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Gain efficiencies making 2-D shapes in stamping applications

Straight-line grinding, tool steels, coatings, and other variables help

Job shops aren’t in the business of turning down challenging stamping orders. In fact, many shops implement nontraditional stamping and fabrication applications for any number of part runs on a regular basis. Whether creating unique forms for special parts or implementing a new design concept that adds value, stamping manufacturers may find that maintaining the finalized product requirements with consistency can be challenging.

What’s more, if secondary operations or additional hits are required in the progression, the loss of time and increased labor can devour budgets and hinder production schedules quickly. Add to these challenges additional headaches posed by weak tools and stripping pressures, and stampers can face major roadblocks when taking on special part runs.

With numerous options in specials tooling, including 2-D shapes, fabricators have choices when it comes to reducing the need for secondary operations and the number of hits in the progression. Plus, the right tools for the application can deliver longer tool life and less material adhesion.

Assess the Application

When a part run requires an operator to take an unfinished part out of the die and perform any number of secondary operations, time and money are lost. Whether the part needs milling, grinding, bending, or any other type of forming, even just one extra step can cause major challenges and inefficiencies.

Special 2-D-shape tooling can help reduce necessary stamping progressions by reducing hits in the progression, but assessing the application and part design before beginning the run can help save significant time and costs. Working with design engineers and the tooling manufacturer can help identify potential pitfalls and determine the best tooling for the job. The right tooling often can complete a special shape in one hit as opposed to three, four, or more in the progression.

Along with forming considerations, fabricators also need to take into account additional details of the application, including material type and final product design requirements. For example, one part design might place more pressure on one area of the part than another; another part might have too narrow of a tip; and still another part might require long point lengths to clear forms in the progression.

Any unique part design can cause stripping pressures; increase material adhesion; and weaken tools, springs, and other die components, which can cause even greater challenges down the line and negatively affect part quality.

Straight-line Grinding

To address challenges associated with producing 2-D shapes, some tooling manufacturers have employed straight-line grinding.

Straight-line grinding (SLG) is a machining process that’s used to manufacture the special 2-D-shape punch. The method can be used for any tool that has an internal radius or feature and delivers a grind that is in line with the punch stroke. This characteristic gives the punch better stripping properties, grain structure, and surface finish, which help reduce galling and material adhesion while improving tool life.

Contrary to a cylindrically ground punch, the machining process of SLG is completed inline with the penetration of the punch. In this process the grinding grooves and the punch are moving in the same direction, whereas in cylindrically ground punches, the grooves and the punch are moving in perpendicular directions. An SLG-ground punch produces less friction and adhesion and strips back out of the material more easily, leaving a cleaner sheet with less hole distortion.

The SLG process also assists in prolonging wear components that support the entire stamping operation. Springs, bushings, pins, and other components suffer from extra stress as the punch dulls, which can cause fatigue and breakage. Prolonging the life of the punch benefits these components with a longer life as well.

The sinker EDM method of manufacturing 2-D-shape punch tools is common, cost-effective, and widely available; however, SLG can deliver greater stripping properties because of the surface finish and grain structure. The SLG process may be available only on certain types of 2-D-shape punches, however, so a stamper should be sure to talk with the tooling manufacturer about the application in detail to choose the right tool.

Choosing the Right Tool Steels and Coatings

Material type can play a large part in the success or failure of a 2-D-shape part run. Stampers often see the most frustrations with sticky materials such as aluminum, copper, and galvanized steel, whereas stainless delivers challenging shrink-back. Any type of premium steel and high-strength, low-alloy can adhere to the punch, meaning the right combination of tool steel and coating is necessary to improve efficiencies.

Punch tools with 2-D shape are available from most tooling manufacturers in just about any shape and size a design engineer can dream up. As well as completely custom tool designs, many 2-D-shape punches are cataloged by the manufacturer and available within a quicker lead time than completely custom designs.

Identifying key characteristics of the material type and application can help fabricators work better with the tooling manufacturer’s designers to select the best tool steels and coatings for the job. Many varieties of tool steels can be utilized, including M2, M4, 3V, 9V, 10V, 15V, Ultima®, S7, A2, and D2.

Coatings can play a significant factor in mitigating challenges associated with using 2-D-shape punches for creating unique products. Coatings can help lower the coefficient of friction, which results in reduced material adhesion. Numerous types of coatings are available for stampers, including Optima, OptimaX®, Wear-Beater™, CrN, ZiCrN, TiCrN, and Forte®.

When working with the tooling manufacturer, stampers should ask questions about the proper combination of tool steel and coating that will work best for the particular application.

Fewer Challenges, Greater Efficiencies

Unique part designs and confounding shapes don’t have to cause production headaches and part-quality frustrations. Taking the time to assess the application, consider grinding options, and identify the right tool steels and coatings can help stampers achieve greater success when using 2-D-shape punches. Greater success naturally translates to greater time savings, more efficiencies, and greater cost savings.

About the Author

Jeremy Edson

Stamping Product Manager

12912 Farnham Ave.

White Bear Lake, MN 55110

800-328-9646

Jeremy Edson is the stamping product manager at Wilson Tool International®. He has worked for the global tooling manufacturer for 21 years.