MK4 Z Axis motors.

I did re-run the XY Axis Test - and the result was that 'Settings' -> 'Hardware' -> 'Current Printer Type' shows that it now believes it to be a Mk4, whereas it identified as as a MK3.9 before the motor swap.  I wonder if it's worth doing a full Factory Reset.

RE: Mk 3.9 with MK4 Z Axis motors.

I would try the factory reset.  I built mine with the new motors from scratch and print quaolity with IS is better than the MK3s ever was.  No VFAs like my MK3 had.  It's not a direct comparison, but from my estimation the new motors did what they were supposed to.

Check my note about the wires too.  It seems the stock wiring has polarity reversed on the second pair.

RE: Mk 3.9 with MK4 Z Axis motors.

No change after a factory reset.  There's another type of factory reset that requires the firmware to be reloaded, but I doubt that'll change anything.

I rechecked the wiring - if either pair is the wrong way round then the axis direction is reversed, so I can't be wrong with just one pair.  For good measure I swapped both pairs, but the test print is unchanged.

But I'm starting to doubt my own findings now.  I ran another print on the MK4, using a different filament (Prusament PETG), and by now the MK4 has a different nozzle on it (Obxidian).  The result is different from the earlier prints - there's more shine to the print, so the VFAs are more noticeable.  All previous tests were done with a Nozzle X, which is all steel, and prints often come out with slightly less shine - Nozzle X requires a slightly higher temperature to get a shiny finish with PETG.

Here's another photo of three of the test pieces.  Top to bottom:

• MK3.9 printer with old 1.8° steppers
• MK3.9 printer with new 0.9° steppers
• MK4 printer

Turning the stack of pieces over in my hands, catching the light in different ways, I'm actually now happy that the new motors HAVE reduced the VFAs, maybe even to the same level as the MK4.