The evolution of turret punch press processing
Improvements in turret punch presses have increased their capabilities and eliminated the need for many secondary operations. These improvements, which include automation options and the ability to perform contour cutting, tapping, and other processes, make these systems viable alternatives to laser machines.
The turret punch press has been used to punch holes into blank sheets for three-quarters of a century. For processing a small volume of parts in a short amount of time, the punch press always has been more efficient than a conventional stamping press. In the last 20 years, laser cutting technology has addressed the tooling requirement with even faster setups, eliminating punches and dies completely. For the turret punch press market to survive, manufacturers had to reinvent the machine.
Today punching is only half of what a new turret punch press can do. Adding secondary operations is key to cutting process time, and adding automation reduces handling time. These capabilities have been incorporated in modern machines.
Earlier turret punch presses had a fixed, single-stroke cycle that moved from top dead center to bottom dead center and back to the top. In new machines the stroke can be started and stopped anyplace in that cycle, which increases the hits per minute (HPM) with less travel in the stroke. Stroke speed also can be controlled, which allows time for the material to flow, as in the case of a forming operation.
Environmental benefits of the new punch cycle are reduced noise from the impacting tool and the elimination of hydraulic oils with the use of electric motor technology.
New Features and Applications
The controllable punch cycle enabled many new applications to be added to the turret press, which eliminated the need for second, third, and even fourth operations. One example is using a tool to feed the material and then moving the material through the tool to perform another operation, such as a diamond-tipped scribe that marks the material. This simple feature can be used for part identification, assembly instructions, and company logos.
The controllable punch cycle also allows forming tool heights and penetration to be adjusted with the machine’s CNC, which enhances forming consistency and improves part appearance and quality. It also makes for faster setups and eliminates trial-and-error mechanical adjustments.
Also made possible by the controllable punch cycle is a scoring process that improves the edge quality of long cuts. Material is scored on the upper and lower surface, leaving a small amount of material in the middle. This scoring can be punched or rolled into the material using the controlled stroke. When the blank is removed from the machine, the scored area is broken apart like a cracker, which leaves the edge with a radius and eliminates a deburring process. This operation also holds parts firmly within the blank so that sensitive tabs are not necessary.
A radius edge can be achieved with a deburring tool, which uses a set of hard transfer balls in place of the punch and die to squeeze the punched burr back into the material.
Controlling the punch cycle has allowed the tapping process to be added to the turret punch press. Taps from 0-80 to 5/16-24 now can be threaded in the turret punch press processing. Prepunching and extruding the material to accept a tap is part of the time savings on today’s machines.
Almost all turret punch press manufacturers offer some type of contour cutting in combination with the punching. Air plasma cutting or laser cutting capability added to the turret punch produces the most dynamic capabilities on a single machine platform. The contouring feature eliminates special punch tooling costs and the wait time from the tooling supplier. Now edges can be made into the form after the form is made. Prepunching a starter hole for the contouring not only saves time by eliminating the pierce time, but also saves on contour consumables damaged by reflection and spatter from the burn medium.
Manufacturing is in a state of confusion in terms of labor, which can be cheap in one location and expensive in another—plentiful here, or nonexistent there. But one fact is clear: to get a handle on labor, automate.
The added ability to load and unload material on a turret punch press with lights on or off gives a precision fabricator a competitive advantage, be it here in the U.S. or as far away as China. Today you can control part production with precise details of timing and status. The sky is the limit on available automation, from a single-pallet load/unload to a full factory warehouse. Production payback on an automated system can take 12 to 18 months for a simple system or years for a large, factorywide installation.
With today’s turret punch presses, perfect holes can be punched in milliseconds; forms like knockouts, louvers, flanges, and embosses can be placed perfectly and raised to the correct height with one setup. If tapping is required, the ability to tap 200 holes per minute can cut part labor in half.
Part edges can be deburred with finished quality. With the addition of a contour cutting device, like laser or plasma, irregular-shaped holes can be produced without waiting and with no tool cost. Any shape now can be cut into forms.
Unattended loading and unloading of today’s machines has defined production as a science, and automation will continue to eliminate manual labor.
The turret punch press has had its place and will continue to have a place in the precision fabrication industry. The new generation of presses has more capability and added value than ever before.