How can I avoid ABS delamination?

I am trying to print some ABS parts for upgrading my Mini Kossel. I have had great success printing PLA parts and small ABS parts, but I am having a problem printing taller ABS parts. Here are some images of the problem:



The ABS is delaminating. It gets really bad approx. 33mm above the base. After doing the print on the left, I put cardboard screens around my printer to a height of 90mm above the bed (the part is 54mm high), in the hope that this would keep the print warmer and reduce the delamination. I then did the print on the right - which came out with much more stringing, but delaminated to about the same extent.

I think some of the delamination may be happening after the print is finished and the bed heater turns off, because I can hear cracking noises as the print cools down.

I am using the following equipment and parameters:

Mini Kossel with E3D V6 hot end, 1.75mm ABS filament
Bed temperature 110C throughout
Hot end temperature 240C throughout
0.4mm nozzle
Layer height 0.25mm
2 perimeters
60% rectilinear infill
Print speed (excluding first layer): perimeters 45mm/sec, x70% for external perimeters, infill 75mm/sec.

Does anyone with experience of ABS printing have any suggestions? Should I reduce the bed temperature after the first layer? Print slower? Adjust the hot end temperature? Make the screens taller? Something else?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The bed temp is a little high, extruder temp is fine. I don't know about the speeds- my printer runs slower. You might try slowing down a bit- maybe 50mm/sec. I solved the delam problem by building an enclosure around my printer using PIR foam insulation board. The 450W bed heater was raising the enclosure temperature to about 45C during prints (with the door propped open a little to prevent things getting any hotter- I was concerned about overheating some of the electronics).

That was before I rebuilt the printer to make enclosing it easier and moved the electronics out of the build chamber. I'd like to run at about 50-60C inside the build chamber- I believe that's where Stratasys runs their industrial ABS printers. Anyway, 45C worked before, so that may be warm enough...

The best (and sometimes only) way to prevent this is with a heated chamber, that is you need to enclose the printer with some sort of box so it gets toasty warm inside. When ABS cools rapidly it shrinks and cracks and the fact that the top and bottom are still hot makes it worse. This is ABS's biggest drawback but it's still a great plastic. The chamber can be as simple as a cardboard box large enough to cover the printer or as elaborate as a custom built box with door and placing the electronics outside.

Warm air rises, if you don't have a closed enclosure it just won't work. You can leave it open at the bottom, but all other sides must be sealed to be effective.

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I was hoping that enclosing the sides would cut down the convection enough to make a difference. But as it didn't make a significant difference to the delamination, I guess cold air is sinking near the edges of the enclosure where the heated bed doesn't reach, and warm air rising nearer the centre. Also there are some small gaps at the bottom of the enclosure that will let cold air in.

I am currently doing another print. This time I am using a full height skirt and a slower print speed (30mm/sec perimeters, 50mm/sec infill). I'll know if that makes a difference about 4 hours from now.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I get good results using the same settings as you first posted.
Maybe it's cooling too quickly after printing.
Looking at the bottom right image on the right hand side it looks split open from the left hand side of the part shrinking faster.
You could try wrap the print up and ramp down the heatbed temp after printing. A bit of a faff on.

The delamination seems to show a regular pattern on the left of that part. Could that be some temperature cycling?

-a
Edit: I meant say that I have a heatbed with some mass that keeps the heat in and it's enclosed.

The part looks like it has a large thermal reservoir at one end and heatsink fins at the other which won't help with even contraction.

Edited 1 time(s). Last edit at 04/10/2015 04:46PM by alan richard.

As a point of reference, the Stratasys FDM1600 at the makerspace prints ABS inside a closed chamber at 70C.

Thanks for all your inputs. I finally got the part to print successfully. I put a plastic bag over the printer, taped loosely to the cardboard screen. Then another bag over that one, to create at least a partial air gap to help keep the heat in:



Here are a couple of prints. The right hand one was done with the plastic bags in place.



My plans to convert my Mini Kossel into a Midi Kossel (fatter but same height) now include an enclosure.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

it looks like your adhesion between layers is bad, I would try going hotter, I typically run 245C for abs, depending on how accurate your thermistor is you might want to try even higher, unless I get wind blowing on my print I dont seem to need an enclosure to print good. I usually use bed temp for first layer 105c and for the rest 100c.

Edited 1 time(s). Last edit at 04/13/2015 10:14AM by lunarkingdom.

Thanks lunarkingdom, I'll try a higher temperature next time. I tried 250C once and it didn't help, but I have since heard that some folks use up to 265C to get better interlayer adhesion.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Print slower, and hotter. Also, as for the stringing, try SLOWER retraction. This was the trick for mine, as well as acceleration values. But mine is not a delta... I would at least try a slower retraction and hotter temps. Make SURE THERE IS NO DRAFTS!!

Quote
iamdarkyoshi
Print slower, and hotter. Also, as for the stringing, try SLOWER retraction. This was the trick for mine, as well as acceleration values. But mine is not a delta... I would at least try a slower retraction and hotter temps. Make SURE THERE IS NO DRAFTS!!

Thanks for your input. I already slowed the printing speed down, which helped, and made the cardboard screen to exclude draughts. I never thought of reducing retraction speed to reduce stringing - I'll definitely try that, as well as printing hotter.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].