Manufacturing processes compared: which one fits your part?
A practical comparison of 16 manufacturing processes: what each one is good at, what it costs, the tolerances it holds and how to prepare your STEP file for it.
Every manufacturing process has a sweet spot: a range of quantities, tolerances and shapes where it is the cheapest way to get a good part. The same STEP file can usually be quoted for several processes, so knowing their strengths lets you pick the right one and adapt the design to it.
The processes side by side
| Process | Typical tolerance | Quantities | Lead time |
|---|---|---|---|
| CNC milling (3-axis) | ±0.1 mm general, ±0.02 mm on selected features | 1 to about 1,000 | 3–15 working days |
| 5-axis CNC machining | ±0.05 mm general, ±0.01 mm on selected features | 1 to a few hundred | 5–20 working days |
| CNC turning | ±0.05 mm general, ±0.01 mm on diameters | 1 to 100,000+ | 3–15 working days |
| Wire and sinker EDM | ±0.01 mm, down to ±0.002 mm | 1 to a few hundred | 5–20 working days |
| Laser cutting (sheet metal) | ±0.1–0.2 mm | 1 to 10,000+ | 2–10 working days |
| Sheet metal bending | ±0.2 mm per bend, ±0.5° angles | 1 to 10,000+ | 3–10 working days |
| Waterjet cutting | ±0.1–0.25 mm | 1 to a few thousand | 2–10 working days |
| FDM 3D printing | ±0.2–0.5 mm | 1 to about 100 | 1–5 working days |
| SLA resin 3D printing | ±0.1–0.2 mm | 1 to a few hundred | 2–7 working days |
| SLS and MJF 3D printing | ±0.3 mm or ±0.3% of the size | 1 to several thousand | 3–7 working days |
| Metal 3D printing (DMLS/SLM) | ±0.1–0.2 mm as printed; machined faces as for CNC | 1 to a few hundred | 7–20 working days |
| Injection moulding | ±0.1 mm for small parts, depends on material shrinkage | 1,000 to millions | 4–10 weeks for the mould, then days |
| Die casting | ±0.1–0.3 mm as cast | 5,000 to millions | 8–16 weeks for the die |
| Investment casting | ±0.1 mm per 25 mm | 50 to tens of thousands | 6–12 weeks |
| Sand casting | ±1–3 mm | 1 to thousands | 3–8 weeks |
| Aluminium extrusion | EN 755-9, roughly ±0.15–0.3 mm on small profiles | Hundreds of kilograms and up | 4–8 weeks for a new die |
How to choose
Start from the quantity
For 1 to a few hundred parts, processes without dedicated tooling win: CNC machining, sheet metal, 3D printing. From a few thousand parts, tooled processes such as injection moulding, die casting and extrusion become cheaper, because the tooling cost is spread over many parts and each part takes seconds.
Then the shape
Flat parts with holes are cheapest by laser or waterjet cutting. Thin enclosures and brackets are cheapest in bent sheet metal. Round parts belong on a lathe. Solid blocks with pockets and precise holes are milled. Shapes that cannot be reached by a tool at all, such as internal channels, need 3D printing or casting.
Then the requirements
Tight tolerances and fine finishes point to machining, or to machining after casting or printing. Strength and fatigue favour machined or forged metal over printed or cast. Heat-sensitive materials favour waterjet over laser.
One STEP file, many processes
The STEP file is the common language of all these processes. A machinist imports it into CAM, a moulder uses it to design the tool, a 3D printing service slices it, a sheet metal shop unfolds it. What changes is what you must design into the model and what you must write on the drawing.
| Process | What the model must include | What the drawing must add |
|---|---|---|
| CNC machining | Inside radii as cut, tap drill holes | Threads, fits, tolerances, finish |
| Sheet metal | Constant thickness, bend radii, reliefs | Material grade, bend direction, hardware |
| 3D printing | Wall thickness, drain or escape holes | Material, orientation-critical faces |
| Moulding and casting | Draft, uniform walls, machining stock | Datums, machined faces, cosmetic faces |
Read the STEP file guide for export settings and the drawing guide for the sheet.
Machining
CNC milling (3-axis)
A rotating cutter removes material from a clamped block while the machine moves in X, Y and Z. It is the workhorse of prototype and small-batch metal parts: brackets, plates, housings, fixtures and mould inserts.
Main benefit: No tooling cost, so a single part is affordable. Watch out for: Inside corners always keep the radius of the cutter.
5-axis CNC machining
The cutter or the table also tilts and rotates, so the tool can reach five sides of the part and work at angles in one clamping. Used for complex housings, impellers, medical parts and anything with angled features.
