10 common quick die change problems
10 common quick die change problems
Tips to improve changeover times
November 7, 2006
Die changeover is one of the few times when a press isn't making money. Why do some die changeovers take hours? It might be the press, operator, die, material, lift truck, crane, or the tools.
Most stampers have the same complaint concerning die changes: "Our setup time is killing us. "It seems as though the stamping industry cannot set standards to save time during die changes. The manufacturing industry has standards for safety, strength, steel, lockouts, and electrical power, but none of these saves time during a die change.
How long does it take to change out a die in a 200-ton press? If you ask six different stampers that question, you will get six different answers.
Why do some die changeovers take five minutes and some take hours? It might be the press, operator, die, material, lift truck, crane, or the tools. The following are 10 common challenges that give stampers the most headaches when changing a tool and tips to solve them.
- Working With Different Die Sizes. If the die footprint is different from job to job, everything from the T-nuts and studs to the finger clamps needs to be changed. One way to address this problem is to make all the dies with the same footprint. This can be quite costly if you have a large number of dies. Another way is a die clamping system that works with a variety of die sizes. Some stampers locate dies with T-slots and simple spacers or locator pins on magnetic clamps to reduce the time it takes to locate a die.
- Changing Clamps. To reduce changeover times, look for clamps that can accommodate all die sizes run on a press. For example, hydraulic clamps that fit in existing T-slots can be slid in and out easily. Magnetic clamps that cover the entire ram and bolster can eliminate all tools while accommodating all die sizes without standardization.
- Locating Needed Tools. A die clamp standard is helpful because it can save time by eliminating decisions like which stud is needed, which finger clamp will work, and clamp placement. Shops that alter studs and clamps so they are similar save the most time. Many stampers create a die change toolkit that contains everything needed so no time is wasted looking for the right wrench, studs, and T-nuts. Automated clamping mechanisms that require very little adjustment with as few tools as possible also will reduce setup times.
- 4. Loading Large Dies. Line-up blocks mounted to the press bolster or a red stripe painted on the center of the die and center of the press can help an operator line up a die more easily. Die lifters installed into existing T-slots can reduce the effort needed to get dies lined up and does not use up precious die space. Die lifters can be used in conjunction with hydraulic or manual die loading and hydraulic or magnetic clamping.
- Recognizing Component Wear and Tear. T-nuts, studs, nuts and bolts, finger clamps, and hydraulic clamps wear out over time and become unusable at inopportune moments. T-nuts can strip, finger clamps will bend with overtightening and normal use, and hydraulic clamps can wear and develop leaks. Even the most organized plants can suddenly find themselves in a pinch. Stampers that have a planned maintenance program or a clamping system with no wearable parts fare the best in reducing this element of changeover time.
- Understanding Die Shoe Thickness. If a shop uses a hydraulic mechanical system to clamp dies, the shoe usually has to be the same thickness from die to die for the clamping system to work. Sometimes the cost of altering the shoe thickness is far greater than the initial clamp investment. This is not an issue for systems that can accommodate any die shoe thickness.
- Making Ram Adjustments. Making ram adjustments is crucial and time-consuming. Altering die heights to a small window reduces the time needed to get the next die running, because some rams can adjust at less than 1 in. per five minutes. For example, running two dies back-to-back with similar shut heights can reduce ram adjustment times.
- Moving Dies in and Out. Reducing a die's total travel distance is a quick way to shave time off of changeovers. For example, one stamper uses a die storage unit with multiple-height die racks. It has enough room to put all the dies on the same level as the bolster. The stamper then installed a simple roller system that extended all the way to the press, which eliminated a lift truck or die cart in the die-changing process. This was a vast improvement because the stamper had 26 dies on four levels 12 feet above floor level assigned to a single press. As a result, this stamper saved enough time to eliminate an entire production shift on two presses.
- Locating the Next Die. This is another time-consuming process if you don't have a system to track where a specific die should be. This seems simple, but many hours are wasted trying to locate dies. Have a place for each die and label it. A die-labeling system tracks where a die is at all times. For example, a labeling system can be as simple as Die #1XB17: 1 is the part number, X is the material, B is a revision number, and 17 is the exact storage space the die should be returned to. This is an inexpensive way to reduce changeover downtime.
- Keeping a Clean Pressroom. The cleaner a pressroom is, the more efficiently it operates. Seeing hydraulic oil on the floor is becoming rarer, but sometimes unusual items end up around presses, such as buckets of oil, clutch parts, broken wrenches, worn-out feeders, and pieces and parts of entirely unidentifiable objects. Catalog noninventory items at least once a year. If you find something that doesn't belong, get rid of it.