In Good Company

If necessity is the mother of invention, then application must be the father of innovation. Without a practical application of a new idea, enhancement or improvement, its merits are fleeting at best. When Benjamin Franklin invented bifocals near the end of the 18th Century, they eliminated the need to keep switching between two pairs of glasses. The bifocals were put to use, and an innovation was born.

If not for the application or use of the invention, its benefits would have remained invalidated and largely unrealized.

Mike Bacidore is the editor in chief for Plant Services magazine. He is an award-winning columnist, earning a Gold Regional Award and a Silver National Award from the American Society of Business Publication Editors. Email him at [email protected] or check out his Google+ profile.So it goes with machine controls and automation. New components are created constantly, and those components often are combined in inventive ways. Some promise benefits to machine builders, and others over-deliver.

This year’s winner of Control Design’s Innovator Awards competition is one of the others. Graham Engineering of York, Pa., changed the controls on the Graham Wheel, a non-PET bottle-molding machine. The main component of the wheel spins around a horizontally mounted axis, where extruders feed plastic into a component known as a flow head to form bottles in virtually any type of thermoplastic to the perfect shape and highest quality available.

In a May 2007 case history, “PC Control Breaks Blow-Molding Mold,” we reported how Graham reinvigorated its 30-year-old rotary blow-molding machine with new PCs to boost I/O speed and flexibility. “We’d determined that our existing PC hardware platform wasn’t going to keep up with our machine design migration, so we needed to find a successor,” says Dave Fiorani, engineering manager at Graham.

Graham engineers test a new PC-controlled Graham Wheel before delivering it to a customer.
Source: Beckhoff Automation

One of Graham’s customers, Ring Containerin Oakland, Tenn., has been using the Graham Wheel for years. Ring owns and operates several proprietary wheel blow mold machines designed in conjunction with Graham. Sam Kerley, controls engineering manager at Ring Container, explains the big benefit of Graham’s change in controls was realized largely in the ability to execute more precise parison programming. “In the past, a lot of what has been produced has been with a PLC system or a DCS with a dedicated card that handles the parison programming,” says Kerley. “There have always been faults with the parison setups. You either had low accessibility and flexibility or a lack of speed. It’s extruded through a mandrel, which controls the amount of plastic. The movement in our application is about 1 in. It’s done with a servo, and you have to have very precise movements in a very short time.”

This is where the speed of the new controls struts its stuff, but a little background on parison programming is necessary to understand the full implications.

We’ll Always Have Parison

The parison programmers control the thickness of the plastic, based on the height of the bottle, explains Kerley. Some plastic bottles have parison programming, and some don’t. “When a bottle is made, an extruded parison comes out, and the length of that parison is divided into 128 profile points,” says Kerley. “The operator programs the bottle by selecting where he wants each pin to be. He can put some master points down, and it interpolates set points in between. In the history of blow molding, parison programming is the key ingredient in making these bottles. It’s important and hard to accomplish well.”

Ring Container Maintenance Manager Brian Best looks at a control screen on the Graham Wheel.

Very few systems offer the speed and control necessary for precise parison programming, says Kerley. “Maybe a dozen are out there. Graham had one up until recently that was based on a large board that provided 40 pins of parison programming,” he says. “With the new control system, you can get up to 256 pins of parison programming. It’s all in the controller. This new wheel uses Beckhoff Automation’s TwinCat soft PLC  and InduSoft’s HMI. Their solution puts the entire control system, including the HMI and the parison programmer, in one computer. Closing the loop on the parison programmers increases the quality of the bottle. It can monitor, in closed-loop servo-type control, and adjust. We can make it faster and lighter. I can program any machine to do 1,000 points, but it may not be fast enough to actually do it. This machine is fast enough to hit those parison points.”

Ring Container’s blow molding wheel has two extruders, an inner and an outer layer, explains Kerley. “It extrudes them together as a single parison,” he says. “The parison extrudes up vertically. After a short amount of time, it blows a bottle inside the mold. As the wheel turns around, it maintains the blow pressure. When it reaches the bottom, the molds open, the pin holders retract, and the bottle falls out of the mold. The wheel is synchronous with the star wheel and the takeout conveyor. The star wheel will rotate and set the bottle down on a conveyor, which takes it to a trimmer.”

The bottles-per-minute rate on the machines is basically fixed due to the cooling stage of the bottles. “You can only make bottles so fast,” says Kerley. “You have to cool them in the mold and out, so you have very little flexibility on the rate. Different products can run at different rates, depending on the bottle weight. The molds are water-cooled. We have a chiller system at each plant.”

The Search for Control

When the durability and processing power limitations of its PC hardware became apparent, Graham completed an evaluation of industrial PCs. Graham chose Beckhoff PCs with 2.4 GHz Pentium 4 processors running TwinCat software as the control centerpiece for the Graham Wheel machines.

“Most of our machines could be controlled using the TwinCat PLC variant, but for a few specialized machine types, we need NC functionality, so we use TwinCat NC across the board to use a standard software package,” says Justin Kilgore, senior electrical engineer at Graham. “We use many languages provided in the programming environment—ladder, function blocks, function block diagrams, structured text and continuous function chart.” TwinCat is an automation software platform, but its TwinCat PLC variant has functions that can be referred to as a “soft PLC.” TwinCat also has NC, NC I and CNC versions.

APPLICATION-TERRIFIC
If there’s an actual application for a new enhancement or invention, then there’s a much greater likelihood of discovering the real benefits of the improvement. Tell us about your greatest solution and why it did or didn’t matter at ControlDesign.com/innovation.

Meanwhile, Beckhoff’s remote I/O also replaced PCI I/O cards supplied by Graham’s prior PC vendor. Graham now uses special-function I/O terminals for its machines’ e-stop functions and temperature measurement. A watchdog I/O terminal is used to eliminate the chance of errors in machine and heater control, says Kilgore. “You can set your timing based on your application, but we chose to see the PC pulse every 100 ms.”

Where the Plastic Meets the Pin
“What’s new for this system is temperature control,” says Kerley. “Graham figured out a better way to do temperature control, system control and parison control. But the real benefit is the capability of the parison controller, and how it’s integrated with the rest of the control system. The parison programmers can fine-tune smaller points with the new system. It makes a big difference to be able to reduce plastic waste and still add more plastic where it’s needed.”

Because the communication between the PLC and HMI are tightly integrated in one package, every profile point in one of these systems is more than just a number, explains Kerley.

“It’s possibly 64 bytes of data for every profile point,” he says. “That computation is done in the controller. There’s a lot of innovation in this machine. The controller is one compact box, and all the I/O modules are distributed on a secure Ethernet network. We have two network interface cards (NICs). One is tied to the I/O subsystem for the distributed I/O subsystem. Some of the I/O is in the main enclosure. Some of the I/O racks are distributed at different points in the machine. The other I/O card is connected back to our network, so we can use it to monitor data or to monitor alarms from a supervisory system we have outside the machine.” 

Methodology To find, evaluate and select the winner of this third-annual Innovator Awards competition, Control Design solicited nominations from its readers, including machine builders, system integrators and automation suppliers. Respondents completed several essay questions, describing in detail the machines they were nominating. They related their machines’ functions, operating parameters, beta testing, end-user installations, notable use of automation and controls, uniqueness compared to its competition, impact on throughput, quality, flexibility, reliability and operator safety and impact on the builder’s market position. The editors at Control Design then reviewed all nominations, conducted follow-up interviews with nominees and customers who could validate performance claims and then selected the winner.