JPH0323281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting breakage in a parting tool, and is particularly applicable to NC automatic lathes for bar processing that have a drive shaft for back processing. This invention relates to a method for detecting breakage of a cutting tool.

In automatic lathes for bar processing, a long bar is inserted through the rear end of the main spindle, the bar protruding from the tip is gripped and rotated by the chuck of the main spindle, and cutting is performed on it. The process of cutting it off with a cut-off tool and making it into a product is repeated. Here, the cut-off bit is not only used to cut off the product, but also normally used as a stopper for extruding the bar material after the product has been cut off.

However, as is well known, the width of the parting tool is very narrow, and it may break due to some kind of impact from the lateral direction or excessive cutting load. If the parting tool breaks, the bar will be extruded without being cut off, which will not only result in a defective product, but also cause interference with other machine parts, push through the cover, or cause the bar to be swung around and be There is a risk of damaging mechanical parts.

For this reason, various types of tool breakage detection devices have been developed and are in use, but all of these require a new detection device to be added to a normal automatic lathe, resulting in high costs. There was a risk of malfunction due to the adhesion of cutting oil or chips due to contact between contacts.

The present invention aims to provide a reliable method for detecting breakage of a parting tool without using such an additional detection device and regardless of the presence of cutting oil or chips.

NC automatic lathes for bar machining, especially NC automatic lathes that have a guide bushing and perform cutting at the mouth of the guide bushing, are suitable for machining long and slender parts. It is possible to perform not only normal turning processing but also various secondary processing operations, and its greatest feature is that the processing of parts is completed in one step. Among these attachments, drive shaft devices for back surface machining are relatively often used;
That is, it is often used for processing from the parting surface side (chamfering, thread cutting, etc.).

Although the present invention is a method that can be used only for drive shafts for back processing, especially those whose shaft center coincides with the center of the main shaft, it is an effective and reliable method for detecting breakage of a parting tool. be.

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a cross-sectional view showing the essential parts of an example of an NC automatic lathe that has a main spindle and a drive shaft for back machining, the axes of which are aligned. It has a main shaft 2 that slides along the main shaft 2, and a guide bush 3 that is provided concentrically with the main shaft 2 and in front of the main shaft 2 (to the right in the figure). Above the guide bush 3, there is a turret tool post 5 that moves up and down along an upright column 4, on which a plurality of machining tools are attached.
It is configured to perform processing such as cutting at the mouth of the machine.

As is well known, the driving force from a drive source 6 such as an NC-controlled DC motor is transmitted to the main shaft pulley 8 via a belt 7, and the main shaft 2 is driven to rotate at a required rotational speed. The rotation of the main shaft 2 is controlled by an encoder 9 using other reliable transmission mechanisms such as gears or toothed belts.
The rotation angle or number of rotations of the main shaft 2 is detected, and it is confirmed that the main shaft 2 rotates at a predetermined number of rotations or stops after rotating by a predetermined rotation angle.

The main shaft 2 slides along the guideway provided in the bed 1 in the direction of the main shaft axis as described above. That is, as the screw 10 of the ball screw is rotated by an NC-controlled drive source (not shown), the main shaft 2 slides in the front-rear direction (in the left-right direction in the figure) together with the nut 11 of the ball screw.

As described above, the turret tool post 5 is provided on the upright column 4, and is driven by an NC-controlled drive source (not shown) to move up and down. A plurality of tools can be attached to the turret tool rest 5, and in the drawing, a parting tool T1 and a side hole drilling drill T2 are illustrated, but in addition, a normal cutting tool and a tool for machining from the front or back are shown. It is possible to attach a drill or tap. The turret tool rest 5 is indexed and rotated via the wheel train 13 by the rotation of the drive motor 12, and is accurately positioned and fixed by the coupling 14, allowing machining with a predetermined tool. On the other hand, the rotation of the motor 15 is transmitted to a rotary tool attached to the turret tool post 5, for example, a horizontal hole drilling drill T2.
It is rotationally driven via a pair of bevel gears 16.

