Complex components used to be clamped at CLAAS Industrietechnik in Paderborn on workpiece-specific special fixtures. Today, flexible standard workholding towers are used on which the workpieces are clamped with component-specific clamping jaws. This enables the output to be increased by 20 percent while at the same time improving the process safety. The clamping solutions developed by ROEMHELD, together with CLAAS Industrietechnik, are used in a flexible production with a pallet system.
Clamping cubic components reliably: This was one of the goals of production planner Stefan Picht when he took over the hydraulics prefabrication department in 2002 as a work scheduler at CLAAS Industrietechnik. So he got offers from well-known suppliers and tested various models. The HILMA TS 125 L tower workholding systems, which offer space for clamping up to 16 workpieces, won the race. Although the components were the most expensive, their purchase is worthwhile, says Picht: “The one-time higher investment I get out every day again.”
According to his statements, the decisive factor was above all the clamping safety achieved with the Hilma TS 125. “Apart from the high process safety, they have the additional advantage that we were able to increase the feed rates of the machines thanks to the safe workpiece clamping and thus work more productively.”
As a result of the positive experience, numerous other tower workholding systems have been added in the meantime. From the four-sided clamping towers, there are eight TS 125 and three TS 125 Vectors for high workpiece weights in use today. Furthermore, a three-sided TS 125 Tristar is used. CLAAS Industrietechnik also clamps components using six MSH multiple workholding systems and a series of other HILMA machine vices.
The system supplier from Paderborn manufactures components for the drive technology and mobile hydraulics of agricultural machinery and municipal vehicles. CLAAS Industrietechnik was founded in 1956 as the extended workbench of the agricultural machinery manufacturer of the same name, based in Harsewinkel, about sixty kilometres away. Today, the system supplier is an independent company with around 700 employees and a quarter of its customers is outside the CLAAS Group.
The clamping systems are used in the department “Prefabrication Hydraulics”, where they are part of a comprehensive production solution that is internally called the “flexible manufacturing system” at CLAAS. The system consists of two horizontal 4-axis machining centres Heckert CWK 400 D and HEC 400, each linked to a pallet station of the Finnish automation company Fastems.
In the two-storey station, there are forty storage spaces for the pallets with the workholding towers. Since ninety percent of the components are machined in two set-ups, each workholding tower contains both raw parts waiting for initial machining and workpieces for final machining. Robots remove the pallets from their storage positions and drive them to the respective machines.
240 different workpieces are clamped with standard components. The four machining centres mainly machine complex hydraulic components such as valve housings and pump components, some 92,000 pieces each year. They consist of equal parts of grey iron and nodular iron or wrought aluminium alloys. The approximately 240 different workpieces vary greatly in weight, dimension and geometry: from less than one to 15 kg in weight, with dimensions from 100 x 80 x 53 mm to 125 x 100 x 242 mm and from cubic to free-form mould casting. The lot sizes vary from ten - in spare parts production - up to 500 pieces.
Ninety percent flexible standard fixtures with special jaws.
As there are more than two hundred different components, it is easy to understand that the original method of clamping the components with workpiece-specific special fixtures was extremely complex, expensive and inflexible. Today's solution is the exact opposite because now only the clamping jaws are adapted to the workpieces, says Picht: “Now we have standard clamping elements with specific jaws. Ninety percent of our jaws are designed specifically for our requirements.” The remaining components of the clamping solution can be used universally and always remain the same.
ROEMHELD already offers an extensive range of interchangeable jaws for standard applications, which is further extended by customer-specific variants. The product range includes quickly interchangeable jaw inserts. The hard-metal grip inserts can thus compensate for non-parallel clamping surfaces or forcefully clamp workpieces with narrow clamping edges. If necessary, they can also be used to reduce the clamping edges of a workpiece. The TUC-coated semi-standard jaws make it possible to significantly increase the retention forces without changing the clamping force, for example, for the safe clamping of thin-walled parts during powerful machining.
All workholding systems used can be operated purely mechanically. CLAAS uses two variants of the Hilma TS 125 workholding towers. The systems with 3rd-hand function are operated via a spindle. The clamping force builds up uniformly at the central jaw. The TS 125 Vector are operated with two spindles. Both clamping points work independently and can be pressurised with different clamping forces. All TS tower workholding systems are operated with a handling system mounted in the loading station.
The pneumatic motor, which is suspended and guided by balancers, is placed on the spindle of the workholding tower by the operator. The operation is made via foot switch. The operator always has both hands free for workpiece handling and the clamping force is always reproducible. This has a very positive effect on ergonomics at the workstation and on clamping safety. To protect against accidents, the operator must first attach the torque motor to the set-up station. Only then the induction sensor signals that the robot can pick up the pallet with the clamping devices.
CLAAS is very satisfied with the long-term cooperation, production planner Picht reveals: “Consulting, communication, project execution and service are very good, the quality of the clamping devices is extremely high, their operation simple and reliable. And the improvements in productivity and safety are greater than we originally expected.”
To further increase throughput, CLAAS Industrietechnik plans to clamp even more workpieces on standard workholding towers with special jaws in the future, explains Picht: “Tools have become increasingly powerful, especially for machining aluminium components. As a result, running times have become shorter and shorter, and set-up is becoming increasingly important.”
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