When your company name (In-Sink-Erator®) is synonymous with your product (food waste disposers), you not only own a place in your customers'' mind, you own a piece of the market -- a big piece. And to serve this market, you must stay productive in spite of production challenges.
For example, In-Sink-Erator®, the world''s largest manufacturer of food waste disposers and hot water dispensers, needed to increase production of the steel motor shell that houses the electric motor and stator.
The company used to take a stamped steel sheet and roll form it to the proper diameter. Next, they would mig-weld or resistance-weld the seam, expand it to the proper diameter, and then put it in a lathe to cut and chamfer each end. This process would help ensure burr-free ends and help keep the ends parallel to within thousandths of an inch. But the procedure was labor intensive, with handling between each station and a significant cycle time for each finished motor shell. It was far too slow to keep up with demand.
Today, In-Sink-Erator®, a division of Emerson Electric Corporation, has found a better way to perform this procedure by using automation from Newcor Bay City Division in Bay City, Michigan.
In-Sink-Erator® manufactures food waste disposers for residential and commercial applications. These food waste disposers range from one-third horsepower to one horsepower for residential units and from one-half to 10 horsepower for foodservice units used in commercial applications.
To keep tight control over product quality and manufacturing, In-Sink-Erator® is vertically integrated with only a small percentage of parts produced by vendors.
Motor Shell Manufacturing
In-Sink-Erator® engineering mechanical technician Darwin Foster says a motor shell starts with a mild cold-rolled steel blank that ranges in thickness from .047 in. to .049 in. (The first cylindrical unit shown here is the electric motor shell produced with the Newcor equipment. Next is the stator that will be precisely pressed into the shell. The third unit is the stator pressed into the shell.) After steel strip is blanked on a press, the blanks are palletized and placed in movable stacks. They are then placed on the Newcor motor shell machine''s conveyor and fed into a destacker where an arm using suction cups picks up each blank. The steel blank is then roll-formed and transferred down the index rail to a mandrel where it is clamped and the edges are aligned to within +/- 0.002 in. The edge alignment is critical because it aligns the motor stator and the rotor. If it''s off, the rotor shaft will not align properly and will cause other manufacturing problems.
"After clamping and alignment, the shell is resistance-welded using a mash seam weld," Foster said. "Then it is sent to the process line part of the machine where the imperfections on the weld are nipped off." (During welding, steel is squeezed out from the shell at both ends due to its molten state and the pressure of the welding wheel.)
Foster said this process is used to keep both ends of the motor shell parallel. At the next station, two witness marks are stamped into the shell to help in aligning all the end parts to the motor shell for down line fabrication. The motor shell is then placed on an expander that increases the diameter about 0.030 in.
"The expander is needed because with roll forming and welding, the motor shell tends to taper and it''s just difficult to hold a perfect diameter to our tolerances," he explained. "Expanding the steel beyond its yield point allows it to hold the diameter better and not be subject to temperature changes as much. So it needs this secondary operation to meet our diameter tolerances. We usually end up with a tolerance of 0.0005 in. on both the finished diameter and taper after expanding."
Foster stated that with the Newcor motor shell equipment, In-Sink-Erator® was able to decrease cycle times, reduce scrap, and get a better shell.
In-Sink-Erator® now has three motor shell welders that run 24 hours a day at least five days a week and five to eight hours on Saturday as needed. They have a 6-second-cycle time per motor shell. Each machine also has the capability to be changed over to a different motor shell easily. Foster indicated that all the shells are the same diameter, but the lengths vary. "We have 3.5 in., 4.75 in., and 6 in. shells. All we have to do is turn a hand crank to adjust the destacker for each size and then input which blank size to run on the machine''s PLC."
Newcor resistance welding machines were originally used to do the motor shell welding before Newcor integrated the process into one machine. "We selected Newcor because it came down to who could do the work. To my knowledge, no manufacturer had a process line that could take a component through all of our operations. So Newcor got the order."
On the latest motor shell welder that Newcor supplied to In-Sink-Erator®, a servomotor is used to control the welding speed instead of an air over oil cylinder system. Now a press of a button controls weld speed for different lengths of motor shells on the PLC, rather than setting switches, Foster explained.
"Currently, one employee services three machines. If the motor shell welder runs out of stock, the machine through In-Sink-Erator®''s data highway system pages the employee. Or, if anything should go wrong with the machine, the machine can also page a repair technician."
Foster said In-Sink-Erator® believes in automation to increase productivity and now with Newcor''s help, "the old grind isn''t what it used to be."