KR101616740B1

KR101616740B1 - Controlling method of machine tool considering material directionality

Info

Publication number: KR101616740B1
Application number: KR1020150135635A
Authority: KR
Inventors: 김태곤; 이석우; 박경희; 김효영
Original assignee: 한국생산기술연구원
Priority date: 2015-09-24
Filing date: 2015-09-24
Publication date: 2016-04-29

Abstract

A method of controlling a machine tool in consideration of a direction of a material includes the steps of arranging a composite material on a machine tool (s10), placing a spindle on a machining position with respect to the composite material (s30) of machining the composite material while moving the spindle (s30); determining (s40) the directionality of the composite material during machining of the composite material; and when the direction of the composite material is different, (S50) of changing the machining speed of the machine tool.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a machine tool,

More particularly, the present invention relates to a control method for an anisotropic laminate, which is a problem that may occur depending on the direction of lamination of an anisotropic carbon fiber composite material (Carbon Fiber Reinforced Plastic) The present invention relates to a machine tool control method considering a material direction capable of processing a carbon fiber composite material.

The carbon fiber reinforced composite material is superior in properties such as nodal strength, inelasticity, and heat resistance to other types of fibers and has an advantage that a high-elasticity composite can be produced. Currently, carbon fiber-reinforced composites are widely used in aviation industry due to non-rigidity, corrosion resistance, abrasion resistance, high strength, etc. inherent in the material, and their use in many fields such as sporting goods, mechanical structures and automobiles is gradually increasing .

Such a carbon fiber-reinforced composite material has a problem of delamination due to its performance in the thickness direction due to the layered manufacturing process.

In the lamination type manufacturing process, four types of test pieces having different lamination structures were prepared using a carbon fiber epoxy prepreg impregnated with carbon fibers in advance. The test specimen is plain and has a very dense and regular structure in which the weft yarns of the abscissa and the warp yarns of the longitudinal axis are crossed one by one. Due to the dense structure, the pores are small and the resin is difficult to penetrate into the structure. Although the saturation drape is reduced, it has the advantage of excellent moldability in the prepreg lamination.

In processing the laminated prepreg in this manner, when machining is performed under the general conditions, there is a problem that machining defects occur depending on the orientation of the specimen.

Figures 1 and 2 are photographs showing the processing conditions and processing defects for a material having a directionality.

Referring to FIG. 1, the materials arranged on the specimen are arranged in the vertical direction. Since the processing conditions are constant irrespective of the up and down, left and right, processing defects as shown in FIG. 2 can be obtained.

In Patent Document 1 (Korean Patent Laid-Open Publication No. 10-1990-0017701), as a solution to such a problem, a tool monitoring device for a small-diameter spindle using a spindle-mounted torque sensor is used to predict the tool life or to monitor the machining state, A system for automatically determining the replacement time of the tool has become possible, but it has been difficult to apply it to the directional cleaning agent having a layered structure.

In order to solve the above problems, the technical problem to be solved by the present invention is to control the processing speed of the composite material stacked with different orientation angles, and to improve the precision and productivity of the composite material And to provide a method of processing a material.

According to an aspect of the present invention, there is provided a method of controlling a machine tool in consideration of material orientation, the method comprising: disposing a composite material on a machine tool; placing a spindle Determining the orientation of the composite material during machining of the composite material, and changing the machining speed of the spindle when the orientation of the composite material is different, comprising the steps of: Wherein the step of determining the directionality of the composite material is performed by a sensor for measuring the directionality of the material, and the sensor for measuring the directionality of the material measures a vibration signal to be converted in accordance with the directionality of the material, And the control signal is calculated by taking into consideration the material directionality A method of controlling a machine tool is provided.

A control device for a machine tool, which takes into account the directionality of a material, which is an embodiment of the present invention, includes: a support for arranging a workpiece; a spindle disposed on the support; and a computer numerical control device electrically connected to the spindle. CNC), and an acceleration measurement sensor electrically connected to the computer numerical control device, wherein the acceleration measurement sensor measures a vibration signal converted according to a direction of the workpiece and feeds back the vibration signal to calculate a control signal .

