A control method for automatic chip breaking of a numerical control system

Abstract

The present application relates to the technical field of numerical control machining, in particular to a control method for automatic chip breaking of a numerical control system, in the process of executing a vibration chip breaking machining program, a numerical control machine tool superimposes vibration based on the X-axis direction of a workpiece on a preset machining track, and combines a spindle speed floating control mode to realize automatic chip breaking while ensuring machining quality, through the use of the control method of axial fluctuation plus spindle floating chip breaking, the function of automatic chip breaking can be realized on the basis of ensuring machining efficiency, not only can the machining quality of parts be improved, tool damage, machine tool damage and part surface finish caused by chip winding can be avoided, but also human accidents caused thereby can be avoided, the machining quality of parts is more stable, the machining process is more convenient and reliable, and a strong guarantee is provided for the establishment of an automated production line.

Description

Technical Field

[0001] This invention relates to the field of CNC machining technology, specifically a control method for automatic chip breaking in a CNC system. Background Technology

[0002] During CNC machine tool machining, excessively long chips are frequently generated. These chips can cause injuries, including cuts and burns. Fragmented chips are particularly dangerous because they can splatter and injure the eyes and other sensitive areas. If operators do not wear appropriate protective equipment or are accidentally entangled in chips, serious injuries may occur. Fragmented chips can also damage machine tool guideways, leading to wear or damage to the equipment. Furthermore, long, ribbon-like chips can become entangled in the workpiece or cutting tool, affecting the normal cutting process and potentially causing tool breakage. Accumulated chips can also affect machining quality, as they may scratch already machined surfaces, reducing product precision and quality. Simultaneously, the presence of chips can hinder the proper spraying of cutting fluid, further impacting machining results.

[0003] Benefiting from advancements in control technology, many CNC systems on the market now offer automatic chip breaking functionality. The main principle is to dynamically adjust the cutting speed during machining, causing fluctuations in speed and resulting in uneven cutting volume per unit time. This produces chips of varying widths, which easily break during the spindle's rotation. This chip breaking method is called floating speed chip breaking. However, this technology also has significant drawbacks. Frequent acceleration and deceleration reduce machining efficiency, which is highly detrimental to product processing. The parts manufacturing industry prioritizes both efficiency and quality; reduced efficiency significantly impacts customer output, increases production costs, and ultimately diminishes product competitiveness. Summary of the Invention

[0004] To address the aforementioned problem that frequent acceleration and deceleration in existing CNC systems using floating speed chip breaking methods reduce machining efficiency and affect machining quality, the technical solution adopted by this invention is as follows: A control method for automatic chip breaking in a CNC system is applied to a CNC machine tool used for cutting machining. The depth direction of the workpiece is defined as the X-axis, and the length direction of the workpiece is defined as the Z-axis. The method is characterized by: Control methods include: It accepts special instructions for vibration chip breaking based on CNC machine tools and executes the vibration chip breaking machining program; Vibration based on the X-axis direction of the workpiece is superimposed on the preset machining trajectory so that the tool changes the width of the chip based on the vibration during cutting, thereby achieving automatic chip breaking. By introducing a floating spindle speed control, the spindle speed is adjusted during the machining process, thereby improving chip breaking efficiency and surface finish while ensuring the cutting speed. Repeat the above steps until the roughing is completed, then control the tool to perform finishing on the workpiece.

[0005] Furthermore, the radial vibration includes periodic vibration and aperiodic vibration. The aperiodic vibration is based on the periodic vibration with the addition of a random number b, so that the tool will remove the ridges left by the previous cutting each time it cuts, thereby achieving the effect of controlling the maximum cumulative cutting amount.

[0006] Furthermore, the vibration chip breaking command includes P parameter, Q parameter and R parameter, wherein the P parameter specifies a machining axis as the vibration axis, the Q parameter specifies the vibration frequency, and the R parameter specifies the vibration amplitude and vibration direction.

[0007] Furthermore, the periodic vibration is a sinusoidal wave vibration, a triangular wave vibration, or a trapezoidal wave vibration.

