N35 Neodymium Magnets for Robotics Projects: Selection, Safety and Applications

Overview: What are N35 neodymium magnets and why use them in robotics?

N35 is a common grade of neodymium (NdFeB) magnet characterised by a nominal maximum energy product around 35 MGOe. These rare-earth magnets offer high magnetic strength relative to volume and are widely used in robotics for hold-downs, couplings, encoders, small direct-drive motors and custom actuators. For many hobby and educational robotics projects N35 balances performance and cost, but understanding selection, mounting and safety is important before integrating them into a design.

Key properties

• High flux density for smaller form-factor magnets.
• Often supplied with protective plating (nickel, zinc or epoxy) to reduce corrosion and chipping.
• Temperature sensitivity: N35 has lower maximum operating temperature than higher grades-consider thermal environment in motors or enclosures.

Common robotics uses

• Magnetic couplings for sealed housings and removable shafts.
• Mounting and fixturing for sensors, end-effectors and quick-change tools.
• Rotor magnets in small BLDC motors or hobby gearmotors where space is constrained.
• Magnetic encoders and Hall-effect sensor trigger magnets.

Standards, specs and how to read datasheets

Datasheets for NdFeB magnets typically list grade (N35), dimensions, maximum energy product (BHmax), remanence (Br), coercivity (Hc) and maximum operating temperature (Tmax). For robotics you will most commonly use diameter/thickness, Br (which correlates to surface field), and Tmax to ensure the magnet won’t demagnetise in your application.

Quick spec comparison table

Selection criteria for robotics projects

Choosing the right N35 magnet requires balancing size, coating, magnetic orientation and mechanical mounting. Below are practical checkpoints with examples relevant to South African makers and students.

Size and pull force

Pull force grows quickly with surface area and gap. For example, a 10 mm diameter x 3 mm thick disc will have far less pull than a 20 mm x 5 mm disc. Use pull-force tables from suppliers when designing mechanical couplings. For classroom prototypes a 10-20 mm disc is common; for small motor rotors, thinner arc or segment magnets might be required.

Coating and handling

Common coatings are nickel (Ni-Cu-Ni), zinc or epoxy. Coatings protect against corrosion and chipping; epoxy-coated parts are preferred for bead-sensitive environments. Handle with care: N35 magnets can chip if struck and strong attraction can cause finger pinching injuries. best practices for handling neodymium magnets

Magnetisation direction

Magnets are magnetised through thickness (axial) or diameter (radial). For encoders and couplings axial magnetisation is common for discs, while radial or arc magnetisation suits rotors. Confirm magnetisation direction on the product page or datasheet before ordering.

For more product browsing and sizing options, review Communica's collections and brand index to compare shapes and coatings: Shop by Category and Shop by Brand.

Calculations and practical examples

While exact magnetic force depends on shape and gap, a useful approximation for small disc magnets is that pull force (N) scales with surface area and square of the surface field. For design work you can also rely on supplier pull-force data. For electronics interfacing, consider Hall-effect sensor placement and target field (typically tens to hundreds of gauss for on-axis sensors).

Simple example: choosing a magnet for a magnetic latch

Requirement: a hand-operable latch on a 1.5 kg tray where you want modest retention but easy manual release. Rule of thumb: design for a holding force roughly equal to 1.5-3x the expected load friction. For a 1.5 kg tray on a vertical face, a 5-10 N holding force is often sufficient.

Example selection: a 15 mm diameter x 2 mm thick N35 disc might provide ~10 N pull in direct contact (exact values vary). If you need a safety margin, use two magnets in parallel or increase thickness/diameter. Remember to account for coatings and any non-magnetic gaps (steel plates, mounting tape).

Mounting and mechanical design tips

• Use countersunk housings or potting to prevent chipping on impacts.
• Keep ferrous backplates thin to avoid flux loss; a thin stainless spacer may help alignment.
• For rotors, glue with epoxy rated for magnets and ensure thermal limits are observed.

Safety and handling

Magnets stronger than refrigerator magnets can pinch skin and damage electronics (e.g., HDDs, credit cards). Store small magnets separately with spacers and label 3D-printed storage boxes. For university labs, provide PPE and clear handling procedures. For South African procurement, request VAT invoices and check branch collection options at Communica’s branches and trading hours page when buying in bulk.

Troubleshooting and common issues

Magnet loses strength in application

Possible causes: exposure to temperatures above the Tmax, mechanical chipping, or close proximity to stronger opposing fields. Replace with higher-temperature grade (if available) or change mounting to reduce mechanical shock.

Interference with sensors or electronics

Use shielding or increased distance to reduce stray fields. For encoder designs, test Hall sensor thresholds with the magnet in situ. Communica's product index can help you source compatible sensors and mounting hardware: All Products.

Where to buy and South African considerations

Communica stocks a wide range of maker and engineering supplies in South Africa from its Samrand head office and branches in Pretoria and Cape Town. Consider ordering quantities that allow for student lab losses and test fixtures; small businesses and departments can request account quotes and VAT invoices when purchasing larger lots. Check stock availability and branch pickup options to reduce lead times at the branches page: Branches & Trading Hours.

Sources

• Communica - About Us
• Neodymium magnet - Overview and material properties
• Typical NdFeB magnet datasheets and pull force references