An alternate method for tube fabrication
May 16, 2002
This article discusses using punching and forming plates within a stamping press as an alternative to tube bending and end forming machinery.
A punching and forming plate is similar in function to a hydraulic press. A typical setup is several forming units mounted to a tooling plate.
Fabricating tubular components often requires multiple operations such as bending, forming, flattening, piercing, notching, trimming, and slotting. Typically, these operations are performed on dedicated machines—a tube bender for bending, an end forming machine for end forming, and so forth. Dedicated machines can require a lot of floor space and personnel to operate them and to move the material from machine to machine.
Another option is to perform one or more of these functions in a hydraulic or mechanical stamping press with tooling. Fast and efficient, this has an obvious cost advantage for a company that already has a press. However, using a press has challenges too. The tooling must fit within the bed of the press and function with the shut height and stroke of a single press, or multiple presses must be used. In addition, unintentional overload can damage the dies. Also, hard tooling and die sets can be costly.
A third option is to use punching and forming plates.
Each forming unit performs a unique fabricating process.
Punching and forming plates are special tooling plates that function similarly to a hydraulic stamping press. Some punching and forming units are mounted on a tooling plate that is mounted to a frame (seeFigure 1). The unit also has an independent hydraulic power unit.
The punching and forming units are sized according to the work required. They can be used for applications that incorporate several processes, such as flattening a section of the tube, punching or piercing a hole, trimming the end of the tube, bending it, or forming the tube either at the end or anywhere along its length.
Special punching and forming units are designed specifically for each application. Often a standard punch or form unit can be used with special tooling. A typical application is a radius form approximately 4 inches in length on one end of a tube. The forming unit for this application is shown in Figure 2.
Punching and forming plates can be operated manually or integrated into an automated system.
Automating Punching and Forming Plates. When the application requires multiple punching and forming plates, they can be integrated into a workcell. The workcell can be loaded and unloaded manually or automatically (see Figure 3). The operator loads and unloads the tube in the first station. The tube then is transferred into station 2, then station 3, then station 4, and then back to the load/unload station. Each station performs a function, bringing the tube closer to the final product.
For another application—one that requires only one or two punching and forming plates—the third and fourth stations can be replaced with idle plates.
This top view of an automated workcell shows four sequential forming operations. For another application that requires only two or three operations, stations that are not used are replaced by idle plates.
Transferring the Tube From Station to Station. The tube can be transferred from station to station with either a walking beam method or rotary dial method (see Figure 4). When the punching and forming plate has completed its operation, the transfer device grips the tube, raises the tube to clear the tooling, and transfers the tube to the next station. Typically, long tubes are transferred faster using the rotary dial method.
Tool Change. When changing from one family of parts to another, the operator lifts each punching and forming plate out of the system as a unit and installs a new punching and forming plate. The hydraulics and pneumatics are connected to their respective manifolds with quick disconnects to ease changeover.
To simplify changes within a family of similar parts, the plate can be designed such that the punching or forming units can be relocated on the plate or moved to another plate, saving the cost of purchasing the same punching or forming unit for different parts. For example, if the plates are for a family of lawn mower handles that have a radius form on the end of the tube and the tubes vary in length, the same forming unit could be used at different locations on the same plate.
Typically, long tubes are transferred from station to station faster with the rotary dial method (shown here) than with the walking beam method.
Punching and forming plates are relatively safe. The units are fairly small, and the gap between the part and the frame typically is less than 0.25 in. This small gap presents little chance for injury. Further, they produce little noise. In fact, most of the noise generated by this type of equipment comes from the hydraulic power unit.
Applications that require several processes can be good candidates for punching and forming plates. For instance, a tube that must be formed, punched through both walls in the middle of the form, then punched at the start of the form could be produced on punching and forming plates. The part is symmetrical, and the other leg has a mirrored form.
However, punching and forming plates are not the ideal solution for every application. If the product requires a simple bend or holes punched in a straight section of tube, conventional tube fabricating equipment usually is the optimal choice.
Keith Chappell is vice president of Tube Fab Machinery Inc., P.O. Box 179, Cary, IL 60013, phone 847-516-0950, fax 847-516-0998, e-mail firstname.lastname@example.org, Web site www.tubefabmachinery.com. Tube Fab Machinery produces tube fabricating equipment, including benders, end formers, punching equipment, and engineered systems.