We recently completed a contract winding job that is worth writing up, because it inverts the usual relationship between a coil and the machine it goes into: the motor coils for a magnetic-levitation bearingless pump, explosion-proof version, built to transfer solvents and high-purity chemicals.
With no bearings, the coils carry the rotor
In a conventional pump motor, bearings locate the rotor and the stator winding only has to produce torque. A bearingless drive removes the bearings entirely. The same stator that turns the rotor also holds it suspended, maintaining radial position through controlled electromagnetic force generated by the windings themselves.
That single change rewrites the tolerance picture. Turn count, layer placement and phase-to-phase balance stop being quality metrics and become functional requirements. An asymmetry between coils does not surface as a deviation on an inspection report. It surfaces as rotor displacement, as vibration, or as a suspension control loop burning current to correct an error that was wound into the stator in the first place.
Practically, it means the acceptance criterion is not "is this coil within specification" but "is every coil in this set identical to the others". A set that is uniformly 2% off nominal is usable. A set where one coil differs from the rest by the same 2% is not.
Heavy gauge makes that symmetry harder to achieve
The conductor on this job is heavy gauge, chosen for the current the suspension and drive functions demand. Thick wire is unforgiving to wind. It springs back after each turn, it resists tight layering, and it magnifies every inconsistency in feed tension into a visible difference in coil geometry and fill factor.
The answer is tension control, held constant across the whole run rather than merely set correctly at the start. As a spool empties and line speed varies, a passive payoff lets tension drift, and drift between the first coil and the last is exactly the asymmetry a bearingless motor cannot tolerate. Every coil in this set was wound under controlled constant tension so the entire set landed inside the same window.
Inside Our Coil Winding Workshop
The complete winding sequence for a heavy-gauge stator coil, filmed on our production floor.
What the application adds on top
The pump this stator goes into is designed for service where a seal failure is not an option: no dynamic seal, no lubricant, no mechanical contact, and an explosion-proof rating for handling flammable media. None of that is our part of the assembly, but it sets the requirements our part has to meet. The winding has to survive the insulation, impregnation and thermal conditions that certification imposes, with no shortcut available on materials.
Job summary
| Application | Magnetic-levitation bearingless pump, explosion-proof version |
| Component | Motor stator coils |
| Conductor | 1.8 mm enamelled copper |
| Critical requirement | Coil-to-coil symmetry across the full set |
| Tension control | Constant-tension winding across the production run |
| Volume | 800 sets |
Contract winding to your drawing
Jobs like this one are why we describe ourselves as a winding partner rather than a catalogue supplier. Most of what we make does not exist as a part number until a customer sends a drawing. Alongside motor and stator work we produce air core coils, bobbin coils and special shaped coils across a wide range of wire gauges and insulation systems.
If you have a winding that has to hold tolerance across a whole production run rather than on a first article, send us the drawing and we will tell you what it takes to hold it.
About WIRESUN
Founded by a management team with over 30 years of hands-on expertise in coil winding, WIRESUN has grown into one of Dongguan's trusted precision coil manufacturers. We provide OEM and ODM custom coil winding services, producing air core coils, bobbin coils, and special-shaped coils, along with coil winding machines and wire tensioners.
Contact us:
tech@wiresun.com ｜ +86-186 2185 7689 (Bi Danfeng)