Laminated stacks are in use everywhere in electromagnetic
products. According to LH Industries Corp., a Fort Wayne,
IN, U.S. maker of die and stamping technologies, whether the
laminations are produced "loose" or in an interlocked, die-assembled
state, the cores have always been the product of the planar
configuration (2D geometry) of the individual lamination and
the height of the stack (altitude). Other than changes in
height, no other variation was permitted along the Z axis.
Varilok, a new technology from LH Industries, is said to
change all that by allowing multiple lamination shapes in
a stack, programmably sequenced, to generate very complex
issue: July 2003 APPLIANCE Magazine
Lamination Die Technology
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Varilok is a proprietary lamination die technology that is said to change the rules by which laminated stacks can be designed.
"The main attribute of Varilok is that it grants the product
designer heretofore impossible control of laminated stack
geometry in the Z axis. That may sound simple, but that allows
limitless enhanced part features," explains Tom Neuenschwander,
vice president of Technology. "Perhaps the need is to fit
more power into a confined space. Maybe integral stator core
mounting features would help accomplish that. The appliance
engineer can design the electromagnetic core to conform more
closely to the allowable space, available mounting surfaces,
and for better control of secondary processes such as winding."
Varilok permits the stamping, collating, and interlocking
of laminations of multiple outside perimeters into assembled
stacks inside the die. The technology is said to be perfectly
suited to the high-volume production of coil-on-plug ignition
cores, specifically the cylindrically shaped laminated parts
often referred to as "pencil cores." However, notes Mr. Neuenschwander,
Varilok's ability to produce previously impossible 3D geometric
shapes, with laminations stamped and assembled in the die,
extends to an infinite variety of parts.
"Varilok is applicable to electric motor design, so it is,
by extension, applicable to any appliance incorporating a
motor drive for any purpose," says Mr. Neuenschwander. "The
technology, however, will also apply to any appliance utilizing
other types of electromagnetic devices as well. These might
include electrically driven linear or rotary actuation, solenoids,
generators, and transformers."
According to Mr. Neuenschwander, all the possible variations
are derived from the primary Varilok principle—the capability
of stamping laminations of varying outside configurations
and interlocking them together in the die. The variety of
lamination shapes is created by a series of selectively actuable
punches. The number of punches, and thus the number of different
laminations permitted in the stack, is limited only by the
linear space available (in the feed direction) in the press
and die. Placing the contouring punches/die openings in a
transversely moving sub-die(s) can mitigate even that limitation.
Precisely positioned by servomotor-driven lead screws, the
sub-die stamps each lamination's contour in the desired sequence.
As the strip advances through the progressive die, the contour
of each individual lamination is selectively trimmed to shape,
and the entire operation is sequenced so that each lamination
arrives at the assembly, or choke station, in the desired
order. The choke station is designed to precisely locate each
subsequent lamination in relation to the previous lam of the
stack-in-process. All the while the choke is holding that
stack and a number of previously completed stacks in an interference
fit, thus providing resistance against the incoming lamination—resistance
that is necessary to facilitate the interlocking operation.