Small Robots Reduce Costs in Paint Cells
Several years ago Rodgers Finishing Tools, Inc. (RFT), a finishing systems integrator and paint tooling manufacturer in Lebanon, Indiana, was looking for the one thing that would make the company's self-contained painting system even better: A compact robot that could be ceiling mounted.
Even without the ideal robot, the company's Cellular Painting System (CPS) was producing a quality finish, protecting humans from toxic chemicals and saving customers money by conserving on consumables. However, owner Steve Rodgers wanted a smaller, more flexible robot, so he could let the part and painting requirements drive the size of the painting booth - rather than being forced to design a larger booth simply to accommodate the size of the robot.
'I had been telling all the major robot manufacturers for years that I needed a small robot that I could invert,' Rodgers said. 'Then about three years ago I got a call from a paint salesman who was in Europe. He said, 'you've got to see this robot'.'
Rodgers saw the robot and knew that it was the solution he needed. He began discussions with the European-based robot manufacturer, Stäubli, about marketing their line of paint robots in the U.S. Although the robot was approved for use in paint applications in Europe, it did not have Factory Mutual (FM) approval at the time.
'We began selling the robots for paint and finishing applications in other parts of the world while Stäubli obtained FM approval,' Rodgers said. 'And then in May 1999 Stäubli introduced their explosion-proof, FM-approved paint robot to the U.S.'
Smaller footprint, ceiling-mount conserves space
Incorporating the Stäubli robot into the CPS allowed RFT to dramatically reduce the size of the painting booth. The smaller booth not only saves precious plant space, it also reduces consumption of air, paint and other materials.
'We pushed to be able to market the Stäubli robots in the U.S. because they offered us a lot of flexibility with six robot sizes - all made the same but with different footprints, reach and payload capabilities,' Rodgers explained. 'This meant our cells could become larger or smaller on the envelopes our customers required. Our customers could have the optimal size robot for different applications and different sized parts and, at the same time, minimize their space requirements for the system.'
RFT customer Tom Rudolph, a 30-year veteran of the injection molding and shielding industry, can attest to that. Early this year, as plant general manager for an injection molding company, he installed a CPS equipped with the Stäubli RXPaint60 to apply functional coatings to cellular telephone housings. Rudolph calculated that they needed 40-60% less floor space for this process because they were able to install a smaller robot ideally-sized for the application. In contrast, he remembers when he had no choice but to work with the traditional, full-size robots that were considered the industry standard just a few years ago.
'The CPS cell I installed this year, with guard rails and all associated peripheral equipment, was only 12' x 12' and that is much smaller than would have been required. (See Figure 1) Typically with a full size robot, the booth itself can be 16' to 18' x 15' to 20'. So much more space is required to give the robot room to maneuver,' Rudolph said. 'If the Stäubli robot had not been available, I probably would have had to install a much bigger robot oversized for what we are doing.'
Rodgers added, 'I can put two of the systems that Tom Rudolph installed in the place of my old cell system. The old cell was twice as big, because we had to accommodate a larger robot - the dinosaur, as we like to call it. We haven't sold one of these 'dinosaurs' since we started offering the Stäubli paint robots.'
How the robot is mounted also gives Rodgers more flexibility in designing his CPS painting booths. Stäubli robots can be mounted on the side of a wall, upside down or on a pedestal. 'How I mount the robot can help me further reduce the size of the booth. If I pedestal-mount it, I'd have to move it back and let it reach over the work area; whereas if I hang it from the ceiling, (See Figure 2) I can put it directly above the work area. That's a big advantage,' Rodgers explained.
Rudolph agreed. 'The arm of the Stäubli robot is right over the part. Other types of robots are probably as big - or twice as big - as a person with an arm that can be 10' or 12' long that has to go back and maneuver and paint and then rest and wait for the next part. This CPS unit and the small robot allows for parts to be presented more consistently and quickly,' Rudolph said.
Precision and maneuverability
Of course, a small robot that saves space is no good if it can't meet the job requirements for accuracy. According to Rodgers, maneuverability is a primary reason for the Stäubli paint robot's accuracy. 'Other robots have to use counter-balances to keep the robot upright on the pedestal and the arm in the right area,' Rodgers said. 'Because of the unique design, the Stäubli robot doesn't work with a counter-balance system. As a result it is more nimble and maneuverable.'
This maneuverability means the robot can be programmed to manipulate around the nooks and crannies of very small parts. 'The Stäubli robot can be accurately manipulated to stop, turn around in a very tight space and move forward. You know the repeatability is going to be there each and every time,' Rodgers said.
He gave an example: 'I'm working on an application for a customer right now where I'm in a very tight area and if the robot varies in position in any way whatsoever I could damage a part. At very high speed when I am manipulating at full action it could create some problems. It's comforting to know that the robot can deliver that accuracy.'
This level of precision was one factor that sold Rudolph. 'There are definitely some process challenges when applying conductive coating. The mil thickness of the coating and the consistency in the film build throughout the part is important because that's where the performance of shielding electromagnetic and radio frequency interference is achieved,' Rudolph explained.
'Cellular telephones, Palm PCs, paging devices - anything that has a microprocessor in it - are becoming much smaller. The areas that require the conductive coating, therefore, are becoming smaller all the time,' he continued. 'The Stäubli robot's ability to get around corners into very tight and difficult to reach areas is a real benefit. It's capable of achieving much tighter, crisper shut-offs than I was used to with the bigger robots.'
The advantage of the Stäubli robot, according to Rodgers, is that it combines precision and maneuverability with a small footprint. 'I probably could use another robot when my manipulation requirements are tight, but then the cell would have to be much larger to give the robot more room to maneuver. So I would lose out on size and the cost of the cell would go up,' Rodgers said.
Positive ripple effect of smaller robot
The ability to build the CPS around the smallest robot appropriate for the application, has a positive ripple effect throughout the entire process. Besides conserving real estate, for example, smaller paint booths can mean shorter cycle times. 'The smaller robot creates a more compact CPS which generally shortens the cycle time,' Rodgers said. 'The old larger cells meant the parts had to be moved a much further distance to get them from the load/unload position.'
Smaller cells also mean less air and material consumption. 'In general, our CPS units result in an 85% reduction in air consumption. About 2,000 cubic feet of air per minute (CFM) is consumed compared to about 10,000 to12,000 CFM in the old, larger cells. We were able to condense the filter bank and reduce the blower size which reduces air consumption.'
Rudolph's experience bears this out: 'Compared to what I have experienced with the same size and type of part in the past, I saw a significant reduction in paint usage and a significant increase in parts per hour with RFT's Cellular Paint System and the Stäubli robot.'
More productivity and lower cost
The benefits of the Stäubli robot, sized to fit the part and painting requirements, combined with the other advantages of RFT's Cellular Paint System result in about a 25-30% increase in production over conventional paint cells, according to Rodgers.
'The Stäubli line of paint robots gives us the flexibility to be able to make our cellular painting cells smaller, which in turn gives our customers more flexibility and more production per square foot of plant space, for less money.'
For additional information, please contact
Stäubli Corporation - Robotics Division
201 Parkway West
Duncan, SC 29334