Additive manufacturing covers the processes that build a part by adding material, layer after layer, from a 3D model, whereas machining removes it. “3D printing” is the common name. The ISO/ASTM 52900 standard classifies these processes into seven families.
The most widespread technologies in the workshop are fused filament fabrication (FDM), where a thermoplastic filament is extruded, stereolithography (SLA), where a photosensitive resin is cured by a light source, laser sintering of polyamide powder (SLS) and multi jet fusion (MJF), as well as laser fusion on a metal powder bed, which processes 316L stainless steel, aluminium, titanium and some nickel alloys. The 3D file (STL, 3MF or STEP) is sliced into layers by slicing software, the part is printed, then post-processed: support removal, depowdering, sanding, heat treatment of metal parts, machining of functional surfaces. The orientation of the part in the build volume affects strength, surface finish and the need for supports.
Additive manufacturing suits rapid prototypes, one-off parts or small runs, shapes that are impossible any other way (internal channels, lightweight structures), jigs and tooling, customisation and spare parts. Its limits are the size of the build volume, surface finish, tolerances generally looser than machining and a high unit cost in large runs, where plastic injection moulding takes over. The guide 3D printing or CNC machining helps you choose, the one on the price of 3D printing details the costs, and the 3D printing page presents the suppliers.
In a quote request. Attach the 3D model (STL, 3MF or STEP), the quantity, the material or technology you prefer (or let the workshop propose), the tolerances and roughness expected, and the surfaces to be machined after printing. State the performance constraints (temperature, UV, chemicals), the finishes wanted (colour, paint, smoothing) and the print orientation if it is critical.