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ascanio

Utimaker 1 Abs - Printed object not remaining sticked to bed

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I've finally managed to start experimenting abs after a lot of issues... So here is my new one.

First layer sticks to bed nicely. 0 warping. It would be really great if it weren't for a thing: after a couple of layers (20 -30 minutes since I print pretty slowly / 0.5 cm height I would say) the object "stops" staying attached to the heatbed and therefore as the extruder head touches it it start moving around on the platform... It didn't happen with smaller object (eg the UM robot logo) but is always happening with flat larger object...

My settings:

speed 35

head 235

bed 110 (That's what is set. I really doubt is really 110 and is, of course, much less the further from the centre)

flow 110

filament size 2.9

no fan

Any idea to have it stay sticked to platform even after half an hour?

 

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No fan is good. 110C is good. 235C seems cold. Here are some ideas:

1) Use ABS glue. Google "abs glue" and use that! Clean glass well before applying abs glue.

2) Use brim. In Cura it is very important to use a brim - this keeps air from getting under the corners - once 1mm lifts the whole thing lifts. Also brim rounds the corners as rounded corners stay down better.

3) For parts >100mm wide, consider a heated chamber. Just cover the sides with plastic food wrap and put a box on the top. Wait until the air is at 40C before you start printing.

ABS has a roughly linear expansion coefficient. In other words if you graph density versus temperature it is roughly a straight line. However shrinkage while ABOVE the glass temperature (around 100C) is not important because above the glass temperature ABS is soft enough that it flows a bit and the forces that cause lifting are small and not a problem.

Once ABS cools to glass temperature, the remaining cooling to air temperature (100C to 20C) is a problem. If you can heat the chamber to 60C then you will get half as much shrinking force. Much hotter than 60C and the steppers can't handle it. Besides the air just above the 110C print bed should be hotter than the other air.

 

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One more thing: levelling is important.

You want the first layer SQUISHED a bit into the glass so that there are no gaps between stripes on the bottom layer. Especially at the edges where all the lifting force occurrs.

And another thing - using less infill will help as there is less pulling force on the upper layers.

 

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I will try brim and relevelling the bad. Maybe also buy abs glue but i am afraid of building a heatchamber... My stepper motors gets really really hot while printing, already... So adding heat scares me of breaking them... I am printing ar only 235 c because I noticed that if i raised temp (experimented up to 255) rhe filament extruded is so soft that the whole object stays soft and it is a problem if you are building support or trying to "expand" the layer in the air. I would love being able to print at hogher temperature (also so as to increase my printing speed) but don't know how..

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I have just realized I was using pla instead of abs, which explains everything... I changed the filament and now all abs realted problem are showing again..... Filament not sticking to bed properly, but only a couple of times, randomly, so that a big mess comes up. I aslo notice extrusion is not as fast as I would expect whe I force it.... I have just finished cleaning everything since I thought I had a clog and REFUSE to think I got another one after 20 minutes...

New nozzle temp 250 (I am afraid of getting to the limit)

Abs filmanet is from ultimaker shop...

In this picture you can see an attempt to buid the ultimaker robot logo with brim.........

https://www.dropbox.com/s/n9h0ilbh2t8mu3k/IMG_20140410_131832.jpg

 

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Leveling looks good but I think you are getting underextrusion now.

I believe you can print 260C no problem, right? I haven't done much at 260 so I'm not sure.

I don't know what is causing your underextrusion. I would turn the big gear by hand and see what is going on. Try to feel the pressure. There could be a clog in the nozzle, the feeder might be slipping or grinding the filament, there could be something in the bowden tube (some old strings of ABS or PLA?).

By the way, "ABS glue" isn't something you buy. It's a mixture of Acetone (which you can buy) and extra junk ABS filament. Google it.

 

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Filament not sticking to bed properly, but only a couple of times, randomly, so that a big mess comes up. I

 

I'm confused - in the photo it looks like it sticks pretty well.

In some parts I see it squished very flat which seems good (maybe too flat?). Other parts there is no filament.

If you level too close to the bed then the filament can't all get out and the pressure builds up until you start grinding the filament at the feeder. But this is not usually a problem.

More likely you have underextrusion caused by something - a head clog maybe?

Switching between abs and pla often is bad. If you get ABS in your PLA print head, it tends not to melt because you are likely printing at 220C or something and the ABS get stuck and cooks slowly for hours until it turns in to gunk.

If you get PLA in your ABS and you print at 260C the PLA can also burn and turn in to bad gunk (although not as likely - usually it will pass through the nozzle).

If you print in a dusty room, the dust can get on the filament, get carried up into the nozzle and clog.

I would try turning the big gear and trying 250C and trying 260C and see if things seem better. You might need to unscrew the nozzle (while hot) and burn out everything in there with gas flame and also soak in acetone for an hour.

 

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To "clean" the nozzle i just unmounted the head, heated it, and force-pushed everything that was blocked inside thoruogh it. After that (brown burned fiament extruded. A lot. I always use white) extrusion seemed cleaner. I always used abs since that

First layer should be a levelling issue. It worked great with pla but I am extruding way less abs then I used with pla so same settings may feel different. Anyway the main problemjis that the new extruded layer (strating with the second) doesn't stick to the previous one nicely and I feel i suffer of underextrusion. For now I have raised tmp and flow, lowerd speed... I'll do some more test and post results. Anyway this topic has no sense anymore, I'll post on an oder one so as to keep ordered. Sorry for the mess

 

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Layer adhesion is much worse with ABS than with PLA. Make sure the fan is off, this helps quite a bit. I guess you already mentioned this in your first post. Also increase the temperature if you are having layer adhesion issues. You can print ABS up to 260C. If you have underextrusion then print slower.

 

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