Working Principle of Gravity Palletizers Conveyor-Based Gravity Drop Stacking Solution

Gravity palletizers are the simplest and fastest type of palletizing equipment. Their principle can be explained in one sentence: sheets exit the end of the conveyor and fall onto the receiving trolley by their own gravity, stacking layer by layer. There is no complex gripping mechanism—the sheets simply "drop" down by themselves.

Although the working principle is simple, there is still much attention to detail involved in stacking neatly and quickly.

First, let's look at how sheets travel from the conveyor to the trolley. Sheets cut on a cut-to-length line or blanking line are conveyed to the stacking position by a conveyor. The end of the conveyor is usually above the receiving trolley. After the sheet leaves the conveyor, it loses support and falls onto the trolley under gravity. During the fall, its speed and posture change. Without control, the sheet may flip, shift, or become misaligned with the sheets below.

To ensure neat stacking, gravity palletizers are equipped with aligning devices around the receiving trolley. After a sheet falls, stops or air-cylinder-driven paddles on all four sides gently tap the edges of the sheet to align it. The tapping force must be moderate—too light and it will not align; too heavy and it may deform the sheet edges or corners. The timing of the tapping must also be well coordinated—the best effect is achieved when the sheet has just fallen and has not yet settled.

The receiving trolley has a lifting function. As the stack height increases, the trolley automatically lowers, keeping the topmost sheet at a constant height. This height is the drop height from the conveyor. If the drop height is too large, the impact of the falling sheet is strong, easily causing sheet deformation and surface damage; if the drop height is too small, the sheet may interfere with the end of the conveyor. The automatic lifting of the trolley keeps the drop height constant, making the stacking process stable.

The advantage of gravity palletizers is speed. The conveyor feeds continuously, and sheets fall continuously, resulting in high stacking efficiency. For fast-paced cut-to-length lines or blanking lines, gravity palletizing can keep up with the shearing speed and will not become a bottleneck. It is suitable for materials such as ordinary carbon steel sheets and stainless steel sheets that do not have extremely strict surface quality requirements.

The disadvantage is that sheets experience impact during free fall, which may cause slight surface bumps. For materials with high surface requirements—such as pre-painted sheets, mirror-finish sheets, and aluminum sheets—the impact of gravity palletizing may cause surface damage. In such cases, magnetic palletizing should be considered.

Palletizers are used with blanking lines, not stamping lines. Blanking lines all use coil feeding, blanking, and stacking. The coil is decoiled, leveled, and fed, then sheared or stamped to blank. The cut sheets are then stacked by the palletizer. The palletizer is the end-of-line collection equipment for the blanking line, stacking the processed sheets neatly for subsequent transfer and processing.



The value of replacing manual labor with automation in the palletizing step is direct. Previously, with manual collection and stacking, two workers stood at the end of the line, stacking sheets one after another onto the pile—by the end of the day, their backs and waists ached. Sheet edges are sharp, and handling them easily cuts the hands. After automatic palletizers replace manual labor, workers only need to come over to change trolleys after a stack is full, greatly reducing physical labor. Stacking neatness and consistency are also better than manual work—manual stacks gradually become crooked, while automatic palletizing places every sheet in the same position, producing neat stacks that are easy to handle. Safety is also improved—workers no longer need to catch sheets beside a running conveyor, keeping them away from hazardous areas.

Guangdong RuiHui Intelligent Technology Co., Ltd. has been deeply engaged in the field of stamping automation for over twenty years. It is a national "Specialized and Sophisticated" "Little Giant" enterprise, headquartered in Dongguan, with more than 400 employees and over 80 R&D personnel. RuiHui has mature technical solutions in the field of palletizers. Gravity palletizers work with conveyors, offering a simple structure and high speed. They are suitable for end-of-line collection on blanking lines for ordinary sheets and are widely used in the automotive, home appliance, hardware, and other industries. RuiHui has nearly 5,000 sets of equipment operating at customer sites both domestically and internationally, serving well-known OEMs and first-tier suppliers such as BYD, Geely, Volkswagen, Tesla, BMW, Mercedes-Benz, Honda, and Land Rover Jaguar.