Designing tooling economically

Cutting costs in four areas

STAMPING Journal January/February 2003
March 13, 2003
By: Robert Harper

With the tooling trade in its current challenging economic situation, some tool companies are being forced out of business, losing money, or entering into highly competitive markets.

Manufacturers constantly are challenged to cut costs and reduce expenses through lower tooling costs while still providing a quality product to their customers. Many toolmakers are exploring existing tool modifications to reduce costs instead of building new tools.

Long-standing, well-known tool companies are restructuring and re-evaluating business practices to economize and compete in this global economy. This article discusses four areas in which a tool designer can economize without sacrificing quality.

Area 1: The Design Process

Years ago tool designers used drawing boards and paper to design tooling. Now all design is done with computers and electronic media. However, the same status given to what type of drawing board was used now applies to what software and hardware are being used during the design process.

When purchasing a tool design software package, look at what actually works to reduce design process time and has the smallest learning curve. Design time can account for 8 to 15 percent of the total cost of a tool. Many die design software packages cost from $1,000 to $10,000.

A software learning curve can cost a company a considerable amount of time, which is reflected in the bottom line. The ideal design software should be cost-effective, easy to learn, and productive from day one. Consider these three areas when you're researching design software.

  1. Help files should be included and contain information that contributes to the design process, as opposed to just telling you what button to press and what it does.
  2. Look at software utilities as opposed to full-blown tooling design packages. If you have a design concept in mind, you might not need or use a complete design package. For example, you may need assistance with only routine tasks, such as creating detail drawings and fasteners.
  3. Software shouldn't force you to work in an unnatural way. It should assist you and not change the way you developed the design concept.

The right software package can cut time off each design job. For example, if your design time accounts for 15 percent of a quoted job, with the right software package you can shave 30 percent off that design time, which yields a 4.5 percent overall savings. Therefore, the cost of a $125,000 tool could be reduced by the 4.5 percent, which is a total savings of $5,625 (see Figure 1a).

Area 2: Design Accuracy

Figure 1
a. Design time accounts for 15 percent of a quoted job. With the right software package, a designer can shave 30 percent of that figure. This $125,000 tooling example shows a $5,625 savings in design costs.
b. Raw materials can be as much as 40 percent of the tooling cost. By cutting 15 percent of that figure as well, a company can save another $7,500, for a total savings of $13,125.
c. Accurate and productive machining processes can diminish waste and scrap, which reduces tooling cost by as much as 10 percent in this example. Improving machining methods to reduce downtime to 3 or 4 percent results in a 6 percent savings overall, which reduces the tooling cost to about $104,375.

All tool designers strive to reduce or eliminate errors in the design. Here is a common tooling scenario: You order a piece of steel and invest time in machining, grinding, electrical discharge machining (EDM), and mounting, only to find a hole was mislaid by 0.125 inch.

Another problem that plagues toolmakers is miscalculating how much press tonnage a tool requires to stamp or strip the part. Formulas for calculating tonnage exist and do work. Here are some common formulas to try.

  1. Stripping tonnage = Length of cut in inches xMaterial thickness in inches x1.5 factor. This yields the number of U.S. tons required to strip a normal blank of material with a pierce punch.
  2. Blanking tonnage = Length of cut in inches xMaterial thickness in inches xShear strength of material in U.S. tons. For example, 35 = 70,000 lbs., which yields the number of U.S. tons required to pierce a shape using standard piercing practices.
  3. Forming pressure = (Shear strength of material in lbs. xMaterial thickness² / (Material thickness +(Form radius on punch/2) +(Form radius on die/2)) xLength of form in inches. This formula yields form pressure in lbs.

Adding these amounts—the blanking, stripping, and forming tonnages—yields the press tonnage required for a tool. The stripping tonnage shows how much pressure will be required of springs or nitrogen cylinders for a particular stripper. It's a good idea to calculate only the cutting area of a particular stripper to find the pressure required for just that stripper pad.

Simply guessing required tonnage instead of calculating it can lead you to discover late in the process that the press needs twice as much tonnage to strip the part. Then you have to disassemble the tool and figure out where to add springs or nitrogen cylinders. The tonnage formulas can help you to avoid this costly scenario.

Area 3: Raw Materials

Another way to cut tooling costs is to consider raw materials. Try submitting a list of needed materials to different vendors. This can be an effective way of reducing costs. In many cases, as much as 15 percent of the raw materials for tooling can be cut by outsourcing materials to different vendors. Because raw materials reflect as much as 40 percent of the $125,000 tool cost example, cutting 15 percent of that 40 percent, which would yield 6 percent overall, could save you another $7,500, for a total savings, including the previous $5,625 design savings, of $13,125 (see Figure 1b).

Area 4: Machining Methods

Next consider the manufacturing processes used to make a tool. Some shops manufacture tooling the way they did 40 years ago. Toolmakers may argue that manufacturing processes have no bearing on tooling. However, if a tool is designed to be manufactured economically, the manufacturing processes can play a big role in reducing the cost of the finished product.

Developing accurate and productive machining processes can diminish waste, which reduces the tooling cost example by as much as 10 percent. In the past much manual labor was put into manufacturing, for example a 3-D punch. Models were built, assembled, tested and used as patterns to make punches with tracing mill equipment. Some shops still follow this practice.

With software and CNC equipment, you can produce a virtual 3-D model that can be assembled and tested on the computer, which eliminates wasted materials. After it's designed, the 3-D punch can be machined using programming software for the CNC machining center.

Improving the accuracy of CNC programming—instead of manually inputting data in the programming phase—and using geometry generated for each detail can save time. Software that recognizes geometry such as circles is more accurate for programming the CNC machine and reduces human error. One example of human error is choosing a 0.500-in. tool to machine a 0.375-in. hole. A computer, on the other hand, can accurately select the proper 0.375-in. tool for the job, thus improving accuracy and decreasing waste. Improving methods of machining rough steel blocks to simplify various operations also can help to reduce scrap and labor costs.

Toolmakers should strive to improve machining methods to reduce a loss of labor-hours to no more than 3 to 4 percent. In this example, a savings of 6 percent is possible, which reduces the example cost to about $104,375 (see Figure 1c).

By evaluating software programs, design accuracies, raw materials, and machining, you can design economically and improve quality at the same time. Improving all of the areas discussed costs money initially, but in the long run it can make money by putting your company back into a competitive position.

Robert W. Harper is owner of CADD Masters, 1134 Franklin Drive, Greenbrier, TN 37073, phone 615-347-3966, Web site CADD Masters is a contract die designer that develops die designing and CNC software. Harper also is a mechanical design engineer for TRANE, an American Standard Company, 2701 Wilma Rudolph Blvd., Clarksville, TN 37040, phone 931-221-3641, fax 931-648-5901, Web site TRANE is a designer and manufacturer of air-conditioning and refrigeration units.

Robert Harper

Contributing Writer

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STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping.

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