FDM, SLA, SLS, MJF or metal: which 3D printing process suits your part?

FDM is the cheapest process per part, because filament is the cheapest material per gram. SLA resin costs two to three times as much per gram and SLS nylon four to six times as much, while MJF and metal are quoted for each job. Use FDM for concept models, fixtures and large pieces, and step up only when the surface or the material demands it.

Choose SLA resin when the surface and the detail matter more than toughness. Resin prints raised or sunken detail down to 0.5 mm, against 0.6 mm in filament, and letters from 2 mm tall, against 5 mm. It comes off the printer smooth, so it paints after light sanding and a primer, it makes good masters for silicone moulds, and it prints clear parts. Avoid it for parts that flex or take a knock, because resin is brittle.

SLS nylon is usually more than a first prototype needs, because it costs four to six times as much as FDM. It earns its price on hinges, snap fits and small runs of end-use parts, where filament layers could split. For a first prototype, FDM almost always wins.

In practice there is little difference between SLS and MJF. Both fuse nylon powder with no supports, so parts nest freely and moving assemblies print in one go. MJF comes out a little smoother, but not by much, so the choice usually comes down to price and preference. MJF is black PA12 or glass-bead PA12; SLS adds grey and white, a glass-fibre grade and a PA11-like grade. A normal-size part takes 8 to 12 working days by SLS and 12 to 15 by MJF.

A normal-size part, about 10 to 15 cm across, takes 4 to 7 working days in FDM or SLA, 8 to 12 by SLS, 12 to 15 by MJF and 10 to 12 in metal (SLM). Filament and resin can go Express in 3 to 5 working days or Super Rush in 1 to 3. Larger parts take longer, so check with us, and tell us your deadline when you order.

SLM metal makes the strongest parts, followed by SLS and MJF nylon. Nylon powder parts are equally strong in every direction and take hinges, clips and knocks. FDM parts can be strong but may split along their layers under load, so a filament part that carries force is printed facing the right way. SLA resin is the most brittle of the five.

Metal earns its cost when the part has to survive heat, load or wear that no plastic will take, or when the shape is one a cutting tool cannot reach. Metal is quoted per job, not per gram, because the alloy, the part's size, the finishing and the quantity all move the price. Send the file, the metal you want and the faces that have to be exact, and we come back with a firm quote, usually within 24 hours.

3D printing loses on simple solid shapes and on large numbers. CNC machining holds tighter tolerances, down to ±0.05 mm, and is often cheaper for a part a cutting tool can reach all over. Injection moulding takes over at around 1,000 identical units, with the crossover between 500 and 2,000 depending on the shape. Between 20 and a few hundred copies, vacuum casting from a silicone mould usually wins. We will say which route is cheaper for your numbers when we quote.

Yes, one order can mix processes, and one quote covers the lot. A common mix is an FDM body with a resin face for the fine detail, or a prototype in FDM that moves to MJF once the design is settled.