3mm vs 1.75mm filament - any news?

[RetireeJay]

It seems the whole FDM world is going over to 1.75mm filament. It's now available in a much wider range of materials and colors than 3mm filament. But is there any TECHNICAL advantage?

In thinking about that question, I have a few theoretical comparisons, but it's hard to put the proper "weight" on each of these without real-world experience. So is there anyone who can weigh in with their own observations?

1) In the space between the drive gear and the nozzle, the 3mm filament is going to be stiffer, i.e. more resistant to bending or buckling. This is extremely important when dealing with flexible filaments, advantage 3mm.

2) In the space between the drive gear and the nozzle, the 3mm filament will have a stronger "spring constant" for longitudinal compression, which seemingly should make the responsiveness of the extrusion through the nozzle be more tightly controlled by the rotation of the extruder gear, advantage 3mm.

3) Both of the above factors are advantages for 3mm if you have a Bowden setup.

4) When the filament reaches the hot zone, heat can penetrate to the center of the 1.75mm filament faster than it can to the 3mm filament. On the other hand, you need to extrude more of the 1.75mm filament for the same quantity of plastic. Actual "3mm" filament is really 2.85mm. So the ratio of diameters is 1.63 : 1 meaning that the 3mm filament might need roughly 1.63 times as long in the hot zone as the 1.75mm filament to become fully melted. So let's say you want to extrude 1mm^3 of plastic in 1 second. With the 1.75mm filament, your area is pi * r^2 = 2.40mm^2 so you need to melt 0.416mm of filament in 1 second. With the 3mm filament, your area is 7.07mm^2 so you need to melt 0.141mm of filament in 1 second. In other words, your 1.75mm filament is traveling through the hot zone 2.95 times as fast as the 3mm filament for the same rate of extrusion. So it would seem, based on the rate of melting versus the rate of extrusion, that the 3mm filament melts more easily for a given quantity, permitting a higher volumetric rate of extrusion (assuming the heater is capable of keeping up with the total energy demand). Advantage 3mm.

5) The total quantity of melted plastic in the hot zone is significantly smaller, so when you Retract for a move, the pressure in the melted zone drops faster and you get less oozing. Advantage 1.75mm.

The one thing I wish my printer did better is stop oozing during moves, so I'm considering whether to abandon several rolls of 3mm filament and transition to 1.75mm printing. I guess I'd get a Ubis 13S because it fits correctly in my Plus without modification, but buy nozzles from E3D because Printrbot doesn't seem to have a good selection in stock.

[Mooselake]

Get a 13HF instead of the 13S. You'll need to adjust your Z home switch, but it has a longer heat zone and a higher plastic output. Might even match up with that of a 3.0mm wades extruder, but I wasn't volume testing in those days because extruder volume wasn't a limiting factor.

The initial reason behind 1.75 was that direct drive extruders were cheaper (no need for additional gearing) and could only handle the lesser push load from the smaller filament. I tried 1.75 because of my interest in dual geared extruders (in the Printerbot beta days; Bondtech is now one of, it not the, leading current version), then found that their original all metal extruder (the AMU) wasn't all that good at melting plastic. I was one of the 10 recipients of the HF beta, no comparison - way better than the AMU and outflows the E3D. I did small reviews and . I'd pair it with the geared extruder, although I'd asterisk that with I have a DIY geared beta and it's too good to replace other than that undersized ninjaflex adventure - that likely could have been solved by using a lower print speed (or the HF!) but I didn't get back to it.

Never did post that video, plus the Printrbot's been idle most of the last year due to non-3D printing stuff, and I think the power supply got leaked on (only ice related roof leak we've ever had is right over my upstairs desk, and survived a re-roofing. It's small and only happens if the roof icing conditions are just right every 15 years or so) and passed on. Really need to spin up a clone, there's probably a Kickstarter project for that

FWIW, if I was replacing my KCSP today I'd look really hard at the real Prusa i3 MK3 kit.

Kirk

[plexus]

I've never been a fan of 1.75. It makes no sense except in Bowden feed. The reason for direct drive was because 1.75 was being used with geared systems because people are sheep. Now, they are really like sheep moving away from 3mm with no sound rationale.

[RetireeJay]

[WayTooManyHobbies]

I have both 1.75mm and 3mm machines, and prefer the 3mm. It is easier to handle, seems to feed better in both direct and Bowden drives, and is generally just more pleasant. Makergeeks supplies both sizes, at least!

Regarding the Prusa Mk3, it seems like a wonderful machine. I'm not in the market, but that's where my money would go if I was.

[Mooselake]

[RetireeJay]

Those motor drivers are amazing. Up to 256 microsteps per step, and nearly a dozen special features to minimize acoustic noise and increase precision and speed. The motor driver chips are so smart they can tell the CPU when the motor stalls just based on the voltage and current going to the motor. So the MK3 doesn't need "endstop" switches on X or Y.

[RetireeJay]

Couldn't resist. I've got a Prusa MK3 kit on order. It's the same price as my 2013 Plus, but looks like a much better printer. So I'll be going over to the dark side and using 1.75mm filament, and bed probing. Not that I see either of those as a good thing, but the rest of the package blows me away. Like "live" adjustment of Z offset when starting up a print, using the LCD display and control knob.

[cbxbiker61]