Types of Impacts
Reverse, forward and combination, and these are named after the principal direction in which the aluminum flows under the pressure developed by the punch.
Benefits of Impacts
- 0 Draft Parts
- Wrought Gain
- No Porosity
- Near Net Reduces Scrap
On impact the metal flows in the same direction as the punch through an orifice in the bottom of the die. Used for forming long, solid or hollow parts and components with varying cross sections along the length.
In reverse impacting a closed bottom die is used. On impact the metal flows through metering points between the punch and die wall in the reverse direction of punch travel. Hollow, open-ended shells or cups in a variety of shapes and sizes are the result.
The combination impact is, as the name implies, a combination of forward and reverse metal flow. The metal flows both backward along the punch and forward through the die bottom making possible more complex parts with variations in diameter, wall thickness, shape and length.
- Fast Production
- Clean & Simple
- Air Tight
- High Tolerance
- Eliminate Machining
- Simplify Assembly
The exact speed, of course, depends on the size of the part and the nature of the equipment producing it. Production rates of 3,000 pcs/hour have been achieved with automatic feeding equipment. However, when the parts are large and complicated, low production rates may be economically justified.
The impacted part is a fully wrought, dense, and porous-free structure. Grain alignment is highly uniform, imparting maximum strength and toughness. This metallurgical condition cannot be secured by casting or by machining a wrought bar. The strength of an impact is, therefore, equal or in excess of the maximum strength obtainable from any other metal forming technique including forgings.
Clean & Simple
There is no flash to be removed, no scale, nor are there parting lines. Surface finish is such that it usually does not require further finishing operations if the part has been designed and produced to the desired size.
Variation and wall thickness can usually be held to ~5% of the wall thickness. Tolerances on diameters will vary with the size of the impact; however, ~.005 are not unusual tolerances. Ovality can be held to approximately .001 per inch of diameter; and interior configurations are draft-free.
The non-heat-treatable alloys are work hardened by impacting. The heat-treatable alloys can be heat-treated in normal fashion after impacting. Some of the heat-treatable alloys including the number 6000 and 7000 series are brought to 60% of their maximum heat-treated and aged properties by impacting alone. Many applications of these alloys require no further thermal treatment.
After removal from the press, the impact may be treated exactly like any other piece of wrought aluminum. It may be machined, ground, soldered, welded, brazed, bent, plated or anodized.
Labor and metal savings alone are tremendous when compared to casting and machining. In many cases, the cost of a finished impact is less than the cost of the bar stock from which it might have been machined. Since impacting tends to develop an alloy’s higher strength characteristics, it is oten possible to use lower cost alloys when the part is impacted.
Impacts can replace machined components directly in many designs. In many others, the impacts are used to reduce machining costs. When stress calls for a wrought aluminum part, excess metal and machining time may be reduced by providing the machinist with an impacted and heat-treated part.
They may be used to replace riveted and welded assemblies with many attending benefits such as increased strength, increased fatigue resistance, reduced weight and improved appearance, reduced or eliminated finishing costs, greater piece to piece uniformity and the elimination or reduction of final assembly costs.