In any production process, the choice of the material not only is the key to creating a suitable and durable product but also ensures successful fabrication. Moreover, the cost of the material can have the most significant impact on the final cost of the product.
FDM, or fused deposition modeling, is the most popular material extrusion process in 3D printing. In almost all cases, it uses thermoplastic materials as feedstock in long filaments that are rolled up and packed in spools.
Generally speaking, the cost of filament material for FDM is mostly affected by the type of polymer used. The overall quality of the material, which includes color and dimensional stability, is also decisive in the final cost of each filament spool.
In any project, material selection is one of the more complex part of product development.
Here’s an example of what that analysis could look like.
Objective: What is to be maximized or minimized?
Free variables: What parameters of the problem is the designer free to charge?
Examples of common constraints and objectives:
- Electrically conducting
- Optically transparent
- Corrosion resistant
- Non-restricted substance
- Able to be recycled
Must meet a target value of:
- Fracture toughness
- Thermal conductivity
- Service temperature
- Thermal losses
- Electrical losses
- Resource depletion
- Energy consumption
- Carbon emissions
- Environmental impact
- Water use
A lot of criteria have to be met or exceeded in terms of mechanical, thermal, chemical, electrical characteristics, environmental impact over the life cycle, etc. Last but not least material cost.
Now, nature teaches us the lighter the better – lightweight is a must, not just a feature.
And so should any project design approach be. And lightweight is primarily achieved by design and secondarily by material selection.
Here’s a graphical representation of the concept of mass-specific cost in a strength-density chart.
As it can be seen, the higher the mass-specific strength, the higher the material costs.
Now, usually a price is given per a given sales unit €/kg , €/liter, €/m², €/m³), not on a density-specific strength metric. This makes any trade-off process incomprehensible.
Usually, this kind of theoretical and application-specific work for mass-produced items is done by highly specialized people and organizations. There exists an entire industry around material selection strategies, data and material testing.
One of the more common questions at this point in our reasoning is: Why is it that many super costly high-performance materials are used even though apparently you would be cheaper off using more of a much cheaper material?
And, as you probably expect, the answer is: There are weight penalties to be considered during the life cycle.
For the first years of open-source and open-material 3D printing, we had ABS, amorphous or low grade semi-crystalline PLA around 30 MPa tensile strength. Now lots of specialized and performance filaments are flooding the market. For the first time in 3D printing history we have to ask ourselves: what material, grade, formulation do I use?
In our daily life of prototyping and small production batches, most of us rely on experience, material availability, manufacturability and often enough on trial-and-error. But when it comes to 3D printing with thermoplastics, we may have to think twice about what the best material choice is – the cheap one or the performance one.
Example: a 20€/kg PLA with 25 MPa and a 70€/kg with 100 MPa
The more expensive material is 4 times faster to print AND 12% cheaper, for a given strength target (assuming they have same density).
In 3D printing, time is your biggest penalty, which in turn is direct proportional to the volume extruded at a given time unit. So the stronger the material, the less the volume, the faster the print and the lighter the final product.
FormWerk Founder & CEO