JPH03281113A - Machining center - Google Patents

Abstract

PURPOSE:To prevent a drill from breaking, by providing the rotation driving source of a drill, an advancing and retreating mean and a torque detecting mean, inside the tool holder of a machining center and controlling the stoppage, retreat and advance of the drill quickly when torque exceeds the threshold value. CONSTITUTION:In this machining center, the motor rotating a drill 15 is provided inside a tool holder 9 and further, the advance and retreat means which advances or retreats the drill 15 to a work 8 and the torque detecting circuit 11 detecting the torque of the drill 15 are provided. Now, the drill 15 is moved to the upper face of the punching position of the work 8 with an MC control device 14 by driving X, Y, Z tables 4, 3, 2 by motors 5, 5', 5''. When the machining by the drill 15 is started, the torque of the drill 15 is increased. This is detected by a torque detection circuit 11 and compared with a threshold value by a comparison circuit 12. An overload signal is output to a notch control circuit 13 when exceeding this and the notch stoppage, retreat and advance of the spindle only of the toolholder 9 inside are controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the depth of cut control during hole machining in a machine tool capable of relative three-dimensional positioning of a tool and a workpiece of a machining center, and in particular, This invention relates to a machining center that does not cause damage to objects.

[Prior Art] In drilling holes using a trill, prevention of tool breakage is an important issue. The main cause of drill breakage is that chips become clogged during hole drilling, which increases the cutting resistance applied to the drill. In order to prevent the drill from breaking, it detects the cutting force, especially the torque, during hole drilling and compares it with a preset threshold.

A method that stops cutting when this value is exceeded and alerts the operator to the occurrence of an abnormality. Furthermore, the cutting is stopped,
A method is known in which the drill is pulled back to eliminate the cutting shoulder that is causing an increase in cutting resistance, then rapidly traversed to the cutting point, and then the cutting is started again from there.

As a conventional method for controlling the cutting depth regarding the latter, there is an invention as described in, for example, Japanese Patent Laid-Open No. 51-93484. As shown in FIG. 6, this invention has a structure in which a drill rotation spindle 51 equipped with a torque detection function is mounted on a table 53 driven by a hydraulic piston 52. Then, this entire table is sent to the workpiece side to perform hole machining, and when the detected torque exceeds a preset threshold, the valve 54 of the hydraulic piston 52 that drives the J1 table 53 is switched, and the entire table is machined. was pulling back.

With this conventional method, the entire table is heavy.

Furthermore, since the table 53 is driven by hydraulic pressure, it takes a long time to pull back the table 53 after the torque exceeds the threshold value, and no consideration has been given to preventing the drill from breaking when cutting at a fast depth.

In addition, in order to improve the response speed, for example,
There is an invention as described in Japanese Patent No. -196347.

As shown in FIG. 7, this invention has a second table 62 mounted on a first table 61 for making cuts, which is normally in a forward position and rapidly retreats only when l-lux exceeds a threshold value. A spindle 63 was mounted on the second table 62, which had a function of rotating the 1-rill and detecting the torque applied thereto.

First, positioning and cutting were performed by the first table 61, and when the torque exceeded a preset threshold, the first table 61 stopped at that position, and the second table 62 was quickly retreated to discharge the chips. After that, the second table 62 is returned to the forward end. When the second table 62 returns to its initial position, the first table 61 is sent again to continue drilling.

This system requires complicated control in which the first table 6] is stopped and the second table 62 is rapidly retreated when the torque exceeds a threshold value.

In addition, in large machine tools such as machining centers, the combination of two tables and a spin I bell increases the weight, so when the first table 62 stops rapidly, vibration occurs in the column supporting the table, and the hole diameter In addition to widening the drill and breaking the drill, there were other problems such as a large overrun from cutting to stopping.

Furthermore, a machining center as shown in FIG. 8 has been proposed (Japanese Unexamined Patent Publication No. 15048/1983). In this figure, 71 is a main shaft, 72 is a holding part of a bearing that supports rotation of the main shaft 71, 73 is a tool holder, 74 is a cover member, 75 is a drill, and 76 is a motor.

