In traditional precast concrete production, securing formwork has long relied on welding, bolts, or mechanical clamps. These methods are not only time‑consuming and labour‑intensive but also damage the surface of expensive steel moulds. The arrival of magnetic formwork has completely changed this picture.

Magnetic formwork systems use the strong attraction of neodymium‑iron‑boron (NdFeB) permanent magnets. Through precise magnetic circuit design, they lock the formwork firmly onto the steel mould table. The core component – the shuttering magnet or magnetic formwork system – has become key equipment for improving production efficiency in modern precast plants.

Core Components and Working Principle of Magnetic Templates

1. Shuttering Magnet Box——The magnetic box is the most common magnetic fixing unit. It consists of the following parts:

Working principle:When the button is pressed, the magnetic core and the steel mould table form a closed magnetic circuit, generating a vertical attraction force (from 450 kg to 3100 kg, depending on the model). Using a special pry bar to pull the button up breaks the magnetic circuit, allowing the magnetic box to be moved easily.

2. Magnetic Side Formwork System——For standardised production lines, the magnetic side formwork integrates the magnetic box inside a U‑shaped or rectangular steel profile to form an integrated magnetic side formwork:

- U60 magnetic side formwork – Suitable for composite floor slabs and double‑wall production. The magnetic box is embedded in a steel channel and held onto the mould table by magnetic attraction.

- Adjustable‑height side formwork – Adapts to component thicknesses from 60 mm to 400 mm by changing the adapter.

- Long‑strip magnetic side formwork – Available in lengths of 1 m, 2 m, 3 m, or even 3.9 m, containing 2–3 magnetic cores. Ideal for large‑area wall formwork.

Complete Processing and Production Flow of Magnetic Templates

 Phase One: Magnetic Circuit Design and Simulation Optimisation

The core competitiveness of magnetic templates lies in the precision of magnetic circuit design. Manufacturers must perform magnetic field simulation using professional software:

1. Magnetic circuit modelling – Determine core size, pole arrangement, steel shell thickness, and flux density distribution.

2. Attraction force calculation – Calculate the required core volume and magnetisation direction based on the target attraction force (e.g., 2100 kg).

3. Leakage control – Optimise the steel shell to concentrate magnetic flux on the bottom working surface and reduce side leakage.

4. Safety factor – Design the attraction force to be 2–3 times the actual working load, accounting for dynamic loads from vibration tables.

Phase Two: Precision Parts Machining

(1) NdFeB Core Preparation

- Material selection – Use N35–N52 grade sintered neodymium‑iron‑boron, with remanence 1.17–1.48 T and coercivity ≥12 kOe.

- Cutting process – Wire cutting or diamond wheel cutting to achieve dimensional accuracy of ±0.05 mm.

- Magnetisation – Saturate the magnets along the axial direction using a pulse magnetiser to establish a stable magnetic field.

- Surface treatment – Nickel‑copper‑nickel triple plating or epoxy coating to prevent oxidation and corrosion.

(2) Steel Housing Manufacturing

- Material – Q235 carbon steel or 304 stainless steel, balancing strength and rust prevention.

- CNC machining – Milling, drilling, and tapping performed on a CNC machining centre.

- Magnetic shielding design – Housing thickness typically 8–12 mm, providing both structural strength and effective magnetic shielding.

- Surface treatment – Blackening, galvanising, or powder coating to extend service life.

(3) Switch Mechanism Machining

- Button assembly – Stainless steel or engineering plastic, with a designed stroke of 8–12 mm.

- Magnetic core rail – Precision‑machined to ensure smooth movement without jamming.

- Locking mechanism – Includes a mechanical stop to prevent accidental demagnetisation due to vibration.

Phase Three: Magnetic Circuit System Assembly

This is the core step in magnetic template manufacturing and must be carried out in a magnetically clean workshop (free of strong external fields):

1. Magnetic core embedding – Install the magnetised NdFeB blocks into the slide rails according to the designed polarity. The arrangement (like poles repelling, unlike poles attracting) must strictly follow the drawings.

