Electrical Steel Lamination Stacking for Precise Bonded Stack Height
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Solution Overview
Problem
Existing methods for producing lamination stacks with hot-melt adhesive varnish layers on electrical steel strips or sheets lack reproducibility and flexibility in achieving precise stack heights due to variations in sheet metal and adhesive layer thickness, leading to inefficiencies and potential loss of short-circuit safety when attempting to adjust stack heights.
Innovation Solution
Preheating the hot-melt adhesive varnish layers above the glass transition temperature and applying pressure to adjust stack height precisely, followed by adding additional sheet metal parts if necessary, and finally baking at a higher temperature to fix the stack height, ensuring geometric accuracy and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If axial pressure is increased to reduce stack height, then manufacturing precision is improved, but reliability deteriorates due to risk of hot-melt adhesive varnish being squeezed out
Solution Approach 1:
The patent applies preliminary action by preheating the hot-melt adhesive varnish layers to a first temperature (above glass transition temperature but below baking temperature) and applying pressure in this preheated state to reduce irregularities and achieve precise stack height. This preliminary pressure application at controlled temperature eliminates the need for excessive pressure during baking, thereby preventing adhesive squeeze-out while achieving the desired manufacturing precision.
Solution Approach 2:
The patent changes the temperature parameter of the hot-melt adhesive varnish layers during the stacking process. By maintaining the temperature between the glass transition temperature and baking temperature during the pressure application, the adhesive becomes sufficiently pliable to conform to irregularities without being挤出. This parameter change enables precise stack height control while maintaining reliability.
2Manufacturing precision
If axial pressure is applied to reduce stack height, then manufacturing precision is improved, but adaptability deteriorates as the method is only suitable for reducing stack height, not increasing it
Solution Approach 1:
The patent performs the preliminary action of heating and pressure application before the final baking step. This allows for stack height adjustment in both directions: height can be reduced by pressure application, or additional sheet metal parts can be added to increase height. The preliminary state enables flexible adjustment before the adhesive is permanently set during baking, thereby improving adaptability while maintaining precision.
3Reliability
If stack height is determined after baking, then reliability is improved as final dimensions are known, but productivity deteriorates due to separation of unsuitable lamination stacks
Solution Approach 1:
The patent determines the stack height in a preliminary state (after preheating and pressure application but before final baking) by adding or removing sheet metal parts as needed. This preliminary determination allows for 100% utilization of lamination stacks since adjustments can be made before the adhesive is permanently set. The final baking then simply confirms the adjusted dimensions, eliminating the need to separate unsuitable stacks and thereby improving productivity while maintaining reliability.
4Manufacturing precision
If preheating and pressure application is applied before baking, then manufacturing precision is improved for stack height adjustment, but use of energy increases due to additional heating step
Solution Approach 1:
The patent merges the preheating step with the subsequent baking process. The first temperature (above glass transition but below baking temperature) is maintained during pressure application and stack height adjustment, then the same heating system continues to raise the temperature to the baking temperature. This merging of heating steps eliminates the need for separate heating cycles, thereby achieving precise stack height control while minimizing additional energy consumption.
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 method allows for flexible and precise adjustment of stack heights with high reproducibility, avoiding oversizing and the risk of hot-melt adhesive varnish squeezing, while ensuring energy-efficient continuous production of accurate lamination stacks.
Implementation Method 1
preheated to a first temperature, which is above a glass transition temperature Tg of the hot-melt adhesive varnish
Implementation Method 2
put under pressure in this preheated state, then the lamination stacking method according to the invention can offer the possibility of a flexible and precise adjustment of the stack height. By means of this layer-bonding using pressure and heat, it is namely possible to reduce irregularities between the individual sheet metal parts
Implementation Method 3
heated to a second temperature, which is greater than or equal to the baking temperature of the hot-melt adhesive varnish, and as a result, its sheet metal parts are baked onto one another by means of the hot-melt adhesive varnish layers
Data Source
AI summary
A method for stacking sheet metal parts composed of an electrical steel strip or sheet in order to form lamination stacks, each with a stack height within a tolerance range from a predetermined desired stack height, including stacking the sheet metal parts, which have a hot-melt adhesive varnish layer on at least one flat side, preheating the hot-melt adhesive varnish layers and putting the hot-melt adhesive varnish layers under pressure, then determining the stack height of the individual lamination stacks and adjusting the stack height if necessary, and then finally heating the hot-melt adhesive varnish layers.