October 8, 2009
When a quality stamped product is needed, operating as a team, communication and a solid understanding of the plan is paramount in efficiently producing a stamping die. The three critical phases of producing a capable stamping die are design, build (manufacture) and troubleshooting. Each phase is intertwined and dependent on one another. A design review is an excellent opportunity to develop a plan and review the construction and manufacturing methods that are going to be used to make the components. Ultimately, the challenge is to have gained a profit for your company and produced a stamping die of superior quality.
The critical phases of producing a capable stamping die are design, build, and troubleshoot (debug). Each of these phases is of equal importance and dependent on one another. If one of these phases is inadequate, determining the effectiveness of the other phases is extremely difficult.
In addition, three concepts must accompany these three phases—understanding, respect, and communication. These are essential for a team to achieve a common goal. In these trying times, achieving your company's goals may be the difference between survival and going out of business.
When working on any project, you will find that there are many ways to design, build, or fix something. Broken down to its fundamentals, the foundation of any project is problem-solving. The "best way" of doing or fixing something usually depends on the perspective of the person who is determining what that best way is.
In producing a progressive die, the die designer often has a very different perspective than the individual manufacturing the details or the troubleshooter. If you were to ask each of these individuals (designer, builder, and troubleshooter) for the best way to build a tool, you likely would get three different answers corresponding with their experience and expertise.
An example of how perspective can affect preference is how punches are held in an upper mounting block (retainer).
Although the contours could, in fact, be machined quickly, the toolmaker did not consider everything involved in producing the details. The details would take about three hours each to design, model, and set up. The final chosen solution required more machining time, but the time needed overall was considerably less. To maximize cost-effectiveness, everyone involved must make decisions based on what is least expensive when considering every facet.
A die design review is a great opportunity to discuss issues that affect the tooling cost, including how the details are designed, how the details will be manufactured, and which stations will be needed to stamp the parts.
It is helpful for members who perform each of the three phases to participate in the design review. When discussing potential changes to a design, each person must keep an open mind, be respectful, and be mindful that what is good for one phase may not be best overall.
Too often design changes are based on a personal preference, and little consideration is given to the cost and risk associated with changing a design.
Changing a design after the concepts have been established increases the likelihood of design-related errors and the need for additional engineering time. It is important that each member in the group communicates openly and all come to a consensus after evaluating the impact it will have on all areas.
Most changes come with advantages and disadvantages. If after weighing the advantages and disadvantages, you see no clear and undisputed advantage to a change, it is best to leave the design as is to lessen the likelihood of design errors and additional costs.Obviously, how a die and its components are designed has a major impact on the build and troubleshooting phases, so many risk-to-reward decisions must be made in the early stages of designing a stamping tool.
For example, how many stations are needed to produce the part, and where are provisional stations needed? The more complex the stamping is, the more difficult it is to determine what is needed.
Considerable risk is inherent in not having enough stations or not having them where you need them. To reduce risk, you can simply design a tool with a lot of extra stations. Unfortunately, this also incurs additional cost—a luxury not usually acceptable.
On the reward side, designing the die with fewer stations may reduce cost and, therefore, increase profit. On the other hand, not having enough stations to make the part correctly is a failure of the design phase that will probably appear in the troubleshooting phase.
During the die build phase, the primary concern is the quality of the die components. If they are not built within tolerance, the design is not going to function as intended, which will make troubleshooting nearly impossible.
Establishing how to manufacture die components accurately and cost-effectively is a huge challenge. With the increasing capabilities and flexibility of today's equipment, the number of ways to use equipment to manufacture components is seemingly endless. Being creative and finding the most cost-effective way of manufacturing components requires imagination and may be key to the survival of your company.
In most cases, how the components are designed affects which equipment can be used and which options are available for manufacturing them. It is important that the designer has an understanding of how the details are manufactured and how to facilitate the manufacturing methods.
Ideally, components can be designed to allow the use of multiple manufacturing methods. For example, the blanking (profile) punch shown in Figure 2 can be made using a combination of wire electrical discharge machining (EDM) and conventional surface grinding or grinding using a visual grinder.
As technology and equipment change, your processes must evolve. Die designs must change to take full advantage of new, more efficient component manufacturing methods. For example, in the past some companies did not have a conventional EDM or a high-speed hard milling machine capable of making coin/deburr tooling with a quality finish around complex contours. As a result, they would split the blocks into several pieces, utilizing multiple stations so they could surface-grind them (see Figures 3a and 3b). Now companies that have solid-modeling capabilities and a quality conventional EDM or a high-speed hard milling machine can create these contours with a high-quality finish on one block, thus reducing the number of details needed.
Because the project as a whole is nearing completion at the troubleshooting, or debugging, phase, the pressure to finish (get a usable product off of the die) usually is at its greatest. Troubleshooting the stamping of very complex products is the most challenging phase of the process. Shortcomings in the other two phases are usually exposed during debugging. Working together and communicating are even more critical during troubleshooting than they are in the first two phases. Having the die designers and builders closely involved in troubleshooting fosters an environment of ownership and pride that is key in producing quality tools.
The knowledge gained from being involved with troubleshooting also helps develop skills that can be applied to future dies. Attention to detail, persistence, patience, and willingness to follow through are common traits of successful troubleshooters. It's not uncommon for many progressive dies that were designed and built well to fail because the debugging was not carried through to completion.
An example is a tool that was not capable of running at the speeds it needed to in order to make a profit. It was discovered that the tool had a poorly designed cam (mandrel) station that would break anytime speed was increased. The part, formed over a mandrel, was designed with excessive travel (see Figures 4a and 4b). The solution—although it required a lot of new tooling—was effective. The station was redesigned utilizing two cams—one from each side—thus cutting the cam (mandrel) travel in half. Before the change, the tool was running around 600 strokes per minute (SPM); after the change it ran at 1,200 SPM.
Because cost is such a major consideration, some companies have one or more phases completed by the lowest-cost source at different locations within their company, or by outside vendors. Typically, companies don't consider the hidden costs in this strategy. When managed correctly, this approach allows resources to be used, based on their strengths. However, facilitating the necessary communication can be a daunting task. In addition, when problems occur, accountability can become a costly problem.All communication should flow through a primary individual. This individual needs to make sure that whenever a critical issue arises, all parties involved work together to form a solution. Many times in this situation, it is difficult to determine which source failed.
When problems occur, each source feels pressure to deny fault because it can reduce or eliminate the source's profit. This inevitably results in additional costs, because more funds are then needed to redesign or rebuild tooling, or perform additional debugging.
The two most common hidden costs are the hours spent by the communication facilitator with outside parties and the funds spent on changes when it is not clear which source failed. To avoid these headaches, some companies have mandated that their stamping dies be sourced only to shops that complete all phases at one facility and don't outsource.
Each phase is intertwined and dependent on one another. Ultimately, the challenge is to have gained a profit for your company and produced a stamping die of superior quality.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.