Most customer accounts begin with small motor repair jobs and then graduate to larger motors and driven equipment repair work such as fans, gearboxes and pumps. A few of our customers have specialized process equipment that also needs service work to keep production rolling. One of our customers produces only one product – cellulous fiber, and they cannot make enough of it to satisfy the consumer demand for this product. Cellulose is found in all plant matter. This customer uses large rolls of white paper as their only source of cellulose. The wood pulp in the paper along with the starch provides cellulose with zero waste. The large rolls of paper are fed into high-speed cutters that cut the paper into thin ribbons. The ribbons are then milled in large rotating ball mills to wheat flour consistency. This cellulose powder is used as a food additive and pharmaceutical applications. Most all low calorie, diet foods have cellulose added to reduce calories and add dietary fiber. If you have ever taken an aspirin, or eaten low calorie food, you have ingested cellulose. The high speed cutters have hardened knives that self-destruct if a piece of metal goes through the cutter or if the knives come loose from the internal spider mounts on the rotor. When there is a cutter crash, it comes into our shop for repairs to get it back into production. The rotors have finger plate star sections welded onto the rotor shaft. The finger plates are sometimes damaged and require replacement. Years ago, Kim Shellabarger figured out how to replace the finger plates on the rotor and have them machined on an angle to duplicate the original rotor design. The hardened knives are set on a slight angle to the shaft center-line and they are set very close to a bed knife. This results in a shearing action of the paper that is fed into the cutter, similar to how a pair of scissors cut paper. Essentially, these cutters are just high speed paper shredders on steroids. The other issue with the repair of these cutters was the bearings. There was a high bearing failure rate so we determined that the root cause of failures. There was insufficient clearance in the bearings to compensate for the high amount of heat generated during operation. Due to thermal expansion, there is a substantial amount of shaft grown, length-wise, so the bearings would lose adequate internal clearance. These cutters have double taper roller bearings so we now machine a spacer between the bearing races and machine the floating end housing to ensure that we have .012” minimum clearance end-float in the shaft. After assembly, the cutters are mounted on our test stand bed plate and driven with an electric motor to check vibration and bearing temperatures to ensure that we are shipping a good product. Learning how to successfully repair these special cutters is an example of our employees having the courage to get out of their “comfort zones” and apply their repair knowledge and experience to develop a solution to a customer problem.
