August 2021 Volume 3

MAINTENANCE

Maintaining Die Space Parallelism on Forging Presses By Jeff Fredline

Now more than ever, die space parallelism is critical in manufacturing today's complex parts. As the industry moves toward tighter tolerances and the goal of cost reduction due to net forgings, die space parallelismwill play a major role. The allowable tolerance for parallelism left to right and front to rear in the die space is .001" per foot of span. On metal stamping presses there are more methods of controlling the slide path. In a forging press you have several areas that must be maintained properly to control your die space parallelism. • Hard Plate • Wedge Surface • Ram Face • Lower and Upper Ram Way Surfaces and Related Ram Guiding Hard Plates The hard plate is a renewable surface that can be ground and changed out as the surface wears. The plate can be ground top and bottom to clean it up flat and true and then reinstalled. Wedge Surface and Assembly One of the typical problems in the industry is wedge assembly maintenance. When you're in a production environment with time pressures, it is difficult to schedule the down time to maintain the wedge assembly. There are different wedge designs dependent on the manufacturer. Ajax machines use a single front to rear wedge assembly. The common wear surfaces are the sides, top and bottom of the wedge. Repairing the wedge is not too difficult; normally pad welding surfaces on the side and perhaps the bottom, stress relieving and the machining to fit the mating surfaces in the frame. Repairing the surfaces in the press frame itself are more difficult and can involve welding and portable machining of the wedge mounting surfaces. Failure to maintain the surfaces will allow the wedge to shift left to right during the forging process and could cause your bolster assembly to move. National Maxipres uses a two wedge assembly, main and auxiliary wedges. You control the wedge height by adjusting the auxiliary wedge in and out. Due to the forging environment contamination is often the problem as it relates to any moving components on the press, particularly the wedge assembly. Like the Ajax wedge assembly, as the components wear and become inoperable the wedge assembly becomes unusable and then the only method to adjust the die space is using shim plates.

Figure 1: Double Wedge Construction

Ram Face There is usually a plate mounted to the face of the ram also, which provides a renewable surface to work with. This plate can be removed, ground top and bottom and installed to maintain the ram face condition. In addition to the ram face, the ram way surfaces are critical to the maintenance of the die space.

Figure 2: Eccentric Shaft, Pitman and Ram

FIA MAGAZINE | AUGUST 2021 16