I just uploaded a model of a small solid wall pipe. Shapeways gave me a price of $2 for strong flexible (nylon). 3D hubs gave me prices ranging from a $6 to $126 in ABS/PLA. In a previous round of getting quotes for a larger model (a router bracket for a CNC machine), shapeways came in at $45, a local guy came in at $240, and everybody else was in-between.
@Eric_Davies That’s surprising. I thought their startup cost was $5-$10.
It depends on what the hub owner puts on as their price per centimeter cubed
I think the 3D Hubs setup goes by the volume of the model. The actual amount of material isn’t figured, it varies by infill density, surface area and thickness of the surface build. The estimation process limitations are annoying. It can’t figure out supports, which can vary a lot by model. More complex models for a given volume can also yield more material used in the part and more time building the part.
You can calculate the colume of a 3D model just from the triangles. Just form a tetrahedron from each triangle by adding (0,0,0) as fourth vertex. Then sum up all volumes of these tetrahedrons that you computed by using the cross product (while keeping negative volumes from back sides)
Remember, this only works with fully closed meshes.
@Carl-Philip_Hansch Not remotely what is being asked here
So here is an update…
I posted the same question on the 3D Hubs forum.
“First of you need to know, what density is and how to calculate with it:
Density is a factor, that describes the mass, that a specific volume of material has. Therefore it’s measured in weight / volume, which is mostly listed as g/cm3.
cm3 does mean cubic centimeters.
3d hubs calculates it’s prices related to the printed volume since that’s what they know about the order, when just the 3d model is available as source of information.
To calculate the weight of one cubic centimeter you will need to know the density of the material, that you’re using. Most plastics have a density between 1,1 and 1,2 g/cm3. Just Polyesters and exotic materials are more dense with a density of 1,4 g/cm3.
Special material blends, like mixtures with wood or other fibres, or metal composites can highly vary in density, look it up on the producers website.
Next up you need to know, how to calculate the weight (or volume) of a random amount of plastic when knowing the density.
Density = Mass / Volume
Mass = Volume x Density
Volume = Mass / Density
Given a spool has 1000g of ABS and costs 25$ then it contains around 833 cm3 of material and has a value of 0,03$ per Cm3.
Taking the 3rd equation:
Volume = Mass / Density = 1000g / 1,2 g/cm3 = 833,3 cm3
Spool cost / spool volume in cm3 = cost per cm3
25$ / 833 cm3 = 0,03$
If you cant find the density of pure plastics (no composites) then you can look it up on Wikipedia. A density of 1,2 g/cm3 was probably a little too high for ABS, but should be OK for an example calculation.
As you can see you can even make quite a big profit (only considering material cost) when charging around 0,2-0,5$ per cm3.
Aiming for around 5-15 times the material cost is a good starting point as you also have to include the working time, investment into a 3d printer, the power consumption, other costs for replacement parts, spares, the initial investment into a set of spools to be prepared for orders,…
You also have to take the 3dHubs fee into account, when setting your prices, just Google a math guide for calculating with percentages, if you need some help on that.
You will have to take a closer look into each model when someone is setting up an order, the prices, that 3d Hubs calculates is for 20% infill. Given the customer requests a more solid print, then you will have to adjust the price to what you think is reasonable anyways.
Also model complexity and variety of printer settings etc. make it nearly impossible to create a tool, that gives out fair prices all the time, the method, that 3d hubs uses is a very general one to have at least a basic idea of how much the model should cost.”
Thoughts?