Interesting extrusion development

[nudelmannrichter 14]

Hi folks,

as you can follow in topic:

http://umforum.ultimaker.com/index.php?/topic/5221-um2-issues-gettin-pla-stuck-to-print-bed/

I made another test print with the 3mm Blue PLA from IGo3D to see how problems may be defeated.

I konw that 3mm is not the best choice but this stuff came with the printer and I am still willing to use it.

Ok, here for the test.

I printed a 40x40 standard profile from Item with a total height of 60mm

Layer thickness 0,1, first layer speed 10, rest 50

Nozzle 230, Bed 50

the first layer was a bit tricky but sticked well enough so I let it run for 10 hrs.

I had the bed quite close to the nozzle to molten PLA squeezed a bit more than usual. (see point A)

At a time some slight underextrusion occured. (see point B )

I did not change any parameter and let it go. At point C the underextrusion became heavy. Between point C and D I fiddeled with nozzle temperature, flow percentage in different combination but nothing helped.

Last try a point D was to reduce speed to 50% and immediately the underextrusion disappeared.

At point E you see a some darker layers. I am quite sure that this is the K-T boundary where the dinosaurs died....

So here my questions:

Who has an idea why the unterextrusion occured somewhere in the middle of the print and not from the start? I checked the filament spool, nothing specila to see, no special extruder sound... nothing. Only the visible result.

What my be the reason for this dark layers of point E? (apart from a meteorite impact...)

This would be quite good to know to see if this can be solved for future prints.

Here some pics.

thanks for watching and thinking about

Stefan

 

[gr5 2,234]

The filament probably had a thick spot and it took that long for it to get through the bowden. While it was stuck in the bowden, the feeder slipped many times.

 

[m3dical 0]

It might have something to do with the bed temperature. It is all about balance. If you extrude more plastic than your nozzle can melt than you get under extrusion. Increasing temperature should help. Reducing the speed also helps. So that is what you should do in this case.

It might have started to underextrude because the temperature influence of the heated bed dissapeared at this height or maybe cooling was too high at this point.

The dark ring might be caused by having the plastic overheat slightly while the nozzle temperature overshoots and finds a new balance with the printingspeed.

Think of what influences your energy balance and you will come up with the correct counter measure.

But since I was not there when it happened, I would not yet dismiss the possibility of a meteore strike!

Maybe this post might also be helpful to you:http://umforum.ultimaker.com/index.php?/topic/5093-how-to-setup-print-speed-temperature-and-layer-height/