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Bug in the spiral vase mode?  

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sbetak
(@sbetak)
Active Member
Bug in the spiral vase mode?

Hello everyone,

For around 2 weeks now i have been unable to successfully print an object with this combination: 0.6mm and/or 0.8 mm nozzle + PETG filament + spiral vase mode ( see: https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/0-6-nozzle-petg-spiral-mode-problem-when-spiral-initiates/ )

The problem happens when the first layers have been put down, and the spiral mode starts, the transition is not smooth at all :

 

This is the settings the caused ^ arc.3mf

It comes straight out of standard settings, so i cannot be the only one experiencing this problem.

What could this be? Is it a slicing bug? I tried editing the g-code directly without much luck. 

I would love to hear from someone who either had the same problem, or successfully printed a PETG object with spiral mode and 0.8 mm nozzle.

/Søren

 

Posted : 16/06/2021 4:04 pm
sbetak
(@sbetak)
Active Member
Topic starter answered:
RE: Bug in the spiral vase mode?

When the clotting/blopping happens, it looks like the extrusion of filament is different than the previous layers, almost as if it stops and then start spitting out unevenly.

As you can see, the rest of the print is smooth and without problems

Posted : 16/06/2021 5:05 pm
Dan Rogers
(@dan-rogers)
Noble Member
RE: Bug in the spiral vase mode?

Couple of thoughts - it's a wierd shape to print as a spiral - - and you turned off bottom and top layers (top would not come out well anyway since it is flat).  Try adding 2 or 3 to 5 bottom layers - and you'll get a quarter arc topless arc with ends with walls.  I am thinking since there are no bottoms, and you turned off skirt, the un-even-ness you are seeing on the very bottom layer is an adhesion problem.  No brim, no bottom layers - just a single strand laid out in an arc with squared off ends.  If your plate is not perfectly flat (and do note even try this on the textured sheet) and perfectly clean, you are going to get all kinds of first layer defects.

Posted : 17/06/2021 1:46 am
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE: Bug in the spiral vase mode?

I don't think this is a bug, I think this was poor decisions making.

The Filament Whisperer...
Posted : 17/06/2021 2:56 am
sbetak
(@sbetak)
Active Member
Topic starter answered:
RE: Bug in the spiral vase mode?

There is a reason why there is no bottom, and adding one would defeat the purpose. 

The first layers are put down just fine, this happens on the 3rd layer. I found some inconsistency in the E value in the g-code, and i think i'm gonna be able to fix it through that. 

 

Posted : 17/06/2021 8:16 am
Diem
 Diem
(@diem)
Noble Member
RE: Bug in the spiral vase mode?

Turn off spiral mode, @dan-rogers is right, this part is not suitable for spiral printing.

There is a reason why there is no bottom, and adding one would defeat the purpose.

Reinstate the top and print it upside down.

The first layers are put down just fine, this happens on the 3rd layer.

The first layer is clearly not sticking properly.  It's a single strand, you need perfect adhesion or good adhesion and a base.

I found some inconsistency in the E value in the g-code, and i think i'm gonna be able to fix it through that.

You're looking in the wrong place.

Rework the original design to have thicker walls, you are using a 0.8 nozzle so 5mm would be a good starting value.  Define the shape you actually want, not a supershape that you must modify by diverting the operating mode away from the machine's intended useage.

Select a printing profile intended for production, not a draft mode.

Cheerio,

Posted : 17/06/2021 10:10 am
sbetak
(@sbetak)
Active Member
Topic starter answered:
RE: Bug in the spiral vase mode?

@ Diem Thank you for the advice, but I don't think you are right. This shape can be printed successfully in spiral mode, it really isn't that strange of a geometry at all. It is basically a vase with a couple of right angle turns. 

Appreciate the input, but diverging from the spiral mode or adding a bottom is not what i am looking for. 

I am making progress by editing the E value in the g-code, it is almost there! 

 

This post was modified 4 months ago by sbetak
Posted : 17/06/2021 10:42 am
Dan Rogers
(@dan-rogers)
Noble Member
RE: Bug in the spiral vase mode?

Just pointing out some more weirdness in your .3mf file - these are definitely not "standard" settings.

The one that I missed - you say you are printing in PETG? Can you confirm?  You have chosen an amazon basics PLA filament profile.  That will run far tool cool to do a good job in spiral mode.  You may simply be printing too cold to get the first few layers going.  Expect adhesion between layers to be off - which does fit the picture - the filament is struggling to melt on those first few layers until the temp bump for higher layers happens.

Another odd-ball setting is a .55mm draft mode for layer height.  That is not standard at all.  With the low temp, and with the first few layers being under heated due to the above, it's amazing you have any bed adhesion at all.  I suppose you have had to squish your Z a lot to get that low temp to stick - which will make a mess in the second or third layer (under extruding, under heated)

For this print you may want to turn off linear advance - that is what is causing the E variations you are seeing in the GCODE.  M900 K=0; is the custom Gcode you would need to modify in the custom GCODE section 

Posted : 17/06/2021 12:09 pm
sbetak
(@sbetak)
Active Member
Topic starter answered:
RE: Bug in the spiral vase mode?

@ Dan R

Sorry, must have mixed up the .3mf file then. I have it set for Prusament PETG (correct, that is what i print with). The temperatures i use are 260 for the first layers, and 250 for the rest, that should be fine. 

The scenario you made with the low temp doesnt really apply, sorry, i must have uploaded the wrong file. 

I have just made the first successful print of the object as intended. Had to do some tweaking of the layer heights and the E value as mentioned, but it worked! I will check out the linear advance setting though, i have not been using that so far. 

Posted : 17/06/2021 1:47 pm
Dan Rogers
(@dan-rogers)
Noble Member
RE: Bug in the spiral vase mode?

Glad you got the mystery vase part going bud.

 

Posted : 17/06/2021 1:51 pm
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