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Coldformer makes precise parts.

True-running accuracies (tir) of 0.002" and diameter tolerances of 0.0004" are possible when specials are produced from coiled wire on high-precision progressive coldformers, according to Hatebur Metalforming Equipment Ltd, Reinach, Switzerland. These machines make better use of the metal's formabil- ity, so they can achieve higher forming ratios., The result of this improved accuracy is that some machining operations are reduced or eliminated altogether.

For example, the radius of a flared "trumpet" of a component for a hydraulic brake system can't have any burrs or sharp edges. Otherwise, the hydraulic hoses could be damaged. In the past it has been formed slightly oversize and then machined down to size. But when the part is made on Coldmatic coldformers, the consistent accuracy of the cutoffs produces filled parts, eliminating additional machining.

Producing higher-precision coldformed parts starts with higher precision cutoffs. Coldmatic five-die coldformers are equipped with a high-speed shearing system that shears on impact. A tube-shaped shearing slide is accelerated by a cam-controlled striker head that severs the metal with a clean cut. Because of the high shearing speed, the metal does not distort. Material distribution and geometrical shape are improved.

The resulting sheared surface is smoother, with fewer serrations and cracks..Also, volumetric consistency is better; the volume variation is only half as large as that of conventionally sheared cutoffs. Production experience shows that tool life is thus about 20% longer.

In one example, the machine forms plungers for hydraulic valve lifters, including an internal shoulder, that would otherwise require a machining step. A special tool design reverses metal flow, so there is no need to machine the contact surface with its sealing radius in the bore.

Hydraulic pipe screws require smooth, clean transitions from bore to radii at both ends. This is a crucial feature of these hydraulic fittings, to make sure the brake tubing is not damaged. In this case, dies are installed on the punch side, and the punches on the die side at the first two forming stations. This places the metal for the hex head on the right side for easy upsetting.

On conventional coldformers, it is necessary to use turnaround grippers for such jobs to turn the blanks end-for-end during transfer,which reduces reliability.

In the case of a door latch bolt, a recessed section between the head and the hexagonal collar is formed with a segmental tool with inserts that open and close. This method eliminates the need to turn down the section from the head diameter.

The machine produces sparkplug 'shells in five operations, where it used to' take a six-die coldformer. The improved quality of the sheared cutoffs makes this possible. Because they are not deformed, there is no need to square them up before forming. The first station can be used for a combined extrusion operation, thus saving a forming operation.
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Title Annotation:Hatebur Metalforming Equipment Ltd.'s high-precision device
Publication:Tooling & Production
Date:May 1, 1992
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