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Components Magnets hold dies securely, allow rapid changeover

Editor: Eric Culp

Clamping and changing systems based on electric permanent magnets enable moulders to save costs and setup time and enhance safety.

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This M-TECS magnetic clamping plate from Römheld is mounted on a 110-ton injection moulding press.
This M-TECS magnetic clamping plate from Römheld is mounted on a 110-ton injection moulding press.
(Römheld)

Magnetic clamping and changing systems can help moulding, metalworking and die-casting companies save costs, reduce setup times, enhance productivity and safety, and improve production quality. Their value is seem especially in small-series manufacturing. A diverse range of Hilma-brand magnetic clamping plates from the Römheld Group are available to answer growing demand for this flexible quick-tool-change technology.

Saving time and ensuring safety during setup are the most common reasons for using magnetic clamping systems, according to Römheld. Even dies as hot as 240°C and large moulds weighing several tons can be changed and prepared for production in less than 30 minutes by one operator using a simple, quick die-changing system consisting of magnetic clamping plates, a die cart and roller bars.

Size doesn’t matter

By means of magnetic clamping plates, dies and tools of any size and shape can be positioned and clamped. Both the expensive standardisation of dies and tools and the need to use various clamping devices can be avoided. The technology thus enhances the scope of application and productivity for companies coping with small batch sizes, a growing variety of formed parts and short deadlines.

Magnetic clamping is based on the principle of the electric permanent magnet, which ensures absolute safety in the event of power failure. An electrical pulse magnetises the system for 2 seconds or so, which clamps the die onto the plates at a force of 3,000 kN or more. Even mould halves weighing several tons are held reliably and without deformation, true to position and in parallel. The magnetic field penetrates only a few millimetres into the die. During production, the permanent magnets—independent from the electrical power supply—keep the plates securely in position. Electrical power is then required only to unclamp the plates and release the die.

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Because the pressing forces on the die are uniformly distributed, the tool is held in place precisely and without distortion, which is vital for high performance precision and process reliability. Plastic products turned out by a magnetically clamped mould will be highly homogeneous, and rejects will be few. Also, the uniform force distribution and precision of the process minimises die wear.

Finally, magnetic clamping technology enhances workplace ergonomics. It eliminates the need for unsafe manual clamping and unclamping activities and for manual labour in hard-to-reach positions.

Römheld offers magnetic clamping plates in seven versions, five of them tolerant of high working temperatures. All are available with optional integral heating and are sized to customer specifications. Römheld’s plates are distinctive in that they are fitted with long-pole rather than square-pole magnets. An advantage of this is a concentration of the magnetic force that enables small dies to be clamped securely without the use of auxiliaries.

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