Transport of sheet metal blanks: ACE industrial gas tension springs relieve blank grippers
Load handling devices can be used to sustainably design safe, gentle lifting and transporting of sheet metal blanks for automated processes. Every percent less sheet metal waste can result in savings of up to 1 million euros in forming and cutting. Two well-known medium-sized suppliers have joined forces to increase safety in the redesign of a blank gripper for the automotive industry.
In the metalworking industry, system suppliers have succeeded in offering tool-free cutting in sheet metal processing. For this purpose, lasers cut directly from continuously running steel or aluminum coils. This increases profitability in the press shop. For example, thanks to CNC programming, a high degree of flexibility can be achieved with simultaneous material savings of up to 10 percent. In addition, the complete effort for transport, storage and maintenance of the cutting tools weighing up to 40 tons is eliminated. Suppliers now supply easy-to-install systems that make blank production possible even in smaller halls and press shops. Compared with conventional, tool-based manufacturing processes, this results in high savings.
Special machines for sheet metal forming
In order not to negate these advantages during the production process, metalworking companies cooperate with specialized partners who can deliver special solutions in high quality quickly and reliably. One such company is Nordgreif GmbH, which is all about lifting and transporting heavy loads. As this application shows, the company's 30-year success story would be inconceivable without experienced engineers and customized designs at its headquarters in Schenefeld near Hamburg. The range of solutions includes tongs, grippers, traverses as well as turning devices with mechanical, electrical or hydraulic drive.
The increasing automation in the automotive industry also requires new solutions in the field 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 by 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 gripping solution. For this reason, Nordgreif solutions are equipped with a special hold-down device: As a result, the stack of blanks is held together very tightly and safe transport is always guaranteed.
Industrial gas springs sought for 10-ton special machine
To enable trouble-free production for the end customer, Nordgreif cooperates with the internationally renowned specialist for damping solutions of all kinds, ACE Stoßdämpfer GmbH. The long-standing cooperation is successful 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, also design new products thanks to their expertise. The current generation of blank grippers is such a case. The task was to provide force support for a height-adjustable add-on table during lifting in the upper end position. The table is equipped with a scissor lift and a stepping mechanism and is responsible for fixing the blank stacks. It prevents the blanks from slipping and, in the worst case, falling off. This would not only interrupt the work processes, but also cause expensive damage to the sensitive sheet 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 after the gripper was placed on it using four powerful, horizontally arranged gas traction springs to release the blanks. When lifting the blank gripper, it must be possible to move the touchdown table down quickly and controllably so that the blanks are secured. To support these operations in the best possible way, ACE's specialists had to overcome several challenges. With the maximum blank load of eight tons, the gas springs to be selected must, on the one hand, be more powerful than commercially available models that are found on hoods, hatches and lids, where they enable controlled holding, lifting or lowering to support human muscle forces. On the other hand, they must be precisely adjustable to provide exactly the desired table movement and speed. Another requirement: While ACE also provides a calculation program online for most solutions, with the help of which the suitable gas spring is designed and supplied in five simple steps, this type of quick, precise determination of the suitable models was out of the question in this application due to factors that had to be taken into account, such as pulleys and the weight during lowering.
Valve technology from ACE proves to be the solution
The sum of these requirements gave ACE the opportunity to prove not only the quality of its products but also that of its service team. First of all, ACE supplied four industrial gas traction springs type GZ-28-600-DD-1200N with the maximum traction force of 1,200 N. Even though this was desired by the design team at Nordgreif, it turned out in practice that this could neither trigger the required lowering of the table as intended, nor could the desired relief be achieved during 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 "feeling things out". The technicians benefited from a special feature of these power-assist solutions, which operate without an external energy supply. Their tractive force can be continuously reduced to the desired value via a valve. After carefully draining 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 are selected so appropriately that the table can move down quickly but in a controlled manner. At the same time, during the lifting process, the dead weight of the gripper is considerably reduced thanks to the combined forces of 3,200 N, so that the movement to the upper end position takes place as desired.
To enable even more designers to benefit from the advantages of these powerful machine elements, special versions are available from ACE on request, in addition to a wide range of accessories and connecting parts. Furthermore, 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 design as well as with end-position cushioning. If the environmental conditions require it, ACE is able to extend the permissible temperature range from -20 °C to 80 °C even further. However, this type of adaptation was not a criterion for the success of the new generation of blank grippers at Nordgreif. Also thanks to the precisely adjusted forces of the industrial gas traction springs from ACE, which act reliably in every transport process, the automated workflows at the end customers are smooth despite the sometimes oily surfaces, so that costly rejects of blanks are a scarce commodity.
