Tips on machining vol.4
Measures for effective handling of drilling chips
－Aluminum alloy－

Chip handling can be classified into two ways. One is to remove chips (including long, tangled ones) properly without affecting machining operation. The other is to break chips into small pieces for easier handling.

The former method includes: removing chips that are winding around the drill like bird’s nest by means of jigs; blowing away tangled chips by rotating the spindle counterclockwise while discharging coolant from around the spindle; and using tools ingeniously to control chip flow.

Take automotive parts as an example. In many cases, the parts need multistep holes machined on aluminum. These holes are often machined in one process taking into account work efficiency and product quality. During the process, chips entering a drilling groove join together, causing the chip flow to be stagnant and the chips to be tangled. To solve this problem, DMG MORI has increased the number of chip grooves of a multistep drill from two to four to prevent chips from joining together in the grooves. The increased number of grooves allows independent flows of two types of chips, that is, chips generated by I.D. machining and chips generated by chamfering or seat surface machining. As a result, chips with different flows do not join together in a groove and are efficiently discharged to the outside of holes.

Meanwhile, the latter method of breaking chips into small pieces can be achieved with tool paths (e.g. step feed) or by conducting hole machining with an end mill and a helical path. However, drilling with step feed or helical paths requires longer machining time, resulting in decline in machining efficiency.

In order to ensure proper chip breaking while maintaining good machining efficiency, it is recommended that a drill equipped with a chip breaker be used. In fact, throw-away tips with chip breakers have already been widely used. A solid drill with a chip breaker, which is relatively unknown, is also one of the effective means for chip breaking.

DMG MORI conducted in-depth study on the drilling mechanism to seek suitable drilling conditions and chip breaker shapes. This enabled us to accumulate know-how for successful chip breaking even in the non-step machining of stepped holes or cast holes. Non-step machining is quite effective in improving machining accuracy, reducing setups and shortening machining time. What’s more, breaking chips into small pieces can reduce discharged chip volume, allowing the chips to be carried with ease and stored in a smaller space. This also leads to reduction in overhead cost.

In addition to the above, we have many other proven solutions for chip breaking, such as the use of a drill flute with finer surface roughness or a DLC (Diamond-Like Carbon) coated drill.

DMG MORI provides technical support for our customers facing chip-related challenges by explaining a chip formation mechanism and suggesting ingenious chip disposal methods. At our Solution Centers in Tokyo and Iga, visitors can see the tools discussed above and seek advice in person from DMG MORI engineers. For those who have problems that cannot be solved merely by technical means, we work out the best possible solutions in cooperation with tool manufacturers. So, please feel free to consult with us for any questions or concerns you may have.

• Consult with DMG MORI engineers on chip disposal

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