As amazing as the machinery is that spits out all sizes and types of metallic parts and assemblies, none of that is possible without the tooling. Forces supplied by the machinery act on the tools and dies, which then transfer that force to a workpiece, creating the finished part. Design, manufacture and testing of tools and dies play enormous roles in lead time and cost of part production. Costs depend on complexity of the tooling and the robustness required (tooling for high-volume part runs or for materials requiring greater forming forces must be stronger). Advances in computer die-design and forming-simulation technology have enabled shorter lead times and tryout times as well as efficiencies in tool build and performance, all helping to make tools and dies more affordable.
Tru-Form utilizes Wire EDM (Electronic Discharge Machine) machines that cut the steal for the tools. We operate three of these machines enabling us to produce or replace our tools on demand. This is a major competitive advantage for us and delivers significant benefits for our customers since most of our competitors have to send lengthening their time of production.
A diverse range of metalforming operations--including blanking, piercing, forming and drawing, as well as variations and combinations of these processes--is frequently carried out with dedicated or “hard” tooling. Such tooling is used in stamping presses and slideforming machines, developed specifically for producing one particular part configuration. We can utilize tools and design specifications provided by our customers or developed internally at Tru-Form.
Dedicated tooling includes upper and lower die components. In operation, the upper die is attached to the press slide, which moves vertically, and the lower die is secured to the stationary bolster. As the slide descends, the workpiece is shaped between the dies.
For increased productivity, two or more basic metalforming operations can be combined in dedicated tooling. Beyond the single operation per press-stroke, other options with dedicated tooling include compound dies, progressive tooling and transfer-die systems. Compound dies allow two or more operations to be combined into one. A compound blank and pierce, for example, permits the entire perimeter and all holes to be cut in one press stroke. Metalformers specializing in smaller production runs (to thousands of pieces) often utilize a compound system built into a master die set. In production, parts typically run slightly slower than normal blanking, but much faster than separate blanking and piercing. In effect, an additional operation is gained in the process. Similarly, compound dies can combine other operations. Among them: blanking and forming or blanking, piercing and forming.
Progressive tooling makes use of one die in which multiple operations are performed in consecutive stations. Normally, stock is fed automatically. The workpieces remain attached to a strip or ribbon of the material, and thereby are advanced from station to station with each press stroke. Unlike single-operation dies, progressive dies perform only a portion of the work at each station. With blanking, for example, single-operation dies cut an entire periphery at once, while progressive dies may cut the periphery in stages.
Good progressive tool design allows the incorporation of multiple forming and piercing operations for economy and reproducibility. Transfer-die systems differ from progressive tooling in that individual workpieces are moved from one die station to the next between press strokes by mechanical fingers, levers or cams built into or mounted on the press. Transfer operations often require additional equipment, such as strippers, eject pins and die cushions. High production volumes are a prerequisite for transfer-die systems, which often require specially designed transfer presses.
Compared to CNC fabrication using single-purpose or universal tools, dedicated tools generally provide superior dimensional precision and uniformity of product throughout a production run, and good reproducibility from one lot to another. Generally more complex and costlier to design and build, they also require longer lead times. In selecting the appropriate tooling method, the designer weighs the minimal tooling cost, short lead times and relatively low production rates of CNC fabrication against the higher tooling cost, greater precision, longer lead times and higher operating efficiencies of dedicated tooling. Ultimately, total production quantity is often the deciding factor.
Many products begin as CNC fabrication prototypes, then evolve into hard-tooled operations when production quantities reach higher levels. Early consultation with the metalforming vendor regarding total anticipated quantities is essential in planning the appropriate tooling approach.
Part size and the degree of dimensional precision may also affect tool selection, regardless of the quantities involved. Parts with extremely large plan-view areas (greater than 30 by 30 in., for example) may be too large for all but the very largest specialized tooling and press equipment.
Tru-Form’s expertise runs the gamut from CNC to compound dies and progressive tooling offering the right production solution to our customer’s product specifications, quantity, and time requirements.