A worm is actually a gear with very few teeth. For this reason, there is now a solution from Liebherr that can machine components of this kind economically: the LC 80 WD milling machine.
In the production of electronic steering systems, the cycle time means everything. But a customer’s existing system was already optimized to the hilt, which meant that further improvements could only be realized with new machine technology.
“At this point, the company turned to us because our machines are already employed there: They machine the steering segment while other machines make the worm,” said Johannes Weixler from the technical quotations department at Liebherr-Verzahntechnik GmbH.
Worms have to be made with very high precision for electronic steering. “Electronic steering is becoming more popular because it offers some advantages over hydraulic power-assisted steering,” Weixler said, explaining the market significance. “It only operates when actual steering movements are carried out and thereby saves a considerable amount of energy. Furthermore, it is very quiet and therefore particularly ideal for electric cars.” New vehicles are almost exclusively equipped with this technology. As such, this is real mass production.
Swiveled cutter head, no steady rest
“In actual fact, a worm of this kind is a gear with two teeth and this is why it should generally be made on gear hobbing machines,” said Weixler. The swiveling range of the cutter head of the customer’s LC machine on which it is based was extended for this special task. A significant advantage of the Liebherr solution compared with conventional worm milling is the elimination of the steady rest. “We solved this problem with an intelligent clamping fixture that is extremely rigid.”
While adapting the machine to worm milling, requirements of the machine table were taken into account, as well as the applied cutting forces, to facilitate a stable process. Tool life tests indicate that it was possible to increase the cutter life by more than 40 percent. Since the price of the tools makes up a large part of the machining costs, big savings can be realized here.
Chamfering and brushing included
Because the gear cutter can produce razor sharp burrs, the machine is equipped with a multi-station ring loader and an additional chamfering unit. Conventional side milling cutters are used for chamfering, which are significantly cheaper than the worm cutters otherwise used. A brush is also installed in the same position, which removes any micro-burrs after chamfering and is readjusted automatically as it begins to wear.
“We were able to provide added value for our customers in several aspects,” Weixler said. “The customer can now cut, chamfer, and brush parts on one machine. Chamfering during the machining process means that a faster cycle time can be realized and the tool costs are also lower. This is a major saving, particularly with the customer’s high volume.”
- Shorter cycle time.
- Long tool life.
- Lower tool costs.
- Workpiece exits the machine without burrs.
- Chamfering and brushing during the machining process.
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