Help with Ultimaker ABS Prints (White)

[Riboflavin 1]

Hi,

 

I'm looking for a little advice on how to deal with a couple of print issues with Ultimaker ABS - the newer formulation that sticks well compared to older ABS material.

 

I am printing in an enclosure with a bed temperature of 100 degrees, nozzle temperature of 250 degrees, fan speed of about 50%.

 

I used to get a lot of bed adhesion problems, so made the enclosure, but lately I have found the newer ABS sticks very well - so I wonder if my enclosure is too hot! I have measured it at about 50 degrees during a print, using a thermocouple sensor. The enclosure is a complete box made from 25mm kingspan insulation foam.

 

Two problems cropping up with my prints

 

1. Elephant footing and poor vertical face squareness - see photos via link below

 

2. Bubbling on top surface - see photos via link below

 

In the example, I am printing at 20% fill with the parts and using a triangle pattern. I am slicing with Cura 3.6.0

 

I have tried reducing the first layer height to 0.1mm to reduce the elephant footing - it was suggested that a 0.3mm initial layer height could be causing the problem, but this doesn't seem to have made much difference.

 

I run the fans set at 50% on the printer and set at 40% in Cura

My print speed is 50mm/s

Nozzle is 0.4mm

Printer is Ultimaker 2 running an Olson Block and standard 18W heating element

 

Photos of prints and issues are here:

 

Photo album of print problems

 

Any help you guys out there can give on the best way to print this material and what might be causing my issues will be very gratefully received.

 

Note that I get different results with different colours - the red ABS seems to print the nicest - but I am not making enough notes about settings so am not sure if it something I have changed or if the different colours do behave so differently.

 

cheers,

Chris

 

[gr5 2,172]

I usually call that "bubbling" on the top of your prints in the photos "pillowing".  That is a symptom of not enough cooling (not enough fan) (which is kind of rare with ABS).

 

So for the pillowing you need to either lower the air temp (I usually print ABS in 35C-40C air) or you need to increase the fan.  What kind of printer is this as on the UM3 and the S5, 50% fan is the same as 100%.  They tend not to slow down until around 10% so anything above 10% is the same as 100%.  On the UM2 the fan at 50% is around half power and half the cooling.

 

The elephants foot in your photo isn't just the bottom layer.  It's many layers.  I'm not sure what to do there.  Maybe a different formulation of ABS.  You could lower the bed temp to 90C but then parts won't stick as well (warping issues).  Seriously consider making the reverse curve in your cad models.  I know it's a pain but it's a solution that will work quite well.

 

The basic problem is that the liquid ABS is acting like snot - like a liquid rubber band - it cools rapidly so it's already stretched tight within milliseconds and you are stretching it around a tight radius so it pulls inwards.  As you get farther from the heat of the bed the layers below are stronger and they can resist better.

 

Printing the inner shell before outer sometimes helps.  This is the default though so you are probably already doing that.  Bringing the fan up to speed sooner helps also.  by default I think it takes 5 layers to get up to requested fan speed.

 

So it's basically a temperature issue.

[Riboflavin 1]

Hi gr5,

 

Thank you for your help with this.

 

You were spot-on, it was indeed it seems a temperature issue.

 

My guess is that Ultimaker have made some significant changes to the makeup of the chemical composition of their ABS, to ensure that it sticks well to the glass. Combined with my effective oven of a thermal chamber, it seems clear now that I was cooking the material during the print.

 

I have now upped the fan speed to 100% on both the Cura setting and the printer setting, dropped the nozzle temperature from 250 to 230 degrees and reduced the plate temperature back down to 80 degrees (from 100) and the change is staggering.

 

I'm printing the parts with no skirt, no brim, no raft - nothing! The prints are sticking and the finish is loads better. 

 

I also increased the top layer thickness and this seems to have helped with the pillowing issue.

 

All in all, a surprise but welcome result.

 

To summarise

 

Material: ABS Ultimaker, White

Nozzle temperature: 230 degrees

Bed temp: 80 degrees

Fan speed: 100%

Glue: White ABS and acetone slurry (note, pretty thin - the new ABS also does not seem to dissolve in acetone like the old ABS

Print speed: 50mm/s

Enclosure: Fully enclosed in 25mm kingspan foam insulation

 

cheers,

Chris