Trimming is usually the mechanical separation of the formed part from the unformed sheet. As defined, heavy-gauge or thick-gauge forming refers to parts formed from sheet having thickness greater than about 8mm. Typically, heavy gauge parts are formed from cut sheet, with the part and the unformed sheet around it. The method of trimming depends on several factors, including the number of parts that are to be trimmed, the accuracy and ﬁnish of the trimmed edge, the planarity of the trim line and the extend of secondary cutting required.
Trimming using a handheld router was at one time the primary way of separating the product from the unformed sheet. Although largely supplanted by numerically controlled routers, hand trimming still has its place in prototyping or when a few parts are needed. Guides and tracking grooves improve the accuracy of the trim line. For many parts, from refrigerator lines to garden ponds to skylights, the trim line is planar or linear. As a result, trimming is usually accomplished with ﬁxed, horizontally mounted rotary saws, vertically mounted band saws and even guillotines.
The advent of the computer-programmed robotic trimming station has revolutionizes heavy gauge trimming technology in the past decades. The computer imparts speed, accuracy and reliability to the trimming process. Compared with hand routing, robotic trimming initially requires much greater technical skills to create the operational trim path, but very little additional labour there after. There are several variations on the CNC routers. Multiaxis stations include two and three axis machining stations, ﬁve axis routing stations and even linear motor-clriven six-axis robots.All these devices require that the cutter path is programmed in a language special to the device or class of devices. Care is required during setup to ensure that the device is indeed following the desired cutter path. During the automatic trimming process it is necessary to support the part. Many solutions are possible. One is showed in the following picture. In this case vacuum is used to hold the part.