Sunday, February 2, 2014

Estimating Cost of 3D Prints in PLA



When I first decided to get a 3D printer, I had no real understanding of what it cost to operate. It's useful to be able to know what a part costs before you print it.

It turns out this is pretty easy. Repetier Host (and probably anything that uses Slic3r as the slicing tool) will output the length of filament, as well as the volume, that the print will consume. For example, the print below shows that it will need 3.5 cubic centimeters of PLA plastic to complete.



An internet search shows that the density of PLA plastic is 1.25 grams per cubic centimeter. A 1 kilogram (1000 gram) spool of PLA costs about $30.

Now we can set up a simple ratio:

1000 grams/$30.00 = 1.25 grams/ (dollars per cubic centimeter)

Dollars per cubic centimeter = 0.0375, or just shy of 4 cents. So the above sample print, at 3.5 cubic centimeters, would cost about (4 x 3.5) = 14 cents.

If your design does not require printed support scaffolding, you can also easily calculate what it will weigh. This is useful for robotics and RC models. 3.5 cubic centimeters x 1.25 grams per cubic centimeter is about 4.4 grams.




6 comments:

  1. This comment has been removed by a blog administrator.

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  2. Question:

    Did you mean to put 2000 grams and not 1000 grams? Since the spool is $30 for 2KG?

    Also, I've been trying to figure out a way to find a cubic centimeter price for more exotic filaments that don't have a well known density.

    For example:

    Proto-Pasta is 69.99 for 1KG.
    Is there a way I can cut off an amount and weigh and then plug this information into an equation to figure out the cubic centimeter cost.

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    1. Ah, I see the error you were pointing me at - you're absolutely right. I'll fix. Thanks!

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  4. Hi Michael - At the time of writing, the PLA I was buying was $30 per KG.

    If they don't publish the density, you could compute it if you have an accurate scale - if you have any friends who reload bullets, they will have one. Since you know the diameter of the filament, you could cut a known length, and treat it like a long skinny cylinder. That would let you compute volume with the standard cylinder volume equation - V = length * (pi * r squared), if memory serves. With a known volume you then can weigh it and calculate density.

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  5. I might just print a 1cm x 1cm cube at 100% infill, and weight the result. Should give you a fairly accurate density. This might use a little more filament, but you would likely cut off a fair bit to do the calculations anyway.

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