Long curls are beautiful – in a magnificent head of hair. In a lathe, however, long corkscrew chips are a big problem: They quickly fill up the working chamber and block the paths, wrap themselves around the parts to be machined or the tools, and they may cause serious damage. In consequence, the operator will repeatedly need to stop the machine to clean out the working chamber. "This costs production time and thus money," says Markus Zepf, Technical Director at ZWT. He knows what the customers need: Short, broken chips are a definite advantage when it comes to speedy manufacturing.
"The best way is to have the short chips carried away from the component and the tool via the draining cooling lubricant" Mr Zepf (on the left) explains. Accordingly, the working chamber is flushed for easy removal of small turning debris, which means that production can continue without clean-out interruptions even with a high throughput.
With some cutting geometries, however, the formation of long chips cannot be avoided if tools of regular design are used. To ensure that the chip breaks at an early stage, a chip groove in the form of an accurately positioned indentation must be provided in the cutting face.
Chip grooves are cut by means of a laser in the precision-ground and lapped cutting face. What makes the difference is how this indentation is shaped, and where exactly on the tool it is made. "Depending on the chip pattern, it may be sufficient to make the chip groove in a small part of the cutting edge only," Markus Zepf explains. Due to their extensive experience in the question of chip behavior, ZWT provides the first general idea of where and how a chip groove should be implemented, followed by coordination to define the details.
"For this type of tool optimization, we always proceed in close cooperation with our customers: Using sample parts, chips, and tools from the production, we are usually able to arrive very quickly at a solution which puts an end to long chips and provides nice short ones." In many cases, ZWT offers different variants for tool optimization to achieve the best result for smooth production. "It often makes sense to compare the chip behavior of one continuous chip groove in a cutting edge with that of two short chip grooves," Mr Zepf says.
Whatever the outcome, one thing is certain: Chip grooves, the little helpers with the great effect, are certainly worth their cost if you think of the significantly reduced machine standstill times that they can help you achieve.