1.75mm Filament vs 3mm Filament

Sorry to ask such a basic question, but I can't find any discusion about this.

I want to order a Prusa from MakerGear today. Can anyone tell me which way to go between the 1.75mm vs 3mm hot end?

Is one size more common than the other?

Thanks for your help!

Steve

Steve - you can stop by the MakerGear IRC channel and chat with other kit owners about it. I prefer 1.75.

Rick

I prefer 3mm and recommend it to everyone, 1.75 costs more and offers no real advantage over 3mm.

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In the UK at least 1.75 is 3 times more expensive than 3mm?
T.

Yes 3mm is 3x cheaper in New Zealand too. The only real difference is 3mm needs a bit more pressure to make it feed but I use it on both a sells Mendel and a Prusa and it's never been a problem

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Thanks for the info guys. So I'm a newbe and I don't know where the best place is to purchase this stuff. However, checking out Ebay, both the 1.75mm and 3mm is right at about the same price of $16 US per LB. Also, MakerGear has both for about $20 per Lb. So it seems in the US, the cost is about the same???

Other than price, Are there any advantages or disadvantages over one or the other? I guess I'm just kind of confused as to why there is a choice of sizes.

Thanks again everyone for the info!

I'll go with the 3mm. It seems like it could be more stiff or rigid going through the hot end. Thanks everyone!

I think the main advantage for 1.75mm over 3mm is that it requires less force to extrude, so compact direct-drive extruders are more viable. I don't think it makes much difference in terms of print quality. I use 3mm and it works just fine.

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It seems that everyone thinks that 1.75mm takes less force but as far as I understand this is not true. A certain volume of plastic going through a certain size hole at a certain rate takes exactly the same pressure regardless of the filament input size. Or to put it simpler, the nozzle diameter determines the pressure required to extrude not the filament.

Its like assuming a hydraulic system with 2" lines some how has more force than one with 1/2" lines. The only difference is the maximum volume per minute that one gives over another. The actual force is determined by the cylinder diameter which is the equivalent of the nozzle hole.

The only difference I am aware of with 1.75 over 3mm is the volume of plastic per step. 3mm puts out almost 4 times the volume of plastic per step as 1.75mm in the same extruder. The only time this matters is when printing really small layers, like 0.1 and less combined with a really complex model. If you want to try and print really tiny layers with 3mm you can make an extruder with a lower gear ratio, like 10:1 instead of the stock 3.3:1

Edited 1 time(s). Last edit at 04/14/2012 10:30PM by Sublime.

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I know the actual pressure at the nozzle is the same. The force is less because the extruder gear has to turn further to push the same amount of plastic through. It's like gearing it down.

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Because the torque required is three times less and typical Wades gearing is 3:1 direct drive becomes feasible, making the extruder smaller and simpler.

Or, if you use the same gearing then a smaller motor can be used making it smaller and lighter.

A smaller lighter extruder is a benefit for small machine. For a large machine the mass of the bed dominates, so no point in having a fast X axis and a slow Y axis. But you could perhaps fit two 1.7mm extruders for dual extrusion and be the same mass as one 3mm extruder.

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I have tried direct drive and I was not pleased with the results with 3mm (maximum speed was limited and electronics and stepper were running hot). I've later tested the same design with 1.75mm and it works great (at just 1A).

Luckily I was able to buy 1.75mm ABS filament at the same price as 3mm. If not, I guess it may make sense to create a 3mm to 1.75mm dedicated extruder to source yourself.

The gearing and stepper setup is secondary regarding the required force.
Just think about it as a hydraulic system: In one case the driving piston is 3mm, in the other case the piston is 1.75mm.
The area is only 34% of the bigger filament so therefor the required force is also only 34% of the 3mm value.
Bertho

Good analogy. It helps. Thanks.

There is another factor here, I think. The 3mm takes longer to melt per milimeter than the 1.75mm at the same nozzle temperature because there is more plastic per milimeter requiring heat, and although both ultimately require the same sum of heat energy to produce a given flow, the rate at which both melt would impact the feed rate, and that would affect the force required to feed one over the other. I think that if the heat generated at the nozzle were higher for 3mm though, you could effectively make both filiments flow with equal force required regardless of gearing and nozzle design, etc...

Imagine how little force would be required to feed 3mm if the temperature were set to 500 degrees? Pretty much none I would think (although that is too high), so I believe that the temperature of the nozzle is really what counts.

