Rough surface finish (horizontal layer lines) on UM2+

[elnadav12 3]

Hey guys,

I have an UM2 with the plus upgrade kit. My prints come out with inconsistent layers - I see uneven lines.

I tried a lot of troubleshooting so far... I think it's an extrusion issue but I can't find any mechanical problem.

 

I replaced most of the old parts in the motion system with new original parts:

-X,Y shafts, bearings and belts (I still use the old pulleys. They're screwed in tight, but some of them seem a little oval. Could that be it? I don't think so because lines come out straight and I do see some groups of layers that are perfect...)

-Z shafts, linear bearings, stepper motor, lead screw and nut

-Bowden tube, PTFE coupler, heater block, nozzle, all 3 fans

 

It visually seems like each couple of layers stick in or out.

I tested multiple rolls of Colorfabb PLA/PHA and a brand new roll of Ultimaker white PLA.

Could the feeder be worn? I took it apart and it seems fine...

 

While reading in the forum, I saw a thread discussing temperature fluctuations that result from the heated bed turning on and off which alter the reading of the temp sensor.

I tried printing with the bed off and saw a big improvement but some lines still remain...

 

How do I solve the heated bed issue? Is it a problem with my old (2015) UM2 logic board that was fixed in newer versions?

Why do I still see lines when the bed is turned off? Nozzle pressure? Old feeder? Motion system issue? Sticky Z axis?

 

@gr5 have you experienced this before?

I added some test prints below for you to see for yourself.

Thanks for helping!

Video from printer: 

 

 

Both printed at default 210C, Ultimaker white PLA, "fine 0.1" Cura present (only changed layer height to 0.15), left printed with the heated bed on and right with it off.

All 3 printed with bed off. The middle one was printed at 200C and 92% flow , the right one at 210C 95% flow, and left one was sliced at 80mm/s (all others 50) and printed at 210C 100% flow.

This one printed at 0.15 "normal" present, silver colorfabb pla/pha

 

Another print with 0.15 normal present

Edited December 2, 2022 by elnadav12
misspell

[GregValiant 1,251]

I read that article.  It made sense to me so I picked up one of these Mosfet boards and printed a box for it.  It sits in back of the printer.  It has an LED and I can see when the bed turns on.  There was a slight difference in prints.  Mostly I'm glad to get that current flow off the mainboard.  Wiring was easy.  The wires from the mainboard to the bed get cut.  The mainboard feed becomes the signal line for the Mosfet.  The other terminals are power in from the power supply and then the old wires are power out to the bed.

 

In regards to your print it does look like a mechanical issue.  The extrusions on the side of the pilot house look to be wobbling.  You have some ringing around the hawser hole in the bow as well.

The line on the hull where the deck meets the hull is a well known phenomenon.  I think doctoral thesis have been written about it.

Go back over the printer for the umpteenth time and see if something is loose or bouncing or vibrating.  All vibrations can end up in a print.

I'm not an UltiMaker guy though.  Maybe @gr5 has a take on this.

[gr5 2,173]

This horizontal banding is usually caused by Z axis issues.

 

So the z screw moves the bed down a tiny amount between each layer so you are relying on the weight of the bed to make it go down the same amount.  But if, for example, the z screw is dirty some layers it doesn't go quite all the way down (imagine some dirty grease that doesn't compress as much) and then on the next layer it might go extra far down because there's less grease a little farther around the screw.

 

And if the bed goes down less than it should then it over extrudes and the layer sticks out a bit.

 

And if the bed then on a later layer goes down *more* than it should then you get an underextruded layer.

 

Am I making sense.

 

One experiment is to add some heavy bricks to the rear of the test bed to see if that helps.

 

Or you can clean the Z screw.

 

Or you can replace some of the Z parts - particularly the Z nut followed by z bearings and the 2 z rods and finally the z screw.

 

Personally I would clean the z screw - near the top - the part of the screw that is in the nut when printing benchy so like the top 3 inches maybe.  Clean with some WD-40 and a toothbrush or just a paper napkin and your fingernail.  Keep in mind that the z screw is a triple helix so if you get your fingernail in the groove and spin it around and around you only get one of the 3 grooves.

 

You probably don't need to add any grease.  Ultimaker says one pea sized drop of grease is enough for the entire z screw.

 

If that doesn't help try my brick idea.

[elnadav12 3]

6 hours ago, gr5 said:

Or you can replace some of the Z parts - particularly the Z nut followed by z bearings and the 2 z rods and finally the z screw.

I already replaced the two Z rods, bearings, lead screw and nut. They should be good...

I tried your brick Idea and added a 2kg weight to the back of the bed. Made no noticeable difference.

Do you rule out extrusion or other mechanichal issues?

 

Left with 2kg weight.

Edited December 3, 2022 by elnadav12
spelling

[gr5 2,173]

You have many issues - the two most prominent to me are (2) the ringing along the letters and (1) the horizontal lines.

 

I'm only talking about the horizontal lines but we can talk about the other issues if you want.

