The connection of the end of the box with the flange is carried out using a TRUMPF TF 350–2 manual press. The fastening element is a "press rivet", which is cut and molded from the material of the workpiece in one working stroke of the punch (punch). This mechanical process of joining metal sheets is known as "offset connection" – the upper sheet is connected to the lower by kinematic closure. Its main advantage over traditional spot welding is that there is no damage to the surface due to heating, the butt joint is corrosion resistant. The TF 350–2 press is designed both for joining uncoated sheets and galvanized, painted, polymer-coated sheets. Preliminary and final processing with such "cold welding" is not required, there are no costs for screws, rivets and other connecting elements. For ease of operation, the punch, which forms the "rivet" with a continuous pressing blow, is installed in a movable lever. Thus, the tool frame can be "opened" with a single movement of the hand in order to easily and quickly install the tool at the desired point of the tire. At the same time, the flange height is allowed up to 40mm. A special cone puller makes it possible to fasten the tire with the box as close as possible to the edge of the duct. Depending on the technical and aesthetic requirements, the connecting element can be concave into the surface of the box or protrude above the surface. It is possible to obtain an almost airtight connection for sheets of various thicknesses by choosing the appropriate matrix size. A set of tools is installed on the TRUMPF TF 350–2 press, in accordance with the specified total thickness of the sheets. Tool change is quick and easy and does not require special tools or skills. The productivity of the TRUMPF TF 350–2 press is 2 rivets per second. The tool is suitable for both portable and stationary applications.
Seam connection. The Pittsburgh fold is an ideal connection method for straight or curved boxes. A smooth, dense and aesthetic connection is obtained without any additional processing when using TRUMPF F 300 series tools. The Pittsburgh fold ("American") is obtained by continuous roller running-in, without damaging the surface and coating. Automatic feed control guarantees seam accuracy and uniform joint density. TRUMPF folding machines are suitable for both straight boxes and bends, with a minimum internal radius of only 300 mm.