Holes in print after cross hatch infill

[kaybie 0]

Hi guys,

I haven't had my UM2 for very long but have been very happy with it thus far. I have done a couple of reels of ABS and have just switched over to trying out PLA. I have played with the settings but try as I might I seem to be getting incomplete layers after cross hatching on the infill.

The initial layers go down fine and as the cross hatch is being printed the print seems a bit hit and miss. As it it becomes time to do complete layers over the cross hatch again each layer seems to miss and the result is a series of holes in the print.

If you can give me some clues as to what to be looking at customising in the settings that would be great. I did have a look online and also try a few settings but to no avail.

I have done this print in ABS and it is ok, so I have ruled out a faulty design.

Many thanks in advance

 

[gr5 2,167]

We usually call this "pillowing" and I'm not surprised it is worse with PLA. This is fixed (or greatly improved) with 100% fan. By default the fan doesn't reach 100% until 5mm up I believe (cura setting) so I would change it so that it is at 100% by the time it hits the top layer fill - 1mm is a good value for this typically as it allows the fan to come on slowly over 5 to 10 layers (depending on layer height).

Also doing more layers will help.

1) What is the thickness total of your part?

2) What is your top/bottom thickness?

Pillowing example:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=17300

 

[gr5 2,167]

You might also have underextrusion - it's difficult to change from ABS back to PLA - ideally you want to print at least a few meters of PLA at high speed and temp (240-250C) to get it all out. You can also use the "atomic" method but your photo doesn't show underextrusion - I guess I would have to see a lower level or a side view.

 

[kaybie 0]

Hi,

Thanks so much for getting back to me. Now I know what it is called it will help in me reading about it

Thanks for the link - handy to have.

The part is 2mm thick - the top .75mm I would say is solid. Personally I don't think this print needs infill - but it happens on my other parts also which are much bigger (this is just a handy piece to print and print again to test).

I have made the fan amendments in Cura and also increased the flow rate and am printing again. I will try and take a side shot but the print is even and solid from the side.

Watching the print in anticipation

 

[kaybie 0]

Wow, what a difference, many thanks - that sorted it out nicely - I will play with the settings some more to find that sweet spot but I am really happy.

Thanks

 

[valcrow 144]

I have this problem since CURA updated to the square infil from the chaos pattern. I'm using PLA on the UM1.

The fan helps, but I only have one on the UM1. Anyways, to fix, you have to push the infil to 25% or sometimes 30%. Just watch the slice so that the squares become half the size.

at 20% infil (default) it makes square infils at every layer. at 25, it makes half sized parallel lines every other layer creating smaller squares. These smaller squares tend to prevent the bubbly pillow action.

It also helps to have at least 5-8 layers of top infilto make sure it's nicely filled in.

 

[kaybie 0]

Valcrow,

Great tip - I will give that a go - it certainly makes sense. When watching the print job I did think if only the infill was tighter in together then it would be ok

 

[Guest]

Hi! My fan is running 100% at 1mm, 20% infill, 0,1 mm layers, 0,6mm layers and I get "pillowing" / air holes in my print. I will try to print with more layers but any other suggestions? Could there be something wrong with my fans?

 

[kaybie 0]

Hi Axel,

I found with some prints that increasing the infill as Valcrow said helps a lot with that.

 

[braddock 1]

A thicker shell will probably help too. I generally use 3 shells, 1.2mm

 

[yellowshark 153]

You need more layers at the top when you reduce your infill %. If I am running 40% - my norm - then I find that 0.6mm is fine, although with .3 layers I go to 0.9mm as I am just used to always using a minimum of 3 layers - my Slic3r background. With 20% infill you need several more layers to get a solid layer laid down for the last two or three to sit on. I cannot be precise as I rarely go beyond 40%. Trial and error will get you there. I have never seen pillowing. Most of the time my fans are running at 70% by 0.6mm unless I have some nasty overhangs at the bottom of the geometry, in which case from layer two the speed is 20mm/s and fans 100%

 

[valcrow 144]

Glad that worked out for you! this one was driving me crazy for a while too...

25% infil is the magic number. it halves the support square size without increasing the filament usage much.

I would do at least 5 layers of top and bottom for a nice surface too.

 

[gr5 2,167]

Could there be something wrong with my fans?

 

Maybe - some UM2 fan cables (a lot! maybe 20%?) got disconnected during shipment. So they might not run at all. Or they might run backwards. I suspect they are fine and you just need to make a thicker top or more infill but to test the fans on UM2 (or do you have UM1?):

Select PRINT (even though we won't be printing), choose anything on the SD card. Then immediately go to TUNE menu and go down to fans and set to 100%. Test that they are both spinning and that they are blowing downwards. The printer will not start printing while you stay in the TUNE menu but if the nozzle is heated up when you exit it might start printing so once you exit do an ABORT. Or you can just kill the power.