[0008] Furthermore, before the step of accepting the vibration chip breaking special instruction based on the CNC machine tool and executing the vibration chip breaking machining program, the following steps are also included: The CNC system acquires the tool information and tool position of the currently loaded tool on the CNC machine tool, as well as the machining information of the current workpiece, and controls the tool turret to return to a safe position.

[0009] Furthermore, the CNC machine tool is a CNC lathe, and the workpiece processed by the control method is a rotating body.

[0010] Furthermore, the processing trajectory can be expressed as equation (1). F(t,x)=f(t,x)+g(t)(1) Where F(t,x) is the actual machining trajectory, f(t,x) is the tool machining trajectory, and g(t) is the vibration trajectory.

[0011] Furthermore, the vibration trajectory g(t) can be expressed as equation (2). g(t) = 0.5 [g1(kt+b)+sign(kt)g1(kt+b)](2) Where k is the vibration period and b is a random number, so that the vibration trajectory g(t) becomes a non-periodic function.

[0012] Furthermore, the vibration based on the X-axis direction of the workpiece is radial vibration.

[0013] Furthermore, the spindle speed floating control adopts a long-period floating change control strategy.

[0014] The beneficial effects of the embodiments of the present invention are as follows: 1. This invention utilizes a control method combining axial undulation and a floating spindle for chip breaking, achieving automatic chip breaking while maintaining machining efficiency. This not only improves the machining quality of parts and prevents tool damage, machine tool damage, and deterioration of part surface finish caused by chip entanglement, but also avoids potential personal injury accidents. The resulting machining quality is more stable, and the machining process is more convenient and reliable, providing a strong guarantee for building automated production lines.

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0016] Figure 1 This is a detailed flowchart of the first embodiment of the present invention.

[0017] Figure 2 This is a detailed flowchart of the second embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the processing trajectory amplitude according to the present invention.

[0019] Figure 4 This is a schematic diagram of another processing trajectory amplitude according to the present invention.

[0020] Figure 5 This is a structural coordinate diagram of a control method for automatic chip breaking in a CNC system according to the present invention. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] First embodiment: like Figure 1 , Figures 3 to 5 As shown, a control method for automatic chip breaking in a CNC system is applied to a CNC machine tool used for cutting machining. The depth direction of the workpiece is defined as the X-axis, and the length direction of the workpiece is defined as the Z-axis. The method is characterized by: Control methods include: S11. Accept special instructions for vibration chip breaking based on CNC machine tools and execute the vibration chip breaking machining program; S12. Vibration based on the X-axis direction of the workpiece is superimposed on the preset machining trajectory so that the tool changes the width of the chip based on the vibration during cutting, thereby achieving automatic chip breaking. S13. Introduce a floating spindle speed control to adjust the spindle speed during machining, thereby improving chip breaking efficiency and surface finish while ensuring the cutting speed. S14. Repeat the above steps until the roughing is completed, then control the tool to perform finishing on the workpiece.

[0023] Specifically, in some embodiments, based on a thorough study of the machining characteristics of lathes, this invention proposes a control method for axial ripple combined with spindle floating chip breaking. Lathe machining generally employs rotary machining, producing workpieces that are mostly rotating bodies. Chip breaking is typically required during the roughing stage of the outer surface of the part. Therefore, we designed a sinusoidal vibration superposition in the X-axis of the CNC system control, superimposing a sinusoidal vibration in the X-axis direction outside the normal machining trajectory. like Figure 1 As shown, where Figure 1 Curve 1 is the programming path, and curve 2 is the path after the vibration chip breaking function is superimposed. The vibration takes the machining trajectory as the trough point of the vibration, so it will not affect the machining dimensions.