 

So do the lines continue all the way around the cube?  I mean taking the 2 most prominent lines on the cube that I see - do those 2 continue onto all 4 sides?  If so then it's most likely a Z screw issue.  If you zoom in with a magnifier check to see if it's exactly one layer sticking out or if it's 2 consecutive layers.  If 2 consecutive then it's probably *not* a Z issue.  Or if a "sticking in" or "sticking out" layer doesn't go quite all the way around then it's also probably not a Z issue.

 

Did it get worse or better when you replaced the Z parts?  Did this start after changing the Z nut?

 

Other possibilities include:

 

temperature fluctuations

 

If the PID is tuned badly or if the sensor has a loose connection then you will see the temperature vary quite a bit - like by at least 5C - then you can see the hotter layers stick out more and the cooleler layers don't.  If you watch the temperature on the front of the printer for 10 minutes it should be pretty steady.  It drops when the fan comes on - that's normal.  But by the time you have done 20 layers the temp should be pretty steady within +/- 1C from goal.

 

If the problem is with the temp sensor then it's even more obvious as the temp can jump around a lot.  Maybe 10C or even 30C instant changes (which obviously don't reflect the actual temp).

 

feeder

 

In theory, it seems like the feeder could be on the edge of it's capability and on some layers the feeder slips more.  You could lower the speed by 50% in the TUNE menu on the printer and if the problem goes away then there is your (partial) answer.

 

[elnadav12 3]

3 hours ago, gr5 said:

I'm only talking about the horizontal lines but we can talk about the other issues if you want.

Regarding ringing, I mostly print using the default Cura profile. These acceleration (3000) and jerk (20) parameters seem reasonable... I know that the Ultimaker gantry is light and stiff. Should I see these ringing artifacts at 50mm/s?

3 hours ago, gr5 said:

So do the lines continue all the way around the cube?

Some are all around, some are not

 

3 hours ago, gr5 said:

If so then it's most likely a Z screw issue

I thought so as well, for that reason I replaced all of the Z axis parts...

I hear crackle noises when the bed lowers and the motion isn't smooth. 

These are all new parts :\

 

3 hours ago, gr5 said:

Did it get worse or better when you replaced the Z parts?

I've had these lines before and still have them now

 

3 hours ago, gr5 said:

temperature fluctuations

Temps stay within 1C according to the display. You can see that in the video linked above. Seems like the heated bed effects the temp sensor readings but all of these prints were done with the heated bed off.

 

3 hours ago, gr5 said:

feeder

In the cube above I think I can see some slight signs of under extrusion but at 50mm/s and 210C the 2+ feeder should handle that easily. That also doesn't explain the lines that are all around... Perhaps a combination of extrusion issues and faulty lead screw?

 

BTW thanks for helping!

Edited December 3, 2022 by elnadav12

[gr5 2,173]

That noise in the video is fine but I'd add triple the weight amount - the idea is to have the weights on there while it prints - after it gets started - right where you put that weight.  The idea is that if there is an issue with the screw - if there is some excess friction, the weights should overcome that such that you get more consistent level heights.

 

So from other's experiences, the most important part to replace is the Z nut.  Someone said you can get the 50 cent version or the 80 cent version and the more expensive one is like 10X better.  Did you order one from UM, a reseller, or did you buy it directly from some store?  I'm not sure but I think you want to get them directly, and you want to get the more expensive version (again - should only be a few dollars/euros).  I mean don't get it from a store that sells Ultimaker printers/parts.  Get it from a store that sells millions of different part types including these z nuts and where they sell at least 2 versions of these z nuts.

 

After you replaced, how much grease did you put on the z screw?  Every UM2 and UM2+ came with a tiny tube of grease.  You need very little.  Just a pea sized drop for the entire screw.

 

Also during the replacement process, while the Z screw is removed it is good to check the friction of the z bearings and rods.  They should very low friction.

[elnadav12 3]

17 hours ago, gr5 said:

Did you order one from UM, a reseller, or did you buy it directly from some store?

I purchased from FBRC8. They should be an official reseller…

17 hours ago, gr5 said:

After you replaced, how much grease did you put on the z screw?

I used a tube of magnalube grease that was included in the extrusion upgrade kit, more than a pea for sure. 

17 hours ago, gr5 said:

I'd add triple the weight amount

That was 1kg in the video. I shared a print with 2kg above… I’ll try again with 3 or 4 to see if that makes a difference.

On 12/3/2022 at 12:55 PM, elnadav12 said:

Left with 2kg weight.

 

[gr5 2,173]

I'd remove as much grease as possible in the top 3 inches (where you are doing most of your printing) and I'd try to get that z nut from mcmaster.com or some other seller.  See if they have a higher quality version.  LIke I said before - I know a guy who got great results ( @neotko ) who replaced his z nuts with a much more expensive (I think it was 80 cents at the time) z screw.  The quality was just another 10X better in precision and smoothness.

 

I'm not 100% convinced it's the Z movement but it seems like the simplest explanation.  Again I'd look at the part with a magnifier and try to identify individual layers where the problem is the worst and see if it's pretty consistent all the way around.  Although it's slightly possible the Z would continue moving another few 0.01mm (yes 1/100th mm) slowly enough that the problem gets slowly worse/better as you go around the print.