best size filament to use ?

What is the best size filament to use or easiest to get 1.75mm or 3.00mm ? I don't understand why there are 2 sizes.I am looking at getting the hot and cold end for my p3steel build I need to make a decision but not sure what to go for.

thanks Nikki

Actualy 1.75mm comes to be the standard, as most of manufacturers build machines which uses that diameter only. Otherhand a 1.75mm filament have less resistance and needs less torque to be driven.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

But if you want to ramp up the speed you want the volume of the 3mm.

I chose 3mm when i built my prusa i2 as at the time there was plenty around.
So far all the abs, pla, nylon and nynjaflex ive usec has been available in 3mm.
Certainly had no pronlems getting it. Or extruding it through the hotend.

The ultimaker 2 uses 2.85 and some of the filament sellers pass of 2.85 as 3mm.
Not much of a problem. The supplier i use sells proper sized 3mm.

Gordon.

Edited 1 time(s). Last edit at 04/05/2015 02:33PM by gordonendersby.

Thanks I think ill go for 1.75 and a j-head just got to decide what cold end parts to use.


thanks nikki

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A common misconception about printing with high flow rates is that 3mm filament is going to be better than 1.75mm. This makes intuitive sense, larger prints so use larger filament. However in reality 1.75mm filament can be melted significantly faster than 3mm filament, giving it a decisive advantage in flow rate. This is because 1.75mm filament has a much higher surface area per unit volume. As we increase filament diameter the surface area increases linearly, but the volume increases by a power of 2. This means that we can melt thinner filament much more quickly than thicker filament.

[e3d-online.com]

I think it is the ability to use a larger nozzle with 3mm that makes it ideal for larger prints. 1.75 you can only go up to like 1mm MAX, I think. 3mm can definitely go larger than that.

The larger the nozzle size, the more plastic you can lay down, the faster you can print.

While, yes, a thinner filament will technically melt faster than a thicker one, I'd bet the difference is negligible.

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greghoge.com

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I think that 1.75mm filament can be extruded more precisely at slower speeds. if you are pushing out a constant volume/s, the 3mm would have to move slower than the 1.75mm. also, get an E3D V6 Bowden hotend. This printhead is AWESOME!! Granted, I have only used it and an Anubis clone. Discount code "reprap" if buying from filastruder.

[Hi, this is my first post on this Reprap forum]

There are those who insist that 3mm is superior, because the effect of the tolerance on the filament diameter is smaller with 3mm than 1.75mm.

A ±0.1mm tolerance on a nominally 1.75mm filament produces a 23% variation in volume, whereas the same ±0.1mm tolerance on a nominally 3mm filament produces a 13% variation in volume.

On the other hand, people say 1.75mm is better for a Bowden setup, but I'm not sure why that would be.

No matter the tolerance, because you're meant to calibrate your extruder and your flow properly, so the output is constant, whatever the diameter of the filament. Otherhand, the melted filament expands. The smaller the diameter, the less friction, the less spring effect, the less tension applied to the printhead.

Edited 1 time(s). Last edit at 04/07/2015 04:37AM by Zavashier.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Zavashier
No matter the tolerance, because you're meant to calibrate your extruder and your flow properly, so the output is constant, whatever the diameter of the filament. Otherhand, the melted filament expands. The smaller the diameter, the less friction, the less spring effect, the less tension applied to the printhead.

Except that thinner filament is compressed easier so when using a bowden you will experience a little bit more spring.

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I was talking of the spring effect of the filament itself, like when the end of the spool comes

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

@Zavashier: I think it is the other way round. You calibrate your extruder by E Steps per mm on the input side. So the only thing yout slicer knows is how much is going in the extruder. And therefore the slicer thinks the filament ha a constant diameter.

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Zavashier
No matter the tolerance, because you're meant to calibrate your extruder and your flow properly, so the output is constant, whatever the diameter of the filament. Otherhand, the melted filament expands. The smaller the diameter, the less friction, the less spring effect, the less tension applied to the printhead.

I'm talking about variation in diameter within a spool, not spool to spool. The latter can be calibrated out, while variations in the diameter (which means variations in volume per unit of extrusion feed) cannot. [Having said that, I could imagine a system that measures the filament as it goes in to the extruder to allow on-the-fly compensation.]

A system able to measure with precision the diameter of the filament in real time should cost at last like 2 or 3 repraps. Otherhand, actualy no firmware can manage filament variations on the fly. Anyways, filament variations should be within a small percentage (or change your provider/brand), that won't affect much the print dimensions. You must admit the FDM technology has its limitations.

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danielis
@Zavashier: I think it is the other way round. You calibrate your extruder by E Steps per mm on the input side. So the only thing yout slicer knows is how much is going in the extruder. And therefore the slicer thinks the filament ha a constant diameter.

Actualy, I don't calibrate my extruder like you say. Obviously, it's just the half way of a proper calibration. First, I calibrate the steps per mm, it's the input calibration. Then I enter the measured filament diameter (an average value within the 2 first meters of the spool). Then, and that's what most of people does not do, I calibrate the fused filament output to adjust the flow value of the slicer to get the expected output dimensions. That's what I call calibrating properly an extruder.

If you do as so, you will notice than the difference of diameter within a spool, is only a fiew compared to the expansion of the fused filament which is in my experience around 20%. That's why the diameter variations of the filament is no big deal.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Slic3r has a field to use volumetric extrusion values and the tooltip indicates it is supported in recent Marlin.

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Zavashier
A system able to measure with precision the diameter of the filament in real time should cost at last like 2 or 3 repraps. Otherhand, actualy no firmware can manage filament variations on the fly. Anyways, filament variations should be within a small percentage (or change your provider/brand), that won't affect much the print dimensions. You must admit the FDM technology has its limitations.

I'm not so sure. I think a cheap shadow projection measurement system could be built using a linear image sensor, simple plastic optics and an LED. Alternatively, a couple of pinch wheels coupled to a hall effect sensor might make a good measurement device.

For sure we'd need new firmeware that would adjust the extrusion rate based on these measurements. The firmware would have to take account of the distance between the measurement device and the nozzle.

Edited 1 time(s). Last edit at 04/11/2015 12:06AM by JonS.

Yep, we need just a firmware to manage that values. But do that small variation percentage on the filament worth the investment ? The diameter variation of the filament is less than 3%. Otherwise, the expansion of the fused filament is about 20%. I guess it anihilates the diameter variation factor.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Zavashier
Yep, we need just a firmware to manage that values. But do that small variation percentage on the filament worth the investment ? The diameter variation of the filament is less than 3%. Otherwise, the expansion of the fused filament is about 20%. I guess it anihilates the diameter variation factor.

±0.1mm on nominally 1.75mm results in a 23% variation in volume. That's a lot.

2.3% not 23%

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Ralph.Hilton
2.3% not 23%

Nope. Do the math. It scales with the AREA of the filament cross-section, which is proportional to the square of the radius.

1.75mm Filament

Nominal cross-section = pi() * (1.75/2) = 2.41mm²
Min. cross-section = pi() * (1.65/2) = 2.14mm²
Max. cross-section = pi() * (1.85/2) = 2.69mm²

Variation from nominal in percent = 100* (2.69 - 2.14) / 2.41 = 22.9%

3mm Filament

Nominal cross-section = pi() * (3/2) = 7.07mm²
Min. cross-section = pi() * (2.9/2) = 6.61mm²
Max. cross-section = pi() * (3.1/2) = 7.75mm²

Variation from nominal in percent = 100* (7.75 - 6.61) / 7.07 = 13.3%