By 2025, use of advanced high-strength steel (AHSS) for automotive lightweighting is expected to double from current levels. Good news for steel suppliers. Not so good for automotive pressrooms. First off, stamping these materials typically requires increased forces, making shear blades or blanking dies wear faster. Often, processing high-strength steels requires moving the job to a larger-capacity press line to achieve the same cut. Not only do tools wear more quickly, the chance of micro-fractures occurring along the cut line also increases in line with material hardness. These micro-fractures can develop into splits during the forming process.
Automatic Feed Company (AFCO), an established provider of traditional blanking and cut-to-length lines, began doing research into laser blanking in 2008, forming LaserCoil Technologies LLC (lasercoil.com) in 2011.
Compared to conventional laser cutting tables, the company says LaserCoil machines can achieve yield rates in the 60,000-piece range, where replacing traditional blanking stations starts looking more favorable. Add eliminating the need (and significant lead time) for dies and that laser cutting can process multiple materials (mild steels and aluminum in addition to high-strength steels), and the process begins looking downright attractive.
How It Works
This process relies on a series of dynamic profile conveyors that support the coil strip while providing a cutting path for the laser heads. These lanes independently and dynamically reposition to maintain a clear path below the moving laser head. This allows the coil to move forward through the system without jogging the strip back and forth and also automatically shedding scrap during the cutting process, delivering a burr-free, ready-to-stack part.
The laser cutting heads, using linear-induction motors, enable cutting of tightly nested, complex curvilinear shapes. These high-speed, three-axis linear motor gantry-mounted laser heads can be stationed in multiple modular cutting cells that travel along the moving strip to balance the workload for improved throughput, achieving rates similar to conventional blanking methods.
LaserCoil's original system featured a single head and a 4-kW fiber laser that cut 1.0 mm-thick material at a straight-line speed of 1.8 m/s. It moved material forward in a feed index mode, enabling higher yield rates and producing small parts as quickly as 32 ppm and larger body-size panels at up to 18 ppm for production runs of up to 30,000. LaserCoil’s most recent system features multiple heads and 6-kW lasers that can cut up to 2.5 m/s under straight-line ideal conditions.
The technology can process materials 0.5- to 3.5-mm thick and coils up to 2.1-m wide. Adding another laser head enables shared balancing of the cutting workload to decrease processing time and improve productivity. Multiple-head machines can improve production rates by an average of 8 percent compared to a single head, making it well suited for production runs of up to 100,000.
Another major development has been the ability for LaserCoil systems to run either in stop/start (feed index) or continuous mode. This allows users to optimize the cutting parameters dependent upon the particular part configuration. For example, large, complicated parts or cuts that require tight edge tolerance will likely run better in feed index mode.
As stated earlier, there are virtually no microfractures produced in laser cutting compared to the shearing or punching mechanical process. It minimizes the hardness change on the edge of the cut, and the dross is often non-existent on light-gauge materials and minimal across the board. This high level of quality improves forming, as it is more resistant to tearing and allows laser welding directly to the cut edge.
Lasers eliminate dedicated tooling, as material can be ordered and programming accomplished in less than a day—sometimes in just a couple of hours. With hard tooling, there is a significant undertaking to make even the smallest of changes. With laser cutting, the program can be modified with a simple 2D CAD software program. Costly changes that would take days to implement can be made for virtually no cost and in five minutes.
When we think 4,000-ton hydraulic presses, making sheet metal body panels comes to mind.
Automotive components could see significant process improvements.
As OEMs and suppliers seek lightweight solutions to meet higher fuel economy standards through multi-material structures, conventional welding techniques are beginning to give way to new solid-state joining methods better suited for creating strong bonds between dissimilar metals.