abs prints de-laminating and spliting apart

[3ddave 0]

hi,

when I do prints using abs they have a tendency to de-laminate and split in a curving fashion, they are also very easy to break apart between layers.

is there anything I can do to reduce this?

thanks

dave

[gr5 2,172]

Yes!

First you have to understand why it's doing this. ABS has a much higher "softening" or "glass" temperature.  About 100C versus 60C for PLA.  To get good layer bonding you have to get the ABS well above 100C - the plastic on the layer below that you are printing on top of.  This is trivial with PLA because the plastic coming out of the nozzle is about 200C and the air is about 20C and heating existing plastic to 60C (PLA) is much easier.

So the solution is heat.  One common solution is to turn the fan off.  If you print at the same speed and so on that you had been printing but simply turn off the fan you will get MUCH better layer bonding.  The problem is if you print overhangs or bridges the quality will suck.  But if your part has only vertical walls (like a gear flat on the bed) then this is a great solution.

Another technique is to simply lower the fan to 30% max.  This usually is not good enough and you will get layer bonding issues still but not as bad. Not nearly as bad. Older slicers before Cura were very good with ABS and would only turn on the fan a few seconds here and there for overhangs and bridging.

Another technique is to heat the air to about 50C.  The difference between 100C and 50C is much less than between 100C and 20C and is usually enough to get good bonding even with the fan at 30%.  This is a very simple technique - just put a spare cardboard box on the top and cover the front with saran wrap.  It will be nice and warm.  Don't seal the back of the cardboard box - you don't want it getting over 50C or the servos start to suffer.

Another technique is to remelt the layer below by slowing the head down to 5mm/sec. Not a great way to do it, but it works great.  With very thin layers - say .05mm you can print a bit faster.  

I would think thicker layers in general would help - say .2mm layers versus .1 because now you have more thermal mass to melt the layer below.  But many ABS experts claim that .1mm works better for layer bonding.

You might think hotter nozzle temp would help but the difference from 100C to 240C versus 260C is not a huge difference and above 250C it starts to get very easy to bake the ABS into nozzle clogging gunk if you aren't printing non-stop and not too slowly.

Edited April 6, 2016 by Guest

[3ddave 0]

hi gr5,

thank you for your very comprehensive and informative reply it has given me a much better understanding of the principles involved. I did notice that the problem occurred more on the cooling fan side of the print and also on the side of a very cold draught as I am operating in a cold draughty and unheated garage and as you say the problem occurred more on angular surfaces with thin sidewalls. I think that you have also hit on the bonding between layers as being a possible cause. I also had another issue and posted a question (oversize prints) in one of the other topics, this was due to large a setting on the x and y steps / mm, so I would also be suffering from weak horizontal bonding as well poor vertical bonding.

you have given me the best possible answer on this problem and how to reduce it just has the contributer on the other topic and would like to thank you again and this site/forum for expanding my knowledge and understanding in the world of 3d printing.

dave

[ultiarjan 1,223]

And also check the specs for your ABS.

I basically see 2 main types in the stores where I buy.

Some, like the Ultimaker ABS (at least in the past, did not buy it for a long time) have a softening temperature around 80c, I can print this fine at lower temperatures, like 245c. The stuff I find more useful for some applications, with a softening temperature over 100c needs much higher temperatures, I print it around 270c using a E3Dv6.

[3ddave 0]

hi ultiarjam,

I did also wonder about the properties of the material, the pla that came with the machine was new and I never had this problem, but the problem always occurred with 4 different rolls of differing colours of abs that I bought at the same time from someone selling it cheaply and I wasn't sure if it was cheap because it was old or deteriorated due to its age and was no longer fit for purpose. I will be experimenting now in light of the answers I have received.

I do not have any data for the rolls that I have and I do not know yet how to accurately measure softening rates but with the parameters you have given me then I guess a thermometer in a pan of water may be an option.

dave

[gr5 2,172]

I guess a thermometer in a pan of water may be an option.

Yes. I just microwave a mug of water until it boils. Pull it out, put a thermometer in it and then dip some unprinted filament into the water pushing against the sides. Find where it starts to get soft and make a note of the temperature. You want the heated bed a little above that temp (5C to 10C above). The higher the softening (glass) temperature the more difficult the material is to print unless you enclose the printer (heat the air).

But a higher glass temperature is also an important property for many uses as a car with windows rolled up in the sun on a hot summer day will destroy all your PLA prints. Any temperature that can kill humans is probably going to destroy your PLA prints so a cell phone holder for a car? Go for ABS, not PLA.

Also note that ABS clogs nozzles easily when baked. So while you can print super hot with PLA (say 240C) without any nightmare problems, if you print ABS at say 260C and things seem fine but then you pause the print for 2 mintues (at 260C) and then try to resume you will probably now have a permanent clog in the nozzle that needs soaking in acetone or burning out or careful toothpick digging while hot.