Resons behind filament sizes?

Hi.
What is the reasoning behind 3mm and 1.75mm? Those are not imperial standard. I guess one could make custom filament size and print with it too.
Why not 1/16 or 5/64?

1.75 mm is about as thin as can easily be pushed into an extruder without the filament bending, kinking, and breaking. Any smaller would just be more issues with an extruder.

And the 3mm? I suppose that was just the size already available for other FDM printers at the time of Reprap's birth?

And as an American, I've been using imperial measurements my whole life, extensively at work also. I know my conversions like the back of my hand, yet even with all this:
-Metric is better.

Metric is a worldwide standard, and S.A.E. is just bleh.

Inches/.0394=The way to be.

Inches/.03937 is much closer...
Or Inches*25.4 is EXACT

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

rhmorrison Wrote:
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> Inches/.03937 is much closer...
> Or Inches*25.4 is EXACT

Very true. For the machines I work on at work that level of accuracy is beyond the tolerances of our equipment.
But I should not forget that some people have to convert for precision work. ;-)

Edited 1 time(s). Last edit at 03/07/2013 10:47AM by xclusive585.

konstantin.neo Wrote:
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> Hi.
> What is the reasoning behind 3mm and 1.75mm? Those
> are not imperial standard. I guess one could make
> custom filament size and print with it too.
> Why not 1/16 or 5/64?

3mm filament was originally used in plastic welding equipment for automotive use etc. this comes as 3mm in a lot of different materials, many more than most people with 3D printers have tried.
Plastic welding rods and spools are very common and so Reprap used the 3mm version as a convenient available material (you can get 4mm, triangular, and other shapes/sizes).

1.75mm was done later as a dedicated size for 3D printing, some 3D printers also use 1.3mm and under 1mm has been discussed.

I had a batch of polycarbonate made, is was about 1.55mm, as long as it's a constant diameter and round (not oval) and it's a thermoplastic you should be able to try to use it for 3D printing.

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[richrap.blogspot.com]

I am soon going to be joining the 3d printing community and was is there any advantage to 3mm or 1.75mm. All the print quality change with either?

I'm new to 3d printing as well (still putting together the printer), but in my research the biggest difference I could find is that the smaller volume of the 1.75mm provides the extruder with more "steps" per unit volume of plastic extruded. This allows more accuracy/control in the amount of plastic being extruded and I think helps enable the machine to be able to more reasonably print thinner layers. I don't have any experience on this, but it does make sense if you consider the math. Maybe someone with experience with both sizes will chime in.

konstantin.neo Wrote:
-------------------------------------------------------
> Hi.
> What is the reasoning behind 3mm and 1.75mm? Those
> are not imperial standard. I guess one could make
> custom filament size and print with it too.
> Why not 1/16 or 5/64?

Because the reprap project originated in the UK where we don't use these funny units! (apart from for driving.....)

...
> Why not 1/16 or 5/64?

Because those are horrible units, to be fought at every turn.

"Because the reprap project originated in the UK where we don't use these funny units! (apart from for driving.....)"

Exactly how many stones did you say you weigh?

In the US, if we're not using metric, we use mils (0.001 inch) for precision work. Fractional values are usually left to carpentry, low grade machine work, or just for "common" speak. So IF filament was made to those specs, it would likely be sold as 100 mil, 200 mil, etc., not as fractional inches.

Edited 1 time(s). Last edit at 03/08/2013 07:08PM by xiando.

cobrageek Wrote:
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> I'm new to 3d printing as well (still putting
> together the printer), but in my research the
> biggest difference I could find is that the
> smaller volume of the 1.75mm provides the extruder
> with more "steps" per unit volume of plastic
> extruded. This allows more accuracy/control in
> the amount of plastic being extruded and I think
> helps enable the machine to be able to more
> reasonably print thinner layers. I don't have any
> experience on this, but it does make sense if you
> consider the math. Maybe someone with experience
> with both sizes will chime in.

This is not really an issue since you can use geared extruders (Wades type or planetary) with a high gear ratio to increase the steps per mm. A more important issue is that 3 mm feed would require more force to extrude than a 1.75 mm feed by a ratio of around (3/1.75)^2 ~ 3 and so it's more likely to have issues with the filament drive gear. Since the smaller feed don't require as much force in addition to having higher steps per mm, you can use smaller and lighter extruders with it. These can be gearless direct NEMA 17 extruders of smaller geared motors like the PG35. Lighter extruders can move faster than heavier ones.

> This is not really an issue since you can use
> geared extruders (Wades type or planetary) with a
> high gear ratio to increase the steps per mm. A
> more important issue is that 3 mm feed would
> require more force to extrude than a 1.75 mm feed
> by a ratio of around (3/1.75)^2 ~ 3 and so it's
> more likely to have issues with the filament drive
> gear. Since the smaller feed don't require as much
> force in addition to having higher steps per mm,
> you can use smaller and lighter extruders with it.
> These can be gearless direct NEMA 17 extruders of
> smaller geared motors like the PG35. Lighter
> extruders can move faster than heavier ones.


So if you have a machine that can use both and has the Wades gear it makes no difference which one? Prices for the filament sizes are pretty close. My main concern was for accuracy of the print, if any differences. Speed can be slower if accuracy is good.

1.75mm (0.070") is also what Stratasys machines have been using since the mid-'90s, so there may have been a bit of "well, it worked for them..."

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[haveblue.org]

Handheld plastic welding guns have been using 3mm and 4mm filaments since before the DIY printer boom, so it's natural to be compatible with them.

... when I joined RepRap 2006 all known handheld plastic welder guns used 4mm filament (mostly from Orbitech) - it was a matter of some years (and many requests) to change Orbitech to make 3mm filament too ... with 1.7mm filament this was much faster/easier, as we've received some momentum

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Viktor
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