Improving laser cutting on the hydroforming line
For years the laser industry has lamented the relatively slow adoption of laser processing technology by U.S. automakers.
For years the laser industry has lamented the relatively slow adoption of laser processing technology by U.S. automakers. Suppliers searching for an explanation point to issues such as lack of training, education, and ownership, while the market has countered with examples of product performance, unrealized or over-extended promises, and inadequate support. In fact, there’s validity on both sides, often compounded by communication, perception, and timing problems. However, as with any industry that is considering technology for manufacturing (and especially true in the high-stakes, multi-shift world of an automotive production line), the bottom line is results.
The challenge a “Big Three” U.S. automaker presented to Laser Mechanisms (Farmington Hills, MI; www.lasermech.com) was the poor performance they were experiencing from the laser robotic cutting cells on their hydroform rail production line. Issues included excessive downtime, an inordinate amount of replacement part expense, and repair of their existing laser cutting heads.
Frustrated with high costs and lack of service support the automaker considered eliminating laser cutting from its operations. They approached Laser Mechanisms with requirements that the final product had to be robust, simple to operate, easy to maintain and repair, and above all, come with a superior level of service and support.
Laser Mech responded with a design concept to the plant managers that led to the installation of a prototype unit into one of the cells on the hydroform production line. By the end of the year, 12 of the new heads were installed-converting all of the cells and completely replacing the previous problematic cutting heads.
“Originally, we thought we’d find a small, out-of-the-way job shop to test our prototype unit,” recalls Richard Lee, manufacturing manager for Laser Mechanisms. “But before that happened, a plant manager from the automobile company saw the design and decided to try it out right on his production line. He told us, ‘If this thing is for real, I’m putting it into my toughest environment. If it will work here, it will work anywhere.’”
“We installed the prototype head on one robot in the line and it began to show advantages immediately. The maintenance people noticed that they rarely had any of the earlier faults and the plant managers noticed that they were spending only a fraction of the old cost on parts, particularly optics,” says Lee.
Since being retrofitted with the new heads the plant slashed optics costs by 87 percent and reduced overall replacement parts costs by more than 90 percent-resulting in savings of more than $60,000 per month. The new head also significantly reduced downtime and improved production by more than 50 percent.
In addition, the use of a Cold Formed Nozzle has led to improved performance of the laser cutting process with cutting speed increased and hole quality improved. Also assist gas pressure was reduced by 40 percent and laser power was reduced by 10 to 30 percent.
These results have impressed plant engineers, electricians, and maintenance personnel, and have converted the plant managers from concern with laser cutting to fully embracing its benefits.
“The new cutting head reduced optics consumption, high spare parts costs, and downtime,” one of the users noted. “We were able to reduce the assist gas pressure dramatically, lowered laser power from 1 kilowatt to 700 watts, and we were getting better quality holes than before.”
In the course of the design process, Laser Mechanisms consistently found the failures of the existing laser cutting heads fell into a common theme-they simply were not robust enough.
Their engineers set a design criterion for a new-style laser cutting head that would become the choice for heavy-duty industrial applications. The key features included:
- No external cables, wires, or air lines at the end of the cutting head to snag, break, or burn
- No dust-pumping motion of the cutting head to contaminate optics and other internal components-also eliminating the need for highly problematic purge air
- Robust, yet lighter weight and slimmer profile head construction
- Easy-access, tool-less cover glass slide replacement cartridge-eliminating service disassembly, handling, and exposure to the focusing optics while reducing changeover time
- Assist gas sensing system to prevent operation without cover gas, or in the event of a loss of cover gas. The system can monitor any small variation in pressure within the head or loss of assist gas altogether and alert the user to a potential overheating situation
The result is a slim, compact package that provides automatic non-contact capacitive height sensing reliably in intensively harsh environments.
A key to reducing the size and weight of the head was the invention of Laser Mechanisms’ patented Remote Actuation drive system that uses a flexible drive cable between the motor and the slide that it is driving, so the motor and drive circuitry can be physically located some distance away from the laser processing area where it is immune to the harsh environment surrounding the process, and is not limited in terms of size or capability.
By retrofitting to a Laser Mechanisms Nd:YAG cutting head, a “Big Three” U.S. automaker was able to reduce operating costs by $60,000 per month and improve production by more than 50 percent.
“We developed the Remote Actuation concept in the process of solving the dilemma of either using a very robust motor and drive system, which would add too much mass to end of the robot arm, versus a lightweight system that would lack performance and durability. And we discovered another advantage,” Lee adds.
“As we looked closer at the failures of the existing heads, we realized that part of the reason that the optics were getting contaminated was because of fine particles wearing off mechanical drive components located inside the head, in the same chamber as the optics, in addition to contamination caused by debris from the cutting process. It just didn’t seem like a good idea to have these components fully exposed to both the optical elements and to the laser beam itself. The new cutting head requires no purge air and its design allows us to contain the optics within a fully sealed chamber.”
One operator on the hydroform line notes, “Between the 12 cells, we were jumping up every five minutes to clear a fault or fix a problem. Not only do the new heads run much more smoothly and uninterrupted, they are also simpler when we do need to fix something, it’s very quick and easy to repair. It’s easy to understand how these heads work. They’re so solid that the robot crash sensors will stop the system before the heads are affected or damaged. With the old heads, the breakaway collision device could be over sensitive and it usually took two or three tries to reset them properly.”
“Basically, we went from having to stop the line every five minutes to going to days and weeks of uninterrupted production. We also went from having to change optics up to three to four times per day to keeping the original optics set that came with the head in operation for months.”
The plant manager sums up by saying, “When you factor in the full cost of the old heads, aside from just the repair costs and replacement parts, with all of the downtime, scrap, rework, and make-up overtime, the new heads paid for themselves very quickly. But more importantly, the cost savings from the continued performance and reliability of these new heads will add up to millions of dollars.”
“By working closely together, Laser Mechanisms not only solved our problems, but they also helped us improve our cutting process, restoring our faith in laser hydroform cutting.”
Mike DelBusso is sales engineer with Laser Mechanisms Inc, Farmington Hills, MI, www.lasermech.com. He can be contacted by e-mail at firstname.lastname@example.org.