Choosing a Process
Last updated September 27, 2026
OpusFab offers five processes: CNC Machining (milling), CNC Turning, SLA resin printing, SLS nylon printing, and metal 3D printing (DMLS/SLM). The right choice depends on what your part needs to do. Work through the five questions below, then check the comparison table.
1. What is the geometry?
- Mostly round, symmetrical around one axis (shafts, pins, bushings): CNC Turning.
- Prismatic with flat faces, pockets, and holes (brackets, plates, housings): CNC milling.
- Complex organic shapes, internal channels, lattices, or interlocking parts: SLS in plastic or metal printing in metal.
- Fine detail and smooth surfaces (small text, sharp edges, cosmetic faces): SLA.
2. Does the part need to perform like the final product?
If the part will take real mechanical load, heat, or chemical exposure, material properties matter more than speed:
- CNC parts are cut from solid stock, so strength matches the raw material exactly.
- SLS nylon is tough enough for many functional uses, clips, brackets, ducts, but printed parts can have directional weaknesses along layer lines.
- SLA resins are more brittle and best kept to visual or light-duty parts.
- Metal printing produces dense metal parts for demanding applications where machining cannot reach the geometry.
Early concept models and fit checks do not need production-grade strength, so SLA or SLS will usually get you an answer faster and cheaper.
3. How tight are your tolerances?
- CNC machining holds ±0.05mm standard, with a Precision (±0.01mm) tier for parts that need it. Use CNC for precision fits and mating features.
- SLA, SLS, and metal printing all hold ±0.5mm standard for printed parts, with some shrinkage as parts cool.
If only a few features are critical, machine the part from solid stock: printed parts ship As Printed and are not post-machined to tighter tolerances. See Tolerances explained.
4. How many parts do you need?
Instant quotes cover 1 to 100 units per part. Within that range:
- One to ten units: 3D printing usually wins on cost and speed because there is no setup or tooling.
- Ten to one hundred units: compare directly. CNC unit prices drop with quantity and can undercut printing for simple geometries.
- Above 100 units, or multi-part assembly files: request a custom quote.
5. What is the budget and timeline?
3D printing has little setup cost, so single parts are cheap and fast. CNC costs more per part at quantity one because of programming and fixturing, but scales well. Metal printing is the most expensive option per part and is justified mainly by geometry that cannot be machined. Production speed (Standard or Expedited) is a batch-wide choice; see Production speed.
Parts that need a process we do not price instantly, such as injection moulding, extrusion, sheet metal, laser cutting, or silicone moulding, go through a custom quote.
Comparison table
| Process | Type | Typical materials | Surface | Standard tolerance | Strength | Best for |
|---|---|---|---|---|---|---|
| CNC Machining (milling) | Subtractive | Aluminium, steel, plastics | Smooth, tool marks | ±0.05mm | Full stock strength | Functional, precision prismatic parts |
| CNC Turning | Subtractive | Aluminium, steel, plastics | Smooth, tool marks | ±0.05mm | Full stock strength | Shafts, pins, round parts |
| SLA | Additive (resin) | Standard, Tough, Wax resins | Perfectly smooth, injection-moulded feel | ±0.5mm | Low, brittle | Visual prototypes, fine detail |
| SLS | Additive (nylon powder) | Nylon | Textured matte, stronger than SLA | ±0.5mm | Good, tough | Functional plastic parts, complex geometry |
| Metal printing (DMLS/SLM) | Additive (metal powder) | AlSi10Mg aluminium, 316L stainless | Rough matte, As Printed only | ±0.5mm | Near full metal strength | Complex metal parts CNC cannot reach |
Printed parts ship in the raw As Printed finish only; finishes such as bead blast, anodising, powder coating, and PVD apply to CNC parts. CNC machining and sandblasting of printed metal parts are planned down the track. Maximum build volumes: SLA Standard Resin (9400) up to 1700 x 800 x 600 mm; SLA Tough Resin (black) up to 800 x 600 x 600 mm; SLS nylon up to 450 x 300 x 300 mm; SLM aluminium or stainless steel up to 420 x 420 x 450 mm. Larger parts can be split and bonded, or quoted for CNC.
For the full material catalogue, see Materials overview; the quote editor dropdowns always show the current live list.
Still not sure?
Upload the part and let the quote do the comparison: prices and lead times update instantly when you change the process. Automatic DFM analysis also flags geometry that a chosen process cannot make, with a “DFM Warning” pill in the quote table. See Understanding your quote and DFM overview.