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Posted · Issue at same point each time

Hi guys. I'm getting what I think I'd under extrusion at the same point on the model as attached. One of them was rotated 90 degrees for the second try but still the same issue. It's abs in an enclosure up to 45° so I'm not entirely sure about this, any thoughts or can I tune this out with cura?

 

Cheers!

IMG_20201117_104249.jpg

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    Posted · Issue at same point each time

    I haven't used ABS myself, but I read it can tend to clog the nozzle after some time, because its melting temp is close to its decomposing/burning temp? Have you cleaned the nozzle?

     

    Maybe printing a bit slower and cooler could help?

     

    If you suspect the bearings anyway (I don't know your printer), then try a small test-cube first, so you don't waste too much plastic and time on a complete big model. And see if it is present there too. If not, it's not the bearings probably.

     

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    Posted · Issue at same point each time

    Thanks Gert, I'm doing just that right now. I'll report back. One thing I noticed is that the bed doesn't fall under its own weight any more though, so I have added steel bars in the gap under the bed to see if that helps. It's an Ultimaker 2+ extended by the way.

    Thanks!

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    Posted · Issue at same point each time

    It's very very common with ABS to have layers split due to shrinking and inferior layer adhesion.  I'd destroy a part on purpose and see how much breaks along layer lines (it shouldn't).

     

    You could be right that it's Z related.  In that case try printing a cube to see if you get layer lines at the same spot.  Or just try cleaning the Z screw.  It's triple helix so make sure you clean all 3 grooves.

     

    But layer adhesion makes sense at "the same height" partly because it gets worse as you get farther from the heated bed.  Partly because of the other geometries on an upper layer that pulls more inward on the layer that cracks.

     

    Try lowering your fan speed.  A lot.  45C is helpful but ABS gets quite hard at about 99C.  So you still need low fan speeds.  So pay close attention to the sound of the fan.  Some printers won't even turn on at 30%.  Other's are still blowing full power even when you have the fan set to 10%.  So experiment with fan speed.  Listen to it. Try different speeds.  Pick one that is more than off but still very low.  Don't pick one so slow that the fan won't turn on at all (these fans usually need a higher % to start and then can stay spinning with a lower % so make sure you can go from 2% to your desired speed and the fan turns on.

     

    The fan should audibly "sound" like it's putting out 1/4 power than normal.  1/4 as much noise.  Or even slower.  If you turn the fan completely off you will get bad overhangs, bad bridging and other issues.  So you need a little bit of fan.

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    Posted · Issue at same point each time

    Thanks GR.

    I've actually been printing without a fan at all for the last maybe month in ABS and its been perfectly fine. The model has no overhangs, it's straight up and down as well.

     

    It seems that it just gets "bitty" at that layer height.

     

    I've ran the model again but I've left it running until I get back in tomorrow. I cleaned the head, the feeder and added weight to the bed, I'll check on results when I get in.

     

    I'll print a cube in the morning that is higher than the model to test it, but I've found printing small items in ABS to be difficult unless I add various printed towers around the bed to allow the layer to cool somewhat instead of being instantly printed on. I'll give that a go to check.

     

     

     

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    Posted · Issue at same point each time

    I guess a decent test would be to try the part again in foolproof PLA, see if it fails at the same point.

     

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    Posted · Issue at same point each time
    20 hours ago, Super_paulie said:

    I've actually been printing without a fan at all

    Okay then I agree with you that it's a Z screw issue.  Adding a weight is smart.  At least 2 lbs/1kg.  Maybe a brick or diving weight or exercise weight.  Testing with PLA is smart.  Make sure z-hop is turned off.

     

    It only takes 2 minutes with a toothpick and a paper towel to do a rough clean the 3cm of screw used for your print.  Just make sure you get all 3 helixes (ultimaker z screws are triple helix).  Just clean at the top of the Z screw where the nut is when the bed is mostly all the way up.

     

    If that helps then consider removing the entire Z stepper and screw out the bottom of the printer - really not hard but you have to remove the electronics cover to unplug it.

     

    Then clean it on newspaper with wd40 and after it's clean add just a pea sized drop of grease.

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    Posted · Issue at same point each time

    I cleaned it all up, cleaned out the feeder and ran again. Exact same issue. So just out of interest I put the file into Cura 4.7, instead of 4.8. guess what, the artifacts and blob issue seemed to disappear...

    It was just on PLA and I left it running when I left work but I didn't see any scars or anything on the print and it was 90% done.

    So settings were the same, only difference was 4.7 and 4.8... so that's interesting as to what had changed.

     

    One problem which is on the model that I noticed is that the travel from one side to the next drops as it goes and leaves hard blobs on the layer which then create issues for the next layer, but that is something I can tune out im sure, see attached. Might not be an issue on soft abs. If anyone has any ideas on how to remove this? I assume it's doing an infill at either side before it does the walls, i could just use retractions over travel but it would likely take forever on the model.

