Walker Magnetics SMART-D SERIES - Manual (Page 16)

O.S. WALKER Co., Inc. SMART-D Control
SMART D MANUAL DD14511L Rev. L, March 30, 2011
4-2
4.1.2 Workpiece Thickness
The greater the number of lines of magnetic force flowing from a magnet into the
workpiece the greater the effectiveness of the magnetic chuck. The thicker the workpiece,
the more lines of magnetic force are able to flow. After a certain thickness of the
workpiece, no additional lines of force will flow because the magnet has reached its full
capacity.
• Thin workpieces mean less iron available, and thus fewer lines of magnetic force flow
from the magnet into the workpiece. Therefore, the chuck holding capacity is reduced.
• Typically, the minimum thickness of a workpiece required to reach full holding capacity
is the same as the thickness of the chuck major magnetic steel poles.
4.1.3 Portion of the Chuck Surface In Contact With the Workpiece
The full surface of the chuck top plate must be covered by the workpiece to achieve the
maximum holding capacity. The surface of the workpiece must contact equal areas of the
chuck opposite polarity major magnetic poles to obtain maximum holding force.
4.1.4 Workpiece Material
Low carbon steel such as SAE 1020 steel, are nearly as good conductors of magnetic
lines of force as pure iron. However, many other alloys contain non-magnetic materials
which reduce the ability of magnetic lines of force to flow. An alloy such as SAE 300
series stainless steel is almost as poor a conductor of magnetic lines of force as air.
Type 416 stainless steel is considered magnetic, but it contains enough chromium so that
a magnet can develop only about one half as much magnetic force as it can on an SAE
1020 steel workpiece. Also, because of the carbon content, the force developed on typical
cast iron is less than one half that developed on SAE 1020 steel. (Chilled cast iron further
reduces the force to less than one quarter.)
Additional concerns regarding Magnetic Holding should be forwarded to O. S. Walker,
Inc.