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From: 中国锻压协会

11.03.2009

Forming processes in close-up: Schuler retrofit gets more performance out of existing lines

Forming processes thought to be offering optimum performance can still conceal considerable potential. Careful examination can therefore pay off for users, as sustained improvements can be made to existing processes on tried and trusted press lines with relatively little effort. Within the Schuler Group there are teams of experts who specialize in such press optimization: for example, existing forming processes are examined with special measurement tools, downtime is analyzed and press dies are checked. The ultimate goal is to achieve even greater performance from existing lines. Schuler’s Center of Expertise for the Optimization of Mechanical Presses recently optimized a transfer press for a major German car manufacturer. In 2008, Schuler’s specialist team for optimizing hydraulic presses analyzed the forming processes of Hirschvogel Umformtechnik, one of the world’s leading automotive suppliers in the field of solid forming and machining, based in Denklingen, Germany. The retrofit enabled Hirschvogel Umformtechnik to reduce cycle times by up to 30 percent.

With careful analysis, considerable speed increases and process improvements can be gained from tried and trusted presses. Schuler first estimates the chances for improvement at the user’s facility. In close cooperation with the works managers, the next steps are then decided.

The optimization of a single press and the forming processes it is used for generally takes one to two working days. Sensors and sophisticated measurement processes play a major role in the process. Numerous press parameters are carefully scrutinized. With regard to the mechanical system, for example, the play and parallel running of the slide gibs is measured. The pressure levels of the hydraulic liquids in the main and ancillary pumps, as well as in the main and ancillary cylinders, are measured using the appropriate sensors. The specialists also measure the speed and time of the forming cycles. Above all, the stroking speed up to the point of impact on the workpiece, the forming speed itself, the holding time – for example at the end of forming – and the speed of the return stroke provide exact details on press performance.

Schuler uses special sensors, value converters (analog/digital converters) and sophisticated software to acquire, present and evaluate the measurement data.

Measurement technology provides accurate data

By skillfully combining speed, displacement and pressure data over time, the forming processes can be displayed and evaluated with the aid of diagrams. Schuler’s experts can generally conclude a number of measures from these diagrams which will optimize the forming process. The pressure curve over time, for example, can highlight errors and defects in the hydraulic system; worn out pumps and valves which are not switching completely can be immediately recognized. Conclusions can also be drawn about valve curves which are not set optimally and defective servo valves.

Schuler’s team of experts also analyze the ancillary drives and peripherals. Moreover, they measure the coordination and processes in connection with insert devices or transfer equipment. “Customers receive detailed documentation about all our diagnoses, analyses and proposals,” explains Rolf Braun, one of Schuler Service’s experts. His team specializes in optimizing hydraulic press systems and was also responsible for retrofitting equipment at Hirschvogel Umformtechnik. “If we detect faulty components in the press, we immediately develop suitable repair measures together with the customer,” adds his colleague Jens Rau. The diagrams enable Schuler’s press specialists to develop detailed possibilities for reducing cycle times in the forming process.

On the basis of their experience and conversations with the machine’s users, for example, the opening and closing of valves can be moved to an earlier or later point in time. In many cases, the switching point from rapid motion to the forming speed when approaching the die can be moved to a later point. In the same way, the holding time at the end of forming can be shortened and the start of the return stroke can be brought forward. In coordination with the machine’s users, Schuler’s specialists then optimize the forming processes. They adjust the initiators, position encoders, relays, valves and flow regulators. They also correct the PLC and process programs for the forming dies.

Rolf Braun stresses: “It’s not a question of simply turning the adjustment screw. Many of the parameters influence each other. You need to have finely tuned instincts.” Raising the pressure settings, for example, may cause the hydraulic oil to overheat. After optimizing the press, the diagrams display the potential achieved.

At Hirschvogel Umformtechnik the team succeeded in reducing cycle times by a third for certain press processes. Schuler handled the retrofitting of an hydraulic cold extrusion press with a force of 2,500 metric tons, which the customer had been using since 2001. The fact that the retrofit was completed in just two days impressed Wilfried Andersen, Operations Manager at Hirschvogel Umformtechnik: “As a user, we may know our forming processes, but we would never have been able to analyze them in such detail without Schuler’s help. You often hear that running processes should never be changed. Schuler’s press optimization proves that this is not true.” He adds: “Even a cycle time improvement of just a few percentage points, such as 0.2 seconds in a total process time of less than six seconds, can exploit tremendous capacity reserves when mass manufacturing in three-shift operation.”

In the automotive industry in particular, a small investment in a two-day optimization process for existing presses can significantly improve economic efficiency. As Rolf Braun says, it can even do away with the need to invest in new or additional presses: “It is certainly worth allowing specialists to carefully examine your existing equipment in order to get the best out of your presses.”

On May 13 and 14, 2009 Schuler SMG is hosting a customer event in Waghäusel under the heading "Experience Hydraulic Press Technology Live". For registrations and enquiries, please contact Birgit Kolb-Liebl - Tel.: +49 7254 988-223. Our experts on optimizing hydraulic press systems will also be present.