Online Exclusive: Case Study: Robotic Porcelain Enameling

August 1, 2005
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A robotic spray system has provided one porcelain enameling company with lower production costs, improved quality and increased flexibility.

The robotic programs allow PMC to coat complex parts without wasting material in cutouts and holes.
Porcelain Metals Corp. (PMC), Louisville, Ky., handles a variety of metal fabrication and porcelain enameling processes. Founded in 1927 as the Louisville Enamel Products Co., the company initially focused on producing stove and refrigerator parts and signs in a 17,000-square-foot manufacturing facility. Over the years, PMC grew to encompass powder and wet porcelain enamel, deep drawing, stamping, welded subassemblies, electrostatic powder painting, contract manufacturing and a range of other porcelain enamel services in 100,000 square feet of manufacturing floor space.

However, by mid-2002, PMC was headed for trouble. The company was feeling the squeeze of low-cost competition from overseas. Additionally, Louisville's labor market was shrinking, making it more difficult to find qualified spray operators, and PMC was experiencing an intolerable amount of scrap and rework as a result.

"We needed to do something," says President John McBride. "We knew that several of the major appliance manufacturers, many of which are our customers, were moving to robotic spray systems, so we set out to find a robotic solution."

Turning to Automation

Unfortunately, many of the spray robots simply weren't up to the job. "The robots didn't have the long reach we felt we needed for our mix of part sizes and line speed. We would have needed more than one traditional robot to get complete coverage," says Randy Smitley, manager of PMC's finishing operations. "We also needed a machine that would be simple enough for a very non-technical person to operate."

Then PMC visited the Cleveland, Ohio, laboratory of Artomation, a company that supplies a gantry-based robotic spray system that can track parts as they move through the liquid spray enamel booth. Over the next few months, the Artomation lab became a proving ground for robotically spraying the wide range of parts PMC needed to handle, from simple flatware to the interior of oven boxes. The engineering teams from both companies worked to develop a toolbox of solutions.

"Coating some of our parts is like coating a slice of swiss cheese," explains McBride. "The robotic programs allowed us to coat everything we needed to without wasting material in all the cutouts and holes. We knew that the robots were going to save us money."

Spray paths or any other of the parameters can be changed while the robot is in production.

Making the Switch

A completely assembled and tested gantry robot unit was shipped to PMC's Louisville plant in December 2001. Five feet of additional overhead space was added to PMC's enamel booth to accommodate the 12-ft-high gantry system, and an encoder was added to the existing conveyor system so that the part position coordinates could be fed directly into the Artomation control system.

The heart of the control is a Windows® PC-based system, which is located in an industrial enclosure close to the gantry robot. The control software was developed to address PMC's requirement that the system be simple to program and operate. PMC operators simply insert a digital photo of each part and draw a paint path for each image. Commands such as triggering the gun or changing its angle to the part are made with a few clicks of the mouse and are then stored electronically as a part "recipe." Most new parts require about an hour of setup time before a complete recipe is developed, fine tuned and ready for production. The recipes for each part style are easily selected by operators and can even be triggered automatically with machine vision and barcode systems. Once triggered, each recipe is executed consistently every time.

"The immediate increase in yield was fantastic," says Smitley. "The robot eliminated drips and sags, and its consistent application eliminated the thin spots commonly known as burn off. We started saving time and porcelain immediately."

Switching from one part recipe to another is a fast process that takes only 30 seconds, or two empty hangers on the production line to execute.

"We can spray any of the parts we make completely by robot," says Smitley, "but because we only have one robot, we use it as the workhorse of the system to lay down most of the porcelain before the parts proceed to a manual reinforcement station. This combination gives us maximum productivity.

"We are talking about adding a second robot, which would allow us to eliminate the manual reinforcement," he adds.

Adding up the Savings

According to McBride, switching to a robotic spray system has enabled PMC to significantly reduce its labor costs by replacing two hand spray operators.

"The enamel booth isn't a fun place to work, so replacing these hand spray positions with a robot wasn't a difficult decision," he says. "In fact, we had a very high turnover rate associated with these positions, so we have saved a great deal of time and effort in recruiting and training spray operators."

PMC has also seen improvements in throughput. Where yields used to be 80-85%, now they are consistently in the 93 to 97% range-even on the most difficult parts, such as oven cans. Additionally, the system has dramatically reduced overspray, leading to porcelain enamel savings between 40 and 60%, depending on the part being sprayed.

However, Smitley notes that the biggest gain has been in quality control. "We have nearly perfect consistency using robots," he says.

PMC also has a much more rapid response time for making customer changes and adding new products. This helps increase their value to customers and compete with lower-cost but less flexible offshore suppliers.

"The beauty of this system is that it allows us to make adjustments on the fly," says Smitley. "Spray paths or any other of the parameters can be changed while the robot is in production. As a matter of fact, we can install a completely different setup, save it, send it to the robot and not miss a beat. If the change doesn't achieve the desired results, we simply recall the previous program."

"We also have the ability to program on another computer from another location. For instance, I can program on my laptop, save to a disc, and bring up the computer for the robot." This enables Smitley to maintain control without having to be on the plant floor, so that he can make programming changes from his office elsewhere in the plant, or even from a remote location while traveling.

Looking Forward

Now an expert in robotic spraying, PMC continues to tweak its process with more subtle electronic commands to control fan air, atomization, fluid rates and other parameters that allow the company to achieve greater quality, consistency and savings.

The company is also exploring other ideas, such as multiple gun mounts on the gantry system and perhaps someday eliminating all manual spraying with the addition of a second machine if production requirements continue to increase. Given PMC's newfound ability to lower costs, boost quality and provide quick turnaround, continued production increases are a likely scenario.

For more information about gantry-based robotic spray systems, contact Artomation at 6909 Engle Rd., Suite 7, Cleveland, OH 44130; (877) 805-1126 or (440) 234-1988; or visit http://www.artomation.com.

More information about PMC can be found at http://www.porecelainmetals.com.

SIDEBAR: Beyond Porcelain Enameling

Robotic spraying isn't just limited to porcelain enamel applications. According to Jeremy Foster from Artomation, benefits such as lower costs, improved quality and consistency, reduced waste, increased flexibility, and faster turnaround can also be achieved by using robotic systems in other ceramic and glass glazing/coating applications. "If a material can be sprayed onto the substrate, it can be applied using a robotic spraying system," he says.

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