A method of processing a laminated material, which is an embodiment of the present invention, includes the steps of laminating an oriented material, arranging the material in a processing apparatus, machining the material into a spindle of the processing apparatus, And controlling the operation of the spindle when the orientation of the workpiece is changed, wherein the orientation of the workpiece in the step of controlling the operation of the spindle is measured by a sensor, and the sensor for measuring the orientation of the workpiece And measuring the vibration signal to be converted and feeding back the vibration signal to calculate the control signal.

A processing apparatus for a multi-layer material, which is an embodiment of the present invention, includes: a sensor for measuring a direction of the multi-layer material; a spindle for receiving a control signal from the sensor and processing the multi-layer material; And a sensor for measuring a direction of the workpiece measures a vibration signal to be converted according to a direction of the workpiece and feeds back the vibration signal to calculate a control signal .

According to the embodiment of the present invention, the generation of the defective ratio due to the processing of the composite material can be remarkably reduced.

Further, the machining process can be continuously performed without replacing the spindle, which is a composite material or a machine tool, and productivity can be improved.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic view showing a conventional method for processing a directional material.
FIG. 2 is a view showing a problem that may occur at a connecting portion of each layer when processing a directional material according to the prior art.
Fig. 3 is a view showing a change in machining conditions according to a machining direction according to an embodiment of the present invention. Fig.
4 is a view showing a configuration of a material having different lamination structures according to another embodiment of the present invention.
5 is a cross-sectional view schematically showing a modification of processing conditions according to the constitution of a material having different lamination structures according to another embodiment of the present invention.
6 is a graph showing measurement of vibration occurring during processing of a composite material, which is an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Carbon Fiber Reinforced Plastic (CFRP) is widely used in aerospace materials, automobile materials, and ship materials because of its excellent material properties that are difficult to obtain from metal materials, such as noble strength, inelasticity, abrasion resistance, fatigue characteristics, heat resistance and corrosion resistance. And general sports goods, electronic parts, and medical supplies.

The study on the machining of composite materials includes drilling characteristics according to the lamination structure of CFRP composites, cutting properties of fiber reinforced plastics by drilling, cutting characteristics by high speed drilling of fiber reinforced plastics, etc. .

However, there is not much research on the cutting characteristics of the carbon fiber-reinforced plastic composite material when drilling materials according to the lamination configuration in which the woven prepregs and uni-directional prepregs are oriented at different angles . In particular, carbon fiber-reinforced plastics have the potential to cause delamination at the entrance and exit of the workpiece during drilling, separation of individual fibers within the laminate material, tearing of fibers and resin at the edge or wall of the workpiece surface, Load phenomenon, wear of a tool due to strong abrasive property of carbon fiber, and the like.

In addition, the chips that can be generated in the drilling process are dust particles of small particles, which is harmful to the working environment and the health of the workers, and penetrates between the machine tools, which shortens the life of the machine and deteriorates performance. In order to minimize these problems and to propose an optimal cutting condition, experiments are carried out for each condition by changing the lamination configuration of each type of each prepreg.

Cutting force according to the change of rotation speed and feed rate and inlet / outlet of machining part using high speed steel drill and TiAlN-Coated drill by forming the orientation angle of fabric type and unidirectional prepreg of carbon fiber reinforced plastic into 45 ° and 90 ° And the shape of the chip can be known.

A method of controlling a machine tool in consideration of material orientation, which is an embodiment of the present invention, includes the steps of arranging a composite material on a machine tool (s10), arranging a spindle on a machining position (s20) (S30) of machining the composite material while moving the spindle; and determining (s40) the orientation of the composite material during machining of the composite material; And changing the machining speed of the spindle if the direction of the composite material is varied (s50).

The machine tool may be a device capable of performing drilling, trimming, routing and boring. Such a machine tool may include a spindle for performing machining. The spindle may further include accessories for winding the yarn into a spinning device at a high speed of about 10,000 rpm (round per minute). The main spindle for rotating the spindle is one of the elements constituting the spindle.

In this manner, the process of processing the composite material 100 using a machine tool having a spindle can be performed. The composite material 100 may include CFRP (Carbon Fiber Reinforced Plastics) or GFRP (Glass Fiber Reinforced Plastic).

CFRP or GFRP is a material that combines two or more materials with different shapes and chemical compositions physically to realize properties suitable for multiple functions not found in a single material. In particular, CFRP is a representative material of composite materials, and has excellent moldability and high strength at high temperatures. It is lightweight and high strength material and is used as a high-tech industrial core material such as aircraft structure, space shuttle, and space structure.