[0024] The principle of vibration chip breaking can be expressed as follows: Let the machining trajectory of the tool be f(t,x) and the vibration trajectory be g(t), then the actual machining trajectory can be expressed as equation (1). F(t,x)=f(t,x)+g(t)(1) In equation (1), t represents time and x represents the machining dimension along the x-axis. Usually, during the roughing of a part, the tool will continuously increase the depth along the same machining trajectory in the x-direction until the surface contour designed for the workpiece is reached. Therefore, during repeated machining, the tool trajectory formed by the cumulative cutting of F(t,x) is still enveloped by f(t,x). At the same time, the workpiece surface has ridge marks formed by the residual uncut parts caused by the vibration trajectory g(t). These residues can be removed by finishing with f(t,x).

[0025] analyze Figure 1 It is known that when the tool continuously cuts the workpiece surface, the peaks and troughs of the blue curve appear at the same point (i.e., the peak is always a peak, and the trough is always a trough). Therefore, the peaks can never be cut, resulting in aggregation, and thus the final contour is the blue curve. However, this is not the ideal effect that this invention aims to achieve. Figure 2 As shown, in order to prevent surface residues caused by vibration of the vibration trajectory g(t) from accumulating at the same location, to avoid very high residual ridges when the machining depth is deep, and to avoid excessive cutting amount during finishing cutting that causes vibration, this invention further optimizes the vibration trajectory g(t): g(t) = 0.5 [g1(kt+b)+sign(kt)g1(kt+b)](2) In formula (2), k is the vibration period, b is a random number, when sign(kt)=1, then g(t)=g1(kt+b), when sign(kt)=-1, then g(t)=0, the following relational expression (3) is provided: (3) Therefore, the vibration trajectory g(t) is an aperiodic function, which allows the vibration trajectory g(t) to randomly appear at any position. In this manner, there is still a possibility that a wave peak or wave trough appears at the same point, but the randomness of each occurrence ensures that it will not repeatedly appear at the same point, and each occurrence point is different. Therefore, the maximum accumulated cutting amount will not exceed one time the vibration amplitude, thereby solving the problem that vibration residues accumulate at the same position; The improved effect is as Figure 2 shown. Since the vibration trajectory g(t) is random, each cutting operation will remove the residues left by the previous cutting, and the final remaining residues are only determined by the last cutting path, so that the final surface residual quality can be controlled; To further improve chip breaking quality, we simultaneously add spindle speed floating control to the automatic chip breaking control method. It is known from the basic knowledge of machine tool machining that when the feed rate is constant and the spindle speed is constant, the width of the machined chip is consistent. Therefore, changing any one of the feed rate and the spindle speed can achieve the change of chip width. The conventional method adopts adjusting the feed rate instead of the spindle speed, because the spindle speed determines the cutting linear speed, and a large adjustment of the spindle speed will result in the cutting linear speed failing to reach the standard, which may damage the CNC machine tool itself. Under the solution of the present invention, with the support of vibration chip breaking that already realizes the chip breaking function, we only need to adjust the spindle speed in a small range to further improve the chip breaking quality on the premise of ensuring the cutting linear speed, and the final machining has the following relational expression (4): F(t,x,s)=f(t,x,s)+g(t) (4) In formula (4), s is the spindle speed, which adopts the form of long-period floating variation. With the dual support of radial vibration and spindle speed floating, the optimal chip breaking effect can be obtained.

[0026] Specifically, in some embodiments, to make it easier for users to get started, the present invention develops a dedicated vibration chip breaking instruction G4.8, the dedicated vibration chip breaking instruction is G4.8, and the dedicated vibration chip breaking instruction includes a P parameter, a Q parameter and an R parameter, the specific parameter contents are as follows P_ : Specify the vibration axis, 0 - off, 1 - X axis, 2 - Z axis, 3 - XZ axis; Q_ : Specify the vibration frequency 0<Q<=600 (times / minute); R_: Specifies the specified vibration amplitude 0<R<=10 (mm), where the ± sign indicates the vibration direction; In use, the user only needs to input the instruction G4.8 Pxx Qxx Rxx in the machining program of the numerical control system to activate the vibration chip breaking function. After machining is completed, the vibration chip breaking function is deactivated using G4.8 P0. No other machining programs need to be modified or adjusted. The operation is simple and user-friendly, can be conveniently integrated into the existing machining system, and reduces the learning threshold and usage barrier for users.

