Competition, they say, is what makes business go strong. That's why, as an engineer, I'm always happy when I read something new about my colleagues at the competition in a trade magazine. Recently, for example, a grinding machine for large dimensions was announced in production. Hobs are to be produced on it at a later date. Sounds interesting, I thought to myself, but was rather disappointed after reading it. Nothing half and nothing whole, as we Swabians say.

Ready to go and complete
On the first Multigrind® CB delivered to the customer, hob cutters are actually machined. These are quite impressive milling cutters, weighing up to 600 kg, 600 mm long and with a maximum diameter of 500 mm. On the Norwegian island of Herøy, I.P. Huse uses such milling tools to manufacture gear wheels for driving large (really large!) winches for cargo and container ships and drilling platforms.

Anchor chains, ship haws or cables are rolled up on the drums, which can be up to 8 metres in diameter. The machining specialists at I.P. Huse have opted for Haas grinding machines because we are the only grinding machine manufacturer on whose machines very large gear cutting tools can be machined in a single clamping, even complete. This is made possible, for example, by a crossed double spindle arrangement, 360° swivel angle in the A axis and 320° swivel angle of the grinding wheel in the C axis.

Hysteresis and the "Muggaseggel"

In order for the gears to run optimally in the large winches even under the heaviest loads, they must be extremely precisely machined, and for this, who would have thought it, extremely precise gear hobbing tools are required. Tool accuracies of 2 to 3 µm are required. To ensure this accuracy during the entire grinding process, we gave the Multigrind® CB an intelligent, integrated 3D measuring system.

The mathematics specialists in our software department succeeded in calibrating the so-called hysteresis mathematically. A hysteresis is the continuation of an effect after its cause has ceased to exist; i.e. when the probe is deflected further than it should, which then has a negative effect on the next cut. But as I said, that's over now: the integrated measuring unit in our Multigrind® CB leads to repeat accuracies of less than 1 µm (and that's less than a "Muggaseggel"!) and also saves time-consuming clamping and unclamping. The Swabian in all of us is happy about this, isn't he?

Thomas Bader

PS: Now I have something nice for all sailors: The milling of a large gear wheel at I.P. Huse takes up to 8 days. The trip by ship through the Panama Canal takes about 8 hours - or in fast motion about 2 minutes.