Printing issue. Can anyone offer any advice?

[ChrisInNewark 0]

First of all apologies if I've posted this in the wrong place.

Currently I'm trying to print this part on my UM2.

Up until now I've never really had any issues printing anything and have been very pleased with the performance of my printer however I'm struggling with this particular print so thought I'd ask if anyone can help.

The issue I'm having is when the printer gets to the very top of the part it doesn't print it (see pictures).

If you look at the picture of the part as it should be you can see that top of the shaft should be tapered but when it comes to printing this its just not happening.

I thought it might be a speed issue as by that point the area being printed is quite small so I've tried printing it at 50mm/s and 30mm/s. I even tried reducing the print speed to 10% when it got to printing the shaft and that got the closest to printing it correctly (the first of the three pictures) but still failed to print the last 10 or so layers (I could see that no filament was being extruded from the hotend at this point).

I've printed lots of other things without any problems and the part itself isn't that small and intricate for it to be an issue (or so I thought).

Can anyone suggest what the issue might be?

Any help would be greatly appreciated.

[jshanemcknight 1]

i would try printing 2 of the part. I have found when printing a small layer like that the lower layer has not had a chance to cool enough before the next layer is placed.

[KevinMakes 22]

it looks like you over extruded a bit I would turn the fans up to %100

and slow the print down, possibly lower the temperature a bit when you get up to the higher layers, or set all of that up automatically in Simplify3D.

[yellowshark 153]

Yup jshanemcknight is right(ish). The surface area at the top of your model is too small to cool in time. I suspect that printing two of the model will not do it because the top area is so small the delay will not be enough. For arguments sake you want a delay of 10 seconds before printing the next layer. I would...

ensure your fans are 100%

print a hollow cube alongside the model (using "print all at once" under the Tools menus)

when you are two or three layers away from the top of the main part of the model- reduce your print speed to 15-20mm/sec

set the size of the cube (ie the perimeter of the cube) so that at 15-20mm/s it takes 10 secs to print a layer

An alternative to the cube is to set minimum layer time to 10 secs and tick "cool head lift" under the Experts menus. You may well get some oozing with this which will probably transfer to your problem section at the top but you can snip that off normally. If I were doing it this way I would set my print speed so that the main part of the model takes 10secs+ to print  a layer so that "cool head lift" does not get invoked

Edited October 17, 2015 by Guest

[Dim3nsioneer 557]

The most important points are already mentioned by @jshanemcknight and @yellowshark. I can only add that if you print two or one with an additional tower of the same height, you should make sure that the air flow of one fan hits the part in question maximally while it is printing the second part / tower.

[ChrisInNewark 0]

Thanks for the advice. Changing the minimum time between layers setting to 10 secs seems to have fixed the problem. That was a setting that I never even knew about but I think will come in very handy in the future.

[yellowshark 153]

That is great news Chris. Those small "conical" shapes can be tricky to get right.