In particular, CFRP, unlike steel, is already used in jet passenger brake systems because it does not deform at high temperatures due to friction, and has strong moisture resistance.

Methods for machining such CFRP or GFRP include cutting using conventional machine tools and special processing methods such as water jet, laser, ultrasonic wave, and electrical discharge machining have.

According to the definition of exfoliation and surface damage due to the change of thrust during drilling of CFRP, surface roughening, straightness, roundness, burr formation, It is possible to grasp the defect layer. As one of these models, according to the fracture mechanics model, it is possible to predict the minimum thrust which does not cause delamination by using the thrust generated in machining.

In CFRP, the separation of each ply at the entrance and exit of the part during drilling, the tearing of the fiber and resin at the edge of the work surface or the wall, the delamination of the laminated material, .

Also, since the fiber is strong in abrasion, the wear of the tool is accelerated and the tool life can be adversely affected. In order to perform the cutting process on the CFRP including carbon fiber, the design should be performed in consideration of the lamination structure of the prepreg and the fiber direction and content of the orientation angle according to the required properties. As shown in FIG. 1 without such design characteristics, when the process is performed under the same processing conditions even if the stacking directions are different, a processing failure as shown in FIG. 2 may occur.

Two basic configurations of [0 ° / 90 °] and [0 ° / 45 °] are possible for such a CFRP stacking orientation angle. As described above, a composite material including CFRP molded by a method such as resin transfer molding can be processed by using a high speed steel or a TiAlN-coating drill so that the number of revolutions and the feed rate are different from each other .

Fig. 3 is a view showing a change in machining conditions according to a machining direction according to an embodiment of the present invention. Fig.

Referring to FIG. 3, the stacking orientation angle of CFRP may have an orientation angle of [0 deg. / 90 deg.]. Accordingly, the machining conditions at 0 ° and 90 ° can be changed. As described above, a material containing a fibrous material and a dendritic material is called a prepreg. The prepreg has various properties depending on the orientation of the fiber and the method of weaving. Therefore, fiber orientation is an important factor in determining the mechanical strength of CFRP. The short, randomly oriented reinforcing fibers become isotropic and the long, unidirectionally oriented reinforcing fibers exhibit anisotropic behavior, the strongest when the applied load is parallel to the reinforcing fibers. The direction of the fiber can be classified into a one-directional, orthogonal, or multi-axial direction.

The carbon fiber-reinforced plastic of Fig. 3 can be said to be a prepreg having a unidirectional orientation or a carbon fiber-reinforced composite material.

The composite material comprising the carbon fiber-reinforced plastic of FIG. 3 can be said to be a uni-directional prepreg or composite material. The composite material comprising the carbon fiber-reinforced plastic of Fig. 3 is characterized in that all of the fibers in the fabric are aligned in one direction. Such unidirectional carbon fiber-reinforced composite materials are characterized in that the amount of fibers used can be minimized while the fibers are not twisted and used in a straight line during the production of the fabric constituting the prepreg.

When a tensile force is applied to a composite material containing such a carbon fiber reinforced plastic, it exhibits very high physical properties, but it can have the lowest physical properties when the tensile force acts on the fiber in a direction perpendicular to the direction of the tensile force.

Therefore, in FIG. 3, a CNC milling machine capable of adjusting the feed amount and cutting depth of the main shaft during the processing of the one-directional carbon fiber-reinforced composite material can be used. A tool dynamometer can be used to measure the thrust and torque generated during drilling. A charge amplifier can be used to amplify the microcurrent from the tool dynamometer.

The physical properties of the carbon fiber composite material having a unidirectional shape may have a tendency that the cutting thrust and the torque decrease as the number of revolutions increases. This phenomenon increases the cutting speed as the number of revolutions (rpm) increases, so that the cutting cross section and the cutting amount can be reduced.

On the contrary, when the feed speed is increased, it can be predicted that the cutting thrust and the torque increase. This phenomenon can be interpreted as a result of the increase of the cutting force because the cutting cross-sectional area increases at the cutting point per unit rotation.

