FDM 3D printing for parts that have to work.

FDM builds a part by extruding a thermoplastic bead and stacking it, layer on layer. That single fact drives almost everything worth knowing about the process: it is fast to start because there is no tooling, it is economical at quantities where injection molding cannot pay for itself, and the finished part is anisotropic, stronger along the layers than across them.

Handled carelessly, that anisotropy is where FDM parts fail. Handled deliberately, it is just another design input, the same way grain direction is in sheet metal. Deciding which way a part lies on the plate is an engineering decision, and at Seabright Mechanical it is made by an engineer who has read your model, not by a default profile.

What FDM is genuinely good at

• Functional prototypes. Parts you can bolt in, load, heat-cycle and break, then revise and reprint.
• Shop floor parts. Parts where fit to your hardware matters far more than surface finish.
• Low-volume production. Runs where tooling cost would dominate the part cost.
• Geometry that punishes subtractive methods. Internal channels, lattices, undercuts, thin ribbing and organic transitions.
• Parts that change. When revision three is likely, a process with no tooling to rework is worth a great deal.

What it is not good at

We would rather tell you before you pay for it. FDM is a poor choice when you need optically clear parts, mirror-smooth cosmetic surfaces straight off the machine, hermetic sealing without post-processing, or tolerances tighter than the process holds without secondary machining. If your part needs one of those, say so early. Sometimes the answer is a printed part with a machined feature, and sometimes the answer is that we are the wrong shop for it.

Tolerances and fit

A tolerance quoted with no length attached to it is close to meaningless, so here is the honest version. On small, well supported features, printed on a tuned machine, our FDM parts typically come in around ±0.1 mm. That figure does not simply scale up. Achievable accuracy falls off as the part gets larger, and it moves with geometry, material, wall configuration and finishing, and shrinkage behaves differently in PLA than it does in a filled nylon. A large bracket in PA‑CF will not hold what a small PLA feature holds, and we would rather say that here than in an email after you have paid for it.

So the number that matters is not ours, it is yours. Tell us which dimensions on your part are critical. A part with three critical fits and forty cosmetic ones is straightforward to plan around; a part where every dimension is presented as equally critical is not. Mark them on a drawing, note them in the quote form, or just say "the 12 mm bore has to take a bearing". That sentence changes how the part is oriented and finished, and it lets us tell you what we can hold on your dimensions before you order rather than after.

Designing for the process

• Wall thickness is built from whole extruded beads. Walls specified as a clean multiple of the extrusion width come out denser and stronger than walls that leave a sliver the slicer has to fudge. Tell us the target and we will set the profile to suit it.
• Load direction should run along layers wherever you can arrange it. Where you cannot, we will often reorient the part, thicken a boss or suggest a small geometry change.
• Overhangs and supports cost time and leave witness marks. Chamfers instead of horizontal overhangs, and self-supporting angles where possible, produce a cleaner part for less money.
• Holes printed vertically come out slightly undersized and out-of-round. For a real fit, plan on a reamed or drilled hole, or tell us the fit class and we will compensate.
• Threads are usually better as heat-set inserts or tapped holes than as printed threads, unless the thread is coarse and lightly loaded.

Materials

We run PLA, PETG, PETG ESD, Nylon (PA) and carbon-fiber nylon (PA‑CF). Each one exists on the list for a reason: chemical resistance, toughness, static dissipation, stiffness, temperature. The materials page walks through what each is actually for and, more usefully, when not to pick it.

Working with us

Upload your file to the instant estimate tool and you will have a price in seconds. The geometry is read in your own browser, so nothing is uploaded to get a number. Submit the estimate and it lands with an engineer who looks at the actual part before confirming it. Instant estimate. Final pricing and manufacturability are confirmed by an engineer before production.

If you would rather look at your model before you send it, the free 3D viewer opens STL, STEP or 3MF files and will cut a section through the part so you can check wall thickness and internal features.