Yes exactly - the annotations of the pix are correct.
Maybe I can make the 1st layer devastatingly slow like 5mm/s and pick up the stray strings....
I haven't dialled my retraction settings - i think they are stock
do you know which ones I should change?
as for the under extrusion..
should my get my print bed levelled closer or add 20% - 30% more flow of the filament? (or both?)
What printer is it? Is it equipped with a Direct Drive? How long have you been printing? I never know if I'm talking basic stuff to an experienced person, or talking over the head of a new kid.
The "Retraction Distance" on a bowden style printer vs a DD printer are very different. Typically a DD will be around 1.0mm and a bowden setup may be 6 or 7mm. There are retraction towers you can print to find the optimal Retraction Distance for the filament you are using, and for your hardware setup. Other settings like Retraction Speed and Prime Speed affect the retractions themselves while "Max comb distance with no retract" and "Retraction Minimum Travel" affect how far the print head moves before a retraction is considered. If you are printing a block that is 25 x 25 and you have Retraction Minimum Travel set to 100 then it's likely you won't get any retractions during that print.
Because the real actual height of the first layer affects the overall Z dimension of the print the best way to fix the problem is to have the bed leveled correctly. Leveling is a stupid word for what is going on. You are really setting the initial Z gap so it is even everywhere. If you have an Auto Bed Leveler then you can probably adjust the Z offset. I use a piece of parchment paper (nothing sticks to it and it's only .04mm thick) and with practice I've gotten very consistent from print to print. Part of that consistency is that I always run the Initial Layer Flow at 105%.
On many printers the E-Steps/mm must be calibrated. When the printer is asked to deliver 50mm of filament then exactly 50 should come out of the extruder. Nozzle size doesn't matter, the amount of filament pushed matters a lot.
Once the E-steps are correct and the Z gap is good then you can test with a regular calibration cube. In Cura you can scale the cube to 100 x 100 x 1mm thick. As it prints you (depending on the printer again) adjust the flow from the LCD. At 100 x 100 you can make two or three changes per layer and see how it goes. When you make the change there may be 7 or 8 moves that were in the printer buffer that have to clear out before the change takes effect.
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GregValiant 980
I just finished a large print and had this problem. Because it was a large model I was able to brush away the ooze before it became part of the model.
There is no setting in Cura to re-order the print sequence other than Infill Before Walls. For the first layer, there is no infill and so that setting likely won't help.
Your retraction distance of 0.8 appears to be for a Direct Drive. I will assume that you have that dialed in.
Looking at the second photo - are you talking about the line I highlighted? That looks like an extrusion with no retraction at all. It almost looks as if the lines that should cross it didn't do so.
BTW zooming in like that I see that first layer is either under-extruded by ~20% or the nozzle is too far up from the bed during the initial layer. There are a lot of gaps in there.) Here is what I'm talking about.
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