The workpiece (bar) is inserted into the hollow hole of the main shaft 2 from the rear end (left end in the figure), and the collector chuck 17
is inserted and supported by the guide bush 3. The collection chuck 17 is a known chuck opening/closing mechanism 18.
It is opened and closed by the handle to grip and release the bar. The bar material is supplied by a suitable material supply means (not shown).
As is well known, it is pushed forward by the

The drive shaft 19 for back processing is connected to the guide bush 3.
It is provided concentrically with and facing the main shaft 2 across the machining area of the mouth. Drive shaft 1 for this back processing
9 has almost the same configuration as the main shaft 2,
The ball screw 21 is rotated by the rotation of the NC-controlled rotary drive motor 20 and slides in the axial direction along a guideway fixed to the bed 1.
driven by. The drive shaft 19 has a collect chuck 22 and a chuck opening/closing mechanism 23, and is adapted to grip the workpiece separated by the parting tool after machining on the main shaft side is completed. A knock-out shaft 24 is inserted into the hollow hole of the drive shaft 19, and is operated by a knock-out device 25 to push out the workpiece after the back surface machining is completed.

Next, the operation will be explained.

The workpiece (bar material) is inserted through the main shaft 2, the tip of which reaches the guide bush 3, and the collector chuck 17
It is gripped and rotated. The required tool attached to the turret tool rest 5 is selected, the turret tool rest 5 is indexed, and descends to reach the machining area, and the forward and backward movement of the main spindle 2 and the vertical movement of the tool rest 5 are combined. The required processing is performed. When all of the above-mentioned required machining is completed, the final step is a cutting-off process using the cutting-off bit T1.

At this time, the drive shaft 19 for back processing moves forward (leftward in the figure), inserts and chucks the tip of the workpiece W into the collect chuck 22, and rotates together with the rotation of the main shaft 2. Next, the tool post 5 is lowered and the cutting operation is performed. When the parting work is completed, the main spindle 2 stops, and then the drive shaft 1 for back processing
9 rotates slowly at a predetermined number of rotations.

At this time, if the parting tool T1 is normal, the workpiece W has been completely separated, so only the drive shaft 19 for back processing rotates, and the main shaft 2 does not rotate, so the encoder detects the rotation of the main shaft 2. 9 indicates that it does not rotate and the main shaft 2 is stopped. If the parting tool is broken, the workpiece W is not separated from the bar, and the main shaft 2 rotates as one unit with the rotation of the drive shaft 19 for back processing, so the encoder 9 The main shaft 2 also rotates, and the rotation of the main shaft 2 is detected.

Therefore, when the spindle 2 does not rotate, it is determined that the cut-off tool T1 is normal, and the process proceeds to the next process, the back surface machining. It is determined that the cutting tool T1 is broken. If the spindle 2 rotates but does not reach the predetermined rotational speed or the predetermined angle, it is determined that the spindle 2 has rotated naturally for some reason, and the cutting tool T1 is determined to be normal.

When it is determined that the parting tool T1 is broken, the machine is stopped, and if the machine has such a function, an alarm means is activated to display the broken parting tool and call the operator. .

When it is determined that the cut-off bit T1 is normal, the back surface processing process is performed as described above. That is, the drive shaft 19 for back processing is moved backward, the main spindle chuck 17 is opened, and the main spindle 2 is moved backward.
The bar protrudes by a predetermined amount for the next processing, the chuck 17 closes, and the turret tool rest 5 rises. Next, the turret tool post 5 rotates to select a tool for back processing and descends, and the drive shaft for back processing moves forward to perform back processing. When the back surface machining process is completed, the completed workpiece is pushed out by the knock-out shaft 24, and the process of machining the next workpiece begins.

Since the present invention is carried out as described above,
There is no need for a special mechanism to detect the breakage of the parting tool, and unlike optical or contact detection, there is no risk of malfunction due to the presence of cutting oil or chips, making it a reliable method. This is a method for detecting a break in a cut-off tool that enables detection.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the essential parts of an example of an NC automatic lathe having a main spindle and a drive shaft for back processing, the axes of which are aligned. 2... Main shaft, 3... Guide bush, 5... Turret turret, 6... Main shaft drive source, 9... Encoder, 19... Drive shaft for back processing, 20...
Drive shaft drive source for back processing.

Claims (1)

[Claims] 1. In an NC automatic lathe for bar processing, which has a main shaft and a drive shaft for back machining that is provided opposite to the main shaft and whose axes coincide with each other, the bar is gripped by the main shaft during the parting process. As it rotates, the drive shaft for back processing grips the machined tip and rotates with the main shaft, and after the parting process is completed, the main shaft stops rotating.
Next, the drive shaft for back processing is rotated, and the rotation detection mechanism for detecting spindle rotation detects whether or not this rotation is transmitted to the main spindle, and when the main spindle rotates more than a predetermined rotation, the cutting tool breaks. A method for detecting breakage of a cutting tool, characterized in that it is determined that there is a breakage in a cutting tool.