3D Printing Forum

I'm not sure how to explain the Pros and Cons of each!

Can someone detail that for me?

1.75 pros cons
Can print at lower temps
Can resist more retractions (and almost infinites with my bondtech fatrobert feeder)
Can handle less pressure on the hotend (less blobs)
Much less dripping (less material at any given time vs gravity)
You can use the end of the spools without troubles.

Cons.
It needs a bit of care, brute force extruder would just snap it inside the bowden.
It's more delicate at ambient temp va feeder hot in summer.

Pros of 2.85
Probably better control and less vibrations at highspeeds, since there's less movement from the feeder to push more filament mm3.

I would add "Bigger selection of available filaments" as a pro of 1.75. Also - since more printers seem to use 1.75mm, you have a better chance to swap filaments between different printers if you have multiple printers (that are not all Ultimakers...)

I hear "Bigger selection of available filaments" a lot, but almost no one can tell me where that rumored bigger selection is, there is very few filaments to date that i have found only in 1.75mm and not been able to order in 2.85mm for my UM printers...

Also 2.85 is often easier to use with flexible filaments (since it acts stiffer because of the larger size)

I am in progress of rebuilding two old CubeX printers with open source electronics and new feeder/hotends, and cant decide on if i should go with 1.75 or 2.85mm, will probably be 2.85mm just to make sure that we only have printers with one filament diameter at our makerspace...

I do not have any scientific research on the bigger selection but if I search on ebay.de for "Filament Spule 1,75mm", I get >1200 hits and if I do the same for 3mm, I get ~750 hits

It's true there's more 1.75 filament, but generally it's bad filament. Good filament brands work 1.75 and 3mm, except that graphene conductor filament and few others there's no much difference. And maybe that TreeD filaments also, but they never released their Wool filament, so I dont care much.

I think there's more future on 1.75mm just because one think, it's easier to make a direct drive that weight little and that can be mounted on almost any hotend (pancake direct drive by anders for example) that could be a really good advantage since Bowden inner pressure adds too many variables and 1.75mm pancake could deliver more precision to the extrusion.

Of course, for just printing any size will do, but for the stuff I need I must keep using 1.75mm. And for big large objects probably 1.75mm it's just a bad idea. (like using a 2mm big nozzle for example). So I think it just depends on what you need to print, and how often you need to repeat it (production vs casual printing)

I have no scientific research or proof that this is true, but I suppose it is because it makes sense:

2.85 mm filament "should" have a better diameter accuracy vs volume than 1.75 mm, because the absolute diameter accuracy of both should be more or less the same (typically +-0.05mm). It's the same manufacturing process, so there should be the same result.
But 2.85 mm filament has more volume per length than 1.75, so the diameter error should impact the result less than with 1.75 mm filament.

Again, I have no proof on that. Maybe someone who uses both filaments (ideally from the same manufacturer), can comment on that?


/edit:
Calculations:

2.85 +-0.05 mm diameter circle area: 8.80 - 9.11 mm2, that is a worst case variation of 3.5%.
1.75 +-0.05 mm diameter circle area: 5.34 - 5.64 mm2 = 5.6% worst case variation.

Ok, I suppose the difference is negligible...

ok

I will do my best to explain in my afflicted ways There is a view by some that 1.75 is "easier" to push through than 3mm.

Some schools of thought support this by suggesting that because the extruder has to turn a greater number of turns for a given volume of filament, it is easier to push through, a bit like riding a bicycle in a lower gear up hill. However when one considers a hose pipe, and pressure, for a given volume of liquid, going through the same exit orifice you will end up with the same back pressure (Bernoulli's equation) since there will have to be the same volumetric flow going in.

There is also another school of thought that states 1.75mm filament will melt a bit faster due to its lower cross sectional area, and this maybe true to an extent, but then by increasing temps with 3mm one can counter this to an extent. However for a given volumetric flow rate you will still have the same flow rates and back pressure factors to consider as in the para above.

Having said that, I do think the heating side of things can play a part, especially in direct drive extruders as they are pushing near their torque limits, but then in such scenarios the stepper motor can tend to act like a bit of a jackhammer on the filament due to the way coils are energised and de-energised during microstepping, which in turn can cause skipped or missed (not the same) steps, or promote filament slips when you are close to the ragged edge on filament tension. Skipped or missed steps are the primary cause of ghosting or ripple, when issues related to machine stability and belt tightess are factored out of the metaphoric equation.

