ABS delamination

My guess is that there is more than a few folk around here that use Reprapsource ABS filament on their Mendel90 printers. I'm using the natural variety.

My prints stick fine to the table (polyamide with the bed at 115C). With an unheated chamber (a prototype made of foamboard, totally ghetto) and extruding at 245C, I get a bit of curling if there is much over-hang (ie. the earlobes, cigar, and bottom of the beard on the Zombie Hunter), but it is very close to acceptable. What is unacceptable is the delamination. On small models (ie. Zombie Hunter at 50%) it is nearly unnoticeable, but on larger ones (Zombie Hunter at 100%) it is obvious.

I'm using Slic3r at the moment. 40mm/s on perimeters and infill. 70% of 40mm/s on external perimeters.

Slow it down? Up the temperature to 250C? Accept that a heated build chamber is absolutely necessary for ABS? Could this be a result of too little plastic being extruded? I'm not sure that the e-steps are bang on, but they can't be that far off because the tops of models look ok.

I use 250C for that plastic. I wouldn't expect delamination on that shape of print but I havent tried it. I would expect it on large thin walled boxy shapes without a heated chamber.

You can use higher width / height to get better layer adhesion.

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[www.hydraraptor.blogspot.com]

BTW, for aesthic objects, where mechanical properties are not important, I would use PLA rather than ABS.

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[www.hydraraptor.blogspot.com]

Thanks Nophead. I've struggled with ABS for a long time and decided to take a methodical approach to dialing it in. Just happened to use the Zombie Hunter as a test model. Otherwise, I'd be using PLA for it.

I've just started a print with the extruder at 250C. We'll see how that goes. Then I'll dial in my e-steps. If I'm still having problems I'll change the width-height ratio from the Slic3r defaults. Since I know everybody on the forum will be on the edge of their seats, I'll keep everyone in the loop.

Shapes that have curved overhangs are particularly hard to print in ABS because it shrinks and curls upwards. A fan will help with such overhangs but will make delamination more likely. That is why PLA is easier.

Before I used a heated bed I used a fan blowing from one side with ABS and got much better overhangs on the fan side. Here is an example: [hydraraptor.blogspot.com.es]

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[www.hydraraptor.blogspot.com]

250C was the trick. That is the first acceptable print I've produced in ABS. Thanks for that.

I've witnessed the curved overhang issue many many times during ABS prints. It is soul-sucking to see the problem worsen as the print progresses until the print finally pops off the bed. I've also noticed that running the fan completely eliminates the issue, but in turn causes severe delamination. Didn't have a procedure for printing ABS acceptably until today.

The curved overhang problem now makes perfect sense. Just had to see it simply stated. Luckily, most of the stuff I like to print is self-designed brackets and mounting plates, and rarely has over-hanging curves. ABS should work the vast majority of the time and I can avoid over-hanging curves and corners in my designs from here-on-out.

solved here - [forums.reprap.org]

Nice! At 250C, I still notice some delamination on large rounded prints.

Is there a drop-in hot-end for the Mendel90 that can heat to +260C?

The E3D MK5 hot end is nearly a drop in for ABS. You just need an M8 washer to pack out the mounting as the mounting groove is a little higher up than it is on a J-Head and remove the fan duct. You loose a few mm on Z and the thermistor is less accurate than the one we supply, so you should calibrate it against a thermocouple and generate a specific table. The fan would need to be on throughout the warm-up, build and cool-down.

For PLA you have the problem that you need two fans. There is an alternative fan duct design around that clears the hot end. You can use the wire intended for a Z probe as the ground for the hot end fan so that it is permanently on.

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[www.hydraraptor.blogspot.com]