Automatic tool change yaw detection system (Figure)

The ATC yaw detection system is composed of an eddy current sensor, a control device, and a display calculation device (V10). When the system is used on a horizontal machining center, the eddy current sensor is first mounted on the flange of the shank by a bracket; the cable of the eddy current sensor passes through the inside of the spindle device and is connected to a control device placed on the gantry. The display calculation device (V10) is connected to the control device by a dedicated cable; the control signals such as the yaw judgment (OK/NG) and the detection command are connected to the NC device. The main technical specifications of the system are listed in Table 1.

High-precision technical points

When using general eddy current sensors and amplifiers, there are still many problems, so it cannot be used for the detection of automatic tool change yaw in actual cutting.

Eddy current sensor characteristics

When the eddy current sensor is used to measure the gap between the shank and the shank, in addition to the gap change caused by the rotation, it is also affected by the state of the structure (quenching condition, material soft point), magnetization, and lettering. Due to the influence of magnetic, drive pin and other factors, the correct amount of yaw cannot be obtained. When using the ATC yaw detection system, the shape data of the shank should be input in advance, and then the measurement result can be compared with the input data to solve the problem.

Problem with the shape of the shank

The inherent yaw of the original shank and the cut data from the drive pin must be removed. There is also the possibility of biting into the chip at the position of the drive pin. Regardless of where the chip is stuck, in order to calculate the correct amount of yaw, the amount of yaw that is rotated one revolution should be separated. In order to solve this problem, the phase of the waveform in the input processor should be matched to remove the notch data, and the separation of the yaw component can be achieved by independent data processing. Due to this method, the small fluctuation components characteristic of the eddy current sensor are negligible.

Application of spindle tool deflection detection system

In order to adapt to high-speed machining, two-sided positioning clamps are becoming more and more popular. However, the two-sided positioning clamp shank represented by HSK may also cause the shank to fall off due to a clamping error and failure during rotation, which may cause serious damage to the machining. The ATC yaw detection system can prevent such accidents before they occur. The tool holder is clamped and rotated at a low speed (600r/min), and the detection system can detect the yaw abnormality before the cutting process has reached the high speed.

Especially when high-precision boring is required to achieve H7 grade, the yaw of the shank is a fatal problem. In deep hole machining, the yaw of the tool tip is proportional to the length of the shaft, and the excessive yaw causes more damage. This system can play a large role in such cutting operations.

In the milling process, the yaw generated by the chip biting has an adverse effect on the precision of the finished surface, and can cause the tool to chip and even cause damage. The detection system can completely avoid the above problems.

Use case

In the past, when machining on a machine tool, it was used to evacuate with compressed air (automatically, when the tool was changed, high-pressure air was blown from the inside of the spindle to blow off the chips). The louvered door prevents chip spattering (isolation of the cutting space and the tool magazine with the shutter door, and the door is opened and closed only when the tool is automatically changed), but there is no means for detecting the presence of sticky chips.

The frequency at which chip biting occurs varies depending on the material of the workpiece, the type of coolant, the method of supplying the coolant, and the method of cutting. It is necessary to test all the processed parts and all the processed parts. In the user who used the ATC yaw detection system, the yaw caused by the chipping was investigated, and the results were as follows.

Company A: The chip biting frequency is 1/800 times. The aluminum parts are cut and the chips are stopped when the chipping occurs.

Company B: The frequency of chip biting occurred 2/1826 times, and the yaw confirmed when chipping occurred was 20 μm.

Company C: The test results averaged 114 times of biting, cutting aluminum parts and using HSK holders.

For users who have to perform a full inspection when a waste product suddenly appears in the cutting process, it is not necessary to perform a full inspection after using the ATC yaw detection system.

As a representative of a machining center machine tool, a compound lathe, a tapping machine, and other processing equipment equipped with a tool quick change device, to achieve high-precision high-speed machining, when the automatic tool change device requires a tool change time to the limit, then The shank used should have various characteristics and its variety specifications should be varied. On the actual production line, the processing failures, especially the unexplained sudden processing problems, are not effective and difficult to cope with.

For this reason, an automatic tool change yaw detection system has been developed, which can effectively prevent sudden machining defects caused by chips. In the future, further research will be conducted to develop a control system for monitoring the state of the tool holder and the spindle to maintain optimal machining conditions.