3D Printer

A 3D printer builds a solid object one thin layer at a time. A spool of plastic wire, called filament, is fed through a heated nozzle that melts it and lays it down along a path taken from a drawing on a computer, layer on layer until the shape is finished. On a working holding its value is repair rather than novelty. When a roller, gear, bracket or fitting on another piece of equipment breaks, the replacement can be made on the spot, which takes the delivery wait and the supplier out of the repair.

The catch is that a printed part is weaker than the same part made the ordinary way, and that is a property of the process rather than a bad print: the layers leave small voids inside the object. The machine's honest envelope is low-load work such as fittings, housings, spacers, guards and jigs. A part that has to carry load either gets a treatment that fills those voids, such as soaking it under vacuum in thinned epoxy, or it is the wrong part to print. The skill that decides whether a printer earns its place is drawing, not operating: a household that cannot model a part, or find a file for one, owns a machine that only copies other people's work.

It needs steady power and dry filament. A job runs for hours and cannot pick up where it stopped, so a supply that dips partway through wastes the whole part; running off stored electricity rather than whatever the sun is doing at the time is what makes it dependable. Filament pulls water out of ordinary room air once its sealed pack is opened, and that water flashes to steam at the nozzle and leaves bubbles and rough surfaces, so sealed storage with a drying agent counts as part of the machine. Printers also release very fine particles and solvent vapours into the room, so an indoor machine needs spot ventilation or a filtered enclosure. Routine care is nozzle changes, bed levelling, belt tension and a clean drive gear.