ABS edges curling

[am001 0]

Hello,

I have just started using ABS in my Ultimaker, I have built a heated base, set it to 110deg and printed on it. Unless I use a raft, which then seems impossible to remove, i get the part curling up at the edges. I have tried with the fan on and off. With it on, I get really nice clean accurate parts, with it off, there is less curling but the parts look awful as the material from the last layer is still soft so lots of movement when the next layer goes on.

Heater bed is a piece of 3mm aluminium with a reprap PCB heater underneath, thermistor in the centre.

The models, once a few mm up away from the bed are fantastic, I just need to get this issue sorted.

Any ideas? What am I missing here?

Thanks

Andrew

[Daid 306]

On which layer do you enable the fan? Maybe you can try printing the first layer, or the first few layers with the fan off. (Cura supports this as an option in the expert settings)

[joergen 2]

As Daid said, turning the fan on 1-3mm above the bed is better. you can also try printing on 120C instead of 110C. if you are printing box like objects, the wall is causing the curling, because it shrinks in a specific way. try adding a thicker bottom or some internal chamfering this seems to help a bit. another trick is adding hold-dowd pads to the model, or use the brim-feature in slic3r (or make more outlines and set the distance to 0 in cura), this may also help.

[am001 0]

Thanks for the replies.

On the part I built last night I started with the fan off and turned the fan on a few mm up the model, which was essentially a box shape, but you can see exactly which layer the fan came on because all of a sudden the lines are straight!

Unfortunately with my current PSU, 110deg is as hot as I can go, and I can only do that if I insulate the bits I am not printing on by putting some card over them.

Maybe I need a 24v PSU? I'll look into it...

Any other thoughts? I am using Kapton tape on the bed, is this the problem?

[joergen 2]

Thanks for the replies.

On the part I built last night I started with the fan off and turned the fan on a few mm up the model, which was essentially a box shape, but you can see exactly which layer the fan came on because all of a sudden the lines are straight!

Unfortunately with my current PSU, 110deg is as hot as I can go, and I can only do that if I insulate the bits I am not printing on by putting some card over them.

Maybe I need a 24v PSU? I'll look into it...

Any other thoughts? I am using Kapton tape on the bed, is this the problem?

I smirk a little bit, since I often had a feeling the PCB heater solution isn't the ideal solution, and the heating power per area, isn't great enough... yes, 18-24V might help to reach 120C.

Kapton shouldn't be the problem, it behaves in many regards like plain glass. some better insulation underneath might help, silicone foam sheets are a good solution. the brim and the pads I mentioned didn't help? another important aspect is also the amount of cooling: running the fan at full power doesn't do the right job with ABS sometimes, and tuning it way down (i.e. M106 S40) might improve the curling

[am001 0]

Sounds sensible. I'm coming to the conclusion that PLA is much easier than ABS...

I will certainly try putting some hold pads in the corners, that seems like a good aproach.

What puzzles me is that some of the reprap community seem to print with ABS all the time and none of these difficulties are mentioned. I understood that the Ultimaker is at the upper end of the capability scale for these machines yet I am struggling.

I'll keep trying.

Thanks for the input!

[joergen 2]

Sounds sensible. I'm coming to the conclusion that PLA is much easier than ABS...

I will certainly try putting some hold pads in the corners, that seems like a good aproach.

What puzzles me is that some of the reprap community seem to print with ABS all the time and none of these difficulties are mentioned. I understood that the Ultimaker is at the upper end of the capability scale for these machines yet I am struggling.

I am printing ABS all the time, and found PLA much harder to work with. The latest version of my project is pure ABS: http://360rig.com/redesign/

It is not so much the fault of the UM, but the physical properties of the thermoplastic you are dealing with. the UM (or any other printer) just does what you are telling it to do. changing the model to include the shrinking properties, or even changing the orientation of your print sometimes helps. but boxes are particularly difficult. practice and observation and careful adaptations or the design are the way to go, the same way any industrial designer is adjusting to the production frameworks.

[peggyb 171]

this might be interesting to watch:

 

he has some nice advise on designing against warping (if your design allows that of course)

he makes big pieces of abs..

[c-ernst 1]

Had some of these same issues... depending on where you got the Kapton you might need to clean it really well with acetone. Mine (from Ultimachine) had coating or something on it. Was driving me nuts, could not get ABS to print worth a darn, and definitely could not get support to print at all (fell off the Kapton almost right away)

I only print with the fan on for very small parts (under 20mm)

Chuck