Print head, First extrusion at a print job, Ultimaker 3

[Pia92 0]

Hello!

Starting a print job, the print head moves to the front left corner and the buiding plate moves up. Then, the print core extrudes material outside the wanted contour. I´m now wondering, by what this "Test extrusion" is controlled´´´´? Is it by time? And what is the reason for it?

For me, depending on the material, it seems sometimes that to much material is extruded for the small distance. 

[Smithy 1,145]

It is called Prime Blob and ensures that your nozzle is primed before starting the print. You can turn it off if you want in the Cura custom settings.

[Pia92 0]

Thanks a lot! Now that I know what it is called, I find a lot about it 😀

[Smithy 1,145]

🙂

For the UM3 it is enabled per default, the S5 has it disabled per default. So if you print a skirt around your object it is not really needed to have also the prime blob, but it doesn't bother me, so I don't really care about it and on the other hand a little more priming before the start always helps.

[Pia92 0]

I had the issue, that the extrusion of the material (iglidur) did not stop and it was a huge amount of material. The job did not stop as well, in the end i turned of the switch. It happend at a temperature test where I started with a high temperature (245°C), so the material might have been very fluent  😅 .

 

[Smithy 1,145]

Normally it is a small blob in the corner, but there was a bug in the firmware which caused the prime blob to never stop.

It happened not always, but I got it several times after I canceled a print job. Then the next job had this issue. After a restart of the printer everything was fine again. I don't know it this bug is already fixed in the latest firmware.

 

So to be on the safe side, I suggest to restart the printer (power cycle) after you have canceled a job.

[SirUlrich 0]

Just now learning about this... 

 

Is there a way to adjust the Prime Blob in Cura, or is it simply "On / Off" ? 

 

Also, is there a "best" or even "suggested" method of priming (in this type of fashion) if one decides to change filament colors mid-print on a design which is sliced as mono-filament? 

[Smithy 1,145]

34 minutes ago, SirUlrich said:

Is there a way to adjust the Prime Blob in Cura, or is it simply "On / Off" ? 

No it is just on/off

 

34 minutes ago, SirUlrich said:

Also, is there a "best" or even "suggested" method of priming (in this type of fashion) if one decides to change filament colors mid-print on a design which is sliced as mono-filament? 

This is easy, when you change filament you usually do a unload and load. During the load the nozzle is primed as long as press OK on the printer. So let it prime as long as the color is fine and not mixed.