2. Magnetic circuit debugging – Before installing the outer shell, test the magnetic field change curve during core sliding to ensure crisp ON/OFF switching.

3. Outer shell encapsulation – Install the magnetic core assembly into the steel shell and seal it with bolts or welding.

4. Magnetic force testing – Measure the vertical pull‑out force using a standard force gauge. For example, a 2100 kg magnetic box must achieve ≥2100 kgf (approximately 20.6 kN).

5. Switch verification – Perform more than 50 consecutive operations to check button rebound and the reliability of magnetic circuit switching.

Phase Four: Adapter and Accessory Integration

The flexibility of magnetic templates is reflected in their rich adapter system:

- Steel corner adapter – Connects to L‑shaped edge moulds for corner areas.

- Wooden formwork connector – Secures wooden formwork with bolts; suitable for irregularly shaped components.

- Channel steel clamp – Quickly clamps standard channel steel side moulds.

- Adjusting screw – Fine‑tunes the height and level of side moulds with an accuracy of ±1 mm.

Phase Five: Quality Inspection and Certification

Each batch of magnetic templates must undergo rigorous testing:

Phase Six: Protective Packaging and Delivery

- Demagnetising packaging – Use iron boxes or magnetic shielding materials to prevent the product from attracting metal debris during transport.

- Identification and traceability – Laser engrave the model number, batch number, and maximum operating temperature (usually ≤80 °C).

- Included accessories – Each shipment comes with a dedicated pry bar, user manual, and maintenance guide.

Technical Advantages of Magnetic Templates

1. Efficiency revolution – Installation is 70% faster than traditional bolt fixing, greatly reducing mould turnaround time.

2. Mould table protection – No welding, no drilling – extends the service life of steel mould tables by 3–5 years.

3. Flexibility and versatility – The same magnetic box system adapts to components of different sizes and shapes.

4. Precision guarantee – Seamless magnetic holding keeps component dimensional deviations within±2 mm.

5. Safety and environmental protection – Eliminates welding fumes and sparks, improving the workshop environment.

Maintenance Points and Common Misconceptions

 Daily Maintenance

- Cleaning – After each use, remove concrete residue from the magnetic core surface with a dry brush. Do not use water or liquid cleaners – moisture will rust the magnetic core and permanently damage its magnetism.

- Storage – Keep in a dry, ventilated place, away from high‑temperature environments (>80 °C) which can degrade magnetic performance.

- Regular inspection – Check the attraction force monthly. If the decrease exceeds 15%, return the device to the factory for remagnetisation or core replacement.

Common Misconceptions

❌ Myth 1: The stronger the magnetic box, the better.

✅ Correct answer:Choose the appropriate model based on component height and vibration method. Excessive force makes handling difficult and may damage thin mould tables.

❌ Myth 2: Magnetic boxes can replace all mechanical connections.  

✅ Correct answer: For very tall components (>3 m) or extreme vibration environments, some mechanical restraints are still necessary.

❌ Myth 3: Magnetic boxes are permanently maintenance‑free. 

✅ Correct answer:Although NdFeB magnets have a theoretical lifespan of decades, mechanical parts (buttons, springs) require regular lubrication and maintenance.

At last the emergence of precast concrete magnetic formwork is a landmark innovation in the industrialisation of construction – a true shift from welding to magnetism. From precise magnetic circuit design and rigorous assembly processes to convenient on‑site application, every step reflects the precision thinking of modern manufacturing.

When a magnetic box is firmly attached to the steel mould table, it does more than just hold the side formwork in place. It upholds the core values of industrialised construction: efficiency, precision, non‑damaging operation, and reusability. Behind that seemingly simple “press‑and‑pry” action lies a perfect fusion of materials science, magnetic engineering, and manufacturing excellence.