In today’s manufacturing environment, precision metal fabricators are constantly searching for ways to increase productivity as they are faced with smaller lot sizes and more complex parts. Turret punch presses have become one of the standard ways of producing these short run jobs – in many cases replacing the stamping presses that had been used in the past. This switch to turret punch presses has been fueled in large part by advancements in the tooling that is used by these machines.
Why were many parts traditionally run on stamping presses?
The ability to make an accurate part very quickly has traditionally been the overriding consideration driving the decision to move a part onto a stamping press. Buyers of fabricated parts were willing to bear the high tooling costs, large lot sizes, and long lead times because it was the only option available to them.
As turret punch presses and tooling for them became widely used, readily available and more flexible in terms of the types of parts that could be produced, sheet metal parts buyers began to realize that they could demand smaller lot sizes, shorter lead times and lower tooling costs for many of their parts without paying a substantial penalty in part cost. This trend has continued over the past 30 years to the point that stamping presses are now generally reserved for very high volume parts that have shown a consistent track record of usage, and are expected to be used for a relatively long period of time with no changes being made to the part.
Tooling Costs
The low cost of tooling for turret punch presses has always been one of the primary reasons that metal fabricators chose to use them. This low cost has continued to decline over the past three decades, contributing to the success of turret punch presses, and the fabricators that utilize them. (Note: In this context, cost refers not to the price of the tool but the price per hole.)
Lower tooling costs are the result of many improvements that tooling manufacturers have made to their tooling. Improved punch and die materials and coatings are two of the more dramatic changes that have been made. For example, the dramatic drop in cost seen in the late 1990’s was the result of the introduction of titanium carbo-nitride (TiCN) coating. Controlled tests have shown that tools coated with TiCN produce five to seven times more hits than uncoated tools before needing sharpening.
Set-up Time
Quicker set-ups are another reason that turret punch presses are able to produce parts with shorter lead times and smaller runs. Tooling manufacturers have developed new types of tooling that are far faster to set-up and can be used in existing turret punch presses. For example: A tooling style that eliminated the need for shimming after re-grinding was introduced in the early 1980’s for the larger stations of machines that use thick turret style tooling. A similar tooling style was introduced in the early 1990’s for the smaller stations. These tools cut tooling set-up time by at least half when compared to older tooling designs while greatly increasing the grind life of the tools by allowing for more adjustment.
Availability of Tools
Shorter lead times are yet another reason that has led to the increased popularity of the turret punch press. Some tooling manufacturers are now able to ship a wide range of standard shapes (such as Round, Obround, Square, Rectangle, Hexagon, Octagon, Single-D, Double-D, Long-D, Quad-D, and Equilateral Triangle) on the same day that they are ordered. Special shapes can be shipped in 2-3 working days. These reduced lead times are increasingly important to fabricators who are constantly searching for ways to reduce lead times.
Special Forming Tools
Tooling has led the way to increasing the types of parts that can be made on turret punch presses by expanding the types of forming operations that can be done. Louvers, electrical knockouts, embosses, extrusions and card-guides are just a few of the more common types of forming tools. Other forming tools have an even more dramatic effect on how a precision metal fabricator produces parts. An example of this is the hinge forming tool. This combination of two tools allows a turret punch press to fabricate completed hinge knuckles directly on the component part that will use the hinge. Traditionally hinges have been fastened to fabricated parts through various mechanical means, or they have been formed in separate operations on press brakes. Forming the hinges on the turret punch press ensures that they will be in the correct position, and eliminates time consuming secondary operations. Explore punching specials forming templates.
High Forming Tools
An emerging technology for turret punch presses is the ability to create higher forms. New machines have the ability to program the movement of both the punch and die allowing forming dies to sit at the level of standard dies when not being used, and then lifting the dies when they are needed to create forms on the metal. This also allows the forms created to be higher and more complex than was previously possible. Another capability of these tools and machines is to create secondary forms on previously formed surfaces.
Wheel Tools
Wheel tools have been developed that are capable of shearing, ribbing, offsetting, and scoring as fast as the machine can move the sheet of material. Some machine manufacturers have enhanced the controlling software on their machines to allow them to make full use of the wheel tools, allowing them to smoothly contour various shapes and to control the height of the cutting or forming wheel as it begins or completes its cut or form. The wheel tools can dramatically decrease the processing time for certain types of parts.
Progressive Tools
Another area of development in tooling for turret punch presses is that of progressive die sets. Progressive die sets can be made to run in turret punch presses in much the same way that traditional progressive die sets are commonly used on stamping presses. The primary difference is that the die set is sheet fed rather than coil fed. The benefits of running progressive dies in turret punch presses include lower tooling cost, shorter tooling lead time, and dramatically reduced tooling set-up time. This reduced set-up time can allow fabricators to economically produce very small runs of parts that traditionally would have required very large runs due to long set-up times. Running this type of progressive die set also provides some of the flexibility inherent to the turret punch press, such as adding holes that were not included in the original part design.
Conclusion
As part complexity continues to increase, and lot sizes and lead times continue to shrink, the tooling used to fabricate sheet metal parts becomes more important. As machines continue to advance, forming operations will continue to expand, helping to eliminate more subsequent operations and/or purchased parts. The increasing popularity of automated manufacturing systems that utilize turret punch presses increases the importance of long tool life for increased reliability and green light time. Research and testing of new tool steels and coatings continues, and will undoubtedly produce even lower tooling costs in the future.
October 25, 2021