Ok here's a question for the masses.

3D Printing
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Ok here’s a question for the masses. Maybe someone with mad math skills can help me out? My brain isn’t working right now and I know the answer is going to be obvious when I hear it.

Here goes…

I’m trying to figure out a way to calculate the per cubic centimeter cost of filament. I want to teach my students how to calculate the price of desktop manufacturing so we can compare the cost of different materials, compare the cost to other prototyping services, and determine the best materials for a particular budget/project.

For example…

If I buy a spool of 1.75mm Proto-Pasta for $69.99 for 1 KG how can I calculate the per cubic centimeter cost based on this info. This way if I have a model that is estimated to use 1256 cubic centimeters I could determine the cost of doing the print before doing it.

In the past I have printed thing for friends but I just weighed the part after and calculated the weight with the per gram cost. This is easy to do but requires I print before finding a cost.

Any help would be greatly apreciated.

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2

You can calculate by meters or cc3. The slicer give you both aproximatly before printing. In the gcode end you can find both

3

Then you can take or measure filament density and convert volume/length to cost.

4

I think there is an app for that.

5

You just need to find the volume of the roll of filament. You need the spec sheet for the density which is usually around 1.2 g/cm3 for standard PLA. Then you just use a simple formula (density=mass/volume). We know the mass and density so 1.2g/cm3=1000g/Xcm3 and X=833.333. If you spent $70 for this spool that amounts to $0.084 per cm3. Then if your model is 1256 cm3 you just do 1256*0.084 for a price of $105.504 for the filament costs.

6

Cura will do this automatically based on estimation if you tell it the price and density.

7

you could use the volume of a cylinder…the filament is round and you know the length?

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@jerry_arnold_jdawgsw Since the plastic is melted and then hardened you need the density of the original.

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So how many mm or meters in 1 kg of filament #mathishard

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@Adam_Steinmark the diameter varies? it’s a long, long skinny cylinder

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@Brook_Drumm 1kg of 1.75mm ABS is about 400m long or 960 cm^3, 1kg of 1.75mm PLA is about 330m long or 800cm^3. (http://www.toybuilderlabs.com/blogs/news/13053117-filament-volume-and-length but you can do the math yourself if you want)

Yes, you get more “bang for your buck” from ABS, assuming 1kg costs the same for either filament. Where you really get screwed is metal-fill filaments… 0.5kg of filled filament is not much volume at all :slight_smile:

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@jerry_arnold_jdawgsw I specifically said density.

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Did I not answer everything concisely?

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@Tim_Lathouwers I was addressing everyone but I did answer both questions.

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OK let me add this into the mix. What sparked this thought was we were thinking of registering on 3D Hubs. This would give the students some experience on a business side of things (quality control, working with the numbers etc.) and would give us a fundraising opportunity.

The reason the whole cost per 1cm^3 came up is that when registering a printer it asks to input the filament types that we can print in and what the 1cm^3 cost would be.

I guess if I already know the density of a material t would be fairly easy to calculate. I’m wondering more about the unknowns. Like I have no clue what the density of Proto-Pasta or bronze fill etc. I mean I know what the cost per 1kg is but the weight per mm is much more so it would be more expensive per cm^3. Correct?

I guess I’m really, really just trying to understand the math behind it.

16

Also read this: http://www.instructables.com/id/Cheaper-3D-Prints/

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@Michael_Spano_Jr_Ama They should tell you on the website. Bronzefill is 3.9g/cm3. I don’t know which Proto-pasta filament you have.

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@Eddy_Castro That only works for websites that offer 3d print services like Shapeways who charge based on complicated algorithms not like 3D Hubs that just charges based on total volume + startup machine costs.

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I know, but because the students have to compare it with other prototyping services…

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@Eddy_Castro Shapeways will always be more expensive