Chocolate-coated sandwich cookies, called Wagon Wheels, are baked, filled with jelly and marshmallow, and packaged by the Biscuit Div. of Aliments Culinar Inc. Until last March, cookie collisions and product pile-ups occurred 20 to 30 times a day at the St. Lambert plant, one of four in Quebec and Ontario. Claude Corbeil, production foreman, describes the results: “Almost 200 lb were scrapped daily due to breakage. Missing cookies at the filling stations allowed jelly and marshmallow to be deposited on the conveyor. At the capping station, where suction is used to lift the closed sandwich, marshmallow was sucked into the machine when a capping cookie was missing. Suction was blocked and valuable production was lost each time workers shut down the line for cleanup.”
The cookie filling and capping operation was controlled independently of the infeed conveyor, and the two machines were manually synchronized at startup to run at the rate of 120 cookies per minute. Rows of nine cookies across on the filler conveyor move onto an accumulator that holds four rows. A rotary indexer transfers the first row onto a cleated conveyor, which takes the cookies past the filling stations to the capping station. Meanwhile, the second row follows, each cookie receiving a dollop of jelly from the first dispenser and a layer of marshmallow from the second. When they reach the capping station, suction cups which have lifted the first row, now press them onto the marshmallow-covered cookies. Then the sandwiches move to a chocolate- coating machine.
During this time, two more rows of cookies advance onto the accumulator. But here is where a traffic problem often arose. Unless the infeed and filler conveyors were synchronized, a fifth row of these fragile cookies periodically plowed into those on the accumulator. Cookies broke, were knocked out of line, and another mess ensued.
“We worked continually to keep the conveyors synchronized,” recalls Jacques Roy, systems technician. “We manually adjusted both drive motors with speed-control potentiometers at startup each morning, but temperature changes affected the motors and control circuitry. The pots had to be reset every 15 to 30 minutes to keep the filler indexing correctly. The operator spent 11/2 hr every day monitoring and adjusting the infeed conveyor. It was clearly time to make a change.”
He found the solution in an electronic synchronizer from the Industrial Automation Div. of Astrosystems Inc., Lake Success, N.Y. This device, called the AstroSYNC/ 180, consists of a programmable motion controller and two shaft-position resolvers, one mounted on each conveyor drive shaft. The operator enters the desired gear ratio (in this case, 1:1) on a keypad. The synchronizer monitors both speeds and position difference between the two shafts, then sends a 0 to 10-V correction signal to either an ac or dc adjustable- speed drive. This signal causes the drive motor to either speed up or slow down to eliminate the error.An infeed conveyor (far left) deposits a row of cookies onto the filler conveyor. Simultaneously, the indexer removes a row from the accumulator and transfers it to a cleated conveyor, which carries the cookies past the filling station to a capping station (far right, not shown). A controller synchronizes conveyor motions to prevent cookie pile-ups at the accumulator."/>
At Culinar, the signal is sent to an Emerson adjustable-speed drive that controls a dc motor driving the infeed conveyor. This causes the infeed to act as a slave to the filler. Any lag or lead of the infeed conveyor generates a correction voltage within 1 msec.
The synchronizer acts as an electronic coupler between the infeed conveyor and the filling machine. It requires no programming other than setting the speed ratio. The resolvers that monitor shaft position require no re-zeroing after a power surge or disruption — they automatically give their correct readings.
“The installation worked out exactly as we hoped,” concludes Mr. Corbeil. “Uniform infeed into the accumulator and automatic synchronization with the filler reduced product damage and downtime by 90%. It has freed 11/2 hr of operator time that can be used for more productive activities. Production has increased by almost 20%. And, although we can’t measure it, the atmosphere here is certainly a lot more relaxed.”
The company is adding a synchronizer to a second production line and plans to upgrade others. These lines may use the synchronizer’s programmable limit switch capability to actuate a series of relays, thereby controlling operation along the conveyor.