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Driving shop productivity with the right punches and dies

Tailor your tooling to the application

Productivity can make or break a shop. Behind safety, productivity should be top-of-mind for design engineers and tool room maintenance personnel when building or refurbishing dies. The metal stamping industry offers a wide-variety of options, each with its own pros and cons, making product purchasing decisions a daunting task.

When deciding on tooling equipment, design engineers should employ a two-fold approach of equating productivity to enhancing the manufacturing operation and lowering cost of tool ownership.

When tools, such as punches and die buttons, suffer premature wear and other failures based on application difficulty, the manufacturing operation can experience detrimental downtime. Additionally, lower-quality tools can cause decreased productivity and result in a higher cost of tool ownership over time. Frequent tool changing or sharpening can increase a product’s cost of ownership dramatically and have a negative impact on productivity and the bottom-line.

Improving ROI Within Your Stamping Operations

The tooling required to maintain a highly efficient manufacturing operation varies based on the application. However, the factors to be considered are universal—material type and thickness, the machine tool, lubrication, tolerance, production speed, and design intent.

Various alternatives related to these factors can improve tool life. It’s important that every situation be treated with the uniqueness it requires as not one job is the same as another.

After assessing your die design and application, review the equipment and verify that tolerances can be held at the speed necessary to maximize productivity. This includes reviewing the press to be sure the accuracy and speeds are attainable for the production requirements intended.

The final factor in determining the best course of action for improving uptime is the material type and thickness to be fed through the die. As the materials become more exotic in nature, so does the need to ensure you select the optimal tooling for the material. The proper steel type and coating can increase machine productivity and decrease time spent on repair and maintenance, depending on the application.

Today’s tooling suppliers offer a variety of quality punch and die components for the stamping industry. Innovative solutions such as tool steel and coating options combined with streamlined tooling improvements allow you to outfit your factory with better quality and longer lasting tools, faster.

Outperforming with Extreme Punching

High-frequency and high-volume stamping are the industry norm, but the increasingly popular exotic materials can wreak havoc on standard tooling, wearing punches and dies faster than cold-rolled steel or aluminum.

Solving tip wear problems is only one facet in maximizing tool life. Many applications stress tooling in places other than the tip. Often the failure point is the head. Head breakage can occur during the initial piercing impact, snap-through, or punch retraction (stripping).

Figure 1

A remedy? Re-design the head on the punch. Adding more stock material to increase diameter and thickness creates more area for the stresses of the application to escape (Figure 1). Additionally, you can have the heads precision-ground to minimize play in the punch pad.

Adding a larger radius under the head and a chamfer to the back of the head centers the impact over the punch body and distributes the force onto the body versus solely to the head. Tooling suppliers currently offer products with these options.

But why is the head failing in the first place? If it is failing on impact or snap through, the larger head and radius should help alleviate the problem. If it’s breaking down during stripping? The stripping force required might exceed the tool’s limits. One way to help alleviate undue stress during stripping is to change the way the tip is made. Change the direction from a cylindrically ground tip to a linear or straight grind method. This puts the tip’s grinding lines in line with the stripping direction, which reduces the forces required to strip. Less strain on the head makes for a stronger tool.

One last thing to consider is the material used to make the punches. Standard punches are M2 or A2 material, which is sufficient for mild steel. This tooling design can be found in a PM-M4 or proprietary steels for extreme applications.

With standard high-speed steels, once tip life is improved, the head or body of the punch typically is the next point of failure. Changing tool steels to a powdered metal, such as 3V or a PM-M4, increases tool toughness and improves the punch’s ability to resist breakage from shock and impact forces. This extends the overall tool life beyond tip life.

Improved Punch Life Through Coating Technology

Coating technology can boost tooling performance to levels far beyond that of untreated steel in any tool. This is especially true for punches, as coatings provide impact relief during the application process. Punches can be treated with various coatings engineered to help stampers achieve higher levels of performance (Figure 2).

Over the past 20 years, coatings centers have popped up all over the world, and for good reason. Matching the coating to the application often is overlooked. Standard titanium nitride (TiN) or titanium carbo-nitride (TiCn) coatings commonly have been used universally for a long time, but while any coating should provide some productivity gains, matching the coating to the application maximize efficiencies.

Some things to consider when determining the best coating for your application are:

  • What material is being pierced or formed?
  • If you already ran product, how is it wearing?
  • Is material adhesion or galling present?
  • Is fracturing occurring on the cutting edge?
  • What is the tolerance of the tools?
  • Do stripping forces need to be reduced?

Coatings come in different forms, such as PVD, CVD, and PACVD, and they continually are evolving to meet industry demands. Work with your tooling supplier to determine the best coatings for your application. The tooling provider can manufacture punches and dies based on the coatings being applied. Matching the surface finish and tolerances to the correct coatings provides maximum durability.

Maintain High-level Manufacturing

Tool failure is a stamping operation’s No. 1 enemy. Premature wear and tear, head breakage, and additional failures cause productivity to halt and operation costs to rise. The best way to prevent this is by investing in high-quality tooling with low cost of ownership.

Changing materials requires a change in punches and dies; the low-cost product is no longer the value it once was. By selecting the best-suited steels, coatings, surface enhancements, and tooling designs, you can keep your system running much longer than with standard tooling and maximize your productivity (Figure 3).

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.