Additive manufacturing — 3D printing in metal and the craft's future
How powder-based laser technology supplements material-removing machining
All the processing you have read about so far is subtractive — it removes material from a larger block to reach the desired shape. Additive manufacturing does the opposite: the part is built up, layer by layer, directly from a digital 3D model. In the metal industry, the most common variant is powder-based laser technology, known by names such as SLM (Selective Laser Melting) and DMLS (Direct Metal Laser Sintering).
§How powder-based metal printing works
With SLM and DMLS a thin layer of fine metal powder is spread over a build plate and a laser then melts the powder precisely where the part should have material in that layer. The build plate is lowered slightly a new layer of powder is laid out and the process is repeated until the entire workpiece is built up. Both designations cover in practice the same basic principle — both processes melt the metal powder completely although DMLS originally described the process as sintering and SLM as melting. The process takes place in a chamber with controlled inert atmosphere so the melted metal does not react with the air.
§What materials and what are they used for?
Typical materials in metal printing are aluminium, stainless steel and titanium. The technology is used especially early in a development process — for concept models and functional prototypes — but also for tools, complex geometries that would be difficult or impossible to mill, and for industries such as medico where custom-made, complex shapes are sought. On the other hand, metal printing is typically slower and more expensive per part than traditional machining for larger series of simpler geometries.
| Property | Subtractive machining (CNC) | Additive manufacturing (SLM/DMLS) |
|---|---|---|
| Principle | Removes material from a block | Builds material up layer by layer |
| Best for | Series simple to mid-complexity geometries | Complex geometries, prototypes, few pieces |
| Post-processing | Often finished directly from the machine | Often requires heat treatment and post-processing |
| Material utilisation | Chips are waste that should be recycled | Only what is used in the part is melted |
§The industrial technician's role in new technology
Additive manufacturing does not replace the industrial technician's core competency — it builds on it. Understanding of materials, tolerances, drawings and measurement techniques is just as necessary when a printed part is to be post-processed and inspected as when it is manufactured from scratch on a CNC machine. Many companies that invest in metal printing specifically seek experienced technicians to operate the technology and post-process the printed parts, because it requires the same understanding of material and precision that the rest of the craft is built on.
§Why it is worth keeping up with
Even if your workplace does not have a metal printer today the technology is winning ground in parts of the industry especially where complex geometries or small series make traditional machining expensive or impossible. Knowing the principles — and knowing when 3D printing and CNC are each the best choice — makes you a more versatile employee regardless of which machine you end up working at.
“Print builds up the part, CNC cuts it — but it is still the same craftsmanship about material, dimensions and tolerance that determines whether the result works.”