Custom DC-Controlled Electromagnets updated

I need three compact electromagnets fabricated for integration into a larger prototype. Final outside dimensions will be supplied once we begin, but each unit must: see diagram attached • Run from a standard low-voltage DC source (anywhere in the 12–24 V range is acceptable). • Provide variable holding force up to 40 N, adjustable via a simple in-line control such as PWM, current-limit circuit, or potentiometer. • Remain within the specified footprint and include straightforward mounting points so I can drop them straight into my assembly. • Operate continuously without excessive heat build-up or noticeable magnetic drift. Deliverables • 3 fully wound and assembled electromagnets built to the agreed dimensions • Matching driver or control interface with wiring diagram and basic operating instructions • Short test report showing measured pull force at minimum, mid-range, and maximum settings • Source files (coil data, CAD, circuit schematic) so I can reproduce or modify the design in future I’m flexible on core material, winding technique, and exact control method provided the 40 N ceiling and size constraints are met. Please allow for reasonable shipping time and let me know if you foresee any alternative approaches that would simplify production or improve reliability.