As a manufacturer of sausage-stuffing machines, Japanese company Hitec wanted to expand to the US market. But it soon discovered that different production demands in North America meant that Hitec needed to make adjustments to its existing meat-processing equipment.
Background
For years, it was considered impossible to make uniformly-sized, natural-casing sausages with machines. Then in the late 1990s, Hitec introduced the Linkwel, an automatic stuffing machine that challenged those views.
To make sausages, finely ground meat and fat are mixed with salt and spices, and filled into long narrow tubes called casings. The ingredients are fed into the casing through a nozzle, which twists to form individual sausage links. The sausages are then grouped into bunches.
Two kinds of casings are used in sausage production: artificial and natural. Made of collagen, artificial casings are considered stronger and more suitable for making uniformly-sized sausages. In contrast, natural casings come from sheep or pig intestines, which are irregularly-shaped, making them nearly impossible to create uniform products using a high-speed machine. In addition, their thin, weak skins make them prone to breakage. Therefore, natural-casing sausages are commonly made by hand with skilled manpower.
Beginning in 1997, Hitec began development of a natural-casing sausage-stuffing machine, which was based on their artificialcasing machine. By 1999, they completed development of the new Linkwel machine, reportedly the world’s first, equal-length, equalweight, and equal-diameter sausage machine for natural casings. Capable of producing both artificial and natural-casing sausages, the machine has reportedly been popular in Japan. It also won an award from the Japan Society of Promotion of Machine Industry for new machine development by a small-to-medium enterprise.
Challenge
In recent years, many Japanese companies cut back investment on capital equipment, which resulted in sluggish sales. To spur further growth, Hitec shifted its focus to overseas markets, particularly the US. As part of its efforts to increase market share, Hitec formed a US subsidiary in 2000.
In the process, Hitec discovered the importance of reliability, durability, and parts availability. In the US, 22-hour production cycles are the norm—compared to 8-hour shifts in Japan. Downtime also had to be at a minimum.
To meet these requirements, end-users requested Allen-Bradley embedded control systems for Linkwel machines. However, Hitec was unfamiliar with the programming software for the SLC 500, which is quite different from programming for the automation products they used in other markets.
Solution
With the help of Rockwell Automation, Hitec designed a control system for the Linkwel machine that provides automated control of recipe management, production scheduling, material tracking, and product changeover.
The solution comprises SLC 500, 1746 I/O, PanelView 550, 1394 servo drive, 160 drive, 1305 standard drive, a 871/800E proximity sensor and push button. The PLC provides drive-frequency control and adjusts the timing of the high-speed counter, while controlling the speed of the looper system which hooks the sausages. The drives perform roller command for the rotating stuffing tube and for the driving pump, looper, and linking chain. The proximity sensor checks if the guard cover is closed, and counts the number of transferred sausages.
The PanelView human machine interface (HMI) is reportedly operator-friendly, providing information about the production run—including the recipe, the number of sausages to be produced, and the desired weight and length of the sausages. It also displays alarms and pinpoints the location of any problems occurring during operation.
Changeover is relatively simple. The operator confirms the correct linking chain, tube size, chuck, and hopper adjustment; selects the preprogrammed product code; and pushes the start button. The information is stored and predetermined, so machine speed, pump speed, casing front-ends and tail-ends, and twist is the same every time. High-speed stuffing of natural-casing sausages is achieved using separate drives with independent electrical control. The drive-metering pump, twister and stuffing-tube rotary head, linking chain, and conveyor are driven independently by different motors, each under separate electrical control.
After stuffing, each sausage is twisted to the appropriate weight and length before being placed on a conveyor. The line of sausages is then transferred from the conveyor to hooks on a hanging system. The drives for the conveyor and hanging system are synchronized together. The rate of synchronization is controlled by the PLC, which determines the timing of the hooks and how many sausages are hung on each hook.
Results
Hitec’s end-customers say they are satisfied with the embedded Allen-Bradley controllers. Automated controls have speeded production, while reducing specialized, manual labor. While 100 pieces of sausages per minute used to be an acceptable rate, the new machines are capable of making from 300 to 400 pieces of natural-casing sausages per minute, and up to 1,000 pieces of artificial-casing sausage per minute.
Using the Rockwell Automation control system, end-users have reportedly reduced downtime by 10%. “When a machine is down for a day, it is a big deal for our customers,” says Mr. Hideaki Arai, assistant manager, R&D engineer. “The faster the stuffing speed has become through recent technological advances, the more serious the economic damage when downtime occurs. The control system is reliable and durable, so maintenance and downtime is minimal.”
As a result, customers have been able to decrease maintenance costs and to reduce stocks of spare parts by 20%. In addition, more and more sausage manufacturing factories are becoming networked, especially in the US. Today, sausage manufacturers expect sausage stuffing machines—which used to be stand-alone machines—to provide networking functions.
More Information
www.rockwellautomation.com
