PC-based Control Delivers the Right Mix

We may all scream for ice cream, but ice cream vendors don't want people yelling for the wrong reasons. In turn, vendors want to deliver what customers want without casting a chill on the bottom line. Achieving that balance is getting more challenging as dairy and ingredient prices rise. However, some vendors are exploring greater use of automation to reduce equipment costs and operating expens...

06/01/2005


AT A GLANCE

 

  • Consumer demands

  • Calibration

  • Variable frequency drive

  • Weighing module

We may all scream for ice cream, but ice cream vendors don't want people yelling for the wrong reasons. In turn, vendors want to deliver what customers want without casting a chill on the bottom line. Achieving that balance is getting more challenging as dairy and ingredient prices rise. However, some vendors are exploring greater use of automation to reduce equipment costs and operating expenses, and improve production flexibility.

A case in point is a state-of-the-art control system used in a line of ingredient feeders from WCB Ice Cream. Based in Northvale, N.J., the company is one of the world's leading suppliers of manufacturing equipment for ice cream plants. WCB's automation engineer, Chris Heckler, says that to meet market demands, the new product line had to meet some basic design goals that included control and mechanical changes.

Controlling market forces

One of the primary market forces driving development of the new control system and mechanics in WCB's ingredient feeders is the increasing demand for premium ice cream. According to a study by the consumer analyst firm Mintel, premium ice cream accounted for most of the industry's 6.9% market growth from 2001 to 2003. Higher-value products often add cookies, candies, fruits, and nuts, presenting an array of sizes and consistencies for ingredient mixers to accommodate. For example, some products may include a paste-like fruit while others may contain cookies. Inaccurate measuring, often on the high side to ensure quality, wastes higher-cost premium ingredients.

"It costs us more money to put these ingredients into the package," says Mark Roberts, ice cream foreman at Victoria, B.C.-based Island Farms Dairy.

The dairy, which produced a record five million liters of ice cream in 2004, uses old and new versions of the WCB ingredient feeders. Island Farms' operations are far from the industry's biggest, and Roberts notes that the dairy produces a number of ice cream varieties. As a result, the company cannot dedicate a separate line to each type of ice cream. It needs to change from one blend to another without impacting output. For Roberts, this means he needs a system that's easy to reconfigure.

Adding ingredients to premium products generally begins when ice cream from a freezer is forced by a discharge pump into an ingredient feeder. In the case of WCB's devices, the feeder has a hopper that holds the ingredients. An augur in the hopper feeds these ingredients at a predetermined rate into an enrobing chamber. The chamber rotates to a position where a piston injects the ingredients into the ice cream stream. At the end of the process, a blender ensures a consistent mixture and the ice cream is sent on to the next step. Temperatures vary, but ice cream is always below freezing.

Handling changes

On the mechanical end, WCB designed its most recent ingredient feeders with larger openings so that bigger ingredients, such as a whole cookie, could be handled. With the mechanical changes and system redesign, the company also decided to upgrade the control system.

Three new WCB ingredient feeders, with mechanical and control improvements, are the IF410P, IF820P, and IF1230P, at 4,000, 8,000, and 12,000 maximum liters/hr, respectfully.

For automation and control components, WCB worked with Schneider Electric. Schneider components in the feeder design included a Magelis industrial PC-based control system, along with the Telemecanique Altivar 31 AC drive, Advantys distributed I/O, and touchscreen computer panel. For more accurate measurements and better process control, a Schneider Electric team developed a weighing module to track changes in ingredient weight. Ethernet connects the PC, Advantys I/O, and the weighing module, while a CANopen network links the drives and I/O modules.

According to WCB's Heckler, one of the design differences between the newer and older products was use of a PC instead of a PLC, which reduced some costs. It also uses one software package. Heckler points out that field technicians, who may be located anywhere around the world, are often more comfortable with a standard PC interface than a PLC. That makes a field update easier and less likely to lead to problems or questions from a technician.

"They're a lot more familiar with a laptop or a computer on its own than with hooking a laptop up to a PLC to download," says Heckler.

For software, WCB used Think & Do Live! from Entivity, a Phoenix Contact company. This package offers PC-based control with flowchart logic for control, integrated HMI, motion control, PID loop, productivity tools, and enterprise connectivity.

Less waste, time

In operation, the new ingredient feeder constantly weighs the hopper. By calculating the difference in weight, the system determines how much mass has been dispensed over a given amount of time, compared to a product-dependent value. Manufacturers start with a desired outcome, such as 100 kilograms of pecans in 100 two-liter cartons of ice cream. From that and the product feed rate, they determine a number to input into the system at the start of the processing of a given product.

As the feeder runs, a variable frequency drive adjusts the speed of the motors driving the augur feeding the ingredients. Higher accuracy of the new weighing module ensures greater consistency. Island Farms' Roberts says the accuracy of the new ingredient feeder is roughly twice that of the old. "It can pinpoint the exact amount of the ingredients that we use down to the kilogram," he says.

Punching in figures for a changeover takes less than half a minute, a slight improvement over the older model. Roberts adds that changing from one type of ice cream to another requires less effort with the newer feeders.

Heckler claims a change in calibration requirements also saves time. The older feeder had a two-stage calibration—one for the machine and another for the ingredients. More sophisticated controls cut calibration time in half, by doing it while the machine is running.

For Heckler, the improved controls produce other savings as well. Troubleshooting requests from the field are fewer and simpler to solve. He credits most of this improvement to the use of a PC and easier calibration. Heckler bases his observation on fewer phone calls from technicians baffled by the system or an upgrade.

"It seems that the systems are up and running easier," he says. "I really define success by sending something to a technician, having him install it, and then call me back and say, 'I didn't have a problem.'"

For related information, search www.controleng.com or go to www.schneiderelectric.com , www.phoenixcontact.com , and www.wcbicecream.com .





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