There are three primary types of impacts: reverse, forward and combination, and these are named after the principal direction in which the metal “flows” under impacting pressures. Often times in order to achieve a customer’s final requirement, Best Metal will develop particular strategies of multiple forming operations to achieve the desired result.

Reverse Impacting
Reverse impacting is used to create specific shell configurations with a forged base and extruded sidewalls. The cold metal billet is placed in a die cavity and then struck by a punch forcing the metal to flow upward around the punch through the opening between the punch and the die. The clearance between the die and the punch determines the wall thickness of the shell. The base thickness is determined by adjustment of the bottom position of the punch ram and should be a minimum of 15% greater than the side wall thickness. Though this appears to be a simple process, expert design will yield an number of configurations including: multi-shell walls, internal or external ribs and circular, oval, rectangular, square and other cross sections. Best Metal offers proprietary methods in ensuring wall thickness to meet customer tolerance requirements.

Forward Impacting
Sometimes called the Hooker process, forward impacting most resembles conventional extruding. The billet is again placed in the die, but this time metal is forced through the orifice of the die by the action of the punch, causing the metal to flow in the direction of punch travel. The punch fits to the wall of the die so closely that no metal escapes backwards. The method is used to form round, non-round, straight, and ribbed rods and thin walled tubing with one or both ends open, and with tapered or parallel side walls. Hollow or semi-hollow parts with a heavy flange and multiple diameters formed on the inside and outside are often made by forward impacting.

Combination Impacting
Combination impacting involves the combination of forward and reverse metal flow. This method is ideal for forming complex-shaped arts. By incorporating a lower punch and a cavity in the upper punch, the metal is allowed to flow upward into the punch, until the cavity is filled. Further punch movement causes forward extrusion of the remaining metal and results also in the formation of a web. Which method is best to meet your requirements? Best Metal can work with you to find a solution that optimizes your return on investment.