     

    But the initial problem of all that crap in the print, I think it's the new version of cura 😔

     

    Please see attached for the movement leaving bits behind and thus the next layer becoming bitty.

     

    Video

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    Posted · Issue at same point each time

    First of all your travel is insanely slow.  You want 150mm/sec travel move MINIMUM.  You can even try 300mm/sec.  The slower it moves the more "stringing" you will get (leaking during moves).  The UM2 firmware limits to 300mm/sec and it should be able to move that fast without losing steps.  Try it.  It should be fine.  I've actually *printed* at 200mm/sec in special situations with travel at 300mm/sec.  You might want to oil all the rods (not Z) with a tiny bit of oil first.  Any light oil is fine (sewing machine oil, 3-in-1 oil, etc).

     

    Also I recommend turning off acceleration and jerk control.  These also slow down travel moves and additionally cause over extrusion on corners.

     

    And your print speed looks nice and slow which is good but I'm not sure what it is exactly.  I usually do 35mm/sec for most prints for nice quality and accuracy but if there are problems with the quality of the print sometimes (rarely) I'll even go down to 25mm/sec.  Make sure all *printing* (not travel) speeds are the same - well except initial layer speed - that can be as low as 20mm/sec but I never go slower than that for initial layer.

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    Posted · Issue at same point each time

    So you are saying Cura 4.7 PLA gives better quality than Cura 4.8 ABS?

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    Posted · Issue at same point each time

    My travel speed is the default of 120. I'll try upping that. My jerk and accelerations are turned off and my print speed is 40.

     

    Yeah it's the travel from one part to the next where it basically goes all around the model and then back again, dropping as it goes on a very thin wall. These drops then make the next layer on top problematic, see attached:

     

    Wall issue

     

    I have a side by side model from 4.7 and 4.8 with exactly the same settings in PLA and the 4.7 is much nicer. I'm happy to stick with it.

    It's just the problem above now that I need to look at, either the travel oozing or a better way move that doesn't go all along the model and then back again leaving behind debris.

     

    Thanks so much for the help so far!

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    Posted · Issue at same point each time

    Debris left during travel

     

    And sadly it's a very thin "wall" it travels around and that kills the next layer.

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    Posted · Issue at same point each time
    2 hours ago, Super_paulie said:

    Yeah it's the travel from one part to the next where it basically goes all around the model and then back again, dropping as it goes on a very thin wall

    Okay - I couldn't see that from the camera angle.  That changes things.

     

    First of all I would consider turning off "combing" just to see how much that helps.  "combing" in your case means it tries to stay in the interior of your part when doing non printing travel moves.  Sometimes going half way around your circle or even 9/10 of the way around.  With combing off it will go directly over the center gap of your part.

     

    There are versions of Cura that do this circular combing move more efficiently (never goes more than half way around the circle).  This version from burtoogle just does a much nicer job of filling thin gaps in walls and does a better job of combing.  So if speeding up travel and disabling combing doesn't help then please try this version of Cura:

    https://github.com/smartavionics/Cura/releases

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    Posted · Issue at same point each time

    great, i'll run some tests right now. Thanks for all the help guys, this has been a great help so far.

     

    I did try it using only retractions but i was getting a lot of debris at the extrusion areas which didnt help so much.

     

    I'll try this Cura version and report back!

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    Posted (edited) · Issue at same point each time

    no dice im afraid. Although the quality is marginally better.

     

    The problem is that travel leaving debris behind. The wall is so thin using a 0.8mm that the debris left buckles the next layer./

     

    See here for a video using 4.7 master and the dropped debris during travel. (upped the travel speed to 250, defiantly helped)

     

    And please also see here for the design, at this stage i might just have to design out the thicker sections on both sides at the front so that it doesnt have to travel over there at all to fill and just continues on its wall-laying path, which is a shame to have to do. Bottom image the potential revised design to counteract the above.

     

    Video of travel

    snip1.PNG

    snip2.PNG

    Edited by Super_paulie
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    Posted · Issue at same point each time

    Something is wrong.  In the video it is STILL DOING COMBING moves.  Maybe that's on purpose?

     

    So another option is to do retraction on combing moves.  This next setting I suspect is only in the "smartavionics" version of Cura.  I've used it before (I need it when printing over 200mm/sec).  It's very useful.  It will eliminate those dots that you are printing on the combing move.

     

    Set: "Max comb distance with no retract" to a small value like 5mm.  It will still comb.  But it will also retract so it won't leak so much.  Again you might have to get the special version of cura (it's better in so many ways - particularly when printing thin walls and cylinders - seriously).  github link is above.

     

     

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    Posted · Issue at same point each time

    Awesome, making real progress here, thanks a bunch!

    I eliminated the combing like you said by making it retract over 40mm which means it doesn't go spinning all around the model, perfect.

    I moved the Z seam to be dead centre in the strongest part of the model, that helped loads as well.

