Problem Solving Article: The Case of the Untimely Caser Machine

An Article from the Series of Problem Solving Articles in an Industrial Setting

While making my rounds on shift at the food plant where I worked, I came across the two area mechanics working on our Duodozen Caser. I offered my help and it was accepted. All the moving parts in the caser must be timed to coordinate with the infeed cans and the fiber cases. This is where the problems came in. The caser kept getting out of time.

Tony is the lead shift mechanic for the area and a very sharp troubleshooter. He told me that he and Dan had been going over the machine for the better part of an hour and were unable to keep the machine in time. He got it back in time again and started the machine. As the cases were filled with cans and reached the flap-folding and gluing area, each case was a little behind the previous case.

After about 5 or 6 cases, the case pusher hit under the case, pushed it up and jammed the machine. We checked it out electrically and all the timers were still at their last settings. It had to be something mechanical. We went through the retiming process several more times while restarting the machine to try to identify the problem.

The caser is set up to have two side by side streams of 4 ounce fruit cans enter the machine on each side. The cans are loaded into three parallel lines of three and channelled into the fiber carton. the carton flaps are folded around the cans, nine from each side for eighteen all together. After folding, the flaps are glued with fast setting glue and then pushed out the end of the caser onto a conveyor that takes them to a palletizer for stacking. On the conveyor the cases have codes printed on them by two VideoJet industrial printers. We use these printers all over the plant. They are fairly complex and require care and maintenance in order for them to operate at full industrial capacity in the sometimes harsh environment of a modern cannery.

The caser has a large motor and gearbox centralized under the operating converyor that drives a set of chains for moving the cartons and cans in unison. These chains are carefully timed so that all elements of the operation function smoothly when the machine is running. The initial operations of the caser were not suspect. That part was okay. It seemed like the problem started about half-way through the case formation. I noticed that Tony had several of the protective covers off the machine sides. I looked under the machine while using my new Maglite AA flashlight. I spotted something shiny going round and round on one of the chain sprockets. It looked like a can.

When Tony stopped the caser, I asked him to come and check out what I had found. I wasn't sure, but it seemed that the can on the sprocket could alter the circumference of the sprocket. The chain had to travel several millimeters farther for each rotation of the sprocket. Could this be the answer to the timing riddle? Tony and Dan locked out the machine and crawled under the machine to remove the can from the sprocket.

They first had to find a masterlink in the chain, break the chain apart, and then remove the can from the sprocket. They had to use a brass hammer to knock the can loose from the sprocket teeth. The brass hammer, being of softer metal, didn't damage the steel sprocket. With the can removed, chain restored and machine retimed, Tony started the caser again. The caser started putting out finished product as per specifications. Case solved.

I have found that when troubleshooting a piece of equipment or machinery, having a fresh pair of eyes look at the situation can sometimes result in a breakthrough. The original troubleshooter can become tired and overlook problems. Sometimes, a problem can be imported. A Krones labeler is installed upstream on each can infeed to the caser. The Krones labeler hot glues a label on each can.

If the labeler glue setting puts too much glue on the label, glue can ooze from under the label onto the can. When the can gets to the caser, the glue can be transferred to the channel walls and other parts of the caser. The excess glue on the channel walls hold up the cans and they are then out of place. Glue also gets on the fiber gearing and causes stickiness problems. Glue from the caser itself can cause multiple problems. The glue jets must be pointed at the correct spots on the case flaps or the glue will spray on the caser parts and cause problems.

It is a complex operation with many variable points to be aware of and know how to fix. Our mechanics, electricians, instrument men, and operators are all highly skilled and talented.

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Author: Larry Bush 
Profile: Electrician in industrial, construction, marine, and food industries for 47 years, with 22 of those years in management.
URL: http://www.reliability-consultant.com