Weird ripping and warping of ABS print

5

I print my ABS at:

  • 240 °C;
  • with a bedtemp of 80 °C;
  • 5 % rectilinear infill;
  • 0.25 mm layer height;
  • 2 solid layers top and bottom;
  • Fan is completely disabled;
  • 0.25 mm extrusion width;
  • 50 mm/s perimeter print speed;
  • 60 mm/s infill speed;
  • 20 mm/s top solid and solid speed;
  • No acceleration.

When printing ABS, I place an aluminum foil lined cardboard box over my printer to help keep the ambient temps up for less warping and stronger prints. I've never actually measured the temperature inside, but the cardboard box insulates very well.

I get this weird kind of tearing in my prints, I'm not sure if it's from too large of gaps in my infill, too fast print speeds, or not enough top layers.

Torn print

Another guess is some kind of drooping because of the high ambient temps.

The tearing only occurs on large top layer surfaces.

patrick jackson

Posted 2017-08-22T19:32:11.643

Reputation: 135

Answers

3

Looking at the infill pattern visible through the tears in the top layer, it looks as if you have unreliable extrusion on the infill layers also.

The solid fill layer is lifted and torn, so it is unlikely that one or two more layers of solid fill will make the result better. In my experience, bumps lead to taller bumps and print failure.

These diagnostic steps have helped me:

  • Print a 3 layer solid fill version, the top surface should be smooth and free of bumps;

  • Print a single layer version, it should be smooth, well attached to the print bed, of even thickness, and a good surface for the next layer.

Given your results, I am suspicious that you may have one of these problems, which I've listed in the order of likelihood:

  1. Partially blocked nozzle

  2. Excessive drag from the filament supply, such as a spool with crossed filament which jams itself, preventing unwrapping;

  3. Extruder feed roller slipping (perhaps full of dust), often a side effect of 1 and 2;

  4. G-code error dropping the temperature;

  5. Bad heater or thermistor, perhaps intermittent short of the thermistor, causing under heating even though the "average" indicated temperature is correct.

Printing gliders is a cool application. It shows off the weight advantage extrusion 3-D printing can deliver. Nice.

cmm

Posted 2017-08-22T19:32:11.643

Reputation: 4 180

I think I need to clean out my extruder. I've been getting weird waves in the lines I've been printing, suggesting some sort of non-uniform extrusion rate. This could also have led to bumps and some things causing the ripping and bubbling. – patrick jackson – 2017-08-25T15:14:54.877

2

I believe it is from the ABS falling into the gaps of your 10% infill. I print ABS with 35% honeycomb infill and I use five or more solid top layers at 240°C. Fewer, and it sags into (or exposes) the infill layers.

I recommend more top layers and a higher infill percentage.

I also recommend starting the cooling fan at 50% capacity or more, before starting the first solid top layer.

Davo

Posted 2017-08-22T19:32:11.643

Reputation: 2 113

You can reduce infill line width along with infill line spacing to keep same mass but avoid wide gaps for top layers to sag into. – R.. GitHub STOP HELPING ICE – 2019-11-25T06:01:27.053

1Ok thanks, I'll try 20% infill this time and 3 top layers, I'm trying to print a glider so it needs to be as lightweight as possible. – patrick jackson – 2017-08-22T19:44:10.960

0

First of all, don't specify the extrusion width, the slicing software does the calculation for the optimal value by itself: if you watch this video about extrusion width and you cross the data with this tweet you will see that the standard value is already optimal.

Second, if you put the printer in a box for insulation you should redo the temperature calibration tower to find out which temperature produces the best results.

Once you do both you'll find the problem will disappear.

FarO

Posted 2017-08-22T19:32:11.643

Reputation: 2 532

0

This looks a bit like you may have a level issue with your printer. I've had similar results when my nozzle isn't clean and my bed is slightly off level. When the nozzle isn't clean (inside and out) either the flow rate out is different than what you set it to be due to back pressure or there is material on the nozzle causing the nozzle to drag through the molten plastic.

I also use a lower nozzle temperature, around 220-230°C. Printing with 10% infill is my standard setting with two shell layers, honeycomb fill or diamond fill.

Diesel

Posted 2017-08-22T19:32:11.643

Reputation: 1 745

1I found that infil of 15% and another top layer fixed my problem. – patrick jackson – 2017-08-23T17:10:52.840