3mm filament: most places but not our local Diamondage. They use 2.85mm.
1.75mm. Good pricing most places, but buy it from diamond age and you pay almost as much for length as for their 2.85mm filament!
1.75mm filament is available from lots and lots of places in all sorts and colours of plastics.
Advantages of 1.75/2.85/3mm filaments:
higher diameter= slightly better volumetric extrusion accuracy for the same filament diameter thickness deviations.
Smaller diameter: much easier to feed as less cross sectional area to push through hot end, shouldn't need a geared stepper motor.
Gearing stepper motors for extruders: generally a bad thing, backlash source, slows retract moves as the steper motor has to rotate further for the same distance as a non geared retract stepper. However... if you can get a low mass, fast stepper to work on your print head (instead of pushing through a bowden) then it's great for retracts and also flexible filaments.
I'm currently using all OMC-stepper on line motors which are great prices and range, I've upgraded from $20 per piece NZ available weak 200 step motors to long 2.7V? 400 step motors with better print resolution and unbelievable speed off 12 volts, way more speed than I can use and they run cool with my conservative potentiometer settings on a RAMP board.
I'll be upgrading soon from my geared extruder, probably with a birdstruder(quick release) and another of my long nema17 400 step motors as above.
I would like to experiment with a 6V nema 8 stepper for extruding, but without a durable worm drive reduction I can't quite see how to get the stepper fitting tidly on top of a rostock effector. A 6v Nema 8 should react pretty quickly for retracts due to it's low rotor mass and diameter, also I should be able to run it reasonably fast to take advantage of it's available power to weight ratio- typically non geared steppers are moving much much slower than they are capable of.
I'm experimenting with a geeetech thermal break from dx.com and a home made water cooled holder at the moment, but I'm finding that the filament forms a fatter plug under pressure and jams inside the thermal break, dissappointing because their thermal break looked good, it has a teflon liner for much of it's length. Must be drilled out excessively wide somewhere though!
It's important for hot ends to be only just greater diameter than the filament for rapid heat transfer, otherwise a plug will form under pressure and start jams.
I use a small cloth piece with a drop or two of vegetable oil clothes-pegged around the filament before my bowden drive for most of my PLA prints. Seems to have no obvious impact on strength, however with glow in the dark green from diamond age, I've had oily drips right on the initial layer, apparently "a small amount of kerosine" is used in it's manufacture.
Layer bonding strength is impacted hugely by accurate calibration of extrusion and by setting of nozzle width in your slicing SW. I get much better layer bonding strength if I set the nozzle thickness higher than it actually is to force filament to flow sideways as well as simply being tracked behind the nozzle.
I've bought filament from matterhackers(USA, sub week lead time), dx.com(hong kong, free freight, about 3 weeks lead time and diamondage(usually overnight courier). For impact resistant structural items I'm currently looking to print nylon though I have about 4.5 Kg of ABS pellets I'm building an extruder for.
