Page 17 - MetalForming Magazine August 2022

Tooling by Design
By Peter Ulintz
The Reality of Problem Solving
Metal forming problems can be very difficult to solve, as determining the root cause often proves impossible. Problem solv- ing becomes more difficult when we make decisions based on what we see and believe is true about the problem at hand.
Let’s address these three statements individually.
Metal forming problems can be dif- ficult to solve. Metal forming involves a collection of process inputs that may include machine selection and its con- dition; tool design, construction and maintenance;
lubrication type,
mixing practice
and application;
sheet metal
properties and
10,000 possible combinations
Fig. 1—Only one combination opens the padlock.
Peter Ulintz has worked in the metal stamping and tool and die industry since 1978. His back- ground includes tool and die making, tool engi- neering, process design, engineering manage- ment and advanced product development. As an educator and technical
presenter, Peter speaks at PMA national seminars, regional roundtables, international conferences, and college and university programs. He also pro- vides onsite training and consultations to the met- alforming industry.
Peter Ulintz
Technical Director, PMA pulintz@pma.org
Machine condition and maintenance Sheet metal thickness and properties Tooling design and maintenance Lubricant concentration and film thickness
Fig. 2—The current combination of variables determines the output.
ordering practices; environmental issues (process-related vibrations, operator inputs, deformation temper- atures, thermal expansion, etc.); and other factors. Because process inputs can and do change over time—some- times in a matter of seconds—they also are called variables. The prevailing combination of input variables inter- acts to produce a process output. In metal forming, the desired output is a product that meets print specifications, and that the customer will accept.
For comparison’s sake, consider a four-tumbler padlock (Fig. 1). Each tumbler contains 10 numbers ranging from zero to nine. When the numbers on all four tumblers match a very spe- cific sequence, the lock opens. Only one combination opens the lock. But how many combinations are possible? Because each of four tumblers offers 10 choices, the possible combinations number 104, or 10,000.
So Many Variables
Now imagine that each tumbler on the padlock represents a process input: machine condition and maintenance, sheet metal thickness and properties, tooling design and maintenance, and lubricant concentration and film thick- ness (Fig. 2). Each number on the tum- bler represents a single input variable.
Machine variables for a stamping press may include counterbalance pressure, running clearances, thermal expansion, ram parallelism, gib clearance, among others. Variables in sheet metal include thickness, yield strength, tensile strength, total elongation, etc.
We easily can find 10 or more vari- ables for each process input in this example, which means that 10,000 vari- ables or more influence the process (stamping) output. But process inputs number more than four (straightening, feeding, material movement, speeds, pressures, etc.), meaning that perhaps more than one million variables can— and do—affect the process output.
This makes determining a root cause to a problem seemingly impossible.
Fortunately, many metal forming processes are robust and the influ- ence of thousands of variables do not adversely affect process output or efficiency.
Other processes, however, prove extremely sensitive to variations and perhaps only a few hundred variable combinations “open the lock” (produce desirable output). These processes require many hours or multiple shifts to get up and running properly, only to experience additional downtime after a shift change, coil change, or minor die maintenance and cleaning.
14 MetalForming/August 2022
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