In the machining center according to the present invention, the drill 75 is rotated by a motor 76, and the forward and backward movement of the drill 75 is performed by a table (not shown). Therefore, the moving weight is still heavy and there is inertia, so there is a problem that speed is lacking.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques and to provide a machining center that can shorten cutting stop time and drill retraction time even when the machining center is a large machine tool.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a table, a main shaft mounted on the table, a holder convertably mounted on the tip of the main shaft, In a machining center equipped with a cutting tool attached to the tool holder, the main shaft does not rotate and the tool holder has a cutting tool attached to the tool holder.
A rotary drive source for rotating the cutting tool, an iJ backward movement means for moving the cutting tool forward or backward relative to the workpiece, and a torque detection means for detecting 1-rook of the cutting tool are provided, and the detection from the torque detection means is provided. If the value exceeds a given threshold,
The present invention is characterized by comprising a forward and backward movement control means that stops the forward movement of the cutting tool by the forward and backward movement means and immediately causes the cutting tool to move backward until it comes out of the workpiece.

[Operation] The relative position of the workpiece and tool is determined by a three-dimensional positioning table such as a machining center, and cutting is performed by a cutting mechanism in the tool holder. At this time, a torque sensor detects the torque applied to the tool, and when this value exceeds a preset threshold, only the spindle in the tool holder is controlled to stop cutting, retreat, and move forward.

The spindle in the tool holder is relatively light in weight, resulting in better responsiveness.

[Example] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a tool holder according to the invention. The collet chuck part 21 that grips the drill 15 is mounted on a bearing 23.2.
3', it is supported within the rotor 10 which rotates at high speed. The rotational force to the collet chuck section 21 is transmitted via an elastic ring 22 that is deformed by torque. The rotor 1o has a bearing 24. ．． It is supported within the spindle 25 by 24' and 24'' and rotated at high speed by a high frequency motor 31.

The spindle 25 has a linear guide 32 and a ball screw part 2.
6 is disposed in the tool holder 9 and supported so as to be slid in the axial direction by the rotation of a nut 27 driven by a motor 30.

In addition, 28 and 28' in the figure are bearings, 33 is a non-contact displacement meter, 34 is a pulse encoder that is provided integrally with the nut 27 and has many slits (not shown) in one circumferential direction, and 35 is a tool holder 9. This is a reflective photosensor fixed inside the pulse encoder 34 and facing the pulse encoder 34.

Next, torque detection of the drill 15 will be explained using FIGS. 2 to 4. As shown in FIG. 2, an elastic ring 22 is installed between the rotor 10 and the collet chuck section 21. As shown in FIG.

As shown in FIG. 3, this elastic ring 22 has a lower ring part 22a, an intermediate ring part 22b, and an upper ring part 22c.
, a narrow first connecting portion 22d that connects the lower ring portion 22a and the intermediate ring portion 22b, and the intermediate ring portion 22.
a second connecting portion 22e that connects b and the upper ring portion 22C;
It is composed of. The first connecting portion 22d and the second connecting portion 22e are provided opposite to each other in the circumferential direction, and 22f is the lower ring portion 22a and the intermediate ring portion 22e.
2b, and between the middle ring part 22b and the upper ring part 22c.

As shown in FIG. 2, the upper ring portion 22c
0, the lower ring portion 22a is connected to the collet chuck portion 21, and the intermediate ring portion 22b is in a free state and faces the non-contact displacement meter 33.

FIG. 4(a) shows a state in which the drill 15 is not rotating, and FIG. 4(b) shows a state in which the drill 15 is rotating. When the drill 15 is not rotating as shown in FIG.
A predetermined distance ahead of 3.

When a driving force is applied to the drill 15 and the drill 15 rotates, the intermediate ring portion 22b is elastically deformed in the radial direction and approaches the non-contact displacement meter 33, as shown in FIG. By detecting the amount of displacement of the intermediate ring portion 22b with the non-contact displacement meter 33, the torque applied to the drill 15 can be measured.

This non-contact displacement meter 33 has a method in which the elastic ring 22 is made of a magnetic material, an eddy current is electromagnetically generated in the intermediate ring portion 22b, and the displacement meter 33 detects the eddy current as an electromotive force. There are methods to detect displacement visually, methods to detect displacement optically using a reflective optical sensor, methods to detect displacement using a strain gauge, and methods to detect displacement from the amount of torsion of a torsion spring. be.

