Indiana gas cylinder producer Manchester Tank and Equipment Co. improved its productivity and lowered its set-up times by installing new feed equipment on one of its stamping production lines.

Overall view of the Coe Press Equipment/Minster stamping line at Manchester Tank & Equipment Company.

A Manchester press operator checks the Servomaster servo press feed controller.

Welded pressurized cylinder tops await "spud" welding operations.

Top and bottom drawn parts are mated and seam welded.

A cylinder collar that was stamped/formed on the Coe/Minster line.

Drawn cylinder halves await processing in foreground.

Automated TIG seam welding operations are assisted by laser alignment/tracking equipment.

Like the cylinders they produce, the manufacturing process at Manchester Tank and Equipment Co., Elkhart, IN, was under pressure. However, by replacing its outdated air feeds and coil handling equipment on one of its stamping press lines, the company reduced manpower, increased production, and slashed set-up times.

Manchester Tank and Equipment Co. was founded in 1945. It is the largest North American manufacturer of cylinders and tanks for propane, chemicals, and compressed air. Products produced at the Elkhart plant include

Department of Transportation-approved steel and aluminum cylinders ranging from 1.4 to 28 gallons in size. Customers and applications include OEMs, gas grill producers, recreational vehicles, air compressors, forklift trucks, fire-suppressant systems, refrigeration equipment requiring chlorofluorocarbon recovery, and rail cars.

Manchester's line of aluminum cylinders, used primarily for forklift tanks, have an average production run (regardless of cylinder size) of about 300 per shift. Roughly 7,000 cylinders a day of all sizes are produced in two production lines.

Steel cylinder tops and bottoms are round blanked on a stamping press and drawn into larger cup shapes. The tops are assembled from two parts, and have multiple holes already stamped into the pieces to attach the valves in a later operation. Although most of the welding at Manchester is done by automated machines (the company builds most of its own equipment for this), a manually operated "spud" welder is used to weld the valve fittings to the cylinder's top.

Stamping Improvements Realized
Steel and aluminum cylinder fabrication begins with flat steel coil or steel coil stock with a thickness ranging from .082 in. to .130 in. for blanking or drawing. To produce the cup shape of the tanks, the operation uses three 300-ton hydraulic presses for forming and one 400-ton mechanical press for blanking. One of the presses punches the blanks from coil stock and draws it into cup shapes. A hydraulic blanking press is fed by a cross feeder that moves the coil stock back and fourth in a zig-zag motion to get the maximum amount of metal from the coil.

Secondary presses draw the metal, punch holes, and produce flanges. These cupped pieces are then cut on the bottom in trimming presses to even out the lips and any irregularities in the bottom caused by the drawing process. The pieces are then formed to put a flange in the bottom of one of the cup halves so that the top and bottom pieces will later fit together when they are pressed together and welded.

Manchester realized it needed to boost production, reduce set-up time, and reduce manpower on their stamping line that was using a 300-ton Minster variable-speed mechanical press. This press produced 44 in.-long steel parts that were blanked, shaped into a ring, and used on tank bottoms for stability.

This part is produced in a 2-stage progressive die. To do this, they decided to eliminate their air feed and coil handling equipment, replacing them with a servo roll feed and coil handling system from Coe Press Equipment, Sterling Heights, MI. Manchester's operations manager, Jerry Burton, said they installed the new coil handling and feeder system in April 2003, and immediately realized a 66 percent productivity increase in that operation.

Previously, an air feed had to grip the stock for this part three different times to get it through the press. Burton said this hurt quality and slowed production. "The new servo feed was capable of moving the stock through the press with one feed stroke and allowed us to continually run our press," said Burton. "With the airfeeder inconsistencies, the fastest that we would run a product would be 30 strokes a minute, probably running high 70s to low 80s in our efficiency percentage. Now I can run at 50 strokes a minute, a 66 percent increase in production."

To get this productivity, Manchester purchased a CPRF-S224 ServoMaster Series 2 Roll Feed (for up to 24 in. wide stock), a CPTT 2410 threading table, a CPPS 250 24 power straightener, and a CPR-PO coil reel and coil car with a 10,000 lb. capacity.

Coe's servo feeder also helped Manchester reduce set-up time by minimizing adjustments. "We can actually adjust the servo feeder on the fly. With the air feed, we would have to shut down production, manually measure the part's length, adjust the air feeder and tighten the feeder's grippers back down, and check to see if we were within tolerance," remarked Burton.

With the air feeder, their average changeover could take half an hour. The new servo feeder lets them changeover in about five minutes. "Everything is programmed into the SmartPac controller. We just punch in the product number, and automatically bring up the coil-feed progression."

Coe's equipment has saved Manchester one man per shift and they were able to cut back to one shift. Also, since they never had a coil car before, the equipment allowed them to reduce crane and operator time required to move coils. "We are able to pre-stage our coils on the coil car to keep a job running more efficiently or pre-stage for the next job. Now an operator just needs to advance the coil car onto the reel," Burton added.

A threading table has helped them manage their coil threading process. "Our operator had to lift the coil from the floor into the air feeder. Sometimes heavier coils needed two operators to do it safely. The threading table has made it a one-man operation. He just needs to guide the coil into the feeder speeding our process up tremendously."

Another important feature of the Coe equipment is the feedroll pilot release. Burton said, "The pilot release is a necessity with progressive dies. Previously, we just had a manual limit switch adjustment for it. The Coe equipment is all programmable and more consistent in opening the rollers and allowing us to align the coil easily. This allows for any set-up inconsistencies, and lets us speed our process, because we know exactly when the rolls are going to open for the pilot pin to align the coil."

On the Coe stamping line, foot rings and collars are produced along with a flat forklift collar that is used on all steel forklift tanks. Job changeovers are done two or three times per shift. Depending on the product, their lot size runs from 2,000 to 10,000 units per day. Foot rings are the company's largest lot size, because they are used on all their products.

Putting it all Together
During assembly, top and bottom tank pieces are pressed together with 800 lbs. of pressure and tack welded. The pieces have been pre-flanged for a press fit. After the tack weld they are set on a conveyor. Cylinders are then placed in an automated seam welder with a laser aligning/tracking system that automatically joins the halves using TIG welding (MIG for steel). This system with controls, by Jetline Engineering, has a laser optical camera that follows the seam of the two pieces and perfectly welds it. The process is displayed on a TV monitor. The foot ring (allows the cylinder to stand up) and top collar (a shield for the valves and integrated carrying handle) are also attached at this time.

Some cylinders have a rough mill finish while others have a smooth one produced by shot blasting for cosmetic purposes. The cylinders are pressure tested at up to two times their service pressure, which can be up to 800 PSI for some designs. Each cylinder's tare weight is then written on it in an automatic process using a Telesis Pin-Stamp marking system. Next, the cylinder is low-pressure tested at about 200 lbs. of pressure and checked for leaks. They are then cleaned, have valve-covers installed, are powder coated, and have safety and instruction stickers added before they're palletized for shipping.

For steel cylinders, the process is the same, with automatic welding used whenever possible for better welds. One of the differences in this line is that the empty cylinder weight is stamped on the side according to DOT regulations. Cylinders are also annealed in an oven (temperature about 1150° F.) to even out the steel's strength.

Currently, Manchester is working toward a lean manufacturing facility using a three-year plan. They have three buildings in Elkhart, IN, producing parts, and they want to move all the equipment from these facilities into one plant. They are focusing on reducing inventory while producing products faster, better, and smarter.

Edited from information supplied by Coe Press Equipment, Sterling Heights. MI Ph. (586) 979-4400; Fax (586) 979-2970; www.cpec.com