A recent comparative vacuum technology study at Daimler-Chrysler found that air consumption could be reduced by 98% by equipping a robot's end-of-arm tooling with a new multistage vacuum generator and check valve.
Flexible robotics drives cost reduction, productivity improvement, and market responsiveness, as shown at last year's unveiling of the Chrysler Group's future manufacturing strategy. Image courtesy DaimlerChrysler Corp.
PIAB Automated Modular Tooling is shown equipped with a Vacustat — a vacuum-controlled device that minimizes consumption of compressed air by controlling incoming air flow to a vacuum pump.
A recent comparative vacuum technology study at Daimler-Chrysler found that air consumption could be reduced by 98% by equipping a robot's end-of-arm tooling with a new multistage vacuum generator and check valve. The study also estimated that if DaimlerChrysler were to replace its older, outdated vacuum systems, the company could experience an annual savings in air consumption costs of more than $400,000 per stamping plant.
More with less
As with many global companies, DaimlerChrysler is constantly challenged to increase output while decreasing manufacturing costs. DaimlerChrysler has been able to significantly improve cost-efficiency through the increased use of robotic technology, particularly for automating material handling of sheet metal during stamping applications. This involves moving sheet metal through a press or series of presses and forming it into a panel or other automotive part.
With virtually all robotic applications, tooling is critical to productivity. It is particularly vital to have flexible tooling when handling metal pieces in automotive stamping applications because changes in size occur each time a part changes. A key component in robotic tooling is the end effector, which accounts for the "hand" of the robot. In the case of sheet metal stamping, vacuum is used to pick up the metal sheet and transport it to the next destination. Vacuum is used for a number of reasons:
- suction cups leave no marks and cause no damage to class A surfaces — in this case, the part is sheet metal and it is very importantthat no marks are left on the surface
- gripping with vacuum can be accomplished from one plane; you need to handle only one side of the part being moved, making it easier
- for the robot to approach the part (this can also result in a smaller end effector)
- end effectors equipped with a well designed vacuum system are lighter than using grippers or magnets — this means less of the available payload is taken up by the end effector
- the flexibility and design of suction cups allows for less precise placement of the end effector on the part; they can be used effectively on curved or uneven surfaces, oreven in some cases when a part changes, and
- a well designed vacuum system costs much less then grippers or magnets.
How to improve efficiency?
In order to further improve robotic system performance and thus, productivity, Dr. Kingman Yee, as part of a DaimlerChrysler's Summer Intern Professors Program, researched manufacturing processes that would lower costs of the company's material handling applications at its automotive plants in Michigan. The challenge was to lower the costs of material handling applications by decreasing air consumption, reducing downtime, and improving the performance and cycle time of robots and other equipment using suction cups to lift and transport parts.
One of the vacuum systems tested in the study was COAX, a new multistage vacuum generator from PIAB Vacuum Products, Hingham, Mass., based on a multi-stage concept for creating vacuum with compressed air. By integrating the internal components of a multi-stage vacuum generator into a vacuum cartridge, COAX provides a smaller, more efficient, more reliable, and highly flexible components.
In side-by-side comparisons with competitive vacuum ejectors and suction cups, Yee found that the multi-stage design of the COAX vacuum generators used 1.1 scfm of compressed air per cycle, up to 78% lower than singlestage vacuum generators. More significantly, COAX components can be equipped with a Vacustat check valve, which shuts off the supply of compressed air when proper suction is reached. If the vacuum level drops due to leakage, the generator will turn on briefly to return the vacuum to the desired level. Yee reports that simply by installing this device, compressed air consumption can be reduced by an additional 98%.
As a result, the cost to Daimler-Chrysler for the electricity to produce the compressed air for a single suction cup is $0.56 per year, compared to at least $61.66 per year per suction cup for systems from other vendors (based on an electricity cost of $0.07/kW-hr). For a typical automotive stamping plant employing 2000 suction cups, the savings is $122,200 annually. If DaimlerChrysler were to replace older, outdated models still in wide use, Yee estimates that the annual savings would be $418,300 for that typical stamping plant.
Make it easy
The modular construction of the COAX system allows for easy maintenance, repair, and replacement of vacuum components and suction cups. For comparative systems, the entire vacuum assembly and its suction cups must be removed or replaced if a malfunction occurs. This process causes significant downtime, which can be detrimental to the productivity of the entire plant.
"The multi-stage design of the COAX ejectors (generators) enhances material handling performance by producing superior vacuum flow and responding almost immediately when compressed air is applied," said Yee.
The ejectors achieve an evacuation flow rate of 85 scfh and produce a holding force of 100 lbs, 25% higher than alternative solutions, according to Yee. The quicker response and better vacuum flow means the suction cups grab quicker and hold stronger, resulting in a faster process cycle time, and higher productivity.
Yee's study also reports decreased noise. The COAX generator is appreciably quieter both during load and no-load conditions. Moreover, the Vacustat check valve significantly lowers noise and practically eliminates the hiss associated with typical suction cup systems.
For more information about PIAB's vacuum systems and components, call 800-321-7422 or visit www.piab.com