     

    Looks like this is almost ironed out. The final hurdle is the mid print warp, see attached. The model is well stuck down, enclosure between 35-45°, wall is large by design in total of 5, 0.8mm head, 0.25 later height, with a 15% infill. Still receding in at the middle which is a shame. Any final tips?

     

     

    IMG_20201120_224644.jpg

    IMG_20201120_224703.jpg

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    Posted · Issue at same point each time

    Oh.  That.  Well it's related to the heated bed and cooling.  You could try upping the cooling fan a bit.  Did you say it was off?  If the fan is off that would explain it.  You want the fan on a very low level.  Pretty much the lowest you can get.  Alternatively you could lower the bed temp by 10C but then your part might not stick as well or you might get worse layer adhesion due to cooler air temp.  So really - more fan is probably a better option.

     

    You just want a little bit of fan.

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    Posted · Issue at same point each time

    I guess another option would be to print two of these "bracelets" at the same time so that one can cool down while printing the other but... fan is probably better.

     

    What is the temp of your heated bed?  I usually like 110C for ABS to get it to stick well, and to heat the air in the chamber well, but 110C can also give you that bowing inward - particularly if your fan is off.

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    Posted · Issue at same point each time

    My bed is at 115 and yes my fan is off completely.

     

    What fan speed could you recommend, all my research suggested it to be off so that's what I went with! I'm new to ABS so still a bit green on it.

     

    Are we talking like 10% fan and 110° bed?

     

    Thanks loads!

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    Posted · Issue at same point each time

    Making major progress here, thanks so much to this brilliant forum and you GR5.

    I lowered the bed temp from 115 to 100. I use ABS juice to adhere and so far that's holding at that temp.

    I turned on the fan to 10%.

    Results speak for themselves, see attached.

     

    I have learnt so much these last few days, I'm very thankful.

    Are there any other suggestions on how to improve? I am ok with what I've got now, but always looking to go a step forward. Still got minor bowing on the sides, but it's not a deal breaker.

     

    Nozzle, 0.8mm, temp lowered from 260 to 230. Stopped air/popping issues.

     

    Moved Z seam to a stronger section, the rear. Improved on under extrusion immediately after Z move in a weaker area.

     

    Retraction on for travels over 40mm, stopped the dropping issue around model.

     

    Travel speed up to 250 from 120, improved above and print times.

     

    Cura 4.7 master seems to improve on my print quality for reasons unknown, no problem using this version though.

     

    Feeder cleaned out, bearings cleaned, rods cleaned and greased, XY oiled.

     

    Any further tips, I'm really getting to be happy with abs now!

     

    Paul

    IMG_20201121_121158.jpg

    IMG_20201121_121147.jpg

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    Posted · Issue at same point each time

    230C sounds too cold.  240C might be better.  Not sure:

     

    I strongly advise you do some experiments to test layer adhesion as this is a common problem with ABS.  Print a small tower 1cm by 1cm and maybe 5cm tall.  then break it like one would break a pencil.  You might need some tools.  See how well the fracture follows layer lines.  If it doesn't follow layer lines at all then you have achieved perfect adhesion  Score=10.  If it follows a single layer then Score=0.  If it mostly follows layers but switches to a second part way through the fraction it gets a score=1.  And so on.  Play with fan speed, temp, air temp.  Make sure you are getting at least an "eight" on the score (whatever that means).  If you are getting a zero then you need to get the temp back to 240C and possibly lower fan even more although 10% sounds pretty damn low for a UM2 - is it even spinning at 10%?  You might have to go up to 25% to get it to spin.

     

    For ABS you generally want the fan speed as low as you can go without stopping spinning so 10-30% on a UM2.

     

    If temp gets too high you are more likely to get a nasty gummy ABS clog.  Especially if you print much too slow (e.g. 0.4 line width, 0.06 layer height, 15mm/sec).

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    Posted · Issue at same point each time

    By the way, line width, layer height also affects adhesion.  If you lay down a thick layer it's easier for it to melt the layer below.  If the layer is super thin and you print slow the nozzle actually can melt the layer below directly.

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    Posted · Issue at same point each time

    thanks for the advice!

     

    I print at 0.25mm on a 0.8mm nozzle.

    40mm/s print speed

    bed at 100, head at 230.

    Fan at 10% after initial layer

    no brim. I was able to remove the brim and still keep it adhered.

     

    So far since i went to these it has been absolutely great, practically no warp, bed adhesion is still great. The parts for their intended purpose are rock solid, i  cant separate it by hand, although i will print a tower like you advise once this job is off the bed.

     

    The fan does indeed spin at 10, see attached. Not sure its actually performing a function, all i know is my print results have improved massively since i changed to the above on eSun ABS. If you say that moving the fan up to 25% might improve thing further im up for it! I'll print the tower as you suggest and report back! See below for video.

     

    Fans at 10%

     

     

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