What is wrong with this pic?  

RE: What is wrong with this pic?

I think that is what is called z-banding:

https://3dprinterly.com/how-to-fix-z-banding-ribbing-in-3d-printing/

It is not the most dramatic one I have seen.

RE: What is wrong with this pic?

Posted by: @sink

Any thoughts/help would be appreciated.=

If you are talking about the horizontal lines - those are print layers - and they can't be adjusted out. They can only be minimize by tuning the mechanics of the printer.

RE: What is wrong with this pic?

At this point with adjustments, the lines are half of what they were. The last adjustment that had a significant affect was changing from .15 layer height to .20.  That small changed reduced the lines by a good 30%. Will try PID tuning, but then it appears that it is mechanical and will try some more tightening, but if that doesn't reduce it again, then the machine comes apart.

On another MK3S+, the lines are basically gone.

RE: What is wrong with this pic?

Too tight on the belts and bearing holders will increase the issues.  Sometimes looser is better for bearing holders - especially on the extruder body back - barely tighten those screws.

RE: What is wrong with this pic?

@dan-rogers

Will try loosening on the extruder back plate after this next run with the PID tuning. I also tightened the Z Axis motor mount screws for this run. Thanks

RE: What is wrong with this pic?

Take the belt off the pulley to test the X axis tension.  Slide it by hand stop-to-stop left to right.  There should not be any hitches or snagging.  If it even has a little bit of un-even movement, the bearings are over-squeezed.  

RE: What is wrong with this pic?

Then tighten the X belt again to the point it makes a low note when strummed.  That will let you successfully print the belt tension gauge pattern - it is tuned to Prusament PETG (it's GCODE only) - if you use other PETG it will work, but the tension will not be tuned right.  I tested with and without prusament and there is a difference that matters.  Once you get the bearing tightness and belt tension set well, your prints will look MUCH better.  And check the grub screws on the X pulley are tightened correctly - screw on flat tightened first, then screw on round gets tightened.

RE: What is wrong with this pic?

@sink

You might want to read the printing handbook that came with your Prusa. 0.15 to 0.20 is actually making the lines larger and more visible.

RE: What is wrong with this pic?

@tim-2

Isn't it better for the print quality and accurate height movement and layering to move at a multiple of .04, like 1.2, 1.6, 2.0? The whole magic number thing? It appears to be from the results. I was thinking of adding a .16 layer height?

RE: What is wrong with this pic?

@sink

No.

Nozzle mostly plays a part horizontally - it can't extrude less that its diameter with any sense of precision. A 0.4 nozzle has a hard time placing a 0.25 wide extrusion accurately. But it can print accurate 0.05 to 0.35 heights with ease.

Height wise - there are general rules about nozzle diameter, extrusion width, and layer height as they relate to interlayer adhesion.  So most slicers set a limit near 75% of nozzle diameter.

But printing a smaller layer, moving from 0.3 to 0.15, improves vertical resolution by 100%.  Going smaller yet to 0.05 mm layers, you gain another 300%.  The return is diminishing, you're still limited by nozzle extrusion widths, so as you step down in layers the best result is by also stepping down in nozzles.

RE: What is wrong with this pic?

@tim-2

Now I am really confused. I thought the whole magic number (0.04) thing had to do with the steppers (200 step, 1.8 degrees, etc.) Smoother layer heights and all having to do with the clean micro-stepping and accurate movements. 

The nozzle size was not my consideration other than staying below the 80% or so level, I never go above 50% anyway.

RE: What is wrong with this pic?

@dan-rogers

Last run .. no improvement .. time to disassemble and try to find the problem..  Will try removing belt from pulley and see how the extruder moves .. Pulley screws are fine BTW .. but something is not right .. thanks for the input ..

RE: What is wrong with this pic?

@sink

I doubt there's that much black magic involved.  The Z is driven by a lead screw, 2mm per turn or some such. Then multiply that step resolution times the 256x microstep engine and correction table.

You might see some effects in X and Y, where the motors directly drive the axis; I'd need to see the math to explain it before accepting that interaction is going on in Z.

Weird stuff I've found in X & Y motion:

That said - if you can somehow calculate values that precisely cause the stepper to only use certain poles and certain steps, you theoretically could improve repeatability ... but I'd think step accuracy would still be random between the poles.

RE: What is wrong with this pic?

@sink

When you have the X belt loose - check the right hand side idler pully.

RE: What is wrong with this pic?

Took the x axis stepper off and there doesn't seem to be any movement restriction on the extruder or x axis rods, that said, while I have it down, think it would be a good time to take the bearings (x and z), soak 'em in IPA to clean 'em, and then repack with new grease.

Never did that before original build, never thought about the original oil the bearings came in.. my bad .. have used them before so should have thought of that .. surprised the build guide doesn't mention this.

Will check the rods to see if there is any obvious damage and then try to rebuild; at the very least in for an educational experience I guess.

It is raining out anyway .. 

Anything else that you might look at while it is in pieces?

RE: What is wrong with this pic?

@sink

Prusa is now telling Mini users to clean and grease bearings before installation. 

If the rods are scored, rotate them 45. the rest of the surface is fine. Or rotate the bearings 45. Though, you'd think linear bearings can spin on the rod and will simply drop into the first available divot. Maybe the rows help keep them tracking in place... ehh.

RE: What is wrong with this pic?

Your prints are nearly flawless already - I think you have covered all of the bases.  Once X is not a concern, there's always Y.  Do you have the clips or the U bolts?

RE: What is wrong with this pic?

@dan-rogers

Clips .. MK3S+, not the U Bolts of the 3S or earlier models. I have really good prints coming off my MK3S machines but have struggled so far with the MK3S+ variety. Have built and am using 2 of them but neither has achieved the same level of near perfekt of the  older MK3 or the MK2 machines for that matter. 

One MK3S+ is clearly better than the other, but frustrated with both being  near misses. Must be something I am not doing right in the Montage.  Maybe not greasing the bearings or something else. Have another coming this week and will try one more time. 😕 But if I can't get one of these three to the same level as a 3S, think I will just wait for 4 before I buy another.

First test print off rebuilt machine and it is the best so far, but still not MK3S..

The XYZ calibration also said slightly skewed, which never happened before either.. sigh ..

RE: What is wrong with this pic?

@dan-rogers

I have to agree.  Those are quality prints.  

@Sink

You could print in a filament that can be acetone smoothed.