Printing Spare Parts

[pyronaught]

The multiplier crushes all the drive gear depth, filament hardness, printing speed, shrinkage, and other imponderables into a single number that works reasonably well.

Make sense?

Actually, yes! It's like one big fudge factor that compensates for all the unknown variables. I guess the key word here is "Then you're set for that particular filament spool." So this has to be done for every spool even if coming from the same manufacturer to be reliable. I guess I'll have to put a label on each spool with the proper number on it. I'm doing gears, threads, press fit connections and stuff like that which needs the accuracy.

[ednisley]

So this has to be done for every spool

The slicer must know the filament diameter, too, so record that on the spool. I tend to run a single spool until it's gone, which means I can measure the diameter, run off a few thinwall boxes, set up the slicing parameters, and that's the end of the adjustments for a long time.

Some machine-dependent factors go into the multiplier (like how deeply the extruder drive pinion bites into the filament), so it's not a galactic constant that's true forever. If you're constantly changing filaments, extruders, hot ends, nozzles, and suchlike, then finding the proper multiplier for each combination will require calibration, but that's exactly what you do while tuning for each combination, anyway.

The thinwall box will be your friend...

[jsc]

So this has to be done for every spool

The slicer must know the filament diameter, too, so record that on the spool.

Can't you just leave the filament diameter at a nominal 1.75mm and record the proper extrusion multiplier?

[Tim]

Can't you just leave the filament diameter at a nominal 1.75mm and record the proper extrusion multiplier?

Note that my first reply in this thread said that if you had an extruder multiplier of 1.0, then you'd want to dial it down. That was a sort of obvious quick-and-dirty solution if your default was set wrong. Since you said your default was 0.9, then that doesn't sound like it's the problem.

I think a lot of us just put in typical values and leave it at that. Ed obviously has a very precision workflow going! For the rest of us, I'd say a good rule of thumb is more or less what you're already doing. Put in typical/default values, and print something that requires good tolerances. If it comes out obviously too loose or too tight, then it's probably a good idea to get out the calipers, measure the filament diamenter, and print a calibration piece.

Generally speaking, spools of the same filament type from reputable manufacturers will have excellent tolerance, and are going to print with nearly identical parameters. You'll probably see a bit of variation between different filament types, much more if you get into exotic filament types like flexible or wood filament.

[ednisley]

just leave the filament diameter at a nominal 1.75mm

I don't do nearly as much filament swapping as you folks, mostly because I use only PLA and don't care what color goes into most parts. Setting the diameter to match the actual filament and leaving the multiplier alone works pretty well under those conditions: the multiplier includes the machine conditions that don't vary (much, hardly, kinda-sorta) from spool to spool.

I can actually measure the filament, so letting the slicer chew on a real number seems, somehow, more fitting than fiddling with the fudge factor.

Not to mention: measuring something gives me a warm fuzzy feeling of competence that I don't get very often... [grin]