[0027] Second embodiment: Different from the first embodiment, in this embodiment, the tool is moved to a safe position before executing the vibration chip breaking machining program.

[0028] As Figure 2 shown, before the step of receiving the special vibration chip breaking instruction based on the numerical control machine tool and executing the vibration chip breaking machining program, the method further comprises: S10. Obtain the tool information and tool position of the currently loaded tool of the numerical control machine tool, as well as the machining information of the current workpiece, and the numerical control system controls the tool turret to return to the safe position.

[0029] The user can manually input the tool information, tool position and workpiece machining information after manually replacing the tool, or after the numerical control machine tool automatically performs tool change, the numerical control system obtains the tool information from the tool turret and obtains the tool position and workpiece machining information from the numerical control machine tool. After obtaining the above information, the numerical control system controls the drive system to drive the tool turret to execute the program of returning to the safe position, so as to avoid possible tool collision accidents or other collision accidents caused by directly executing the machining program, improve the safety of the machining process, and further protect the numerical control machine tool.

[0030] The above description only further illustrates the technical content of the present invention through embodiments to facilitate the reader's understanding, but does not limit the embodiments of the present invention thereto. Any technical extension or re-creation made based on the present invention shall fall within the protection scope of the present invention, which shall be determined by the appended claims.

Claims

1. A control method for automatic chip breaking in a CNC system, applied to a CNC machine tool used for cutting machining, wherein the depth direction of the workpiece is defined as the X-axis and the length direction of the workpiece is defined as the Z-axis, characterized in that: Control methods include: It accepts special instructions for vibration chip breaking based on CNC machine tools and executes the vibration chip breaking machining program; Vibration based on the X-axis direction of the workpiece is superimposed on the preset machining trajectory so that the tool changes the width of the chip based on the vibration during cutting, thereby achieving automatic chip breaking. By introducing a floating spindle speed control, the spindle speed is adjusted during the machining process, thereby improving chip breaking efficiency and surface finish while ensuring the cutting speed. Repeat all the above steps until the roughing is completed, then control the tool to perform finish machining on the workpiece; Wherein, the vibration based on the X-axis direction of the workpiece being processed is radial vibration; The radial vibration includes periodic vibration and aperiodic vibration. The aperiodic vibration is based on the periodic vibration with the addition of a random number b, so that the tool will remove the ridges left by the previous cutting each time it cuts, thereby achieving the effect of controlling the maximum cumulative cutting amount.

2. The control method according to claim 1, characterized in that: The vibration chip breaking command includes P parameter, Q parameter and R parameter. The P parameter specifies a machining axis as the vibration axis, the Q parameter specifies the vibration frequency, and the R parameter specifies the vibration amplitude and vibration direction.

3. The control method according to claim 1, characterized in that: The periodic vibration is a sinusoidal wave vibration, a triangular wave vibration, or a trapezoidal wave vibration.

4. The control method according to claim 1, characterized in that: Before the step of accepting the vibration chip breaking special command based on the CNC machine tool and executing the vibration chip breaking machining program, the following steps are also included: The CNC system acquires the tool information and tool position of the currently loaded tool on the CNC machine tool, as well as the machining information of the current workpiece, and controls the tool turret to return to a safe position.

5. The control method according to claim 1, characterized in that: The CNC machine tool is a CNC lathe, and the workpiece processed by the control method is a rotating body.

6. The control method according to claim 1, characterized in that: The processing trajectory can be expressed as equation (1). F(t,x)=f(t,x)+g(t)(1) Where F(t,x) is the actual machining trajectory, f(t,x) is the tool machining trajectory, and g(t) is the vibration trajectory.

7. The control method according to claim 6, characterized in that: The vibration trajectory g(t) can be expressed as equation (2). g(t)=0.5 [g1(kt+b)+sign(kt)g1(kt+b)](2) Where k is the vibration period and b is a random number, so that the vibration trajectory g(t) becomes a non-periodic function.

8. The control method according to claim 1, characterized in that: The spindle speed floating control adopts a long-period floating change control strategy.

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