help with ABS setting- I have mad cracks between layers

[hawulim 0]

Hello,

 

I recently purchased ultimaker original + and printing with ABS filament and getting serious cracks between the layers.

 

A complete newbie.

 

https://drive.google.com/file/d/0B2pxOf9xVJqWZ19RZWRPdVF2RUU/view?usp=sharing

 

 

The crack was so severe that the print actually broke in half.

 

https://drive.google.com/file/d/0B2pxOf9xVJqWS3dsVzFCdkgxem8/view?usp=sharing

 

 

I looked up on line on the forums and tried speeding it down to 70-80 and below is the temperature setting.

https://drive.google.com/file/d/0B2pxOf9xVJqWaHZ4eldwM3c1SFU/view?usp=sharing

 

 

 

https://drive.google.com/file/d/0B2pxOf9xVJqWZzBVUXYtbE1LOEU/view?usp=sharing

 

 

 

This is when I continued to print with reduced speed.

 

Any idea why this is happening? Is it a under extrusion problem?

 

Also, is there any way I can avoid the messy stringy stuff?

https://drive.google.com/file/d/0B2pxOf9xVJqWVlNYR2tPekFsdm8/view?usp=sharing

 

 

 

Last question.

We tried to separate a tall model into parts by using the "split into parts" but the scale is different, so it would be right when I put the two together. Any solution to make them the right size?

 

We also manually split the model into two obj files but is there a way to match the size perfectly?

 

Thank you for your time and Happy New Year!

 

Any help would be appreciated!

 

[pm_dude 26]

What layer height are you using.

You are probably printing to fast for the temp. Try printing at 50mm/s at 250-260C. Reduce fan to 50% (128) or even less. Fan too strong will reduce layer bounding with ABS.

[pm_dude 26]

The cracks are underextrusion. Heavy under extrusion in this case.

[tommyph1208 53]

Hey

 

I don't think your problem with the cracks is an underextrusion problem, but rather a classic result of the ABS material shrinking when cooling down, which tears the layers apart... The best ABS prints are achieved by closing off the printer... Adding something in the holes, and top (like acrylic plates or similar), to keep heat from escaping the build chamber... Given some time, your heatbed will heat up the air inside the printer, and this "oven effect" will help keep the ABS from shrinking, and thus help prevent your print from cracking... Its hard to enclose the top of the printer, due to the bowden setup, but it has been done... (Do a search for Ultimaker heated chamber)...

 

BUT:

Is there any particular reason you are printing this in ABS in the first place?

PLA is a much easier material to work with, it prints cooler than ABS, shrinks less, and you will likely have no issues with that, even without a heated chamber... Just a thought.

 

About the stringing (which is what the "stringy messy stuff" is called...):

This is a result of print material leaking from the nozzle while the print head is traveling to a new destination... It can be reduced by tweaking the "Retraction" settings in Cura... Enable retraction, and start with something like 40 mm/s speed, 4 mm. distance... Work your way up from there...

Lower print temperature and higher travel speeds (also Cura settings), will also reduce stringing...

 

About the splitting objects question... Cura doesn't rescale your models unless you tell it to... So just cut it apart in your modeling software (maybe add some tabs and holes to make precise and stronger assembly easier) and import them to Cura one at time... If ou want to scale in Cura, just scale all parts equally...

 

[pm_dude 26]

Ha your right about the shrinking and warping. Sorry for the confusion.

[woofy 12]

This is a result of ABS shrinkage.

Turn the fan off, you do not need it for large ABS prints.

I'll bet you are printing in a cool/cold room. You need to enclose the printer, a large cardboard box will do for that.

I print at 250c nozzle, 100c bed.

[skint 61]

Yeah I agree with Woofy, cover the printer which allows the ABS a little more cooling time. If it cools quickly it will crack apart.

 

[hawulim 0]

Thank you all for the help! I will try with a structure to contain the heat and turning off the fan as well and post the results soon!

 

[kris 28]

I always print ABS @ 230C, with the bed @ 110C and enclosed build volume. Almost no warping and very uniform shrinkage.

[aviphysics 9]

Would just throwing a towel of the printer work? Maybe make a simple structure with some coat hangers to keep the towel off the bowden.

 

[skint 61]

Even simple cardboard on top and front helps.

Have a quick browse through this too:

http://umforum.ultimaker.com/index.php?/topic/7211-um2-enclosure-plan/