Main benefit: Many faces machined in one setup, so features line up accurately. Watch out for: Machine hour rates are typically 30–80% higher than 3-axis.
CNC turning
The part spins while a stationary tool cuts it. Turning makes round parts quickly and accurately: shafts, pins, bushings, spacers, fittings and knobs. Lathes with live tooling can also drill and mill flats.
Main benefit: Fast and cheap for round parts, especially from bar stock. Watch out for: Only features around the turning axis are cheap; flats and cross holes need live tooling or a second operation.
Wire and sinker EDM
Electrical discharge machining removes conductive material with sparks instead of a cutter. Wire EDM cuts through-profiles with a thin wire; sinker EDM burns a shaped electrode into the part. Both make sharp inside corners and cut hardened steel.
Main benefit: Inside corners as small as the wire radius (often under 0.1 mm). Watch out for: Slow: removal rates are a fraction of milling.
Sheet metal
Laser cutting (sheet metal)
A focused laser beam cuts flat shapes from sheet or plate. It is the cheapest way to make flat parts with holes and contours in steel, stainless and aluminium, and it is the first step for most bent sheet metal parts.
Main benefit: No tooling, fast and cheap per part. Watch out for: 2D only (bending is a separate step).
Sheet metal bending
Flat laser-cut blanks are folded on a press brake into enclosures, brackets, chassis and covers. Bent sheet metal is light, stiff for its weight and cheap in batches.
Main benefit: Light and stiff parts from cheap sheet material. Watch out for: Tolerances add up over several bends.
Waterjet cutting
A very high pressure stream of water mixed with abrasive cuts almost any flat material, including thick metal, stone, glass and composites, without heating it.
Main benefit: No heat-affected zone, so material properties do not change. Watch out for: Slower than laser on thin sheet.
3D printing
FDM 3D printing
Fused deposition modelling melts a plastic filament and lays it down layer by layer. It is the cheapest way to make prototypes, jigs, fixtures and one-off plastic parts.
Main benefit: Very low cost for one-off parts. Watch out for: Visible layer lines and weaker strength between layers.
SLA resin 3D printing
Stereolithography cures liquid resin with a laser or light source, one thin layer at a time. It gives the smoothest and most detailed printed plastic parts: visual prototypes, moulds, dental and medical models.
Main benefit: Smooth surfaces and very fine detail. Watch out for: Resins are more brittle than thermoplastics and can degrade in sunlight.
SLS and MJF 3D printing
Powder bed fusion prints strong nylon parts without support structures. Selective laser sintering (SLS) and HP Multi Jet Fusion (MJF) are used for functional prototypes, low-volume production parts, housings and clips.
Main benefit: Strong, durable nylon parts close to moulded properties. Watch out for: Slightly grainy surface (can be smoothed or dyed).
Metal 3D printing (DMLS/SLM)
A laser melts fine metal powder layer by layer into dense metal parts. It suits complex, lightweight and consolidated parts in aerospace, medical, tooling (conformal cooling) and motorsport.
Main benefit: Shapes impossible to machine or cast: internal channels and lattices. Watch out for: High cost per cm³.
Moulding and casting
Injection moulding
Molten plastic is injected into a steel or aluminium mould. After the tooling is paid for, parts cost cents and come out in seconds. It is the standard for plastic parts in the thousands to millions.
Main benefit: Lowest cost per part at volume. Watch out for: Mould costs from a few thousand euros (aluminium) to tens of thousands (hardened steel).
Die casting
Molten aluminium, zinc or magnesium is forced into a steel die at high pressure. It produces near-net-shape metal parts such as housings, brackets and covers in large volumes.
Main benefit: Thin walls and complex shapes in metal. Watch out for: Expensive dies.
Investment casting
A wax copy of the part is coated in ceramic, the wax is melted out and metal is poured into the shell. It makes accurate, complex parts in steels and superalloys that are hard to machine.
Main benefit: Complex shapes close to the final part. Watch out for: Wax tooling cost.
Sand casting
Metal is poured into a mould made of compacted sand. It is the cheapest way to make large or heavy metal parts in small quantities: pump housings, machine bases, manifolds.
Main benefit: Large parts possible. Watch out for: Rough surface and loose tolerances.
Aluminium extrusion
Heated aluminium billets are pressed through a shaped die to make long profiles with a constant cross section: heat sinks, frames, rails and enclosures.
Main benefit: Low die cost compared with casting or moulding. Watch out for: Constant cross section only.
Draw your own part
Drop a STEP file into DrawMyPart. It finds every body, asks you to confirm threads, fits and tolerances, and draws a sheet your manufacturer can build from.
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