Flow Rate Sanity Check

I was printing a popular machine vice model and came upon a huge problem: the threads looked horrific! They were OK while there were other features in the layer being printed but as soon as only the screws were left to print, it all went sideways.

I tracked the problem down to material flow rate: somehow I accidentally bumped the rate to 1.17 and didn't notice. I adjusted the flow and the problem went away. But this gave me an idea: checking threads is less subjective then a typical flow rate calibration procedure, like the one in Orca slicer, for example: 

https://github.com/SoftFever/OrcaSlicer/wiki/Calibration#Flow-rate

Personally, I always had a hard time deciding which slide to pick as the best one.

So, I used Fusion 360 to split the model, kept the tips of two screws and made a series of tests: 3rd and 4th (the 4th was printed horizontally, to see if it makes a difference - it didn't) pictures show the flow rate = 1.17, 5th = 1.03, and 6th = 0.98. I then used a standard M12 nut to check printed threads: only those with flow rate = 0.98 worked as expected.

Last picture shows both PLA+ (grey) and ASA (black) printed threads. ASA does look a bit sharper.

I'm new to this hobby, so if any other noob out there can benefit from this little tidbit, you're most welcome. And, I still have no clue why the problem only starts when there are no other features left to print.

I repurposed this popular model's thread feature for testing flow rate. I split a portion of the two screws used in the original without any modifications.