What Is a Lathe Tool Post?

The tool post is a very important part of a CNC lathe. According to the function of CNC lathes, the number of tools that can be installed on the tool holder-generally 4, 6, 8, 10, 12, 20, 24, and some CNC lathes can install more tools. The structure of the tool holder is generally rotary. The tool is installed on the tool holder in the circumferential direction. Radial turning tools, axial turning tools, drills, and boring tools can be installed. Turning machining centers can also be equipped with axial milling cutters and radial milling cutters. A few CNC lathes have straight tool holders, and the tools are mounted along a straight line.

The knife holder is

1) Short tool change time to reduce non-machining time.

2) Reduce the interference of the tool changing action on the machining range.

3) The tool repeat positioning accuracy is high.

4) Reliable knife selection and selection, simple and reliable tool change.

5) The storage capacity of the tool magazine is reasonable.

6) The tool magazine covers a small area, and can cooperate with the host to make the machine tool look beautiful.

7) The tool is easy to load, unload, adjust and maintain, and can be cleaned and maintained.

The faults of several tool holders are mainly mechanical or electrical failures. To find and troubleshoot the tool holders as soon as possible, you must first understand the internal structure of the CNC tool holder and be familiar with its mechanical and electrical control principles. This is more important for beginners. ^{[2 -3]} .

Working principle of turret

After the host system sends an index signal, the tool post motor is turned on and starts to rotate. The motor rotates clockwise and clockwise through the coupling on the coupling seat to drive the worm shaft to rotate, thereby driving the copper material worm wheel to rotate. The external thread is screwed with the internal thread of the inner hole of the upper tool holder. The inner hole of the worm gear and the outer circle of the center fixed axis of the tool holder are in a dynamic fit. When the index is changed, the center fixed axis is fixed and the worm gear rotates around the center fixed axis. When the worm gear rotates clockwise, the upper external thread of the worm gear lifts the upper tool holder body, the upper and lower knife holders are disengaged, and the backing pin leaves the slot of the backing disk. After lifting to a certain distance, the end teeth are disengaged. The two holes on the end face of the worm gear are connected to the two holes of the indexing sleeve. The indexing sleeve rotates with the worm gear. Cylindrical pins on the front and back sides of the upper tool holder body enter the grooves of the indexing sleeve under the force of the spring to drive the upper knife The frame body is indexed. When the number of the knife position specified by the program is changed, the Hall element on the transmission plate is aligned with the magnetic steel on the upper knife frame body, and a signal is sent to the host system, and then the system sends a reverse delay. At the time signal, the motor is reversed, the upper knife body is slightly reversed, the two backing pins at the lower end of the upper knife body enter the grooves of the backing disk, and the rod of the upper knife body and the rod of the lower knife are combined and locked. Reverse delay is over. In this way, the tool holder has completed the tool change procedure, and the host can execute the next procedure. With an understanding of the tool holder structure and mechanical principle, it is convenient for us to analyze the failure.

Tool holder mechanical failure

In the manual state, press the manual tool change button on the panel, the lathe tool post does not move, and the sound of the tool post motor rotation is not heard. The alarm number {05} on the machine panel screen is too long.

(1) Troubleshooting: After this fault occurs, when the manual tool change button on the panel is pressed and the diagnostic panel button is pressed, the diagnostic information No. 005 is found. The signal level of the forward rotation of TL + tool post is 1, and the reverse of The level signal is 0, which proves that the system has a forward signal output.

(2) Further check whether the signal transmission from the system to the motor is normal. Remove the tool holder motor cover, first press the reset button on the panel, then press the manual tool change button, and then test the three connections of the tool holder motor with an electric pen. Check whether there is power at the input end. The electric pen indicator light is on, which proves that the control motor has power and the signal transmission is normal.

(3) When the key on the diagnosis panel is pressed, the serial number 000 code is 00001110, because the last four digits indicate the state parameter number of the four-digit tool post, and the undigited 0 represents the tool post working state tool position number T1, and the tool position is also T1 The remaining tool position numbers are high potential, which proves that there is no problem with the tool post signal.

It is inferred that it is a mechanical failure. When the bulkhead on the side of the tool holder is disassembled, the tool holder cannot rotate when the nut on the end of the worm shaft is turned forward with an allen wrench. dead. The knife holder must be disassembled and inspected.

Tool holder removal sequence

When disassembling, it was found that the clutch pin connecting the index sleeve and the worm gear screw was broken, and dirt was stuck in the worm gear and the worm gear. Replace the clutch pin. Pay attention to the following points when assembling and disassembling:

(1) Pay attention to the terminals of the Hall element and make a mark. You can use a color pen to mark the Hall element corresponding to the four-digit knife position number and make a mark to prevent the wrong control line. The Hall element of the tool position number corresponds to the magnetic steel on the upper tool body.

(2) When disassembling, follow the disassembly order. Do not use random objects to disturb or knock, which will affect the accuracy of the parts.

(3) All parts are cleaned during assembly, and the transmission parts are greased. Do not turn the indexing set upside down.

(4) After assembling the big nut and tightening it, use an Allen wrench to rotate the worm shaft forward, observe whether the tool holder body rotates normally, and then check with power.

(5) After power-on, pay attention to check and rotate and adjust the position of the transmitting tray, make the Hall element of the tool holder align with the magnetic steel, and stop the knife position at the accurate position.

Tool holder repair summary

The failure of the turret of a CNC lathe is less difficult than the failure of the NC internal system, but the number of turret failures is relatively large. Therefore, as soon as possible to repair and improve the utilization rate of the machine tool, it is necessary to check that the turret is controlled by the internal CNC system The principle of PLC system, electrical control, and mechanical transmission can distinguish the causes of various failures of the tool post, summarize and master the detection methods, and thus improve the speed of machine tool post fault repair ^[4] .