Hella Werkzeugbau Paderborn GmbH, a 100% Hella subsidiary with 280 employees, develops and manufactures thermoplastic and duroplastic dies for headlights and taillights. "We cover the entire lifecycle of the die, from consulting and planning through development and manufacturing to service, including maintenance and repair," explains Hermann-Josef Hartman, head of Sales at Hella-Werkzeugbau in Paderborn. Every year, 80 to 100 dies on the order of 2 to 16 tons are developed and manufactured and the injection molds tested in the company's own prototype test center. Injection molding machines with 75 to 1,450 tons of clamping force are available for this purpose; they are also used for batch production. Hella uses 16 Tebis CAD/CAM workstations, two Tebis Viewer stations and 10 floating licenses for the new Tebis Simulator.
Collision testing for roughing is based on the part geometry that has currently been achieved.
In late 2003, Tebis started a project for developing comprehensive simulation options in collaboration with the Hella specialists in mold and dye manufacturing. The purpose of the project was to account for the holder in addition to the cutter, including head kinematics and clamping position, as well as the overall organization of the NC programs to be processed in sequence. "Using the Tebis software, we can implement a closed information chain at Hella in Paderborn, in which manual data transfer and therefore a critical source of errors are limited," summarizes Klaus Kussmann, head of NC programming at Hella-Werkzeugbau. "The Tebis CAD space is now available to us right up to the machine, with the result that the operator has access to all data including the geometry and the simulator functions."
A limit switch test is run to determine the optimal setup orientation for a part. If any areas are outside of the travel range of the machine (such as for drilling here), they are highlighted in red in the graphical display of the machine axes.
"We want to use the Tebis simulation software to improve the processing reliability and utilization rate of our machines, because the Simulator should be used in both programming as well as in the shop," says Kussmann. "Since we manufacture dies with large projections of up to 600 mm per die half, we use various high-speed milling centers. We work with the shortest possible tool pads and flexible orientations to achieve the best possible surfaces."
If a collision of a part with the machine head is detected, it is corrected by taking a tool clamped farther out from the tool management integrated in Tebis and assigning it to the calculated toolpath.
Short-term changes can be more quickly implemented
Short-term reorganizations of machine assignments frequently occur. For example, dies received for repair take priority and have to be made available again for series production as quickly as possible. Other projects must then be reassigned to other machines, which usually results in adjustments in the NC programs. "Previously, an entire work day was often necessary for the adjustments – and in the end there was still little certainty about risks of collision. Using the Tebis Simulator, the program adjustment for a change in machines can now be completed in 30 to 60 minutes, plus an extremely high degree of process reliability is achieved," explains Norbert Hansmeyer, responsible for the introduction of the Simulator at Hella-Werkzeugbau.
Finishing of half of an injection mold for manufacturing a reflector cover frame on a Fidia Digit 218.
Virtual machines prevent damage to the workpiece, tool and machine
The NC programmer has access to virtual 5-axis machines as well as parts in the setup orientation and true-to-life tools. The Simulator software now enables the entire procedure to be defined, checked and visualized in advance, so that critical areas can be examined very closely before the first chips are even cut. The Simulator serves as an interactive planning module for the programmers, for example, to determine the optimal tool orientation for machining deep contours without touching anywhere. "By visualizing, testing and optimizing the manufacturing processes and the setup and tool orientation, and by collision testing with limit switch monitoring of the NC axes, we can prevent most of the damage that previously occurred to the workpiece, tool and machine," summarizes Karl-Heinz Uhle, head of machine operations in Hella-Werkzeugbau. "At the same time, we were able to significantly reduce processing times, setup times and idle times as well as documentation expenditure. "
All of the toolpaths used for fabricating the die half are organized in the NC list based on the required machines.
No more elaborate paper documentation required
Using the simulation software along the process chain also eliminates the usual elaborate paper documentation for the machine operators, as they can obtain all information directly from the Tebis model file
In the shop, machine operators check the NC programs provided by NC Programming on the Tebis Simulator, and organize these in the NC list for finishing on one of the Fidia finishing centers.
Using the Tebis software, we can implement a closed information chain at Hella in Paderborn, in which manual data transfer and thus also a critical source of errors are limited.
End-to-end information chain in design and manufacturing
- Flexible control of projects and fast response to changes
- Paperless access to design and NC data in the shop
- Increased process reliability
Mold manufacturing, Automotive
Hella Werkzeugbau Paderborn GmbH
Klaus Kussmann, Karl-Heinz Uhle
Head of NC programming at Hella-Werkzeugbau, head of machine operations in Hella-Werkzeugbau