ABS warping mid print

[AxelMateo 0]

Hello. So yesterday I did my very first ABS print and all seemed fine with the first few layers so I decided to let the printer do it’s thing while I was out. I came back and found that certain areas had warped (I think) and I can’t quite understand why it happened. I used a heated bed at 95 C and extruder temperature was at 230 C with a print speed of 20 mm/s and I printed with 20% infill. One thought I’m having is that it may have been affected by the cooler surrounding temperature (I don’t have an I closed printer), but then I would think that the problem would be found towards the top area, further away from the heated bed...or maybe I need more infill...Any thoughts/suggestions? I have attached some photos to show how it turned out. Thanks.

Edited January 27, 2018 by AxelMateo

[AxelMateo 0]

Ok. Now I’m pretty sure what the issue is. I need an enclosure. So I’ll try building my own and see how that changes things.

[gr5 2,172]

Okay so this is very common.  And very easy to fix.  ABS is a trickier material to print only because of it's higher softening temp which causes about 10 issues and this is one of the 10 issues.  Most materials with higher softening temps have this issue (not nylon though).

 

The basic problem is layer adhesion aka layer bonding.  While printing a layer, the layer below is too cold and the current layer is not melting the layer below to get a good bond.

 

The fix is typically 3 things: warmer ambient air, less fan, hotter nozzle.  

 

The warmer ambient air is typically the easiest to achieve - at least for me - just enclose the printer and if you have a heated bed it will just take care of itself.  If you raise the air temp from 20C to 35C that will make a huge difference.  softening temp of ABS is around 99C so air at 20C is about 80C cooler, air at 35C is about 65C cooler.  Not quite twice as good but a huge improvement.  On the original reprap machines that printed ABS they didn't enclose the machine so they relied on the next 2 methods.

 

Fan - in the old days people didn't do much fan with ABS.  Fan really helps with overhangs and tiny parts but you want much less fan.  In fact the older slicers designed for ABS would turn the fan on for just a few seconds during bridging and overhangs and turn it off for infill and such.  You want the minimum fan but where it still rotates.  If you have zero fan the part won't look as nice.  A little fan is a good thing.  On an UM3 you want around 1% or 2% fan.  9% fan is MUCH too much.  On a UM2, or UMO, 30% fan is decent.

 

Nozzle temp - this is the hardest.  ABS has a very narrow temperature printing range.  If you raise the temp too much and let the ABS sit in the nozzle for a few minutes it will turn into a gummy substance that can only be removed with heat and a toothpick or similar tool.  It's horrible stuff.  If you print too cold you get bad layer bonding.  In the old days they printed .2mm to .4mm layer height which meant the ABS didn't stay in the nozzle long so they could print hotter.  That's one solution (print fast and hot).  But if you want 0.1mm layers you will have to keep raising your nozzle temp by 1C at a time until you clog it some day and then go back down a bit.  And be very careful not to preheat that nozzle and let it sit for several minutes not printing.

 

[AxelMateo 0]

Thanks for the tips gr5. I’m pretty sure my issue was the ambient air temp. I left it printing in a poorly heated room during the winter season. I’m currently working on making one of those “IKEA LACK” dyi enclosures for my printer. I’ll be sure to post here when I print something with that new set up.

[gr5 2,172]

Was your fan on during the print?  Turning the fan off might be good enough.

[AxelMateo 0]

It was on. I’ll do a little test print with it off tomorrow if I’m not too busy and post it here.

Edited January 29, 2018 by AxelMateo