Stamp Out Misfeeds:
Progressive stamping line
gains increased productivity
with servo feeds.

Frustrated by the inability of his progressive stamping operation to hold 0.002" tolerances on stamped parts, Bill Herron, tool and die and maintenance supervisor at Lau Industries [Rochester, IN] turned to Coe Press Equipment Corporation [Sterling Heights, MI] and their servo-roll feed technology.

Lau Industries, headquartered in Dayton, OH, manufactures air-moving components and fan systems for the heating, venting and air-conditioning and refrigeration industries. The Rochester facility manufactures I" to 15" centrifugal blower wheels, blower wheel housings and blowers for residential, and light commercial applications. Its customers include Trane, Tonair and York. Depending on demand, sales volume for its particular products range from $1.2-$2.3 million per month.

The company prides itself on meeting and exceeding customer expectations by applying cutting-edge technology. The time came to apply that philosophy to its progressive stamping operation.

Simple Enough

Most of sheet metal product fabricated at the Rochester facility are 9, 10, II, 12 and 15-in. blowers for residential and some light-industrial furnaces. The steel sheet is progressively stamped to create squirrel-cage wheels, along with brackets, center disks and housings for the wheels.

To fabricate the wheel, steel strip moves through progressive dies to create the blades and roll them up. Further down the production line, the rolled up wheel receives a ring then a center disk or hub using a staking operation. The squirrel cage wheel is now trued, a test that ensures the wheels are aligned and will spin true without wobbling. A second spinning operation is to balance the wheel and eliminate any vibration during service. Here a machine spins the wheels while operators balance them much the same way as car wheels are balanced.

Depending on the type of wheel product, the wheel is placed in a housing and receives a shaft and bearing. "Some of the product is painted. All eight of our wheels are galvanized," explains Herron. The paint line is adjacent to the assembly line. Parts receiving paint are synchronized to move alongside their counterparts in assembly. Once a housing is painted and dried, it is transported across the aisle to house its corresponding wheel assembly.

The older air feed systems on the production line required a lot of TLC to meet the company's production goals. "Set up of the air feeds could take from one to four hours," says Herron. "We also would spend an hour every morning before the shift just cleaning the valves on the feeds. This required us to take the valves apart, lubricate them and clean them. "

Stamping variations were also a problem with the air feeds. According to Herron, the company preferred to hold part tolerance to 0.002". "We just couldn't hold that tolerance with the air feeds. We saw a lot of variation on the blades we were fabricating, which would cause roll-up problems or other processing problems further in the fabricating process."

Squirrelly Sheet Feeding

Misfeeding was a real headache with the air feed systems, according to Herron. "The problem with air feeds is they don't have accurate dialing on them. Each feed change requires the operator to measure, then adjust the adjusting screw, then re-measure the screw. Accuracy on these feeds was only as accurate as the operator could eyeball it. It is easy to misread the scale by 0.030"

To adjust for this inaccuracy, the operator would have to hit a few pans, make any necessary adjustments to the feed-length adjustment screw, then hit some more parts. This method is repeated until the operator believes the material is being fed correctly to the die. This process requires a great deal of time, since the operator must walk from the control at the front of the press to the back of the press to adjust the lengthening screw then back to the front to test that adjustment.

Inaccuracies do more than cost time. Inaccurate feeding of material to the die can damage the die. Operators didn't always catch this occurrence. The result was double hits and breakage of the punches. "Whenever you have to pull the tool, you automatically lose hours of production time," explains Herron. "You have to pull out the die, repair it, then put it back into the machine. Also, when an air feed sits idle for a few minutes, it won't start back up right away."

Servos to the Rescue

Under Herron's supervision, and with the help of Coe Press Equipment, the company is retrofitting its presses from air feeds to servo-roll feed systems. Lau Industries has many older presses that have been stripped down then retrofitted with new press controls and electronics. "To me, there isn't a lot of difference between doing this and buying a brand new piece of equipment," claims Herron. "The electronics and controls are where you have to put your money in either case."

Servo-roll feeds were the right choice for Herron due to their greater accuracy and better coil-feeding characteristics. "The repeatability on them is very good. Set up is also a lot easier than for air feeds. " The new servo feeds can be set up in as little as 15 minutes. According to Herron, "If I want I V* in. from the coil feed, all I do is punch in 1.25 and I'm done."

Herron went with servo coil feeds from Coe because he says they are the best on the market. "They are built for heavy-duty use. Also, with Coe, we have service and support nearby so I can have someone here quickly when we need it." Herron has worked with other feed suppliers that did not meet his needs. "The technical assistance we would get from the other company would start at $2500 just to get someone to come to our plant. That is a big expense, especially if you only paid $14,000 for the feed."

The controls for the feeds are also an important feature to Herron. The servo feeds, such as the Servo Master CPRFSM 112, feature computer controls. Herron noted that operators were intimidated by the controls, but this changed quickly. "The controls on the coil feed are very easy to learn. Operators found setting up the feeds was just a matter of basic reading and math skills. The operators love the computer controlled servo roll feeds, especially since they have gained a lot more productivity with them. " The operators also preferred the safer operation with the servo feeds since they no longer had to go to the back of the press to adjust a lengthening screw.

The 3-2-1 Warranty from Coe on its servo roll feeds is another worthwhile feature to Herron. "I prefer to buy equipment I need for the job at hand and also look at the long-term investment. I've learned that with feeds you get what you pay for. " That warranty proved itself when Lau made a mistake when wiring up one feed, notes Herron. "It was on a Saturday night. I was able to call someone at Coe that night and they arranged for a replacement to arrive the next day. Who else can you call at 9:00 p.m. on a Saturday?"

Rewards And Increased Productivity

Retrofitting the presses to servo roll feeds offered Lau higher productivity by increasing machine uptime. Productivity comes from the significantly shorter setup times of the servo feeds over that of the air feeds—15 minutes versus up to 4 hours. Lau was also able to eliminate the overtime associated with the pro-shift cleaning necessary on the air feeds. Greater feeding accuracy means the stamping presses will have greater up time. No longer do operators have to contend with misfeeds that result in damaged punches, which can halt production for several hours.

Lau Industries offers its employees a gain share program to reward them for any gains in productivity. According to Herron, "We take all the expenses to fabricate a product, such as materials and labor, then subtract out sales revenues. Whatever is left over is shared with the employees. When we first started the program, we didn't make any payouts. But after putting in the Coe feeds and the Data Instrument Controls, the company could make its first gain share payments."

The feeds at Lau Industries are tied into the data instrument press control. "This allows us to talk to the feed from the Data Instrument press control," explains Herron. This frees the operator from having to go back to the feed to change feeds. The data instrument press control also provides parameters to a dual push-pull feed system on the company's turn press.

The turn press at Lau is used for special, low-volume work. The new feed for this press is a dual feed system that can push and pull material through the dies. This type of feed suits the progressive stamping operations necessary for small wheels, according to Herron. "The small wheels are made from very thin material that passes through a fairly long progression of dies. The strip isn't strong enough to support itself so we placed a pull feed on the far end of the die to pull and keep the strip straight."

The dual feeds are synchronized to work together to provide the type of feeding preferred by the operation. "We can program in a slight delay between the two feeds to create either a little tension on the strip or to create a slight droop."

This type of operating flexibility combined with increased productivity and safer operation makes Lau's retrofit a smart investment.

Back to Top