Understanding the what, why and where of triple action presses is useful when examining if the technology is right for a specific application. The following outlines criteria that may help you make the determination.
What
The three actions of a triple action press include main punch, cushion and blankholder platen. In general, triple action presses are used when performing multiple operations on a component during one set-up. These presses are typically used in the manufacture of products such as aerospace components and others that require several actions from multiple cylinders to produce the part in one set-up.
Why
Essentially, if one has multiple requirements on a single component, the triple action press is a good choice. Triple action presses can help to eliminate some additional tooling requirements, as well as enable manufacturers to produce a more uniform component, versus having to manipulate the part several times with different tools.
Typically, a triple action press will offer complete control over the various RAM movements. The ability to both set and manipulate parameters will result in the most efficient cycle possible, for a better-finished part. Parameters can include establishing the speed of the draw, the reverse tonnage on the cushion and when to actuate an eject function.
Depending on the application at hand, the press can be custom-designed to meet specific requirements.
Where
For some applications, a triple action press includes a main slide (where the tooling is mounted), a knockout/eject mounted on or above the main slide and a cushion/eject mounted below the press bed. This design is useful, for example, if while drawing a deep pan, the part draws over a punch but sticks in the upper tool when the main slide is retracting. At that point, one would use the knockout/eject to keep the part down on the punch or to strip the part from the upper tool. In this example, the cushion/eject is used primarily for providing some pressure on the material to allow it to be drawn, without any wrinkling or tearing.
Alternatively, keeping the design as described above but with the punch mounted to the main slide, the cushion/eject provides blankholding of the material during the main slide down stroke. The cushion/eject would then be used as an eject to push the part up and off the lower tool or punch.
For other applications, the triple action press is designed with a blankholder slide that allows a higher tonnage ram to run through the middle of the press, and includes a bed-mounted cushion/eject. The triple action press can offer any combination of cylinders to provide power to form, punch, coin or draw, etc. to be performed on a part during one set-up.
For example, this type of triple action press configuration is seen in the manufacture of jet engine cowlings. The main slide is actually a blankholder platen that applies adjustable tonnage to the material as the main ram (located in the middle of the main slide) comes down to form the cowling. In this application, the cushion/eject may be used to push the part back up out of the lower tooling.
The triple action press can also provide for a reverse draw. Suppose you have a part that you are drawing and the part requires another reverse draw on the bottom of it to produce a "wave" form. In this case the main punch comes down while the blankholder is clinching the material. When the main ram reaches its full depth, it holds position while the cushion/eject cylinder is pressurized to push back against the main ram, producing a small form or "wave" on the bottom side of the drawn part. In this example, the cushion is used on the down stroke to help draw the part, and reverts to an eject to produce the form.
Authored by Thomas M. Lavoie, Applications Engineering Manager, Greenerd Press & Machine Company
For more information contact:
Greenerd Press and Machine Co., Inc.
41 Crown Street
P.O. Box 886
Nashua, NH 03061
603-889-4101
sales@greenerd.com
www.greenerd.com