Die Science: Data, data, data

Quality icon W.Edwards Deming once said, “In God we trust; all others, bring data.”

What a true and unshakable statement. My livelihood as consultant revolves around being able to do three basic things: collect, provide, and extract data. By extract, I mean to look to others more familiar with the process to provide meaningful data.

There are literally thousands of reasons for a process or a die to fail. Trying to find a single source or combination of sources that contribute to failure can be quite overwhelming task. Solving bigger, more complicated problems usually requires the skills and talents if many individuals who contribute to the success of the process.

Data—both the collecting of it and how it is collected—is important. It takes more than just technical expertise to solve a problem. Regardless of how much data you collect, data itself will not correct your problem. Data is useless unless somebody react to it.

I have been in several shop that have piles and piles of data, but nothing is ever done with it. Why? People often lack the motivation to use it and put it to work.

Troubleshooting has both a technical and a human side. In a case example, a company’s pierce punches continue to break. This is a common problem. There may be 16 possible causes for punch breakage.

Who Is Needed for the Fix?

1. Poor punch-to-die Alignment. Obviously, if the punch is not aligned with the lower die button or matrix, it will break. You will need a toolroom die technician to investigate and correct this problem.

2. Worn-out Guide Pins and Bushings. If the die set is not guiding properly, the punches will not work as well. Once again, you will need a toolroom technician and possibly a machinist to bore and refit new pins and bushings.

3. Unbalanced Shear Angle on the Punch. Unbalanced shear angles may force the punch to deflect on impact. You may need a diemaker or grinder specialist to regrind the punch.

4. Poor Die Setup Procedures The die or press bed may have been dirty, and the die is not sitting down flat on the ram or bolster plate. You will need a die setup technician to correct this.

5. Insufficient Pad/Stripping Pressure. If the pad doesn’t have enough pressure to adequately strip the punches on the return stroke, the punches may become defective and break. You’ll need a die designer or engineer to redesign this station and add more springs.

6.Improper Cutting Clearance.Small cutting clearances create high loads on the punches, sometimes resulting in punch breakage. You will need a diemaker or engineer to recalculate engineered clearance and correct the die.

7. Poor Tool Steel Selection Many tool steels have great wear resistance but lack toughness. Using a tool steel that has poor shock resistance in severe cutting operation may result in punch breakage. You will need an engineer or metallurgist with in-depth knowledge about tool steel selection to correct this.

8. Poor Heat Treating of the Tool Steel.The heat treating factors into the tool steel’s performance. Quenching temperatures that are too high or too low can affect the performance drastically. In addition, the tempering prices is critical. You may need a metallurgist to solve this problem.

9. Sloppy Press Ram. If the press ram is not coming down parallel or is moving horizontally, it may cause the piece punches to enter crookedly. This really is a problem if the ram is cocking after the punches have entered. You will need a press maintenance technician to correct this one.

10. Poor Ram-to-Bolster Parallelism.The ram and bolster must be parallel ignored for the punches to enter properly. You will need a press maintenance technician to correct this.

11. Poor Press Selection.This is perhaps one of the most common causes of punch breakage. The press ram must be parallel to the bolster plate and remain as parallel as possible through the entire press stroke.

Poorly maintained presses and gap-frame presses are not good candidates for high-tonnage cutting and piercing operations. This is especially true if the press has a greta deal of defection. Certain gap-frame presses are allowed to deflect as much as 0.002 in. bed, this calculates to as much as 0.060-in.overall deflection.

This deflection presents a serious problem as the press deflects “open” during punch impact and “closes” up after the punch enters the die. Excessive deflection that occurs after the punch has entered will most likely result in punch breakage.

On the other hand, a well-maintained gap-frame press can perform cutting and piercing when the cutting force required is considerably less than the available tonnage. You need an engineer or press specialist to select the correct press for the application.

12. Incorrect Press Counterbalance Adjustment.Counterbalance not only helps to reduce the energy needed to move the press ram, it also helps to level the press ram. You need a press technicianto perform this adjustment.

13. Insufficient Pad Balancers Present. During the initial strip starting of the material in a progressive die, the metal sometimes only partially feeds underneath the spring-loaded pressure pads. If pad balancers are not present, the pad may tilt, resulting in punch breakage. You will need a die designer or engineerto correct this.

14. Poor Strip Start Location.If the material is not started in the correct position in a progressive die, it may result in half-forms. This may result in die shoe deflection, as well as punch deflection and breakage. The die must be clearly marked by the diemaker ,and the die setupperson properly educated on the importance of starting the strip in the proper location.

15. Improper or Inadequate Heeling in the Die.In a die that is cutting and forming on only one side of a part, heels are usually necessary. A die designer, engineer, die maker or machinist may be needed to correct this.

16. Poor Retainer Fit.The pierce punch must properly fit into its respective retainer. Avoid sloppy fits or “floating” a punch. The punch must be a precision fit into the retainer to reduce the vibration that occurs when the punch contacts the metal. A die designer, engineer, die maker or machinist may be needed to correct this.

The Human Side—Teamwork

Outlining the possible causes is the easy part. Now the real work begins. Which of the 16 possible causes is it? It may be a combination of several factors. The key to getting the data needed to make the corrections is involvement

Good consultants don’t have all the answers. Consultants encourage ideas and consider all hard data presented.

A good problem-solving consultant looks to the experience and expertise of others who may have more experience with a particular machine or die.

Creating the team. Gets as many people who have knowledge of the process together in a meeting. It’s a simple fact that people will support a world that they are allowed to create. Good problem-solvers create an environment of interdependency. Only through the combined efforts of everybody can the desired results be achieved.

If possible, bring an individual with very little knowledge of the process in as well. Why?Sometimes the answer to the problem is so obvious that the most technically intelligent individuals cannot see it. Set Communication Ground Rules. All ideas should be entrained. Everyone’s opinions should be respected.

Often the answer to a problem already exists, but somehow through a lack of communication in an organization, the group has failed to arrive at it. Do the “five whys.” It works.

Until next time… Best of luck!