Which Tool Type for Which Application?
Cold forming is not a one-size-fits-all process – depending on part requirements, production volume, and complexity, different tooling systems are used. But the choice of tool isn’t just about the part itself; it also heavily depends on the available press systems in the plant. Here's an overview of the three most important types:
Progressive Dies – The Pace-Setter for Simple Parts and High Volumes
With progressive dies, everything follows a clear sequence: with each press stroke, the part moves to the next stage – cutting, then punching, bending, or embossing. Each operation happens step by step, station by station. If the part geometry and process allow, multiple forming steps can even be combined in one station – for example, forming and trimming in one go. The sheet metal is fed directly from a coil and pulled into the tool as a continuous strip. This strip automatically transports the part from one forming stage to the next. Only at the very end is the finished part separated from the strip and ejected.
However, when dealing with highly complex geometries or large part dimensions, this system reaches its limits. Tight space conditions, restricted accessibility, and the fixed strip feed can make certain parts simply unfeasible.
Typically used for:
- Large production volumes
- Simple to moderately complex geometries
- Small to medium-sized parts
- Parts requiring high repeatability
Advantages:
- High output with minimal space requirements
- Very cost-effective for standardized parts
- Process reliability through a continuous operation chain
- Compact design
- Lower press costs due to integrated strip transport
- No separate blank handling required
Transfer Dies – When Things Get Complex
Transfer dies come into play when part geometries are too demanding for traditional progressive die processes – for example, parts with multiple deep-drawing steps, pronounced radii, or asymmetric shapes. Unlike progressive dies, the forming stations in a transfer die setup are physically separated. This allows operations like deep drawing, cutting, punching, or calibrating to be performed one after the other, in a targeted sequence.
Instead of moving a continuous metal strip through the stations, here the individual part is transferred – step by step. This transfer happens fully automatically via a transfer or handling unit, which precisely places the part into the next forming stage. Since each station is specialized for a single operation, complex forming sequences can be better controlled and decoupled.
Typically used for:
- Complex parts with multiple forming stages
- Medium to high production volumes
- Parts with significant deep-drawing requirements or critical geometries
- Materials with challenging forming behavior (e.g. high-strength steels)
Advantages:
- Greater design freedom due to separated forming stations
- High flexibility in part shape and process control
- Automated part transfer ensures stable and reliable processes
- Ideal for demanding forming operations
- Adaptable to material behavior – e.g. targeted springback control
- Cost-efficient for complex geometries and medium to high volumes
Tandem Tools – For Large Parts with High Demands
Sometimes a part is simply too large or too complex to accommodate all forming steps within a single tool – whether due to the part’s dimensions, the required press force, or simply the limited space available in a single press. This is where tandem tools, also known as line dies, come into play.
A tandem tool consists of several interlinked individual tools installed in a series of presses – a so-called press line. Each tool performs a defined step in the process: from initial deep drawing, intermediate reshaping, and punching, to the final trimming. Depending on the process, combinations within a single station are also possible – such as cutting and forming in one stroke.
The part – usually a blank prepared from a coil – is loaded into the first press at the beginning. After each forming step, robots or handling systems transfer the part to the next station. The parts can even be flipped during transfer, which provides additional flexibility in tool design for specific geometries.
Typically used for:
- Large or deep-drawn structural components
- Parts that cannot be manufactured in a single press
- Complex manufacturing processes with multiple forming steps
- Small batches, pre-series, or prototypes requiring adjustments
Advantages:
- High flexibility in tool and process design
- Suitable for larger part dimensions
- Parts can be flipped and repositioned during the process
