What could be causing these problems?

Hi all!

I'm printing on a Vellemann K8200.

I have run into these printing issues(look at picture).
The bottom plate prints flawlessly without any weakness or warping, however, when the "pillars" is to be printed they end up as shown in the picture.

I have tried tweaking these settings for the different prints:
- Raising print bed temp to 55C.
- Raising extruder temp to 195C.
- Disabled fan.
- Running fan at 100%.
- Slowing print to 20mm/s.
- Slowing print to 10mm/s.

The filament is PLA.

Still no noticable improvement.
Any ideas? :)

Attachment 791Attachment 792

How long does it take for the printer to complete one layer on each pillar? It may be that there's not enough time for the previous layers to cool down enough before the next one. I'm not familiar with your printer, does it have a cooling fan directing air into the part being printed?

I would guess around 15-20 seconds per pillar.
Yes, there is a small fan aimed just below the extruder.

I am slicing with Slic3r. Is there a way to configure the slicing to "pause" to cool down between quick layers, or do I have to edit the G-code manually?

Quote:

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Originally Posted by Ka50

Hi all!

I'm printing on a Vellemann K8200.

I have run into these printing issues(look at picture).
The bottom plate prints flawlessly without any weakness or warping, however, when the "pillars" is to be printed they end up as shown in the picture.

I have tried tweaking these settings for the different prints:
- Raising print bed temp to 55C.
- Raising extruder temp to 195C.
- Disabled fan.
- Running fan at 100%.
- Slowing print to 20mm/s.
- Slowing print to 10mm/s.

The filament is PLA.

Still no noticable improvement.
Any ideas? :)

Attachment 791Attachment 792

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Higher temp, you are not printing hot enough. I have PLA here that wont melt properly until 210c and at even at 200c, it looks like that plastic goop. Almost hot-glue gun like.

Super slow speed and low heat, not a good combo. I would be printing much faster 40ms even - the slower you print the longer the nozzle is near the printed layer which takes longer to cure.

Yep up that extruder temp to 210C and 30mm/s and start playing with the temperatures 5C at a time. People always say PLA can be printed at 185-195C but I have yet to buy a filament that could print that low without jamming.

Quote:

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Originally Posted by Ka50

I would guess around 15-20 seconds per pillar.
Yes, there is a small fan aimed just below the extruder.

I am slicing with Slic3r. Is there a way to configure the slicing to "pause" to cool down between quick layers, or do I have to edit the G-code manually?

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15-20 seconds per pillar... yikes! I think that's your problem there. You need to move faster there, check in Slic3r's filament settings > Cooling > Slow down if layer print is below: xx. Change the xx to 5 seconds or so.
You can also give the part more time to cool down by printing two copies at the same time, as widely separated on the print bed as possible so that the travelling time adds to the cooling period; or if you don't want to print two parts maybe place a small object to be printed at the same time, a small cylinder or something, to get the same effect.
I would also try not using the heated bed, it is not very important for PLA, specially with a shape like the one you are trying to make.

Quote:

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Originally Posted by MeoWorks

Yep up that extruder temp to 210C and 30mm/s and start playing with the temperatures 5C at a time. People always say PLA can be printed at 185-195C but I have yet to buy a filament that could print that low without jamming.

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I do print at that temperature without jamming. Keep in mind that there can be a difference between what the thermistor/thermocouple measures and what the actual temperature in the melt zone is; if the temp sensor is very close to the heating element for example.

I have tried to print at 210C, still same result.
I have tried with and without fan running, no difference.
I have tried slicing with Slic3r and Cura, no difference.
I have tried prininting other objects simultaniously to let the pillars cool down, still same problem.
Flat surfaces and non-detailed shapes prints fine, but the pillars get messed up.
The prints ends up like this:
Attachment 839

It is a little hard to tell with that pictures since the object is in the shadow. Have you tried to print the 20mm test cube? I make everyone in our class start with that so we can judge filament volume and x/y calibration. When they get a perfect cube, we move onto regular prints. Did you speed the print speed up, to maybe 35-40mm a second to see if that helps?