How long is a 1 kg 1.75mm/3mm spool?

[Guy Dascalu]

Just found http://www.faberdashery.co.uk/ site and wondered which one
is cheaper, makerbot's or faberdashery's plastic...
so how long is a 1 kg abs spool? 1.75 and 3mm

Thanks
Guy

[Whosawhatsis]

I don't think anyone's gone to the trouble of measuring one, but we
can estimate it with math. I quick google search tells me that ABS has
a density of 1.04 grams per cubic centimeter, so a 1kg spool should be
about 962cc. The nominal cross-sectional areas of 1.75mm and 3mm round
filaments are .02405 and .07069 square centimeters, respectively.
Divide the volume by those areas and you get a length of 39976
centimeters for 1.75mm and 13603 centimeters for 3mm.

Actual lengths should be more than this because the filament has a
certain tolerance in its diameter, and resellers like MBI will request
that the filament be under rather than over the specified diameter, so
that it is less likely to jam an extruder. It's also a common practice
when selling goods in lots of a specific weight to err on the side of
selling more than the specified weight rather than less, so that your
customers to not feel cheated if they go to the trouble of checking
the weight.

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[Bill Culverhouse]

If the Faberdashery has acurately measured the weight of 100m

for 3mm at 880grams per 100m I get 113.6363m in 1000 grams.

 

At 1.75mm and 300grams per 100m I get 333.33m in 1000grams.

 

I could have something screwed up in the maths but its close to

whosa's numbers.

 

-b

[Whosawhatsis]

In both cases, your number for the length is smaller. This could be
accounted for by assuming, for example, that the 3mm filament weighed
at 880 grams per 100m actually had a diameter closer to 2.7mm, which
is probably about the smallest filament you want to use in a hot end
designed for 3mm filament, and they could be selling 2.7mm filament as
3mm. Keep in mind that you can print about 10% more stuff with 100m of
3mm filament as with 2.7mm filament. OTOH, when the filament is sold
by weight (which is proportional to volume), you get the same total
volume of prints no matter what the diameter is (as long as it's not
so far out of spec that you have to throw it away).

[Bill Culverhouse]

Or that 880 grams is a rounded off number.

 

Or that there are many flavors of ABS and probably many densities.

 

And lastly, Faberdashery doesn't sell ABS, only PLA. I'm

reasonably certain there is a difference in density between ABS and PLA.

 

-b

 

[Whosawhatsis]

Ah. I hadn't checked the site, so I didn't know that bit, but yes, that's definitely the explanation. PLA is about 1.25 g/CC, so that would explain the discrepancy pretty perfectly.