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Description:
Taylor-Winfield's patented Prep/Lap process is a refined version of the Narrow-Lap seam welding technique.
In the
Narrow-Lap method, strip is clamped, sheared, narrowly overlapped and resistance seam welded in the conventional manner. This produces welds of excellent quality, but the joint is 30 to 70 percent
thicker than the strip. Although acceptable for many purposes, this added thickness, in certain applications, causes problems in subsequent processing operations.
This objectionable
characteristic was eliminated by development of the Prep/Lap process, which gained immediate and widespread acceptance. Since 1964, over 150 Prep/Lap welders have been furnished to the steel mills of the
world. The process was named for the manner in which the strip ends are prepared and lapped during the overall joining operation.
The radical reduction in joint thickness which takes place in
Prep/Lap Welding results from a sequence of machine functions, detailed on page 1. As with the Narrow-Lap process, the strips are automatically clamped, sheared square, and narrowly overlapped. A
planishing roll then reduces the thickness of the weld area by about 25 percent and widens the overlap approximately 75 percent. The interfacing planes are also angled.
Next in the sequence, one
strip is retracted slightly along the inclined plane to create triangular spaces at both ends to receive excess weld metal as it extrudes laterally during the joining and final planishing operations.
This results in a smooth, flat and extremely strong joint that is virtually as thin as the strip. If, without the retraction step, an attempt is made to achieve equivalent joint reduction, either
extremely high planishing force or additional passes are required, fusion is less complete and the strip is wavy at the joint. These joints typically display greater hardness compared with Prep/Lap
joints.
Taylor-Winfield Prep/Lap Welders are also available as fully automatic units where a computer controls the weld parameter setup and (if required) the welder sequence.
Preloader/retractor mechanisms can be added to minimize time and assure the best alignment of coil ends. All Prep/Lap Welders include the capability of being used as a single-pass Narrow-Lap Welder.
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