We supply Neodymium cylinder magnets (also called rod magnets).
They are defined by length exceeding diameter.
These high aspect ratio magnets are used in:
– Coreless motors, Hall effect sensors, reed switch triggers, and magnetic separators.
Available from Ø 0.2 mm micro-rods to elongated cylinders like Ø 3mm × 13mm for sensor activation.
Longer cylinders are challenging to manufacture without warping or breakage.
We maintain strict geometric tolerances to ensure your rods are straight and fit precisely into narrow housings or bores.
The “Aspect Ratio” Challenge
Structural Integrity & L/D Ratio:
A magnet with a small diameter and long body (e.g., 3mm Diameter / 13mm Length) is mechanically fragile.
The Risk:
– Sintered Neodymium is brittle.
– Long, thin cylinders can snap easily if subjected to bending stress during installation.
Our Advice:
– We recommend strict Tube Packaging (see below) to prevent breakage.
Straightness:
– For cylinders used in pistons or plungers, we monitor camber (bowing) to ensure the magnet doesn’t bind inside your tube.
Magnetization Directions (Critical for Cylinders)
The function of a cylinder changes entirely based on how it is magnetized.
Axial Magnetization:
– Definition: The magnetic poles are on the flat circular ends (Top/Bottom).
– Use Case: Activating a Reed Switch, stacking into a longer rod, or “end-on” sensing.
Diametric Magnetization:
– Definition: The magnetic poles are on the curved sides (Left/Right).
– Use Case: Rotors for coreless micro-motors, angular position sensors.
Surface Coatings & Fit
Since cylinders are often inserted into holes/tubes, coating thickness is vital.
Parylene:
– The best choice for micro-cylinders (Ø < 3mm).
– It adds negligible thickness (0.005mm)
– Provide a low-friction surface for sliding inside tubes.
Nickel (Ni-Cu-Ni):
– Standard durable finish.
Zinc:
– Not recommended for high-precision cylinders.
– The plating can sometimes be uneven on long rods.
Packaging: The “Tube” Solution
Row-Packed Plastic Tubes:
We do not dump small cylinders into a bag.
We supply them stacked in rigid plastic tubes.
Benefit 1: Protects the magnets from snapping during transit.
Benefit 2: Allows your assembly team to slide the magnets directly from our tube into your product housing without touching them.
Benefit 3: Keeps the polarity oriented in the same direction for automation.
Applications
Fluid Level Sensors: Cylinders inside floats activating switches.
Micro-Motors: Coreless DC motor rotors (Diametric).
Musical Instruments: Magnetic pickups for guitars.
Medical: Biopsy needle guidance markers.
Ordering Guide
To quote your cylinder magnets accurately, please specify:
1). Dimensions: Diameter x Length (mm).
2). Magnetization: Axial (Ends) or Diametric (Sides)?
– This is the most common error in ordering cylinders.
3). Tolerance: Does it need to fit inside a tube?
– We can aim for a negative tolerance, e.g., +0 / -0.05mm.
4). Grade: N35 is standard for reed switches; N52 for high-torque motors.
