Low Cost Linear Synchronous Motors – Designed & built by William Bowley (primary) & Lawson Gallup

Overview

OpenLSM is an experimental project with the objective of designing low-cost permanent magnet linear motors for Cartesian motion systems such as pick-and-place machines or CNC machines. The project will fulfill this goal by using readily available materials and tooling, combined with reduced-order and finite element models.

Objectives

Important

• Design low-cost permanent magnet linear motors for Cartesian motion systems.
• Develop computational models that are validated against experimental measurements.
• Demonstrate continuous thermal steady-state operation under defined operating conditions.

More specific targets (force density, efficiency, cost, etc.) to be defined as the domain becomes clearer.

Methodology

The methodology for openLSM is to design a reduced-order or finite element model to compute the expected results for a specific motor topology. The resulting model is used to tune design parameters either manually or via algorithmic optimization. The parameters are then used to produce a CAD model, which is fabricated and experimentally tested. Discrepancies between predicted and observed performance are used to update the model for subsequent iterations.

Conceptual Design ↔ Reduced-order / FEA Model
      ↓
Design Parameters ↔ Detailed Design (CAD)
      ↓
Fabrication & Testing
      ↓
Post-Analysis & Model Validation
      ↺

Figure 1: OpenLSM design methodology. Computational models are iteratively refined through experimental validation.

Prototype Alpha

An ironless planar linear motor with a polylactic acid (PLA) armature featuring 6 slots, hand wound using 0.2 mm diameter enameled copper wire and 5 mm wide Kapton tape, with 2 slots in-series per phase (WYE). The stator, similar to the armature, was printed in PLA and had 4 pole pairs per armature length and 10 pole pairs total. The motor produced measurable force, though the magnitude was not quantified before the PLA coil forms deformed due to thermal stress.

Figure 2: Prototype Alpha. Top-down view of the planar linear motor showing the slots & poles.

The main conclusion from Prototype Alpha is that planar linear motors likely require laminated silicon steel armatures to produce force efficiently. In response, Prototype Beta shifts to an ironless tubular topology with the goal of quantifying force output and thermal performance.

Prototype Beta

TBD (Conceptual). Revision 2 of the ironless tubular linear motor design. Not yet validated for fabrication.

An ironless tubular linear motor with a carbon fibre nylon (PA6-CF) armature featuring 12 slots, mechanically wound using 0.4 mm diameter enameled copper wire, with 4 slots in-series per phase (WYE). The stator, unlike the armature, is made of layered carbon fibre epoxy to form a tube with an internal radius of 5 mm and outer radius of 6 mm. The poles are 20 mm in length and 5 mm in radius such that they can be inserted into the stator tube in this pole arrangement (N-S|S-N), using generic superglue to secure the end poles.

Figure 3a: Prototype Beta REV 2. Cross-sectional view of the tubular linear motor showing the stator & armature.

Revision 2 uses a radial heat-sink design which may improve steady-state characteristics, but the grade 6061 aluminum does introduce eddy currents which produce opposing magnetic fields that decrease efficiency. The design hypothesis is that thermal benefits outweigh eddy-current losses at the expected operating frequency. This is evaluated in the linked analysis.

Figure 3b: Prototype Beta REV 2. Close-up cross-sectional view of the radial heat-sink.

The radial heat-sink is made of aluminum as mentioned above with radial fins pitched at 1.50 mm, axial thickness of 0.50 mm, and radial thickness of 7.30 mm. The thermal interface material is intended to be generic thermal paste. This is expected to improve thermal steady-state conditions, though both this assumption and the analytical eddy-current model remain to be validated experimentally.

Important

See the motor design notes for the full electromagnetic and thermal rationale of Revision 2.

Documentation

All internal documentation can be found within this repo's issues.

Credits:

Acknowledgements and credits can be found in the credits file.

Bibtex Citation:

@misc{openLSM_2026,
  author = {William Bowley and Lawson Gallup},
  title = {{openLSM: Low Cost Linear Synchronous Motors}},
  url = {https://github.com/wgbowley/openLSM},
  year = {2026},
  note = {GitHub repository},
  license = {MIT}
}