1.75mm vs 3mm

the 1.75 is better if you can run that, your flow control resolution is much greater, for a start, you'll get less ooze because there is less molten plastic behind the nozzle with the correct retraction settings you should be able to get some very nice prints

if you can afford to put a direct drive extruder on your machine i would highly recommend it, however if you are stuck with a wades type of geared extruder then it's worth the money on one of those hyena hobbed bolts, unless the bolt that comes with it is really good and nice and round (not all are)

"Imagine how little force would be required to feed 3mm if the temperature were set to 500 degrees?"

I wouldn't recommend that. ABS decomposes into some unfavorable things at such a high temp

Not to mention I'd think it would cause the extruder nozzle assembly to clog.

I have quite some ooze going on on 3mm filament with a wades type of extruder. But I did not yet try a reduction tube to convert it to 1,75mm. Does anybody have experiance with this? Is the ooze reduced?

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Sublime
It seems that everyone thinks that 1.75mm takes less force but as far as I understand this is not true. A certain volume of plastic going through a certain size hole at a certain rate takes exactly the same pressure regardless of the filament input size. Or to put it simpler, the nozzle diameter determines the pressure required to extrude not the filament.

Its like assuming a hydraulic system with 2" lines some how has more force than one with 1/2" lines. The only difference is the maximum volume per minute that one gives over another. The actual force is determined by the cylinder diameter which is the equivalent of the nozzle hole.

The only difference I am aware of with 1.75 over 3mm is the volume of plastic per step. 3mm puts out almost 4 times the volume of plastic per step as 1.75mm in the same extruder. The only time this matters is when printing really small layers, like 0.1 and less combined with a really complex model. If you want to try and print really tiny layers with 3mm you can make an extruder with a lower gear ratio, like 10:1 instead of the stock 3.3:1

While all of that is true there's other factors at play, I believe the friction at the not-so-melted zone must be much higher for 3mm filament Vs. 1.75 since there's more surface area in contact with the extruder barrel, therefore more friction. Also the thicker filament must have a longer melt transition zone (exacerbating the first issue) because the surface area to radiate away the heat coming up from the melting zone into the barrel heatsink is proportionally smaller than the cross sectional area that is drawing heat up the filament.

Besides that one advantage of 1.75mm filament I can think of is that it is easy to use all the filament in the spool, even the last meters tightly wound around the spool hub.

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Sublime
It seems that everyone thinks that 1.75mm takes less force but as far as I understand this is not true. A certain volume of plastic going through a certain size hole at a certain rate takes exactly the same pressure regardless of the filament input size. Or to put it simpler, the nozzle diameter determines the pressure required to extrude not the filament.

Its like assuming a hydraulic system with 2" lines some how has more force than one with 1/2" lines. The only difference is the maximum volume per minute that one gives over another. The actual force is determined by the cylinder diameter which is the equivalent of the nozzle hole.

The only difference I am aware of with 1.75 over 3mm is the volume of plastic per step. 3mm puts out almost 4 times the volume of plastic per step as 1.75mm in the same extruder. The only time this matters is when printing really small layers, like 0.1 and less combined with a really complex model. If you want to try and print really tiny layers with 3mm you can make an extruder with a lower gear ratio, like 10:1 instead of the stock 3.3:1

That's true for determining the working pressure in the system, but to generate the pressure in a cylinder you need to apply force over the area of a piston. With (3/1.75)^2 times the area, you'd need about 3 times the force to generate the same pressure.

I have just joined this forum after building a Prusa i3. I have learned from mistakes, posts to this forum
and other local 3d printer fans. I have done some calibrating extrusions tweaking the firmware. The extrusions
x,y are within 1% but my details like letters, degree marks leave something to be desired, I am using 3mm
filament and my extruder end is .5mm.

I am going to try a 1.75mm filament to see if my detail will improve.
I am thinking of an all metal extruder, one that will also extrude more of the exotic
filaments!
Any pros and cons?

From this thread I noticed the dated 2012 post leaned towards 3mm mostly based on price.
Posts with dates of 2014 lean towards 1.75mm maybe because price has come closer to 3mm and
detail has improved? (I'm guessing)

Read up on the all metal hot ends before buying. Some are really terrible at printing PLA. While some people swear by them, others curse them.


Prices have evened out on filament.
It also used to be that 3mm had a greater selection, today, it's pretty even.

