On the web and at work, I often get the question from many die and stamping shop people, “Can you tell me how to get these die people better at making the dies run better? ”
I often hear the complaint, “We do have a lot of downtime and scrap, not to mention the usual problems with burrs and product quality. Our progressive dies have erratic feed lengths, we have frequent breaks or splits in stretching, etc., and we can't seem to keep the dimensions of critical parts stable. Clearly, our mold maintenance staff was not doing a good job of troubleshooting and maintaining the molds! ”
Does it sound familiar? While it is certainly true that certain stamping problems are the result of inadequate mold repair capabilities and poor maintenance, there is also a large percentage of problems that have nothing to do with the mold at all, but rather with other factors. Often, people involved in material procurement, tooling, spare parts purchasing, press maintenance, product and die design, and die setup don't realize how their decisions affect stamping production.
Product Design
Many problems in the press shop are the result of poor product design. Products are designed with many unrealistic feature requirements that cannot be obtained through a certain number of manufacturing processes; products are designed with features that require an additional annealing process in molding to obtain; and harsh, non-applicable part tolerances.
Consider this typical example: A product is designed to extrude a very tall cylinder in the center of a large blank. The process engineer calculates that five forming stations are required to achieve this feature. These five stations require a large press that is 100 inches long. The company had a press with a maximum length of 70 inches. The typical solution was to remove two molding stations to fit the press, with the end result being scrap.
Product designers need to understand how stretching and forming work in a mold. The product designer needed to work with a mold specialist to help develop a product that was functional and formable enough for the job.
Mold Sourcing
As the saying goes, what you want is far from the truth. If you purchase a mold or part using is inferior steel or the heat treatment is not up to snuff, you will be lucky if your mold can produce a million products.
Molds should be viewed as an investment. Too often we only see the cost of the mold and not its value. Downtime caused by molds made from cheap or poor mold steel; difficult repairs due to poor mold design; lack of mold pads; thin, weak mold design; no adjustment mechanism; plates not annealed. The additional costs incurred in the use of these dies can exceed the cost of a better die. The success of a stamping company depends in part on the quality and performance of its dies.
Material Purchasing
I often hear material buyers say, “My job is to buy stamping material. As long as the material is within specification, I can get it from any vendor at the cheapest price. If the stamping shop breaks down, it's not my fault. I've done my job.”
We know that the material for stamping is usually a nationally led compilation of a generalized standard that allows for wide variations in the specification of the material. While materials at the average mechanical properties may be usable in the mold, they may cause process failure at the specification limit.
When ordering materials, consider the following: Who defines the material specifications? How are they defined? Has a formability study been performed on the parts to be molded to determine if the material is still suitable for molding at the limit specification states?
The material buyer should work with the tooling and product designers to determine the minimum mechanical properties (elongation, n-value, r-value, and yield strength) of the material that is best suited for the stamping process. Ordering unsuitable metals can be very expensive.
Press Maintenance
Some people think that it is the mold that produces the product and that the press is only an aid, but I believe that the press has the same importance as the mold.
The press must be carefully maintained with preventive maintenance of the flatness and parallelism of the slide, adjustment of the balance cylinder, flatness of the table plate, seals on the slide, lubricants, etc.
Mold Installation
A perfect die incorrectly mounted on a perfect press cannot produce properly. When setting up a die, the die setter must consider closing height, pad and gas pressure, lubricant type and use, feed time, die parallel to feeder, feed height and feed length. If one of these factors is not set up correctly, the result can be excessive downtime or severe damage to the die.
The success of a press shop depends on the cooperation of all parties involved. It is also important that die personnel fully understand the tasks and responsibilities of the rest of the company. It is only through understanding how our work affects the work of others and through full cooperation that we can be successful and competitive.