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zews

Yet another bad print

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I have been trying to print this part. It is a very small part, the overall length is 20 mm, and the thickness is 1 mm. The height of the little knob is 3 mm. I am not expecting the fillets as in the drawing to print at this small a scale.

 

 

This is the result of two separate attempts to print this part. Please note that the size of the little vertical knob is very similar in size to the two antennas on top of the head of the Ultimaker robot, which print just fine

 

 

 

For the one on the left:

Layer height: .05

Initial layer: .15

Speed: 30

For the one on the right:

Layer height: .10

Initial layer: .20

Speed: 10

It seems that the layers of the vertical section did not have a chance to cool and harden before the next layer was laid down.

What should I have done differently to print this part properly. BTW, on a small and thin part like this the brim of .2 mm in height is very difficult to remove cleanly.

One idea I just had is to create another random part of the same total height as this part with maybe a bit larger foot print, and then set Cura to "Tools/Print all at once", to give this part a bit of time for the layers to cool.

Or should I change some settings regarding Cool in Expert config?

 

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@Zews: You said it. The Ultimaker antennae print fine because they are TWO.

I recommend to decrease the temperature as far as possible (190°C for 10mm/s) and set the minimum layer time to 7s. Then print two (or even more) of the object at the same time. Alternatively you may try the cool head lift feature.

 

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Yes - either use cool head lift or print two (or more!) of these at the same time.

Cool head lift will offer a great improvement but still you will get some strings while it does it's thing.

printing two will give you none of the melting issues but now you will have stringing between the 2 parts if your retraction settings aren't dialed in. Although for me 220C, 35mm/sec should come out extraodinarily nice but you can cool it down more and slow it down more. No need to go below 20mm/sec even at 190C.

 

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I use cool head lift in the layer view in cura to know when that specific case will occur (see the blue tool path lifting). This way I can:

A: adjust the model

B: add some useless support/geometry close to that section just to add print time

or C: add a tower on the side of my model that will cover the min print time.

 

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my guess is that you are extruding to much try reducing the fill density to 40-50%.

 

This is a very small part. There is no infill, even if I would set it at 40-50% it prints without infill.

 

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printing two will give you none of the melting issues but now you will have stringing between the 2 parts if your retraction settings aren't dialed in.

 

What settings do you suggest for retraction?

 

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I followed some of the advice given. Here are my (terrible) results.

With "Cool head lift" checked. When I watched the nozzle closely I saw that when it moved away from the part it was fine, and as the part cooled the nozzle would leak a little bit of filament, that would then be deposited onto that random mess on the side each time as the nozzle moved back onto the part to continue to print. This is not a stinging problem, this is something else.

 

I then did two prints while printing the same part twice each with the setting "Print all at once". The first time I did this was at the default temperature. As you can see, bad horizontal alignment on the vertical section of the part. The second part at this first double print was just as bad.

 

 

I then did the same print again and lowered the temp to 190. Now the horizontal alignment is very bad, and I also got bad under extrusion on the first layer again.

 

 

 

 

I have been reading a lot through the entire forum the last few days, and it seems that a lot of people are having serious issues with under extrusion under many different circumstances. I am beginning to think that it is not me, but that there may be something wrong either with my machine or with the Ultimaker 2 in general. I have now had this machine well over 2 months, and I have yet to produce a flawless print.

 

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Well these are both improvements, right? Better than the original?

Okay next thing to do: Is your fan at 100% by the time it reaches the post? Make sure fan is at 100% by say 1mm off bed. I think the default is 5mm which is too late.

Also like nalath said, print even more. Print 3 or 4 or 7 at the same time and it should get better and better the more you print. The ones in the middle will be the best. The 2 on the ends will be the worst.

 

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The blobbing when using cool head lift is exactly the same as stringing, it's just stringing to itself. The upside is that it should be quite easy to cut off, as the ooze is only even attached to the print at the very bottom.

Like George says - given how Cura reverses the order of island printing on each layer, you get two layers back-to-back on the first and last pieces on each layer, so you need at least 3 to get the best possible results.

Also, there's probably no need to print with a brim on a small part like this; it's a quick print with a relatively high contact area, considering the height of the piece.

Given that the layer alignment is a lot worse when printing multiple pieces at once, it seems that you have some backlash issues. I'd check that your short belts are properly tight; power the machine off and grab the print head and move it quickly back and forth in one axis then the other. Watch the corresponding short belt move, and make sure that there are no signs of twisting and jumping. If you squint at the belt, you shouldn't really be able to see it moving, because it should be moving back and forth in exactly the same path (aside from any visible motion of printing on the belt). If the belt is jumping or twisting at all, then loosen the four screws holding the motor, and press down on the motor while retightening them.

 

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