Therefore, considering this fact, considering the Fig. 3, the processing feed rate interpolation considering the direction of the specimen can be performed. That is, the arrangement of the carbon fibers 110 may preferably be such that the feed rate is lowered and the number of revolutions (rpm) is increased when the cutting process is performed perpendicular to the direction (processing condition 1). On the other hand, when the machining direction and the cutting direction are parallel, the feed rate can be increased and the number of revolutions can be increased.

The composition for such processing conditions is set so that the carbon fiber differs depending on factors such as surface roughness, straightness, roundness, burr formation, defect layer, etc. which affect the life of the structure disposed in the prepreg Lt; / RTI >

As one of these models, according to the fracture mechanics model, the tool operating condition setting can be made by predicting the minimum thrust which does not cause machining error by using the thrust generated in machining and reflecting the machining condition 1 or 2 in machining condition 1 or 2.

Further, in order to apply appropriate processing conditions according to whether or not the arrangement direction of the carbon fibers is vertical or parallel as described above, the ply constituting the composite material may be arranged in a direction perpendicular to the processing direction.

The fibrous material contained in the composite material may be arranged in one direction as shown in Fig. 3, or may be in a form having mutual orientation angles of 45 or 90 degrees.

And, the processing speed of the spindle as referred to herein may be one that includes the rotational speed and the conveying speed, as described above. The feed rate may be a direction parallel to the machining direction.

4 is a perspective view showing a structure of a material having a different lamination structure according to another embodiment of the present invention.

Referring to FIG. 4, the first through fourth ply 102, 104, 106, and 108 may form an angle of 45 degrees between the upper and lower layers.

5 is a cross-sectional view schematically showing a modification of processing conditions according to the constitution of a material having different lamination structures according to another embodiment of the present invention.

Referring to FIG. 5, fibrous materials having different orientations according to their heights are aligned, and the processing conditions can be set to the processing conditions 1 to 4, respectively.

The machining conditions 1 to 4 may be machining conditions for the feed rate and the number of revolutions of the spindle. It is possible to change or adjust processing conditions depending on the configuration of the material constituting each layer, such as surface roughness, straightness, roundness, burr formation, defect layer and the like.

A control device for a machine tool in consideration of the orientation of a workpiece according to an embodiment of the present invention includes a support for arranging a workpiece, a spindle disposed on the support, and a computer numerical control device electrically connected to the spindle (CNC), and an acceleration measurement sensor electrically connected to the computer numerical control apparatus.

In a control device of a machine tool in consideration of the directionality of a work, a support for supporting the work may be a jig for fixing the work. When the material is a jig having a curved surface, the shape of the jig can be changed according to the shape.

The computer numerical control device (CNC) may be a device for controlling the feed speed and the rotation speed acting on the spindle. To explain more simply, the orientation of the workpiece can be predicted from the acceleration signal measured through the acceleration sensor and the machining conditions can be changed.

Accelerometer (acceleration sensor, Accelerometer) has been applied to various sensors since the material with piezoelectric effect was discovered by French Pierre Brothers. When the mass attached on the piezo-electric material moves, the inertia force acting on the piezoelectric element is measured, and the vibration acceleration is measured by dividing the inertia force by the inertia mass. In principle, the fastening method is particularly important so that the accelerometer can be attached most positively to a vibrating object and vibrate together. In the conventional accelerometer, a charge amplifier is used to amplify the minute charge of pC (pico coulomb) unit generated by the sensor in a unit that can be seen by a meter. In recent years, an amplification circuit is inserted in the sensor, An ICP sensor (or Voltag type sensor) that generates this mV unit is used. The acceleration sensor according to an embodiment of the present invention may use an acceleration sensor of the ICP type.

6 is a graph showing measurement of vibration occurring during processing of a composite material, which is an embodiment of the present invention.

Referring to FIG. 6, the acceleration measurement sensor may be configured to measure two signals.

The two signals may include a signal 20 having a large amplitude and a signal having a small amplitude. It can be judged that the processing directions are not coincident with each other when the signal 20 having a large amplitude is measured from the accelerometer. If a signal 20 having a large amplitude is found from the accelerometer sensor, the processing condition can be adjusted so that the value measured from the accelerometer sensor can be changed to a signal 10 with a small amplitude. The sensitivity of such an accelerometer sensor may be about 10 to 1000 mV / g depending on conditions.

The interpolation for this machining speed is a result of reflecting the results measured from the vibration accelerometer sensor measured during machining with the spindle.

