How to Choose & Use Lifting Magnets - ERIEZ - #9

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EXAMPLE: 4' x 8' x 1" (1219mm x 2438mm x 25mm) plate is to be handledalmost all the time with a lift magnet assembly. Occasionally, much heavier, larger, and thicker plates are to be encountered. Rather than sizing the mag- netic system for the heavier plates, consider sizing the magnet lift assembly to the common lightweight plates and plan to use other approaches on the rare heavier and larger plates.You could (a) use a sling and hook arrangement to lift the heavier plates bywelding temporary lift eyes on the heavier plates, or (b) perform any burning or cutting that would normally be done on the larger plates before you unload them.Often a very large load variation as described would dictate a high initialmagnet cost for total magnetic handling. With the approach described, the user gets the laborsaving and speed advantages of magnetic handling on 95% of the material handled. Further, the lift beam can be designed for future possible magnet additions that would make the system completely automatic.The point is that a study of all factors of economy, cycle time, manpoweravailable, and a clear definition of the actual number of times an outsized load is encountered can result in a significantly reduced initial magnet system cost. Did you know? “Breakaway force” is the force required to seperate the loadfrom the magnet when pulled in a direction perpendicular tothe magnet’s face. The breakaway force of a lifting magnet isproportional to the thickness of the material being lifted. Amagnet’s breakaway force increases until the material beinglifted exceeds the saturation thickness. Accordingly, thinnermaterials will not yield as high a breakaway force whilethicker materials will not yield a greater breakaway force. PARTIAL MAGNET FACE USE FOR LIFT Whenever the load surface is not uniform over the magnet face, flat liftingmagnets can be used but must be derated in proportion to the load area actually contacting the magnet face.When lifting a sheet of expanded metal therewill be poor contact on the magnet face because of the high points on the expanded sheet. Further, the openings in the sheet will not offer a solid path for the magnetic circuit. Almost the same consideration is required when handling flat perforated sheet. Although these sheets are flat, with no high points that prevent flush load and magnet contact, the holes in the sheet also prevent a solid path for the magnetic circuit. With both applications the effective lifting power of the magnet will be a function of: 9