Designing the metal stamping die to produce a new precision part is one of the most important steps to ensuring long-term success in production. Depending on the manufacturer’s requirements for the part, the metal stamping firm may be able to design a die that produces multiple parts in one stroke of the press, known as a multiple-up die. The advantage of a multiple-up die is its ability to significantly reduce the piece-part price and increase production volume.
How a multiple-up die works
A multiple-up die may produce two or more of the same part or several different parts nested together on one metal strip. Compare it to a baker rolling out cookie dough to cut into shapes. The smart baker will find a way to cut as many cookies from one piece of dough as possible, which may mean using just one shape or nesting multiple shapes together. Although designing a metal stamping tool is a much more complex process, of course, engineers will take into account the amount of material required, the dimensions of the part, the operations needed to form the part, and how multiple parts might fit together on a single metal strip layout.
However, not every part can be produced with a multiple-up die. Metal stamping engineers must take many factors into consideration when designing a new tool and die, as well as the metal strip layout. The optimal design may result in producing a single part rather than multiple parts per die.
Factors in multiple-up die usage in metal stamping
- Expected production quantity and timeframe
- Material costs and anticipated scrap
- Tooling development and maintenance costs
- Variations in production and tight tolerances
Handling high production volumes
Manufacturers that are launching a new product in a tight timeframe may require a large quantity of metal stamped parts to be produced very quickly. The quantities that call for multiple-up dies may number as high as millions per week. Depending on the metal stamping firm’s press capacity, the best solution may be a multiple-up die, which can produce two or more parts on a single pass through a press.
By forming multiple parts on a single metal strip, production times can be cut in half, even though presses may run slightly slower with multiple-up dies. While tools can be designed to produce as many as 18 parts per die, the higher quantities produced in a single die often result in greater variances in each part’s measurements.
Reducing scrap and material costs
When designing a metal strip layout, engineers will take into consideration the cost of the material and the amount of scrap that will be generated after the part goes through the press. The more expensive the material, the more expensive the scrap becomes. In general, the design of any metal strip layout is created to keep scrap to a minimum, although the types of metal-forming operations that the part requires will dictate how many parts can be produced in a single press pass.
In order to accommodate multiple parts, the strip design for a multiple-up die may use a wider piece of metal that can fit interlaced multiple parts, or the parts may be offset, facing different sides of the press. Multiple-up dies can increase material yields by as much as 20 to 50 percent.
Keeping tool and maintenance costs down
A large component of the cost of metal stamping is the development of the tool and die for a new part. Not only must the tool produce a part to exacting specifications, but it also must be able to consistently do so over time to meet quality targets. Given the complexity of design, tooling costs for multiple-up dies average 50 percent higher than single dies.
A one-up die is simpler to maintain, while multiple-up dies tend to require more maintenance, resulting in greater downtime and higher maintenance costs.
Manufacturers who request a two-up die should keep in mind both the positives and negatives of multiple-up dies. For example, if a multiple-up die is producing a set of four different parts at once, manufacturers run the risk of a mismatch on their inventory, if one part encounters quality issues or a box of one of the parts is damaged in transit. In that case, all four parts must be run again simultaneously, resulting in scrapped parts, because the tool and die were designed for a multiple-up die to produce four parts at once.
Minimizing variances and achieving tight tolerances
For complex, precision metal stampings, multiple-up dies can be problematic. If a part has numerous critical measurements and no room for variances, then a single die is likely the better choice. In fact, many manufacturers are willing to forego the cost and volume benefits of multiple-up dies to avoid bimodal distributions on tightly toleranced parts. On the other hand, if the manufacturer can accept a specified variance in part measurements, a multiple-up die can be more efficient overall.
Estimating the multiple-up die option for metal stamping
When a metal stamping firm receives a request for a quote for a new project, their engineers will take into account the part’s critical dimensions, material specifications and costs, and annual volume projections. Using computer-aided design programs, the engineers will go through the process of determining the design of the tool and die, as well as the metal strip layout, in order to accurately estimate costs. If annual volumes are high enough, a manufacturer can request a quote that compares the costs of using a single die to a multiple-up die.
Keep in mind that the piece price does not tell the whole story, as tooling and maintenance costs and the ability to maintain tight tolerances over the life of the part’s production must also be considered. The metal stamping firm’s team should be able to advise you on your options and recommend the optimal type of die for your project.