FIG. 4 shows a block diagram of a cutting control system during hole machining using a machining center. An X table 4 on which a workpiece 8 is mounted, a Y table 3, a Z table 2 on which a main shaft 7 is mounted with a tool holder 9 attached to its tip, and these x, y, z tables 4, 3. 2, a torque detection circuit 11 that receives a signal from a non-contact displacement meter 33 for torque detection in the tool holder 9, and a torque detection circuit 11 that receives a torque signal from the torque detection circuit 11.
Comparison circuit 12 that compares the torque with a preset threshold value and outputs an overrot signal when the torque exceeds the threshold value, and a depth of cut control circuit that controls the axial drive of the spindle 25 in the tool holder 9 based on this overrot signal. Consists of 13.

Now, the MC control device 14 controls the X, Y, Z tables 4,
3.2 is immediately moved by the motors 5'', 5', 5 to move the drill 15 to the upper surface of the workpiece 8 at the position where the hole is to be drilled.
While rotating rotor 1-0 at high speed, cut control # circuit 1
3, the motor 30 is immediately operated, and the nut 27 is rotated to send the spindle 25 to the workpiece 8 side.

When the drill 15 cuts into the workpiece 8 at a preset speed and machining is started, the torque applied to the drill 15 increases. This torque is detected by the torque detection circuit 11 and compared with a threshold value by the comparison circuit 12, and when the torque exceeds the threshold value, an overload signal is output to the cutting control circuit 13. When the cutting control circuit 13 receives the overload signal, the motor 30 immediately stops the rotation of the nut 27, rotates it in the opposite direction, and pulls back the spindle 25 at high speed.

When the spindle 25 retreats to the position before cutting, the nut 27 stops turning. At this time, the drill 15 is removed from the workpiece 8, and the chips that have risen along with the drill 15 are removed by centrifugal force, air blow, or the like.

Next, the nut 27 is turned again, the spin 1 heel 25 is rapidly forwarded to the overload signal generation position, and then fed at cutting speed from the overload signal generation position to continue drilling the hole. And when the detected value of 1 Herc exceeds the threshold, -
Repeat the above operations to drill the hole to the required depth.

When the hole is drilled to the required depth]- and the spindle 25 is pulled back to the position before cutting, the MC control # device 14 performs
The Y and Z tables 4 and 3.2 are immediately moved to relatively move the 1-rill 15 and the workpiece 8 to the next hole machining position. Then, hole machining is repeated by the same operation as above.

[Effects of the Invention] According to the present invention, even in a machine tool such as a machining center where the spindle system is heavily stacked, highly efficient hole drilling can be performed without the drill breaking.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a tool holder for a machining center according to the present invention, FIG. 2 is an enlarged sectional view of a main part of the tool holder, FIG. 3 is a side view of an elastic ring, and FIG. 4(a). (b) is an explanatory diagram of the torque detection principle, and FIG. 5 is a block diagram of the hole machining control system by the machining center. FIG. 6 is a hydraulic control circuit diagram of a first conventional example, FIG. 7 is a partial side view of a second conventional hole drilling machine, and FIG. 8 is a sectional view of a main part of a third conventional example. 1. Machining center body, 7. Main spindle, 9.
...Tool holder, 10...Spindle, 1]...
・1-luke detection circuit, 1-2...comparison circuit, 13...
... Cutting control circuit, 14... MC control device, 15
...Drill, 21...Collet chuck part, 22...Elastic ring, 23...Bearing,
25...Rotor, 26...Ball screw part, 27
... Oak 1-130 ... Motor, 31 ...
High frequency motor, 32... Linear guide, 33...
...Non-contact displacement meter. A sea not shown Fig. 3 Fig. 2 Fig. 4 (a) Fig. 8

Claims (1)

[Claims] (1) A machining center comprising a table, a spindle mounted on the table, a tool holder convertably attached to the tip of the spindle, and a cutting tool attached to the tool holder, in which the spindle is a rotational drive source that rotates the cutting tool in the tool holder without rotating;
A forward and backward movement means for moving the cutting tool forward or backward relative to the workpiece, and a torque detection means for detecting the torque of the cutting tool are provided, and when the detected value from the torque detection means exceeds a predetermined threshold, the A machining center comprising a forward and backward movement control means that stops the forward movement of the cutting tool by the forward and backward movement means and immediately moves the cutting tool backward until it comes out of the workpiece.