Prime blob knocked down (Cura/UM3)

[upatamby 9]

7 minutes ago, robinmdh said:

@Remote-Pizza I would simply advise you to turn off the prime blob, this is currently the default in Cura AFAIK.

 

The prime blob is enabled by default.
I find the prime blob very useful because it reduces the chance that the filament will start extruding too slowly.

The change I'm asking for seems extremely simple to me: just don't let the build plate rise before the print head has taken some distance. It surprises me that this simple change isn't realized, and it keeps me from bothering to report several other small bugs (the priorities apparently lie elsewhere).

[paoletto 3]

Happens to me too: Latest cura (4.8.0.something), Ultimaker 3 with latest firmware (self updated itself).
Also, it happens every time. Prime blob, then build plate start rising and head starts moving, smashing the prime blob down.
I do not want to disable the prime blob because i had issues without it. Sometimes the extruder got stuck in the beginning and screwed the print. So i find priming the material a must.
As for @upatamby suggestion, i'd go a step further and rather ask the build plate to go down a bit and then rise, because

the prime blob is a bit unpredictable and it would be good to ensure clearance till after the head is gone.
Please add this, it's a nasty bug and it happens all the times.
UM3 is also not a cheap piece of hw, one would expect that such a simple problem would be fixed, given what it costs..

Edited December 31, 2020 by paoletto

[upatamby 9]

35 minutes ago, paoletto said:

... one would expect that such a simple problem would be fixed, given what it costs..

I agree, but the developers have other priorities, such as a fancy Marketplace... 
That's why I've stopped giving free feedback, because it takes a lot of effort and is not very rewarding.

[ghostkeeper 105]

The last real change to the Marketplace was in July when the rating system was removed. Our main focus lately (the last 3 months) has been the variable line width algorithm.

 

But that all doesn't matter since the prime blob routine is implemented in the printer's firmware, and focus/resources in Cura development do not detract from what happens in firmware. All Cura does is output the "G280" command. We have absolutely no control over how the printer moves the bed then. For that reason it'd be better to post this in a place that is more frequented by firmware developers: https://community.ultimaker.com/forum/109-firmware/

[upatamby 9]

11 minutes ago, ghostkeeper said:

...

But that all doesn't matter since the prime blob routine is implemented in the printer's firmware, and focus/resources in Cura development do not detract from what happens in firmware. All Cura does is output the "G280" command. We have absolutely no control over how the printer moves the bed then. For that reason it'd be better to post this in a place that is more frequented by firmware developers: https://community.ultimaker.com/forum/109-firmware/

 

Great. After 3 years, someone from Team Ultimaker tells me that I should have posted my issue in another place in the Ultimaker community so it would end up with someone else from Team Ultimaker. 
In other communities it is not uncommon for a moderator to move an incorrectly posted message directly to the right place. 
Great teamwork, Ultimaker!
😒

[paoletto 3]

On 1/2/2021 at 5:21 PM, ghostkeeper said:

The last real change to the Marketplace was in July when the rating system was removed. Our main focus lately (the last 3 months) has been the variable line width algorithm.

 

But that all doesn't matter since the prime blob routine is implemented in the printer's firmware, and focus/resources in Cura development do not detract from what happens in firmware. All Cura does is output the "G280" command. We have absolutely no control over how the printer moves the bed then. For that reason it'd be better to post this in a place that is more frequented by firmware developers: https://community.ultimaker.com/forum/109-firmware/

I was thinking: what if you output G280, then you output g-code to lower the build plate then you bring it back to the printing position?

Or, alternately, what about not sending G280, but emulating it instead?

Edited January 20, 2021 by paoletto

[UltiDad 0]

Hello

Apologies for bumping an old thread but have any of the new drops of Cura addressed this? I'm due to update but haven't got around to doing it on all workstations.

I still get the prime blob "smash and drag" on my UM3 from the print head and although I use workarounds whenever possible (skirt or staying in front of the machine with needlenose pliers to pluck it) it is quite annoying and uneccessary. There is no reason for the head to drop down on the prime blob. It is a bug and one that can easily ruin a print if you're running the machine remotely.... no clue why UM won't fix?

 

[gr5 2,170]

It's a feature, not a bug.  It's called the "prime blob".  I don't know if it's in the firmware or in cura.

 

What material are you printing?  Maybe you should add some thing to your glass bed so the prime blob stays in the corner.  The head is supposed to push the blob downwards so it sticks in place.  I think?

 

I'm not a big fan of the prime blob since I do a "skirt" which takes care of priming.

 

Anyway for PLA, PETG, nGen, and Nylon I use a mixture of elmers wood glue and water.  That keeps the prime blob from dragging into my print: https://www.youtube.com/watch?v=t58-WTxDy-k

 

The above video has an index early on in the video and you can skip to surface preparation where I demonstrate 3 ways to prepare your glass such that the prime blob will stay in the corner.

 

[UltiDad 0]

Thank you for the fast reply. Yes you are correct, not  BIG issue as it is used in a small percentage of my prints, only where I have the combination of need for priming and I'm tight for space or have a large intricate perimeter (and the skirt consumes way more material than the quick blob).

I use EasyFil PLA and it works great with the bed heated to 60C as-is. I can get a mirror finish on the part and great first layers without the need for adhesion aids. No cleanup once done, just remove the part and ready for the next print.

The issue really is the heads squishes down the prime blob (which is OK) and then begins translation right away which just drags the blob. My thinking was just moving the bed down a bit after squishing so there is no contact with the head before translating would greatly improve this feature.

 

I also run a UM2 and the prime blob isn't squished by the head so I had no idea why this "feature" was added to the UM3 which requires more manual intervention from the user (and risk of the prime blob ruining the print). 

Anyways, thanks for the suggestions and sounds like my question is answered with respect to the solution being in Cura. Thanks! 

[Torgeir 242]

Hi there,

 

Prime Blob is found in Cura under "Build Plate Adhesion".

It's normally hidden, but go to Preference then select "Cura Settings" and next press settings.

Write "Prime Blob" in the search window.

Here you'll see that "Prime Blob" is selected by default, so just deselect it here.

 

Thanks

Torgeir

[UltiDad 0]

Thank you

 

Yes I disable it when I can and use the skirt option (or brim if the part might warp) then no need for the blob.

 

I just find when I do want the blob the behaviour a bit weird, especially considering the UM2 never did that and it could easily mess up the first layer.