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Hi All,

 

I'm having great difficulty utilising my UM3 to get good quality parts using the standard profiles / printcores. I'm using Filamentive PLA filament and after limited success using the AA0.8mm printcore together with the default Cura PLA parameters, I invested in 3D Solex print cores to see if I can get better results but unfortunately I did not. I'm sure it's due to my lack of experience and nothing to do with the hardware. Therefore I'm here trying to bring my issue to your experienced eyes and hopefully your advice will make my UM3 usable.

 

I tried 2 nozzle sizes with 3D solex, 0.8mm and 0.6mm and the results are shown on the attached images. I compared the 0.6mm results to the same exact part printed on a Prusa MK3 (using a 0.4mm nozzle thoguh) and I could not even come close to that level of quality with my current ultimaker profile settings. I took my UM3 to the UK service provider, thinking maybe i have mechanical issues and they admired how well looked after my machine was and confirmed there were no issues with it at all.

 

If you can guide me through a trouble shooting process I would be very greatful. I know the UM3 is a very capable machine and it's a real shame to not be able to use it.

Many thanks for your advice in advance.

3dsolex_0.8mm.JPG

3dsolex_0.6mm.JPG

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Wow.  Okay.  I could talk for 3 hours about this.  I was expecting something more severe.

 

First of all glossy black filament shows up changes in surface angle if you hold it up to the light just right.  You have to get the angle perfect to see these surface bumps.  However it's extremely easy for a human to do this as we do it all the time.  We just naturally are experts at holding something so the light catches it just right to see these specular reflections that show off tiny changes in surface slope.  However if you tried to measure them with a micrometer you would have a lot of trouble.

 

So one person's "horrible quality" is another persons "fit's so beautifully - the precision is amazing!".

 

And again, dark glossy colors will show this the most.  If you go with a matte filament you will have trouble seeing this or if you go with white or off white.  With dark glossy colors you get bright reflections and in between the reflections you have vary dark so you get good contrast.

 

These imperfections are pretty normal for me.  I don't mind them.  They can be removed but it's not easy.

 

Okay - now to how to fix this (for black glossy).

 

Well I would definitely try to find a filament that is less glossy (like carbon fill) but you can still improve all these.

 

Issue #3, "ringing" is caused because of the tension on the belts and spring factor of the belts combined with the heavy head gives you a particular harmonic ringing frequency.  The frequency is worst if you decelerate for half the period of ringing.  You can fix it by setting the acceleration and speed such that you get a whole period of ringing.  Think of pushing someone on a swing.  If you push half the period (when they move away from you) then you can maximize the swinging.  If you push equal amounts when they move away and also when they come back, the swing only swings once.  If you measure the distance between lines and know the print speed for that wall you can divide speed/spacing to get frequency of ringing.  Those look like 1mm and if print speed was 30mm/sec then your ringing is 30Hz.  To cancel ringing you want ringing frequency = acceleration / speed.  So if outer shell speed is 35mm/sec and ringing is 30Hz you want acceleration to be 1050mm/sec/sec.  If you print at 100mm/sec you want acceleration to be 3500mm/s/s.  UM3 can handle acceleration up to 5000 no problem.

 

#2 The vertical lines in the last photo are almost certainly infill showing through.  If you are only printing vertical walls you can uncheck "infill before walls".  Or you can do more shells.  3 shells should hide this nicely usually.  2 shells might be enough.

 

#2 The #2 arrow to "ghost lines" may be infill or it may be just a common oscillation related to extruder, print speed, resonances.  If it's resonances, I have found lowering the print temperature helps a lot - right to the point of almost underextruding.  You can play with this in the TUNE menu and keep notes such that you can test 10 different temperatures all on one part (say a cube) and use something to mark the part as you print it to know which layer had the change (like whiteout for a black part or a sharpie for a light colored part).  If cooling doesn't help try slowing down also.

 

#1 - I'm not sure what this points to.  Is this the horizontal line?  it could be underextrusion but more likely it's a dirty Z screw where the bed moves down too little on a few layer changes then suddenly moves slightly more on this layer change.  Using thicker layers (e.g. .2mm layers) can help with this but best is to also clean the Z screw.  A dirty Z screw will create lots of horizontal layer lines like this.  Typically always in the same or similar spots.  Since your parts don't seem very tall you might just clean the top half of the screw or top 1/3.  I use paper towels and a screw driver to get in the cracks.  Or you can use q-tips.  WD-40 is okay for cleaning only - not for lubricating.  I recommend some limited cleaning to see if it gets better.  The Z screw is a triple helix so get all 3 grooves. It helps to have one person moving the bed up and down (with power off) while the other keeps something in the groove.

 

In general printing slower and cooler will fix all of these issues but who wants to print everything at 10mm/sec?

 

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Oh - I just saw the prusa benchmark.  That's completely unfair.  The lighting is different.  Either it's a matt black filament or you didn't position the light to maximize reflections.  I see zero reflections on the benchmark.

