Tackling Tough Jobs with Progressive DiesBy Richard
G. Green
Size alone doesn't determine a company's ability to be successful, at least not in the slumping business. What counts is a willingness to respond to challenges and take on tough jobs—even those that some say can't be done.T.A.P.E., Inc., located in Wellington, OH, is a 22-employee company that builds large progressive dies. They also have the capability to run first production parts on one of several large presses, as well as clean, deburr, assemble and test components. What sets this company apart from its competition, however, is its ability to take jobs that others consider too tough. Company President Forrest (Bud) Mohrman says. "There is little competition out there for the tough jobs. There are dozens of shops between here and Cleveland that will fight over five dollars in bidding on a washer die. We can pick and choose the tough jobs, doing what we are good at. The alternative of tough pricing on ordinary jobs is not attractive." Meeting Tight Tolerances What T.A.P.E. does very well is design and build progressive and deep-draw dies used to produce some exceptionally high tolerance parts and assemblies. A recent project illustrates the company's approach, which has been instrumental in growing the business started by Bud's father, Ken, 26 years ago—from a garage operation to the 40,000 sq. ft. facility it occupies today.
A Case in Point T.A.P.E., Inc. was approached by a Pennsylvania company interested in developing a new type of oxygen canister, a life-supporting device used by coal miners, Fig. 1. The design called for manufacturing and assembling parts, formed and machined to exceptionally close tolerances, to create an air-tight unit that can be carried by miners on the job. Because of the working environment, the unit had to be able to withstand tough handling, bouncing against metal and rock surfaces, without losing its structural soundness and reliability to function in an emergency situation. With only a concept drawing as a guide, T.A.P.E., Inc. produced a hand-fashioned prototype unit, made of 0.025 in. thick, 304 stainless steel. Tooling was then designed to replicate the prototype. A key decision during initial development stages revolved around using reverse draw techniques to combat anticipated metal hardening during the reduction and deep draw steps. According to Bud Morhman, few companies take advantage of the benefits that reverse draw techniques offer; few invest enough in R&D to make it work. When deep drawing proved practical in the making of prototype units, which were tested and approved by the purchaser, the engineering department then designed and produced the dies to be used for production runs.
For the canister body, a 1000-ton Verson press, set up with 50-ton air cushions and a 10-in. stroke is used for blanking and the first and second draws. As the metal uncoils prior to these operations, Franklin Oil TufDraw® 1730R, a straight-oil type drawing compound, is applied by roller coater. Following the first draw, the formed cup which is approximately 2½ in. deep, is removed from the ram by hand. An additional coating of drawing compound is brushed on and the piece is positioned for the second draw—a reverse draw. The third draw, also a reverse draw, is performed on a 150-ton Dennison hydraulic press. At this stage in the forming process, the stainless steel stock has hardened to the point where annealing is required to prepare for the fourth and final draw. Formed parts are shipped to Hi Tecmetal Group, Cleveland, OH, where they are annealed in batches of 200 to 300 units at 1900 deg. F. Upon return to T.A.P.E., the fourth and final draw, again a reverse draw, completes the reduction and lengthens the cup to its designed configuration. A 100-ton hydraulic press is used for this step. A fourth press,
a 400-ton Minster with a 14-in. stroke, is used for a series of
secondary operations after all draws have been made. These operations
include re-striking; piercing; Good Design Pays Off It is in the assembly process that the extraordinary die design and production process capabilities of T.A.P.E. become evident. At this point, the hose connector unit, consisting of a screw machine part and two stampings is fitted to the canister body. The allowable gap where metal is joined to metal must not exceed 0.005 in. A furnace brazing operation using a chrome-nickel alloy (again done by Hi Tecmetal Group) seals all seams to make the unit air- tight. The most difficult stage of the entire project now comes into play and it tests the versatility of the company's relatively small workforce. All units go through a passivating bath to remove any residual hydrocarbons and free iron that may remain on the metal. Each piece is rinsed and individually hand-dried, to assure surgical cleanliness before testing for air-tightness and, finally, filling with oxygen-releasing chemicals used in the completely assembled device. A Can-Do Philosophy
The entire production sequence of the canister assembly, from blank to final shipment, requires approximately 10 working clays. Maintaining production efficiency, quality control and attention to detail at every - step reflects well on the company's philosophy and the attitude of its workforce. Bud Mohrman remarks, "We take the team approach seriously. We believe in a hands-on management style, working together to solve problems. Our employees know that management will lend a hand when needed, and not simply issue orders from the office." Not all jobs at T.A.P.E., Inc. require the complex logistics and scheduling as the previously described project. However, other factors can add to the difficulty of a job and require a high degree of skill and knowledge to overcome. Coating Extends Die Life One such challenging job handled by T.A.P.E. involves a very abrasive material. The flame retention heads seen in Fig. 3, are made of 18SR stainless steel from Armco, which proves to he very tough on tooling, causing a high rate of wear. Bud Molirman reports that they started with D-2 tool steel carbide coated (TIC coating). However, they found they were able to double tool life by using the TD coating applied to the carbide coating. With this, they achieved a run of 75,000 flame retention heads before performing any maintenance on the tooling. The parts were run on a progressive die using Franklin Oil TufDraw® 1730R lubricant. Another example of the company's ability to design deep-draw tooling is found in the water-cooler facing component seen in Fig. 4. In this case, one die handles both 0.032 in. thick 301 stainless steel and 0.044 in. thick vinyl coated stock. More typical of the large progressive dies built by T.A.P.E. is the motor mount for a trans-axle assembly, Fig. 5. This component is stamped from high-strength, low alloy steel and requires 700-tons of pressure to form on a 1000-ton Verson press. The die uses a bed length of 144 in.
In addition to the unusually large size of this progressively formed part, T.A.P.E. also adds value by staking of nuts to the stamping and by spot welding of studs, the longest of which is 2-1/2 in. Stud welding is done with a 300 KVA welder. It is very evident that Bud Mohrman and his employees find their work challenging. It is also evident that their approach to tough jobs has been rewarding. Mohrman says, "Too often, stampers don't want to experiment beyond the parameters set by the rules and design guidelines. They simply follow the 'book'. In such cases, the resulting prototype will often work, but trouble will come when they get into production. "To do the job right you must be willing to investigate the real-world operating parameters. You have to engineer for the average conditions, not just the ideal conditions. Having a satisfied customer is proof that you've done it right." |
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