Bridging the Skills Gap – Part 4: Magnetic Workholding Means Reduced Setup Time

Traditional workholding for machining centers can require large amounts of time to install, set-up and load/unload. Additionally, the use of simple vises or clamps on the worktable may not provide a secure and vibration-free method of holding the part, thus reducing the cutting rate and the life of the cutting tools. Flexibility is also a major concern, especially in shops that currently use more time in setup/change-over than in the actual machining process.

One technology to consider is magnetic work-tables. These provide a very fast and secure way of holding parts made from ferromagnetic material. The entire work surface of the magnetic table thus becomes a fixture area. These tables allow rests and stops to be attached, thus providing a repeatable position like a dedicated fixture while allowing other areas of the surface to remain open for that “hot job” to be quickly set-up and made. The holding strength is extremely high, and the holding forces are distributed over a larger surface area, thus reducing the distortion (spring-back action) of the part once removed from the cutting area.

Using probing in the machine to identify work offsets can further reduce the set-up time, allowing the part to be placed on virtually any area of the magnetic table while still allowing access to the other 5-sides. The expense of the magnetic workholding is quickly recouped through setup reduction and the reduced need for dedicated fixtures and other types of workholding.

One drawback to magnetic workholding is that the material removed from the part is also ferrous material and is therefore attracted to the magnetized area. These chips are quickly removed, however, by coolant flush or sweeping.

Magnetic tables may or may not be the answer to your specific quick change-over needs but they can facilitate many change-overs in just minutes. Partners in THINC member, Schunk, can provide more information about the use and application of this and many other workholding options. For more information, please visit their website at www.schunk.com.