Two years part-time on a transformer production line, then eighteen days back on it as a product tester — winding, insulation, weld inspection, electrical test and the paperwork that follows each.
Two spells, and they taught different things. The first ran from August 2020 to August 2022, part-time through school holidays and weekends: winding, soldering, lamination stacking, sub-assembly and final assembly on a 24 V 40 VA line. Long enough to build the same thing badly, then adequately, then quickly.
The second was eighteen days in May 2023, back on the same line as product tester rather than as a pair of hands. I was moved between stations rather than kept at one, so I saw a transformer built from lamination stacking through winding, insulation and varnish, assembly, electrical test and packing. Testing and inspection were where the time went — turns ratio, insulation resistance, no-load and load checks, and reading TIG welds rather than assuming they were sound.
The bobbin and end caps are bought in, not made on site, so I visited the supplier factories that mould them. That was the more useful half of the 2023 placement: the parts arriving on a line are already constrained by a tool cut months earlier, and a drawing that ignores draft or wall thickness gets quietly reinterpreted by whoever makes the mould.
The other thing a shop floor teaches you is how much a drawing leaves out. Anything ambiguous becomes a decision someone makes at the bench, usually without recording it.
Interactive 3D model — EI-core transformer assembly, 54 components.
GLB · 0.5 MB · loads on demandA moulded part is expensive to be wrong about, because the tool is cut once. Printing the bobbin and caps first is the cheap way to find out whether the drawing and the part agree — whether the bobbin seats in the lamination window and the caps clear the terminals — while changing the model still costs nothing.
Built during the earlier part-time stint at the same unit: an Arduino-controlled arm that carries the TIG torch along a fixed path so the joint is laid down the same way every time. Hand welding on a repeated joint drifts; a fixture and a motor do not.
The bobbin and the end caps are moulded, not made on the transformer line, so seeing them made meant going to the factory that makes them. This is where a drawing stops being a drawing and becomes a steel tool that will not be recut.