Modular Hard Dies
What are they and how do they compare with other tooling options
Modular Hard Dies are uniquely different from conventional hard dies, yet are
similar in function to any of the conventional methods for hole punching.
Conventional Hard Dies:
Custom hard dies are usually designed to produce a single stamping, either in a single hit, or progressively, through the course of multiple hits or stations. They can be fed manually or automated from coil, for high-volume production.
Although by their nature no two custom dies are alike, they all have a common component called a “die set”, which consists of the top and bottom steel plates or “shoes” – held in vertical alignment by two or more guide pins and bushings.
The die set is the foundation that keeps all of the punch and die cutting or forming steels in correct vertical alignment throughout the “up and down” cycle action of the punch press used to produce the stampings.
The actual design of the cutting components in a custom die is unique to the subject being produced – there is little or no standardization or reusability of custom die components. A portion of every custom die’s cost is associated with its basic die set.
Modular Hard Dies:
With modular tooling, the basic die set – if there is one – becomes a single, reusable component of a complete system. The die set is purchased only once and used for all jobs. In keeping with the reusability theme, modular dies have reusable punch and die bushing retainers, each used to hold a series of interchangeable, reusable punches and die bushings. Unlike custom dies, these modular components are used on multiple applications to produce a variety of different stampings.
The concept of modular hard dies is to reuse standardized, individual punching members – the die set, retainers, punches, die bushings and strippers are all reusable components.
Many companies design their products to have the same punched features, i.e. the same holes, shapes, notches etc. If the punches and dies made for these features can be reused to produce a variety of different jobs, the resultant cost savings can be significant.
Modular hard die system components are shared and reused to make many different subjects, even long after the job they were originally purchased for has been completed.
With modular dies, your tooling dollars are grouped into (3) basic categories: Capital Investment (Die Set, Holders, Gages, etc.), Tool Package (standard, reusable punches and die bushings, etc.) and Job-Specific (typically templates and any special tools).
Depending on the Whistler system you select, you may wish to purchase enough tools to permit setup of the next job while the first is in production. We call this the “second highest quantity” – or the number of tools required to simultaneously run your two most complex parts.
If your press area and selected modular system are large enough, it may even be possible to run more than one job per press cycle.
CNC Turrets and Lasers:
Other conventional methods for producing punched stampings include turret punch presses and lasers. While these high-tech methods will produce most of the common features associated with flat piercing and notching, their use requires the addition of technical support personnel and programmers to write the necessary CNC program codes.
In turret punch presses, the work piece is gripped and moved under the turret head of the machine while the turret rotates as required to present the desired punch size. Movement of the work and rotation of the turret are CNC- coordinated and controlled.
Turret punch presses are good choices for short to medium production runs of primarily flat stampings. Within constrained limitations, simple forms or extrusions can be achieved but these can typically done only in the “up” direction, to prevent interference with free movement of the work as it travels across the machine table.
Lasers use similar CNC technology to control movement of the work under the laser head, however lasers cannot achieve forms or extrusions of any kind. A laser can be a good solution for short run quantities and for work having large or irregular peripheral contours.
C Frame Tooling:
C-frame tools – so named because the tool holder frames are shaped like the letter ‘C’ – are well known as a low cost way to punch holes in sheet metal and other materials. C-frames are self-contained, meaning they can be used alone to punch a single hole or can be arranged in groupings to make complete stampings with multiple features. They don’t need any die set and are available in various sizes, each of which accommodates a specific range of interchangeable punches and dies. Since the frames themselves are not particularly stable, vertical punch-to-die alignment can be variable and therefore die clearance less than .006” / 0.15 mm is generally not recommended. Objectionable burr conditions can often result when C-frames are used for punching materials less than 18 GA mild steel, or equivalent.
C-frames are generally located in position through a concentric pin protruding from the bottom of the frame, into a mating hole that has been machined into a ½” / 12.7 mm thick template. Because of frame instability and since the actual point of punching takes place a few inches / several centimeters above the pin and template surface, hole location tolerances less than +/- .03” / 0.8 mm can be difficult to achieve. C-frames are usually available in several throat depths, ranging from 4” up through 18”. Throat depth limitations can present problems when used on larger stampings and depending on stamping complexity, the large “footprint” area of C-frames can often result in the need for additional hits to complete a job. C-frame tools are often used for in-line punching or for lower-volume production of non-critical pierce & notch applications, such as box covers for example. Due to limitations in the feed opening, C-frames are generally not able to accommodate formed features like extruded or embossed holes or lances and bent tabs.