We supply precision custom Skewed Arc Segment Magnets.
They are specifically for high-performance Permanent Magnet (PM) motors and generators.
As seen in our product photo, this magnet features the standard curvature of a motor arc (Convex Outer Diameter / Concave Inner Diameter).
But it comes with a critical modification: the side profiles are cut at a specific Skew Angle.
This “Angled” or “Parallelogram” geometry is a sophisticated engineering solution.
It is used to reduce Cogging Torque (torque ripple).
By skewing the magnet shape rather than the stator laminations, motor designers can achieve:
– Smoother rotation, reduced vibration, and quieter operation.
– But without complex stator winding adjustments.
Why Skew the Magnet?
1. Eliminating “Cogging” (The Jerky Motion):
The Problem:
– In a standard motor, as the magnet passes the steel stator teeth, it snaps into alignment.
– This causes a “step” or vibration known as cogging.
The Solution:
– The Skewed Edges ensure that the magnetic field enters the stator tooth gradually.
– Not all at once.
The Benefit:
– This creates a “Soft Magnetic Transition”.
– And offers silky-smooth rotation (critical for Electric Power Steering, Robotics, and high-end Audio Turntables).
2. Noise Reduction (NVH):
The Function:
– Smooth torque transition significantly reduces audible whine and physical vibration.
The Application:
– Essential for EV (Electric Vehicle) motors where cabin silence is a priority.
Geometric Definitions: Defining the Skew
To manufacture this part, we need a drawing that defines:
1). Radii: Outer Radius (OR) and Inner Radius (IR).
2). Thickness: Radial height.
3). Length: Axial length.
4). Skew Angle (ฮฑ): The angle of the side cut relative to the axis.
Note:
– Are the sides parallel (Parallelogram) or Radial?
Manufacturing Method: Wire EDM & Grinding
Process:
Standard block slicers cannot cut skewed angles easily.
We utilize Wire EDM or 5-Axis Profile Grinding to create this geometry.
Sharp Edges:
The acute angles created by the skew are extremely sharp and fragile.
We apply a controlled Edge Rounding / Tumble Finish (as seen in the photo).
It prevents these corners from chipping during motor assembly.
Handling & Assembly
Skewed magnets are tricky to handle.
Assembly Warning:
Due to the “twisted” nature of the magnetic field at the skewed edges:
Force:
– These magnets can jump/rotate unexpectedly when brought near steel.
Gluing:
– We recommend using custom fixtures to hold the magnets in place on the rotor hub while the adhesive cures.
– Because the magnetic centering force is different from standard arcs.
Applications
Electric Power Steering (EPS): Motors that must feel perfectly smooth to the driver.
Servos: High-precision robotics actuators.
Spindle Motors: High-speed CNC spindles.
Medical Equipment: Silent motors for hospital beds or pumps.
Ordering Guide: What We Need
Standard text descriptions often fail for this shape.
We require:
1). 2D/3D Drawing: A STEP file or PDF is mandatory to confirm the Skew Angle.
2). Motor Temperature: “What is the max operating temp?” (To determine Grade).
3). Quantity: (EDM cutting is slower than standard slicing, so lead times may vary).