In the apparatus for processing a laminated material according to an embodiment of the present invention, a sensor for measuring a direction of the laminated material, a spindle for receiving a control signal from the sensor and processing the laminated material, And a CNC (Computer Numerical Control) control device for transmitting a machining signal to the spindle.

The layered material may be one in which the layers are arranged in a direction perpendicular to the processing direction including a directional material. I. E. The multiple layers of directional material may comprise ply 202, 204, 206, 208 comprising carbon fibers.

The sensor for measuring the directionality of the material may measure the vibration signal converted according to the directionality of the material and feed back the vibration signal to calculate the control signal. With these sensors it is easy to use (vibration) acceleration measurement sensors, for example.

More specifically, the sensor for measuring the directionality of the laminate material can perform a role of interpolating the processing speed by measuring the vibration signal.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: composite material 110: fiber
102: first ply 104; Second fly
106: third fly 108: fourth fly
200: second composite material

Claims

A method of controlling a machine tool in consideration of material directionality,
Disposing the composite material on the machine tool (s10);
Disposing a spindle on the machining position with respect to the composite material (s20);
Machining the composite material while moving the spindle (s30);
Determining (S40) the orientation of the composite material during processing of the composite material; And
And changing the machining speed of the spindle when the direction of the composite material is changed (s50)
Wherein the step of determining the directionality of the composite material is performed by a sensor for measuring the directionality of the material, and the sensor for measuring the directionality of the material measures a vibration signal to be converted in accordance with the directionality of the material, And a control signal is calculated by feedback of the control signal.

The method according to claim 1,
The composite material,
(CFRP) or glass fiber reinforced plastic (GFRP). 2. A method of controlling a machine tool according to claim 1, wherein the carbon fiber reinforced plastic (CFRP) or glass fiber reinforced plastic (GFRP) is used.

The method according to claim 1,
The composite material,
Wherein the resin ply having different orientations is oriented in a direction perpendicular to a machining direction.

The method of claim 3,
Wherein the resin ply having different orientations are mutually oriented at an angle of 45 ° or 90 °.

The method according to claim 1,
Wherein the machining speed of the spindle includes a rotation speed and a feed speed.

In a control device of a machine tool in consideration of the directionality of a material,
A support for placing the material;
A spindle disposed on said support;
A computer numerical control (CNC) electrically connected to the spindle; And
And an acceleration measurement sensor electrically connected to the computer numerical control device,
Wherein the acceleration sensor measures a vibration signal converted according to a direction of the workpiece and feeds back the vibration signal to calculate a control signal.

The method according to claim 6,
The material is formed in a laminated structure,
And a fiber is contained in the laminated structure.

8. The method of claim 7,
Wherein the fiber includes glass fiber or carbon fiber. 2. A control apparatus for a machine tool according to claim 1, wherein the fiber comprises glass fiber or carbon fiber.

The method according to claim 6,
Wherein the acceleration sensor includes a piezoelectric element for converting external vibrations into an inertial force.

In a method of processing a laminated material,
Stacking the oriented material (s110);
Disposing the material in the processing apparatus (s120);
Machining the material into a spindle of a machining apparatus (s130); And
And controlling the operation of the spindle (S140) if the orientation of the workpiece is changed,
In the step (S140) of controlling the operation of the spindle, the orientation of the workpiece is measured by a sensor, and the sensor for measuring the orientation of the workpiece measures a vibration signal converted according to the orientation of the workpiece, And calculating a control signal based on the control signal.

11. The method of claim 10,
Wherein controlling the operation of the spindle (s140) comprises adjusting the feed rate of the spindle or the rotational speed of the spindle.

In a processing apparatus for a laminate material,
A sensor for measuring the directionality of the laminate material;
A spindle for receiving a control signal from the sensor and processing the layered material; And
And a CNC (Computer Numerical Control) controller for receiving a control signal from the sensor and transmitting a machining signal to the spindle,
Wherein the sensor for measuring the directionality of the workpiece measures a vibration signal converted according to the directionality of the workpiece and feeds back the vibration signal to calculate a control signal.

13. The method of claim 12,
Wherein the plurality of layers of the layered material include directional materials and are arranged in a direction perpendicular to the processing direction.

delete

13. The method of claim 12,
The sensor for measuring the directionality of the laminate-
And a vibration signal is measured to interpolate the machining speed.