Where 1.75mm shines is that you don't have to gear it down as far, or at all. You get the effect of a higher ratio extruder without having a higher ratio. Some users do get away without any gear reduction, however, I don't recommend trying that on any head with a nozzle smaller than .4. At .4mm, even the best motors are hard pressed at times to keep pushing it at any decent speed which is why you see lots of geared stepper motors on deltas (which almost exclusively use 1.75mm), which are actually geared even lower than a Wade's extruder. At 5:1 on 1.75mm, you get a very precise filament extrusion with lots of power behind it. This is especially important on smaller nozzle sizes. Another benefit to 1.75mm is weight and flexibility, on a bowden tube, the 1.75mm weighs less and is more flexible, which is more important in a delta.

It's not all roses.
1.75mm has a smaller contact patch and cross section, as such, you're far more likely to strip or crush the filament. Most hobbs are designed for 3mm filament, making the problem even worse. This isn't a huge issue until you start ramping speeds up. I have one hobb that slips at just 150mm/s, but most will handle 200mm/s on a .35mm J-head. Things get complicated fast beyond that speed.

Another problem is filament precision, anything over 10% out of spec is considered problematic. On 3mm, this is .3mm that is a HUGE deviation and very easy to stay within spec, on 1.75mm, you are allowed only .17, which is troublesome for some manufacturers. I have had some 1.75mm filament that was .24mm out of spec and jammed my bowden tube so bad I had to hammer a stiff metal rod into the tube to get it out.

Why do Chinese people always think the way to start out a message is "hello dear" or "my dear"? I get 5 spam emails a week like this from Chinese companies. I find it hilarious.

So sheepdog43, you think 1.75 mm jhead would be a better place to start and compare results with the one I have now?

If I do decide on metal I will research it well, thanks.

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andyinyakima
So sheepdog43, you think 1.75 mm jhead would be a better place to start and compare results with the one I have now?

If I do decide on metal I will research it well, thanks.

At this point you'll get more out of tuning the machine you have now rather than getting another hot end. Plenty of people make good prints with a .5 nozzle and 3 mm material. It's more forgiving to learn. Once you get your machine more dialed in, print faster, use a bowden, etc you will be in a better position to judge what you need and reap the benefits of using 1.75 material. Make some prints then post the pics on the forum and ask for opinions on what could be done to improve the prints.

I agree with vegasloki. You will get more out of calibrating your machine than changing the filament. In the german forum the user Hardwarekiller is using 3mm filament to print to the highest standards i have seen yet. The filament size does not make the difference in quality, the calibration of your machine and the quality of the hotend does.

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Srek
I agree with vegasloki. You will get more out of calibrating your machine than changing the filament. In the german forum the user Hardwarekiller is using 3mm filament to print to the highest standards i have seen yet. The filament size does not make the difference in quality, the calibration of your machine and the quality of the hotend does.

The last part of your statement is what I suspect on my hotend, not so great quality. That's why I was thinking of a metal hotend.

I have also been thinking about direct drive extruder versus gear drive; any comments appreciated.

One last question how critical is g-code? I am using Slic3r 1.0.1.

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andyinyakima

Open Book, Open Source, You have to Open it to Know what's in it!

I used to think direct-direct drive was the way to go, and for simplicity and basic printing, it is. But if you want better prints, get a geared motor. I can't think of any other way to achieve really low layer heights and more consistent extrusion while maintaining power [increased power makes your motor jump to whole steps, causing inconsistencies, lower layer heights need to have finer accurate steps].
I'm not speaking with experience, so take it with a grain of salt, but from I can see, go geared for quality, 1:1 direct for simplicity and ease.

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andyinyakima

The last part of your statement is what I suspect on my hotend, not so great quality. That's why I was thinking of a metal hotend.

I have also been thinking about direct drive extruder versus gear drive; any comments appreciated.

One last question how critical is g-code? I am using Slic3r 1.0.1.

I tried both direct and geared, honestly, there isn't much of a difference most of the time. The geared ones have more power, the direct ones are faster. With 3mm filament a direct drive is usually to low powered for any kind of printing speed so those are mostly used for 1.75mm.
Currently i only use geared extruders (Wade derivates, own construction and Bulldog).
G-Code is actually very critical. Adjusting the slicing software is an important part of the over all adjustment of the system and is needed to achieve not only optimal but actually useable results.

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sheepdog43
Another problem is filament precision, anything over 10% out of spec is considered problematic. On 3mm, this is .3mm that is a HUGE deviation and very easy to stay within spec, on 1.75mm, you are allowed only .17, which is troublesome for some manufacturers. I have had some 1.75mm filament that was .24mm out of spec and jammed my bowden tube so bad I had to hammer a stiff metal rod into the tube to get it out.

10% is far too high. I see no reason to use a supplier who can't guarantee 5% .