IN A NEVER-ENDING quest to remain competitive, machine builders exercise a variety of tactics to execute cost-efficient design strategies. For example, engineering and building new machinery on a modular theme with standardized control components now is commonplace. This permits builders to configure and reconfigure their designs to meet myriad customer requirements without having to re-invent the wheel each time with a dedicated, application-specific solution.
With control software increasingly based on open, more flexible platforms, it only makes sense to pursue machine programming and implement HMI software in a similar way. Why create expensive dedicated HMI software when todays standardized software platforms deliver cost efficiencies and design flexibility that provide customers with a more reliable, better-performing machine?
Its a Package Deal
Charlotte, N.C.-based machine builder Roberts PolyPro works with consumer products companies to design, construct and commission equipment that installs/assembles plastic fixtures such as handles, spouts and plastic seals on consumer packaged goods. The company also builds paperboard finishing equipment for package converters and contract packagers (See Figure 1).
Figure 1: Simplicity and More Speed Required
Roberts PolyPro built two similar paperboard assembly machines, but its engineers were still looking for ways to decrease time and boost machine performance.
In 2002, Roberts PolyPro received a request to build a beverage carrier machine that would assemble two-piece cardboard open basket carriers with a throughput of 425 pieces per minute. The company had built two similar machines prior to this request, but Roberts PolyPro engineers were still looking for ways to decrease programming time and boost machine performance.
A Better Machine
The Roberts PolyPro machine uses Kraft board and recycled pressed board to manufacture a stronger, lighter carrier in less time and at a significant cost savings when compared to traditional one-piece carriers.
The beverage carrier machine starts with two pieces of cardboard. A plain piece of cardboard goes on the inside of the carrier and creates a web for the beverages to fit in. The other piece of cardboard has a printed graphic on it that acts as the outside of the carrier. The machine takes the two cardboard pieces, and through an automated sequence of precise folding and gluing, produces beverage carriers of speeds of up to 500 per minute (See Figure 2 below).
Roberts Polypro says speed is the real benefit here. It is relatively easy to do this process slowly, but once you start increasing the speed it becomes more challenging. According to the OEM, this is where the motion control decisions made during designfor both hardware and software--really come apparent.
The company built its first beverage carrier assembly machine in 1999 using Allen Bradley SLC 5/04s for control. To help reduce engineering time for the second machine it produced, the machine builder relied on the Rockwells ControlLogix technology for machine control functions.
|Figure 2: You Gotta Know How to Fold Em|
|The machine takes the two cardboard pieces, and through an automated sequence of precise folding and gluing, producing assemblies at speeds of up to 500 per minute.|
The HMI is key because it allows the operators to make such real-time changes while the machine is running (See Figure 3 below). If a downstream worker sees that product isnt folded correctly, he can adjust the settings through the HMI without turning the machine off. With each new machine we build, we want to make sure we use technology that will improve machine performance and reduce engineering and installation time and costs, says Ray Neel, controls engineering manager, Roberts PolyPro.
Reduce Programming Time With VBA
In designing the third beverage carrier, a critical goal for Roberts PolyPro engineers was to further reduce programming time. While fundamentally satisfied with the Wonderware HMI package used on its previous two machines, they were looking for improvements and wanted to explore other options.
While attending a customer event held by their local distributor, Neel watched a demonstration of Rockwell Softwares component-based RSView32 HMI software package.
Among its features, RSView32 can integrate ActiveX controls and use Microsoft Visual Basic for Applications (VBA) as a built-in programming language.
Its very empowering because it allows me to do a lot more with it, says Neel. I already was familiar with VBA so I didnt have to learn anything new, I could just walk in and write code. Neel says if he needed anything special, he could just go to the Internet and find it. It provides a huge reservoir of code snippets and application information that I can find on the Internet, he explains. Its an easier way of doing things because I can just cut and paste code and move on to the next task.