How do you calculate the material cost for an ABS CNC job?

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1

I have a Solidoodle 3 that uses 1.75mm ABS filament. I know the cost of a 1kg roll but I haven’t found any information on the approximate length of filament on a roll. Repetier gives the filament requirement in length (both in millimeters and cubic centimeters) but it doesn’t say anything about weight.

If I knew the estimated weight I could just divide 1kg by the weight of the object, then multiply it by the price of the roll (ex. a 25g object divided by 1kg times $31 per kg would cost $1.24). If I knew the length of the filament on the roll I could divide the length required for the print by the length of a roll and multiply by the cost of a roll.

But since filament is sold by weight and the estimates are in length I honestly have no idea how to calculate the cost. For example, an object I loaded up was estimated to require 113178.9mm. I don’t know how many rolls that would be but I know it would be more than one as that’s about 371 feet (I think. 113178.9/25.4mm per inch/12 inches per foot, can someone more mathematically inclined than me check this?) and I don’t think there’s that much on a 1kg roll. Estimated weight was never mentioned, however.

I’ve hit Google pretty hard and couldn’t find an approximate length for a roll.

2

A quick search gives ABS a density of 1.05g/cm^3 = 1.05 mg/mm^3

From that you can calculate the weight of one mm of the wire.

Assuming a round wire:
Weight of one mm: (0.875 mm)^2 * 3.14 * 1 mm * 1.05 mg/mm^3 = 2.52 mg

For longer pieces you might want to use more decimals to increase the accuracy

so 1 g is about 396 mm

3

I found on a german page that ABS plastics have a weight of 1.07g/cm3
http://www.hug-technik.com/inhalt/ta/kunststoff.html

So, 1cm3 equals around 1/[(0.175cm / 2)^2*pi] = 41.5751687282cm

So a roll of 1000g (1kg) equals 1000g/1.07 = 934.5794392523cm3
And that equals 934.5794392523 x 41.5751687282cm = 38,855.29787682cm = around 388.5m or 388552mm

So you would need almost 0.3 rolls of filament

It might be posible that the 1.07g/cm3 aren’t constant (I think I saw on a diverent page 1.05g/cm3) and I dont know how color affects the weigth. The math should be right I think

Edit: Ohh, didn’t see Morio’s Post

4

Thank you, guys. This helped me out a lot. Pricing is something I’ve always had trouble with but my dad’s boss suggested 30% over production cost. With that formula I was able to make a spreadsheet template where I just have to enter the length in millimeters and now it automatically calculates the production cost and what I should charge for it, plus when I change to a new roll of filament it will even let me keep approximate tallies on how much I have left.