Stamping Production Increases Through Automation
Manufacturers are always looking for ways to improve the rate of production. Many metal stamping companies now subscribe to the quick die change philosophy -- a concept originated by the Japanese. The whole focus is to be able to change dies quickly and efficiently to optimize press time.
Job shops trying to stay competitive need to start implementing this concept. For without it, the amount of time it takes to change dies is staggering. Before embracing the philosophy, it typically took Ultra Tool & Manufacturing, a tool and die/metal stamping job shop just outside Milwaukee, several hours to change a die with one setup person. But by adopting new setup techniques, and learning to use equipment rather than labor, the entire process dropped to 30 minutes with one setup person.
Quick die change usually requires changing a plant's logistics. Die clamping methods must be selected, and operators must have the proper tools, to make the necessary maneuvers.
At Ultra, simplicity is the rule. First, they establish a standard clamping height and hardware in which all dies are clamped. The hardware consists of a Tee-nut, threaded stud, flat washer, and a flanged nut. All dies were modified to accept the hardware without the use of strap or bridge clamps.
The die shoe is clamped to the press by slotting several parallels that extend beyond the die set to accept a 5/8 inch threaded stud. The parallel is then machined down to our standard clamping height.
In the punch holder, or upper half of the die set, we have the slot torch-cut when the die set is purchased. This eliminates flatness problems that may occur when machining this slot later.
Clamping a die in a press now consists of sliding the die into the proper location, lining up the slots over the Tee-slots, sliding in the clamping nuts and studs, and tightening.
Electronic Roll Feed
A major piece of equipment to help implement quick die change is the electronic feed of rolled sheet material into the press. Electronic feeds have many advantages over air or mechanical feeds. The most obvious, of course, is efficiency.
With air or mechanical feeds, the operator has to laboriously make all the necessary adjustments for the feed to operate correctly. When using a mechanical roll feed for example, an operator climbs up and down a ladder to make the necessary adjustments. Whether it is a short run or a long run, all the steps must be taken. It is not at all unusual to have an operator go through a lot of trial and error before the roll of material feeds correctly into the press.
With an electronic feed, all the operator has to do is push a few buttons to enter the settings to run the job -- how fast, how far, and when in the press cycle it should feed.
If more adjustments are needed, the operator punches in the new settings. Best of all, the operator doesn't have to start over for every repeat job. All the settings can be saved and pulled up on the computer when needed.
Obviously, saving on labor is a big advantage. However, it is not the only one. An electronic feed is much more accurate than an air or mechanical feed and adjustments can be very precise. Try adjusting an air feeder to feed 0.001 farther than the current setting.
Another advantage is that the electronic feed allows faster production rates when operating with electronic die protection. Increased press speed means an increase in the time it takes for the press to stop the ram and tool before engaging the material, or, put another way, faster speed -- slower stopping time.
The electronic feed gives you the ability to feed earlier in the feed cycle. Higher press rates can now be achieved and still protect the tool from closing on the material if there is a tool or feeding malfunction. The previous generation of press feeds either had to be tricked to feed at different times, or just lived with.
Electronic feeds have few limitations. One possible problem is in feeding some types of light, thin material such as a foil. Because foil bends easily, there is a possibility that it would not feed well with an electronic feed unless the feed is mounted on the press in such a way that the material can be pulled through the die.
The only other disadvantage is, of course, the expense. Most stamping shops are able to implement the technology only as fast as they can afford it. Progressive shops are embracing the technology; as a result, the manufacturers of electronic feeds often have a difficult time keeping up with demand. It is not at all unusual to have to wait three months for the delivery of the equipment. Obviously, deliveries vary between manufacturers.
An electronic feeder can cost between $15,000 and $45,000. The price for an electronic die protection system is relatively inexpensive; starting at around $5,000. However, the real cost of electronic die protection goes towards setting up the tooling so that each die has a custom sensing package.
In most metal forming shops, the size and amount of the production determines if to invest in the equipment. Ultra Tool & Manufacturing has been in the metal stamping business for over twenty-five years. Like many shops, Ultra started with a few old, slow, and small presses, but over the years, has developed into a modern, dynamic facility able to handle many difficult challenges.
Ultra specializes in difficult jobs -- tight tolerances, difficult draws, abrasive materials, etc. -- the kind of jobs that other stampers sometimes avoid.
Ultra's stamping department is equipped with Minster straight side punch presses ranging from 45 tons to 200 tons. Ultra's first electronic roll feed was purchased in 1993 and installed on a 45 ton straight side press. The style L model 4-12 was made by Littell.
After the installation of the first electronic feed, it was obvious that all the automatic presses should be equipped with electronic feeds. Over a three-year period, Ultra Tool began investing in the machinery. Ultra now has five electronic feeds manufactured by either Littell or Minster Automation.
A side benefit of buying electronic feeds was that it forced Ultra to update its press controls. Some of the controls were updated along with complete press rebuilding.
One press was sent back to its maker for re-manufacturing. Known as 'The Press', it is a 100 ton Minster press that has been with the company for many years. Built in 1956, 'The Press' has a 42 inch bed size, and a three inch stroke.
'The Press' has been updated to 1996 standards. Almost like restoring an old car, 'The Press' was stripped down to its base casting. All the old electronics were thrown away. Many of the mechanical components were replaced, others were rebuilt. All major castings were re-machined to new specifications. Finally, it received a fresh new paint job.
Taking advantage of improving technology ultimately benefits the customer. One of Ultra's customers, a manufacturer of scissors blades, was having problems getting enough production volume, and getting parts made to print. Like the previous stamping shop, Ultra struggled with the existing die. Nevertheless, they were able to meet the production volume because of their philosophy of using enhanced equipment, and focusing on tooling improvements such as cutting material upgrades, minor die design changes or, as in this case, die replacement. Today, weekly shipments can exceed 200,000 parts per week from a one-out die.
Another important client is Harley-Davidson. It was Harley's insistence on quick die change that became the impetus for refurbishing and/or installing the new equipment.
Because Harley-Davidson's production requirements are consistent, Ultra is able to run smaller batch sizes. And because the information is stored in the feed, the jobs can be set up faster. As a result, for the past two years, Ultra has been able to offer Harley more frequent inventory turns and price reductions on an average of two percent per year.
These examples reflect Ultra's philosophy of working in partnership with customers to determine the most efficient and cost effective way to produce the part.
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