Laser Welded Step Motor End Cap and Stator Assembly

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Solution Overview

Problem

Conventional step motor designs face challenges in achieving consistent assembly quality and precision due to tolerance stack-up issues, particularly in maintaining concentricity of end caps and stator diameters, which affects performance and efficiency.

Innovation Solution

The method involves using thin-walled end caps with integral side walls, positioned at opposite ends of a stator with multiple laminations, and locally laser welding the edges to the stator laminations at spaced locations, eliminating the need for precise tolerances and allowing for accurate alignment and assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional assembly methods are used with tight tolerances to maintain concentricity, then manufacturing precision is improved, but device complexity and manufacturing cost increase due to tolerance stack-up problems

Engineering Contradiction:

Improveconcentricity of end caps and stator diametersVSAvoidtolerance stack-up control

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces conventional mechanical fastening methods (screws, clips, interference fits) with laser welding to join end caps to the stator. This substitution eliminates the need for complex mechanical tolerance control systems, as the laser welding process inherently provides precise, consistent joints without requiring tight dimensional tolerances on the mating surfaces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the joining parameter from mechanical (requiring tight dimensional tolerances) to thermal (laser welding). By using laser welding, the process can accommodate larger tolerances while still achieving consistent, high-quality joints, thereby eliminating the tolerance stack-up problem that plagues conventional mechanical assembly methods.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If tight tolerances are specified for end cap concentricity, then manufacturing precision is improved, but productivity decreases due to difficult and time-consuming assembly

Engineering Contradiction:

Improveconcentricity of end caps and stator diametersVSAvoidassembly speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent replaces time-consuming mechanical assembly operations (alignment, fastening, inspection) with rapid laser welding. The laser welding process can be automated and performed quickly, eliminating the manual manipulation and alignment time required by conventional mechanical methods while maintaining or improving concentricity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs a fixture that pre-positions and aligns the end caps with the stator before welding. This preliminary action ensures correct positioning is achieved quickly and consistently, eliminating the need for time-consuming manual alignment during the actual assembly process, thereby improving both precision and productivity.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If conventional fastening methods are used, then ease of manufacture is improved, but manufacturing precision deteriorates due to tolerance accumulation

Engineering Contradiction:

Improveassembly simplicityVSAvoidconcentricity consistency

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces conventional mechanical fastening (screws, clips, interference fits) with laser welding. While laser welding requires specialized equipment, it eliminates the cumulative tolerance problem inherent in multi-step mechanical assembly. The welding process creates a monolithic joint that does not suffer from tolerance stack-up, thereby improving concentricity consistency despite the initial complexity of implementing laser welding infrastructure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach ensures consistent quality assembly, reduces the tolerance stack-up problem, and enhances the overall performance and compact construction of step motors by maintaining concentricity and allowing for higher torque output.

Implementation Method 1

locally laser welding said edges to said stator end laminations

Methodology Applied

Scientific EffectLaser welding: Laser Beam Welding

Data Source

PatentUS7752733B1Laser welded step motor construction with compact end cap and stator lamination positioning

Publication Date: 2010.07.13 LIN ENGINEERING INC

AI summary

The method of providing a motor, includes providing a first thin-walled end cap having first inner and outer walls connected by a first integral side wall, the first outer wall defining a first terminal edge; providing a second thin-walled end cap having second inner and outer walls connected by a second integral side wall, the second outer wall defining a second terminal edge; providing a stator, having multiple parallel laminations defining an axially extending bore to receive a laminated rotor, the stator having end laminations, positioning the end caps so that the edges extend adjacent stator opposite end laminations.