Personally I use both. I dont see that much difference between the two but I use highly geared extruders. I do find 1.75 can tangle or break much easier compared to 3mm filament. 1.75 is overall a little more tricky to handle than 3mm. going though a bowden 3mm is going to be stiffer and less susceptible to compression or scrunching up in the tube, and there is less filament to bite onto.

All said and done I am not 100% sure on the math at this point as it is something I have looked at before and been meaning to revisit as I was not convinced by the points raised in either camp. I have a couple of good threads on the irc forum bookmarked and whilst there were some very knowledgable and academically astute people commenting, in my mind I still wasnt convicned of the arguments for and against.

In summary, in all honesty.....I dont know.....yet

Well. A smaller filament through the same hole is less pressure. But the most important is that the amount of metal vs filament.

Anyhow I been using 2.85mm on a um3 and I must saynis horrible, and a bondtech for me isn't about using a bruteforce feeder but precision extruder gears that actually move the filament instead of just destroying it like um2+/um3 feeder. Is just horrible...

I think such effects of the 1.75mm filament going easier through the machine than 2.85mm are mostly due to the fact that many parts are made in fully metric sizes. So 2mm-1.75mm=0.25mm is just a bit more than 3.00mm-2.85mm=0.15mm which helps a lot...

Dim3nsioneer wrote:I think such effects of the 1.75mm filament going easier through the machine than 2.85mm are mostly due to the fact that many parts are made in fully metric sizes. So 2mm-1.75mm=0.25mm is just a bit more than 3.00mm-2.85mm=0.15mm which helps a lot...

Don't think so... For example olsson and umo use 3.15-3.20 holes for 2.85 filament (I mean bowden & hotend) so there's actually more room for 2.85 than 1.75

No it wont have to do with the sizes available, supply meets demand, people switch to 1.75 and so demand increases hence they are more prevalent. There is likely a slight advantage given it will melt quicker than 3mm for a given length, but it is less volume being melted.

1.75 can be fiddly, easy to tangle, easy to break << these are the cons of it.

However if one had a powerful enough extruder that didnt struggle like a direct drive can, ie due to running high currents (one main cause of ghosting/ringing), motors getting so hot they melt their plastic mount points, filament slips and grinds etc due to the impact of heavy stepping, Then 3mm is a very viable option as motors can run a bit slower, cooler, lower vref and less ghosting, avoiding the sometimes delicate nature of 1.75

I hope that all reads right....

Fiddly. Maybe, I only had problems with it on summer with the room temp at 32C, fixed it by sticking a heatsink to the feeder, never got the problem again.

Easy to tangle?, afaik I had more tangles with the UM3 2.85 than in two years of 1.75, but ofc I use colorfabb, and smart materials.

Easy to break? That depends on the feeder, with my FatIRobertI using Bondtech I can use spools that have been on a box for a year and a half without any issue or break. In fact for fun I did a 65k retraction test (a print for 3h, so very concentrated retractions) and the filament went without any flatness, nor break. But ofc, like for any 3dprint, to get reliability you need quality.

Filament snapping into the Bowden on happened to me when I started to do the 2.85 to 1.75 mod on the first uno, and was due hysteresis inside a too wide (standard 3,20 ID Bowden). That's why a proper Bowden for each filament is a must, to have all under control (unless you do like the 'Adafruit' guys that say stupid things like that UM3 can work with 1.75 'out of the box'). There's always a difference between 'work' and 'really work'. But ofc, they print mostly boxes and on their 1.75 on um3 they just printed a few lines that don't requiere anything) But well, this is for other posts.

The thing is that 2.85 can endure much more 'brute force' than 1.75, so you could put the filament under much more stress than 1.75 (but extruding by brute force don't give high quality prints). So again, there's a difference between extruding and printing.

Ofc 2.85 can have a much easy extrusion for 1mm nozzles, just because it needs to move less motor steps per mm, and 1.75 would need much faster feeding. But also, to print 0.25 with some materials you have less problem because there's actually less amount of plastic on the nozzle/heater, so there's less risk of burning it for slow prints.

Anyhow I think any system, with the proper components can deliver as good prints as any other. It depends on how good and how well you have your machine. But just extrusion, yea, even Adafruit can do it.

More data to the subject. Posted by @Rigs on twitter

Use google translate. Very interesting stuff

http://www.genapart.com/2016/11/14/quel ... -utiliser/