3D printing is often seen as a very cheap and fast manufacturing method. But why is that, especially considering that producing a single item is often more expensive and time-consuming compared to other technologies? In this article, I’ll explain this phenomenon and outline why — and when — additive technologies can be competitive with traditional manufacturing methods.
A Few Words About Additive Technologies
These methods, also known as additive manufacturing, involve depositing successive layers of material. The most popular among them is FDM Technology (Fused Deposition Modeling), which builds parts layer by layer by extruding material through a nozzle heated to the appropriate temperature. It is the only method used for producing large-format parts. Next are technologies based on curing liquid material layer by layer (such as SLA, DLP, and PolyJet). These offer the best surface smoothness and detail accuracy, though printing large objects can be problematic with this approach. There is also powder-based technology, such as SLS and MJF, which involves fusing finely ground polyamide powder using a laser beam or heat.
It’s important to remember that none of the above methods is universal. Choosing the right technology for the specific application is essential to avoid unnecessary costs.
3D Printing vs Injection Molding
3D printing is most commonly compared to injection molding. The main difference lies in the mechanical strength of the parts — a 3D-printed component typically achieves around 30% of the strength of the same part made through injection molding using the same material. The key advantage of 3D printing is that it does not require production setup, such as creating an expensive steel injection mold. However, aside from the significantly longer manufacturing time per part, even the raw material for 3D printing is more expensive. A simple example is FDM filament — a plastic in the form of a precisely dimensioned wire on a spool — which is on average 20 to 100 times more expensive than the raw material used in injection molding.
That said, producing an injection mold for a small production run is rarely economically justified. The situation is even less favorable when a mold is needed to manufacture just a single item. Regardless of the part’s size, this will always be significantly more expensive—both compared to additive manufacturing and to subtractive methods like CNC machining. In summary, 3D printing is a viable alternative to injection molding for low and medium production volumes. The greatest cost savings for short runs are typically seen with small-sized components.
3D Printing or CNC Machining?
Another group of technologies commonly compared to 3D printing are subtractive methods — mainly milling, EDM (electrical discharge machining), and turning. In conventional machining, also known as subtractive manufacturing, parts are produced by removing material. The material is gradually cut away with a tool until the desired geometry is achieved.
Subtractive technologies often require the use of specialized tooling, especially for more complex geometries. They also demand carefully planned material fixturing and precise positioning of the tool relative to the workpiece. These limitations of conventional methods contribute to higher initial costs. For this reason, 3D printing of plastic components is often a much more cost-effective solution.
Even greater cost differences arise when the part has a complex geometry—especially if it requires the use of machines with more than three axes. A common example would be holes positioned on perpendicular axes. In three-axis machining, the tool remains in a fixed orientation. Subtractive technologies also do not allow for the creation of internal structures (such as channels), which are achievable with additive manufacturing methods.
In summary, 3D printing can be a viable alternative to CNC milling. However, much depends on the production volume, geometry, and required dimensional accuracy. Tolerances below 0.1 mm are still the domain of subtractive manufacturing.
When Is 3D Printing Not Worth Using?
3D printing is definitely not cost-effective when it comes to flat parts. Flat parts are those that can be fully defined by their outline shape and thickness. In such cases, cutting processes—typically waterjet cutting or laser cutting—are significantly cheaper. These technologies are commonly used to produce 2D parts and are not direct competitors to additive manufacturing. However, they should not be overlooked when selecting the most suitable production method.
These are very fast manufacturing methods, with lead times and costs that are not comparable to additive technologies. Producing flat parts using 3D printing is not economically justified. Generally speaking, 3D printing makes sense when the part would otherwise require the removal of a large amount of material.