 

Remember - these tiny ripples are too small to measure with a micrometer.  Too small to feel.  The only reason you can see them at all is because the black filament is so shiny that it shows very very tiny changes in slope as either a reflection off a ceiling light or off of the ceiling next to the light and the difference of a tiny change in angle is the difference between black and white.  Literally black and white.

 

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Also know that you can use Simplify 3D for UM3.  I don't have S3D and don't know much about it but there are people on this list who only use it.  If you want more details, just ask on this list.

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I can't thank you enough for your prompt response. I'm trying to implement all your suggestions now and I'll report back with updates.

 

Regarding the Prusa comparison, it is exactly the same Filamentive black PLA. The only difference is the diameter, being 1.75mm for the Prusa. But you are quite right in saying it's matt black on the prusa, but that's the printer's outcome. I'm not sure why it comes out Matt on the MK3 compared to the UM3. It maybe due to print temperature as it's 215C on the Prusa but 195C on the UM3.

 

I also have S3D, so I would be extremely grateful if anyone here has 3DSolex 0.8/0.6 profiles that they can share.

 

Once again, thank you so much for your support and I will report back with results later this evening.

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I normally use Magnalube PTFE grease that you get with a new UM3 to lubricate the Z screw but it gets dirty very easily. When I give it a good clean, can i replace it with lithium grease instead, even though there maybe still remnants of the PTFE grease in the bearings and areas I can't reach?

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Unfortunately I can't. It's a confidential customer part.

But the geometry is basically a rectangular cross section, built vertically with holes along the length.

 

Orientation is clearer from the layer lines on my images.

 

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To my experience with different nozzle sizes, it's - unfortunately - almost impossible to compare different sizes. It's not just the reduced resolution with bigger nozzles, but the entire extrusion system loses some controllability, especially with 0.8 and above. 

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Always a good option ?

 

I've worked out my ringing vs acceleration calculation as follows:

-Distance between lines 1.1mm roughly

-Print speed at the time 45mm/s

-Frequency: 45/1.1= 35Hz (rounded up)

-Acceleration 35*45=1575 mm/s2

 

I dialled this into Cura with my 3D Solex 0.8mm nozzle and I will report back with the results in a few hours.

 

The dirty lead screw seams to be the cause of the horizontal lines. I tried cleaning it using some kitchen cloth and a screw driver while moving the bed up and down but it is still dirty i think. Are there any more thorough ways of cleaning it?

 

I'm planning to stop using the Magnalube PTFE grease as it hold onto the dirt very quickly and replace it with MG Chemicals Lithium Grease. Do you guys have any advice for or against this change?

 

Thank you very much for your support.

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I don't know much about grease.  UM recommends one pea sized drop.  I've never added grease except when I clean which is about once per year (and not done as well as I should).  But to do a really good job of cleaning it's pretty easy to take the whole thing out of the printer.

 

The screw is basically permanently attached to the stepper so you first have to remove the (larger) cover under the printer (with power off!).  That's the hardest step but it's only 2 screws.  then unplug the Z stepper.  Then remove the 4 screws holding the stepper in place, then pull it straight out the bottom of the printer.

 

Then you can put it on newspaper or something and clean thoroughly with WD40 and toothbrush without making a mess.

 

Me, I'm too lazy and just clean the top part of the screw that's used for small prints as I mostly do small prints, lol.

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Yeah, replace the Z parts.

 

I've never done it but you can replace the Z screw with a misumi bearing.  I don't know the part number.  Are you in USA?  Getting a super high quality, extra expensive Z nut costs only maybe $5 I think and it's much better quality than the default bearing that comes with UM printers I believe.  That's what people say who've replaced their Z bearing.  If you google this list and misumi:

site:ultimaker.com misumi bearing

or

site:ultimaker.com misumi nut

 

Like that - you can find quickly a part number (trust any post by neotko - he has replaced these items and is a 3d printing genius).  Looks like maybe LHFSW12?  That's just looking at google search results - I didn't click on the forum topic.  Oh - maybe that's the bearing and you need the Z nut instead which leads us to:

 

There's also the Z rods and bearings.  Those Z bearings have a channel with lots of ball bearings in them.  When you had the z screw out it would have been good to slide the bed up and down and feel the resistance - see if there are bad spots.  Sometimes the two Z rods are not parallel or some other strange thing.  

 

Usually the problems are with the z screw being dirty but it's quite possible it came from sticky bearings. It's also possible (less likely but it happens) that you are having intermittent underextrusion.  This seems likely if it happens only on one layer and on the entire layer because it should happen more throughout and sometimes on only half the layer.  But I've seen what looks like Z issues solved by simply cutting the speed in half and later diagnosing some feeder problem or a bad core nozzle, etc.

 

More pictures for us are helpful to see if it's always the same spot and if it's entire layers or just the outer shell ocasionally and so on.

 

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These 6 parts, shown on the attached image, were all on the same print with the Y-axis parallel to the horizontal line defect.

 

When I took the lead screw out I did not notice any bad spots as I moved the bed up and down it was all pretty smooth. Which make intermittent under extrusion more likely I guess. It looks like this horizontal defect is on the same layers more or less.

 

 

IMG_2267.thumb.jpg.7b39015e450a3e6720728c48f7d67256.jpg

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