89 Principally, it is the machinist’s job to consider what problem the part design is meant to solve. Aerostructures, for instance, are quite often designed to beat the challenge of strength-to-weight maximisation. Thermal dissipation is another perennial problem among vehicle subsystem housings as well as some fairings and engine parts. Whatever the exact issue or target, the most competitive machine tool operators today will not unquestioningly follow a customer’s requests and CAD diagrams, but holistically advise customers on the dynamics and particulars of CNC machining, in ways that can save the uncrewed vehicle manufacturer staggering costs, weight, power consumption, lead times and more. Tight tolerances, for example, can drive up costs, and machinists know better than UAV engineers how to correctly analyse whether all tight tolerances across, say, a bulkhead, enclosure or cylinder head are necessary. On top of that, CNC machines have constraints of their own – such as the X, Y, Z volume of their internal chambers, the materials they can work with or the geometric complexity they can manage – and any customer that asks for a part at the limit of (or slightly over) those constraints will find their per-unit costs shooting up exponentially. Knowing some of the particulars of those machine tools, and of the considerations their operators may run through, will be key to the success of the uncrewed world in the years and decades ahead. 3-axis milling 3-axis milling machines are arguably the most basic form of CNC machines routinely used in vehicle industries. For the unfamiliar, one may effectively picture a sculptor, chiselling away at a cubic marble block, starting with broad strokes before moving to light grinding and sanding, to achieve the curvature of the intended sculpture. 3-axis CNC milling machines works on the same principle: one starts with a block of material larger than the desired part, and a tool is rapidly spun for cutting material away (potentially spraying a cutting fluid such as water, oil or a combination of both to cool and lubricate the tool against the material), until the desired shape – both positive and negative features – is achieved. As a sidenote, CNC turning machines operate similarly, but by rotating the billet against a stationary implement; for brevity’s sake, we refer here to just milling, rather than turning (or both). All the while, the block (or workpiece, as one might call it after milling has commenced) is clamped in place as rigidly as possible. Obviously, maximising that rigidity represents a non-trivial barrier to precise machining because otherwise the block will move and slip as the cutting tool makes contact. In a 3-axis machine, the cutting tool can only move orthogonally, meaning that its movements are limited to the X-, Y- and Z-axes with its path being guided by a computer control system. While AIgenerated tool paths are gradually being experimented with, the foreseeable future of CNC programming will still likely be dominated by human engineers, specifically those who can closely understand the order of operations: where to cut material away first (and then subsequent cutting step-by-step) to achieve the desired shape and surface finish, and how to minimise the chances of tool errors and breakages. The importance of a mind capable of seeing the initial billet around the final Machine tools | Focus Uncrewed Systems Technology | August/September 2025 The machine and its cutting tool are largely blind, sensorless entities; therefore, it takes both experience and training to program for an accurately milled component (Image courtesy of Syncro Design)
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