With the help of load handling devices, safe, gentle lifting and transportation of sheet metal blanks for automated processes can be designed sustainably. Every percent less sheet metal waste can result in savings of up to 1 million euros in forming and cutting. In the metalworking industry, system suppliers have succeeded in offering tool-free cutting in sheet metal processing. Lasers cut directly from continuously running steel or aluminum coils. This increases profitability in the press shop. Thanks to CNC programming, for example, a high degree of flexibility can be achieved with simultaneous material savings of up to 10 percent. In addition, there is no need to transport, store and maintain cutting tools weighing up to 40 tons. Suppliers now provide easy-to-install systems that make blank production possible even in smaller halls and press shops. Compared to conventional, tool-based manufacturing processes, this results in high savings.

Special machines for sheet metal forming

Nordgreif is one of the companies that can supply these special solutions. The Nordgreif range includes tongs, grippers, traverses and turning devices with mechanical, electric or hydraulic drives. Increasing automation in the automotive industry also requires new solutions in the area of load handling. This leads to increased efficiency and speed in the ongoing production processes, in which the sheet metal blanks are first punched out of a coil and then stacked on special pallets. These pallets are then transported to the presses using a blank gripper, where they are separated again and formed into the desired shape under pressure. When transporting oily blanks, the smooth surface is a special requirement for the gripper solution. For this reason, Nordgreif solutions are equipped with a special hold-down device: This ensures that the stack of blanks is held together very tightly and safe transportation is always guaranteed.

Industrial gas springs wanted for 10-ton special machine

Nordgreif cooperates with ACE shock absorbers, partly because both companies approach projects in a similar way: Building on a high-quality, large product range, they are able to further develop customized solutions and, if necessary, design new products. The current generation of blank grippers is one such case. The task was to support the force required to lift a height-adjustable table into the upper end position. The table is equipped with a scissor lift and an indexing mechanism and is responsible for holding the stacks of blanks in place. It prevents the blanks from slipping and, in the worst case, falling down. This would not only interrupt the work processes, but also cause expensive damage to the sensitive sheet metal blanks. The 2,000 kg table can be loaded with a blank load of up to 8,000 kg. To securely fix the load, one of Nordgreif's solutions was to lift the table with the help of four powerful, horizontally arranged gas tension springs once the gripper was in place in order to release the blanks. When lifting the blank gripper, it must be possible to move the set-up table downwards quickly and controllably so that the blanks are secured. In order to provide the best possible support for these processes, the specialists at ACE had to overcome several challenges. With a maximum sinker load of eight tons, the gas springs to be selected had to be more powerful than standard commercial models used on hoods, hatches and lids, where they enable controlled holding, lifting or lowering to support human muscle power. On the other hand, they must be precisely adjustable so that they enable the exact desired movement and speed of the table. Another requirement: While ACE also provides an online calculation program for most solutions, which can be used to design and supply the right gas spring in five simple steps, this type of quick, precise determination of suitable models was not an option in this application due to factors such as deflection pulleys and the weight to be taken into account when lowering.

Valve technology from ACE proves to be the solution

ACE initially supplied four GZ-28-600-DD-1200N industrial gas tension springs with a maximum tensile force of 1,200 N. Even though this was what the design team at Nordgreif wanted, it turned out in practice that it was neither possible to lower the table as intended nor to achieve the desired relief when lifting. The gas springs were oversized with regard to the tensile forces. For this reason, Kai Boelingen, the expert responsible for technical sales in the region at ACE, made his way to Schenefeld to enter into a test phase with the team at Nordgreif, which he describes as a "trial and error" phase. The technicians benefited from a special feature of these power assistance solutions, which operate without an external power supply. Their tractive force can be continuously reduced afterwards via a valve to the desired value. After carefully releasing the nitrogen, it turned out that at 800 N each, the forces of the components placed next to each other on both sides of the structure were selected so that the table could move downwards quickly but in a controlled manner. At the same time, the gripper's own weight is significantly reduced during the lifting process thanks to the combined forces of 3,200 N, so that it can be moved to the upper end position as desired.

For applications with strict hygiene guidelines, such as in medical and food technology, variants are also available that are filled with special oils and can be supplied in stainless steel and with end position damping. If the ambient conditions require it, ACE is able to extend the permissible temperature range from -20 °C to 80 °C even further. However, this type of customization was not a criterion for the success of the new generation of sinker grippers at Nordgreif. Thanks to the precisely adjusted forces of ACE's industrial gas tension springs, which act reliably in every transport process, the automated work processes at the end customer's premises run smoothly despite the sometimes oily surfaces, meaning that costly rejects of blanks are a rarity.