Pneumatic Valve

The brief called for a 3/2-way valve for commercial vehicles: 10 bar pressure resistance, thermal stability to 175 °C, 9–16 V across −40 to 80 °C ambient — the target was material cost, not performance. The architecture came together fast, sized with classical analytical formulas. Alongside it I built an Excel-VBA tool for the preliminary sizing, one that solves the magnetic circuit, derives winding and wire diameter, and sweeps the whole parameter space for the cost minimum.

The reality check in FEMM said no: the armature delivered only 8.43 N against the 14.77 N required, because stray flux forms around the air gap that the analytical calculation never sees. Thermally it was the opposite: the coil hotspot sat at 134 °C, well under the 175 °C limit — so the part ended up too big and wasted material.

Trial and error wasn't going to settle this trade-off, so the VBA script swept systematically across more than 65,000 parameter combinations. The dashboard makes cost drivers instantly tangible, showing how cost tracks coil width, for instance. The ideal parameters it found, ones that fully use the thermal envelope, became the basis for version 2. Version 2 pushes the thermal margin to 161 °C, hits the required force, and cuts material cost by 64% to 1.19 € against 3.33 € in version 1 — with less material, smaller volume and higher current density.

To keep production costs down, it skips tight manufacturing tolerances; the critical air gap gets set precisely during final assembly instead, right before the housing is welded. A version 3 with a square housing instead of round could push material cost below 1.00 € — none of it has been built yet, every number here comes from simulation, and the honest next step is a force-stroke test rig.