3D printing production

Conventional machining is subtractive: start with a block larger than the part and cut away what is not wanted. 3D printing is additive — material is laid down layer by layer, each roughly 0.02 to 0.3 mm thick, until the part exists. The formal name is additive manufacturing.

The important consequence is not speed or cost. It is that complexity stops being expensive. A mould insert with curved conformal cooling channels has to be split, machined in pieces and rejoined — every operation is money and risk. Printed in metal, it costs about the same as printing a solid block of the same volume. Lattice structures, one-piece thin shells, undercuts no cutter can reach: all the same principle.

The converse is also true. A plain cylinder is faster and cheaper on a lathe. A mating face that must hold ±0.01 mm is beyond every printing process and needs machining afterwards. So the usual answer in practice is not either/or — print near-net shape, then CNC the critical faces.

3D printing is not one technology but a family of them. They build differently, so tolerance, surface finish, available materials and practical size all differ — and the price can vary tenfold. The tolerances, minimum wall thicknesses and build volumes below are our in-house machines' actual specifications.

Most people pick the wrong process because they start by asking which one is best. None of them is; they match requirements or they do not. Asked in this order, three questions usually settle it.

First: is this part to be looked at, or to be used? For looking at — a pitch, a display, an appearance check — choose SLA. Its surface is the only one that photographs well without finishing. For something that carries load or moves, choose SLS or MJF.

Second: how many? At one to five, SLS and MJF cost about the same; take whichever ships sooner. Past twenty, MJF's part-to-part consistency starts to matter and its unit price falls faster. Past five hundred, the thing to re-evaluate is injection moulding, not printing.

Third: is metal or heat non-negotiable? Metal means SLM, full stop. For plastic above 80°C in service, use FDM in PC or PEEK, or a high-temp SLA resin — ordinary PLA and standard resin soften inside a car or an enclosure.

Most shops are vague about how they quote, because vagueness leaves room to negotiate. For the buyer it removes the ability to make design decisions — you cannot tell whether dropping a wall from 3 mm to 2 mm saves anything. So here it is in the open.

Printing is not priced by weight. It is priced on volume plus surface area. Volume sets how much material is consumed; surface area sets how long the machine spends tracing contours — at equal volume, a part with a broken-up surface costs more than a smooth one. Multiply those by material rate and a process coefficient and you have the base.

Quantity brings the unit price down, but not linearly. What actually falls away is the setup: nesting ten parts in one build carries the same preparation, warm-up and de-powdering cost as nesting one. This is why ten parts genuinely cost less than ten times one in printing, while in CNC that holds far less.

Lead time is a separate multiplier. A rush job jumps the queue, and jumping the queue pushes someone else back — the premium is opportunity cost, not a service fee. Equally, if your schedule has give in it, standard lead time is always the cheapest option.

Material choice is almost entirely decided by service environment, not preference. Establish what the part will meet — temperature, UV, oil, sustained load, drops — and pick from there. Done the other way round it goes wrong.

The whole cycle is typically three to five working days. Printing is only part of it — the checks before and the finishing after usually decide the quality.

The file: STL is the universal format, but it records only a triangle mesh, with no dimensions or tolerances. If the part has to fit something, send STEP instead — it keeps the solid and surface definitions, which is also what lets us compute real wall thicknesses at quoting time.

DFM check: on upload the system checks wall thickness, overhang angles, detail below process resolution, and whether the part exceeds the build volume. This happens before the quote, so you do not discover a failure after printing.

Orientation and supports: the same part oriented differently changes surface quality, the direction of its strength, and how much support it needs. An engineer decides this; it is not automatic.

Finishing: support removal, de-powdering and bead blasting are standard; appearance parts add polishing, dyeing, painting or plating; metal parts usually need heat treatment and wire-cutting off the plate.