Magnetic chuck: An alternative workholding solution

Magnetic chucks are becoming recognised as the first option for workholding steel parts on a milling machine. Today’s magnets have become more powerful to the extent that high-stock removal rates can be achieved. In addition, the workpiece does not have to be “flat”. Simple top tooling (pole extensions) can be utilised to accommodate most geometric shapes.

Workflow efficiency

Manual work holding often requires multiple fixtures or the changing clamps, vises or screws over the course of different phases of a milling operation. Replacing manual clamping with magnetic milling chucks eliminates the inefficiencies of conventional work holding devices. They provide better work piece accessibility, reduced vibrations for machining accuracy, five-sided accessibility, and reduced setup time, which summed together improve workflow efficiency. This makes them quite adaptable to workpiece clamping for a wide range of vertical or horizontal machining applications, including but not limited to, profiling, face milling, edge milling, plunge milling, slotting, surface grinding and drilling.

Construction and control

Magnetic milling chucks a r e constructed with high-powered ceramic or neodymium permanent magnets that are usually controlled by permanent magnetic or electro-permanent magnetic technology. The magnetic pole surface is manufactured with an all-steel design, facilitated by the use of tee slots that allow the clamping of non-ferrous workpieces. The poles are configured in a longitudinal or square geometry. The pole distribution ensures a uniform magnetic force over the entire surface area of the workpiece. The magnetic field is designed such that the top plate of the chuck does not have any stray magnetic fields, which prevents chip collection on the work piece and the cutting tool. Magnetic milling chucks can be controlled in two ways: mechanically with a lever or electronically wi th a chuck controller. The permanent magnet type uses a lever to engage or disengage the magnetic field. It requires no electrical power to operate. The electro-permanent magnet type uses a chuck D.C. controller to energize or de-energise the magnetic field, which takes about 1 second. However, it does not need electrical power to operate, which gives this control type a failsafe feature.

Riser blocks and double magnets

To increase the variety of machining operations suitable to magnetic work holding, riser blocks or pole extenders can be used with a magnetic chuck to increase accessibility and reduce interference. These blocks are essentially stand-offs tHombre