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bsaygan

Active leveling off? Over-extrusion?

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Hi all,

 

I've had my Ultimaker 3 for a month now, and it's been amazing having one.  So, generally very very happy.  However, one weird thing - the prints that I was making out of the box at least with the first layer seemed immaculate, and now, I feel like I'm running into some inconsistencies in surface.  Looking around the forums, I think it seems like my nozzle is too close to the plate potentially?  Other people had issues with uneven glass, but since I was printing perfectly at the beginning and less so now, I just wonder what's changed?

 

Here are some photos, the silver PLA is probably my 3rd print ever, and then the red is a print I did today.  As I watch my first layers go down right now, they do seem to have the nozzle drag through which leads me to believe its too close.  Active leveling perhaps not working quite right?  Or differently than before?

 

Thanks in advance!

Bobby

 

 

 

IMG_1908.JPG

IMG_1909.JPG

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I can't tell in the photo if the red is any better or worse but what you describe - "dragging through" - on the bottom layer sounds like you are indeed "close".

 

There is a thin line - or not even a line - there is a tradeoff between too close and too far.

 

I personally prefer "too close" because the more you squish that bottom layer the better it sticks to the glass.  I mean I can print a UM robot and literally pick up the entire printer by that little robot.  But for smaller objects (say under 70mm in x,y) that have a large surface area (say as opposed to printing a table where only the 4 legs touch the glass) you probably don't need it to stick as well to the glass.

 

So for some prints I prefer it too close.  And other prints I prefer it a little farther.  Just so you know what to look for.  If it's too close the bottom layer will be transparent.  If it's too far the bottom layer will be ropy (like a rope).  You want it somewhere in between.

 

90% of my prints are not meant to be pretty so I don't really care how it looks so I want it close.  I'd really rather not have any chance of the print coming loose.

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Gr5 - Thanks for the input.  I guess the photo just having a hard time showing any difference.  It's easier to tell by the touch, the silver is glassy smooth whereas the red is rough.  

 

I'm definitely more on the close side, but I guess there's just such a small margin of error here.  I think its just my OCD kicking in - thinking that I haven't done anything different since getting the UM3 and getting different results somehow.  I also wonder if ambient temperature has anything to do with it has it has been a little bit on the cooler side lately, but again, just being OCD.  All things considered my prints are coming out good.  

 

Bobby

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In general, both look fine and I wouldn't worry too much about it. But I can relate to your OCD about this ;-)

 

There is a hack if you want to fine-tune the nozzle distance for the first layer:

https://community.ultimaker.com/topic/16975-active-leveling-too-close/

(it's somewhere at the bottom of the first page)

 

It is very difficult to get the first layer aesthetically perfect on the UM3. Something which I found a lot easier on my previous Prusa i3 clone. However, the UM3 is much better in all other regards.

 

Two things you want to do to get the silver one better (the red one is a little hard to see and judge):

  • the lines that are not parallel to the others are caused by travel moves. I believe you need to completely disable "combing" in Cura to get rid of them. It's been some time, but I don't think there's a setting to disable this only on the first layer
  • the waves/ripples are caused by the nozzle distance. Check out the link above to reduce them. Other tips: try with different materials. Especially with the shiny ones you can see this much better. And try other build surfaces (sometimes a little more or a little less adhesion makes a difference)

 

 

Edited by pbackx

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pbackx:

 

Thanks for your solidarity in OCD-ness.  I did see that thread, but haven't tried it out yet since took me a while to figure out where to add those gcode start settings.  I've been using Ultimaker material, but I will definitely try some different filament that I just ordered.  Just wasn't sure if it was something that I did inadvertantly that messed up my Ultimaker since I'm new to this.  Sometimes it seems like that line teetering between too far and too close is small.  I was watching the printer last night, and lines on the first layer started to curl up a little after they were set down and then pressed back down as it went back and forth.  Also, the combing setting looked to be off by default, but you have definitely given me some extra stuff to try tonight! 

 

Thanks,

Bobby

 

 

 

 

 

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Sometimes I get too much oil on my glass in one spot.  Either from dripping from above or from my fingers.  In this rare case sometimes I get just one spot where the PLA won't stick to the glass.  I don't think that's your issue though.  But cleaning the glass with soap and water and then glass cleaner fixes that issue.  This is all explained in the video and much more.  LIke how to apply glue to the glass (3 different ways to do it right).

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Looks good to me.  This is how I like to do my first layer as this way my part will stick very well.  And this is the top of the bottom layer. The bottom will look much better.

 

What you are seeing here is some overextrusion on the bottom layer. Which again, is how I like it.  Believe me, having a part like this come loose, and having it slide around like a hockey puck following the print head around, and resulting in molten PLA getting inside your head and then cooling and creating a massive glue bomb inside the print head - that's much worse than the bottom of your part feeling a little rough.

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If you want to risk the part not sticking though you can just turn the 3 leveling screws the exact same amount - about 1/2 turn CW to pull it down, away from the head.  And you won't get these bumps as bad.  But if you go too far the part won't stick well to the bed.

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Cool, I think you're right about the closer being better than farther.  I tried the gcode start up that moved the head -.1 away at start and it looked better but as it laid down I definitely felt the nervousness about stuff not sticking well.  95% of what I currently have is good, its just random times that it drags a little more on one part which creates like a dimple on the surface.  But all things considered it really is like a 0.1% defect on an otherwise perfect looking print.

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Gr5:  Question - 

 

So, in the last week I've tried a couple things corresponding to modifying the gcode start as listed on another thread.  I've done both .1 closer and .1 farther.  There were some pros to cons to both, but actually the .1 closer was better in more ways.


My question is this - making the nozzle even closer makes certain parts of the first layer, primarily the brim if I build it, transparent-ish.  It was good in some ways because it made it even easier to remove the brim, but is there potential damage that I can do to my printer by printing this way?  Will it make the filament grind more? is it bad for the nozzle? Is it bad for the printer?

 

Thanks in advance!

Bobby

 

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It's definitely possible to make the filament grind more.  Usually it will just skip backwards one full step and then underextrude for a few seconds.  Which is also annoying.  Also if you make it so thin it is transparent *and* you use glue then you will likely find yourself sticking so well that tiny chunks of glass come up with your print.  So I recommend you don't go so close it's transparent.  I mean for 3 reasons:

1) print sticks TOO well.

2) pressure gets very high and so feeder might skip a step and result in underextrusion for a few seconds

3) pressure gets too high and sometimes it suddenly all leaks out in an ugly blob - particularly when it starts the second layer.

 

There is some give when you are a bit too close. The pressure builds up and then the filament slides a bit in the feeder and you can get as much as 20% underextrusion/slippage without filament slipping suddenly.  I say "underextrusion" but what's really happening is it's printing only what it possibly can in the space it has to work with and so less 20% less filament is passing through the feeder than requested - typically the diamond holes in the filament made by the feeder are elongated.  Which is all fine.  but when you are at 50% slippage then it's too much squish.  There isn't a fine line between too close and just right - there are lots of right answers so don't sweat it so much.  I like to remind myself when I have too many choices that many of the choices are excellent (applie pie versus blueberry pie - crest versus colgate) and not to worry too much but to be aware.

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