Ounces count, especially when the cost of a product runs almost $2,000/gal. In that case, filling a container as accurately and precisely as possible is important. Thanks to mechatronics and associated controls, the ability to hit a weight target in a bottle-filling machine has been improved by 75% (Figure 1). A similar combination of electrical and mechanical components along with controls can improve product quality, particularly when new-to-an-application capabilities like machine vision are integrated into a system.
Fill ’er up
Take exactitude in bottle filling. It can pay off for more than just expensive products. Even common, high-value, high-volume liquids like honey can benefit, says Todd Cannon, president of Apacks. The LaPorte, Indiana-based manufacturer makes a complete line of liquid filling equipment.
Filling bottles and the like in the 1-oz to 2.5-gal size creates a challenge. They cannot underfill a bottle, since customers purchase product by weight, and accidental or deliberate shortchanging invites trouble. So, the tendency is to overfill, typically at about 1%, says Cannon.
However, that wastes product and money. In a twist to the story of Goldilocks, the goal is to get things just right without being short.
That’s what Apacks set out to do in its latest machine design, and Cannon says the company succeeded. “If you’re targeting your weight in grams or fractions of pounds, we are less than 0.25% over, instead of being 1% over,” he says.
Achieving this performance required careful attention to design and proper implementation of technology, including mechatronics and the associated controls. The fill process starts when bottles are indexed into the machine. Servo motors then drive nozzles individually down to the bottom of the container. After that, a pneumatic actuator integrated into the nozzle opens valves. The liquid begins to be dispensed, driven by clean, compressed air or nitrogen and gravity.
Individual Micro Motion Coriolis flow meters track how much weight has been dispensed by each nozzle. As the bottles fill, the nozzles retract, moving up at a rate calibrated to keep the nozzle in a fixed relationship to the liquid. Thus, when half the fluid has been dispensed, the nozzle will have pulled halfway out. This approach provides several advantages.
“The benefit of a bottom-up fill with this type of precision control is it reduces indexing time, increases fill speed in most applications and greatly reduces the foam and air encapsulation,” Cannon says.
After the target weight has been reached, the valve shuts off and a servo motor pulls the nozzle completely out. When the entire batch is done, the bottles move on, and the cycle begins again.
The machine can switch between different bottles and liquids, with an adjustment to rails and gates to account for the various sizes of containers. Changing a value in the HMI takes care of setting a different weight. The controller can also store recipes and log data, as well as offer other useful capabilities.
For instance, the software on the machine has some proprietary algorithms and techniques that enable it to reliably come in at almost exactly the perfect weight. “It’s adaptive. It compensates for any changes in temperature or viscosity,” Cannon says.
As for the future, one possibility being pursued by Apacks is the elimination of dead time in the fill cycle. The current process has several steps where bottles or machine components are moving and liquid is not. Eliminating the nonproductive time could substantially increase throughput.
“It could nearly double the speed,” Cannon says.
Controls in hand
The current machine is built upon a control platform from B&R Industrial Automation. Cannon says this offers the needed processing power and expandability to handle the present situation, as well as being able to supply what will be needed for the faster future version of the machine.
Derrick Stacey is a solutions engineer at B&R Industrial Automation. He notes that the trends in mechatronics controls, such as the drive toward modularity, flexibility and scalability, can be seen in the Apacks machine. The idea is that a control system will span everything from a single machine to larger systems and vice versa, as well as supporting the switching in and out of subsystems.
“We’re really trying to focus on a single software development package for all of the components of the machine, including safety, motion, vision, control and the I/O, all built into one software package,” Stacey says.
That all-in-one yet flexible approach can also be seen in the fact that the controls are not tied to a specific fieldbus or network architecture. This means that a machine maker can use whatever fieldbus the builder or user prefers and not be forced to convert to Ethernet or PowerLink. B&R Industrial Automation tailors its products to this fieldbus because it offers the best performance, says Stacey.