Getting the Most From Your Punching Process
Tooling advances can help create products that were previously impossible, eliminate downstream operations, and reduce per-part costs
January 1, 2010
There is more to the punching process than simply the machine, the material, and the tool.
According to the experts, as products become more complex and lean practices become the norm, an examination of your part from the design phase through completion can lead to the creation of a better-quality part at lower cost.
The ability to upform, an increase in the feed gap, a move toward servo-driven punching machines, and integrated automation all have improved the overall productivity of these machines.
Upforming, for example, is now possible because the punching machine itself has been changed. In some machines tools now can move upward, producing higher forms; previously the location of the bottom tool made these tall forms impossible.
“This change is only one of many that now make the punch press a more productive machine,” said Dennis Lowry, custom engineering manager for tooling supplier Mate Precision Tooling.
Changes such as these mean that a more complex, higher-value part can be created using only a punching machine.
Tonnage, the number of tools needed, and form heights must all be taken into account in the design phase because the parts being designed must fit the capability of the machine being used.
“If the manufacturing group and the design group aren’t in sync, the design group may end up creating a product that is difficult to manufacture,” said Lowry.
Design for manufacturability (DFM) is the art of designing products in such a way that they are easy to manufacture. By adopting this strategy companies can create better parts in less time.
Designing parts in this manner is only one way to reduce bottlenecks and wasted time, however.
Reducing setup time, utilizing new tooling, and maintaining both the tools and the machine properly will all lead to a more productive punching process.
“All shops should properly organize their tools,” said Lowry. “You need to know how long it takes to find, organize, and load tools into the machine because this is all nonproductive time. Also, when you put your tools away, make sure they are ready for use the next time.”
It’s important to define the costs associated with caring for tooling and not just the cost to purchase tools, he added.
“You should sharpen and lubricate your tools when it’s convenient for you, not when they are in desperate need of maintenance,” explained Ron Windingstad, product engineering manager for Mate.
Storing and organizing tooling properly is just one way to reduce costly setup time. Others include quick-change tooling, additional operations within the press, and eliminating nonproductive operations.
Use Quick-change Tooling. Quick-change tooling will help eliminate non-value-added time and increase productive time, especially in high-variation work.
“Quick-change tooling is important in a lot of environments but not all,” said Windingstad. “If you have a long, steady run, you don’t necessarily need to use a quick-change setup.”
Add Operations. Thanks to new tooling technology, you can now maximize value-added time by performing postpunching processes, such as tapping, forming, and marking in the punch press.
“Every separate operation done to the part is another potential bottleneck,” said Windingstad. “You need more WIP for every move and process, so you should weigh the value of adding time on the punching machine for each process rather than moving the part from machine to machine.”
You do need to ensure that you are saving time and money elsewhere in the part creation process, he said. If your turret capacity is already at its limit, adding operations may not be possible.
Eliminate Operations. New tooling can replace nonproductive operations with other, more productive means of production.
According to Lowry and Windingstad, nibbling should be done only when it is the most efficient way to make the part because it is a time-consuming process. Nibbling also prematurely wears the tool’s cutting edges, causes galling and overheating, and can result in more frequent maintenance required. It can also lead to guide wear, turret wear, and nibbling debris falling into the tools and machine.
Specialty tooling and the associated costs should be weighed against any improvement in quality and productivity. Specialty tooling should reduce WIP, decrease lead-times, eliminate downstream processes, and increase press capacity.
“You might spend more money on tooling, but your end product might end up costing less,” explained Lowry.
The Tooling
In addition to new types of tooling being produced by suppliers, new heat-treat processes and coatings also have been introduced.
“From the perspective of perishables, there have been advancements to the raw materials, heat-treat processes, and coatings, all of which result in increased tool life,” said Scott Tacheny, design specialist for Wilson Tool International®.
As for the assemblies, advancements have made them easier to use as well.
“Our large-station assemblies have push-button punch length adjustment mechanisms, while our newly released HP2™ adjustment system for small stations has been simplified ever further by eliminating the button altogether,” said Tacheny.
These new tools reduce setup time, which is often identified as the area where the most amount of time can be removed from a process. Software can be used to optimize a machine, and robots and conveyors can move parts, but tools still require someone to sharpen, assemble, and adjust them, all of which take time.
Complex Parts, Specialty Tools
As parts become more and more complex, more complex tooling is also required.
The part’s size plays a factor in selecting the machine, because machines have differing feed clearances (Z heights), tool station sizes, number of stations, ram controls, and features such as upforming/high-forming die units and autoindex capabilities.
Complex parts and specialty tooling are definitely linked in the punching process.
Specialty tools are the correct choice when any of the following criteria is met:
- The tooling can be used on many different parts or projects.
- A medium to large number of parts are required.
- You want to eliminate operations that would otherwise be done on separate machines.
“By adding specialty tooling, you can pretty much guarantee that your quality will improve,” said Tacheny. “In a medium to large number of parts, they can also pay for themselves quite quickly.”
Return on investment (ROI) often depends on how “special” the tool is, but according to Tacheny, using a specialized tool always results in a reduction in scrap.
“Often the ROI can be achieved on a single product or project, whereas other times it requires either a large run or multiple products or projects,” said Tacheny.
A great example of a specialty tool is a progressive pierce, form, and blanking tool. On a small run of parts, the cost may not be justified. But on a large run, you may eliminate the need to build an expensive and time-consuming hard tool (die set) and minimize cost per part.
The applications for specialty tools are nearly limitless. If a product designer can imagine forms, bends, marks, and even textures on the sheet, and as long as the material and machine allow, then tools can be created to produce them.
For more information, visit www.mate.com and www.wilsontool.com.
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