A control method for automatic chip breaking by using long period floating variation strategy

Abstract

The application relates to the technical field of numerical control machining, in particular to a control method for automatic chip breaking by adopting a long-period floating change strategy, 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 machining workpiece on a preset machining track, and a spindle speed floating control mode is combined to realize automatic chip breaking under the condition of ensuring machining quality; by using 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, machining quality of parts can be improved, tool damage, machine tool damage and part surface roughness caused by chip winding can be avoided, and better chip breaking effect can be achieved under the double-layer support of radial vibration and spindle speed floating by adjusting the spindle speed and adopting the long-period floating change strategy; under the premise of ensuring the cutting linear speed, the chip breaking quality is further improved.

Description

[0001] This application is a divisional application of application number 2024106063402 filed on May 16, 2024, entitled "A control method for automatic chip breaking in a CNC system". Technical Field

[0002] This invention relates to the field of CNC machining technology, specifically a control method for automatic chip breaking using a long-cycle floating change strategy. Background Technology

[0003] 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.

[0004] 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

[0005] 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 employing a long-period floating variation strategy is applied to a CNC system controlling a CNC machine tool. The CNC machine tool is used for cutting operations, defining the workpiece depth direction as the X-axis and the workpiece length direction as the Z-axis. The control method includes: 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. 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; The spindle speed floating control adopts a long-period floating change control strategy, which can be expressed as equation (4) by combining equation (1) with the final machining of the spindle speed: F(t,x,s)=f(t,x,s)+g(t)... ...(4) Where s is the spindle speed.

[0006] The control method for automatic chip breaking using a long-period floating change strategy, as described above, includes P parameters, Q parameters, and R parameters in the dedicated vibration chip breaking command. 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] The control method for automatic chip breaking using a long-period floating change strategy, as described above, uses sinusoidal wave vibration, triangular wave vibration, or trapezoidal wave vibration.

[0008] The control method for automatic chip breaking using a long-period floating change strategy as described above further includes, before the step of receiving a vibration chip breaking instruction based on a CNC machine tool and executing the vibration chip breaking machining program: 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] The control method described above, which employs a long-period floating change strategy to implement automatic chip breaking, uses a CNC lathe as the CNC machine tool and a rotating body as the workpiece processed by the control method.

[0010] As described above, in a control method for automatic chip breaking using a long-period floating change strategy, 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.

[0011] The beneficial effects of this invention are as follows: This invention utilizes a control method combining axial undulation and a floating spindle for chip breaking. This method achieves automatic chip breaking while maintaining machining efficiency, improving part quality and preventing tool and machine damage and deterioration of part surface finish caused by chip entanglement. It also avoids personal injury accidents. Furthermore, by adjusting the spindle speed and adopting a long-cycle floating variation strategy, combined with radial vibration and spindle speed fluctuation, an even better chip breaking effect can be achieved. While maintaining the cutting speed, the chip breaking quality is further improved, resulting in more stable part quality and a more convenient and reliable machining process. This provides a strong guarantee for building automated production lines. Attached Figure Description

[0012] Figure 1 This is a detailed flowchart of the first embodiment of the present invention.

[0013] Figure 2 This is a detailed flowchart of the second embodiment of the present invention.

[0014] Figure 3 This is a schematic diagram of the processing trajectory amplitude according to the present invention.

[0015] Figure 4 This is a schematic diagram of another processing trajectory amplitude according to the present invention.

[0016] Figure 5 This is a structural coordinate diagram of a control method for automatic chip breaking that employs a long-period floating change strategy according to the present invention. Detailed Implementation

[0017] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] First embodiment: like Figure 1 , Figures 3 to 5As shown, a control method for automatic chip breaking using a long-period floating change strategy is applied to a CNC system controlling a CNC machine tool. The CNC machine tool is used for cutting operations. 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 control method includes: 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.

[0019] 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.

[0020] 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).

[0021] analyze Figure 1It 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 equation (2), k is the vibration period and b is a random number. When sign(kt) = 1, then g(t) = g1(kt + b). When sign(kt) = -1, then g(t) = 0. The relationship is expressed as follows in equation (3): ... ...(3) Therefore, the vibration trajectory g(t) is a non-periodic function, which allows the vibration trajectory g(t) to appear randomly at any position. Even with this method, it is still possible for peaks or troughs to appear at the same point, but the randomness of each occurrence ensures that it will not repeat at the same point. Each occurrence point is different, so the maximum cumulative cutting amount will not exceed one times the vibration amplitude, thus solving the problem of vibration residue accumulating at the same position. The improved effect is as follows Figure 2 As shown, since the vibration trajectory g(t) is random, each cut will remove the residue from the previous cut, and the final remaining residue is determined only by the last cutting path, thus the final surface residue quality can be controlled. To further improve chip breaking quality, we also added spindle speed floating control to the automatic chip breaking control method. As we know from the basic knowledge of machine tool processing, when the feed rate and spindle speed are constant, the cutting width is consistent. Therefore, changing either the feed rate or the spindle speed can change the chip width. The traditional method uses the feed rate instead of the spindle speed because the spindle speed determines the cutting linear speed. A large adjustment of the spindle speed will cause the cutting linear speed to be substandard, which may damage the CNC machine tool itself. Under the scheme of this invention, due to the support of vibration chip breaking, the chip breaking function can be achieved. Therefore, we only need to adjust the spindle speed slightly to further improve the chip breaking quality while ensuring the cutting linear speed. The final processing has the following relationship expression (4): F(t,x,s)=f(t,x,s)+g(t)... ...(4) In equation (4), s is the spindle rotational speed, which adopts a form of long-period floating variation. Under the dual superposition of radial vibration and spindle speed floating, the optimal chip breaking effect can be achieved.

[0022] Specifically, in some embodiments, to make it easier for users to get started, the present invention develops a dedicated instruction G4.8 for vibration chip breaking. The dedicated instruction for vibration chip breaking is G4.8, and the dedicated instruction for vibration chip breaking includes a P parameter, a Q parameter and an R parameter. The specific parameter contents are as follows P_: Specifies the vibration axis, 0 - off, 1 - X axis, 2 - Z axis, 3 - XZ axis; Q_: Specifies the vibration frequency 0<Q<=600 (times per minute); R_: Specifies the vibration amplitude 0<R<=10 (mm), 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 enable the vibration chip breaking function. After machining is completed, G4.8 P0 is used to turn off the vibration chip breaking function. There is no need to modify and adjust other machining programs. It is simple and easy to use, can be conveniently connected to the existing machining system, and reduces the learning threshold and use threshold for users.

[0023] Second Embodiment: The difference from the first embodiment is that in this embodiment, the tool is moved to a safe position before executing the vibration chip breaking machining program.

[0024] As Figure 2 shown, before the step of receiving the dedicated instruction for vibration chip breaking based on the numerical control machine tool and executing the vibration chip breaking machining program, the method further includes: S10. Acquire the tool information and tool position of the currently loaded tool of the numerical control machine tool and acquire the machining information of the current workpiece, and the numerical control system controls the tool post disc to return to the safe position.

[0025] The user can manually replace the tool and then input the tool information, tool position and workpiece machining information by himself, or after the numerical control machine tool automatically changes the tool, the numerical control system acquires the tool information from the tool post disc and acquires the tool position and workpiece machining information from the numerical control machine tool. After acquiring the above information, the numerical control system controls the drive system to drive the tool post disc 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.

[0026] The above examples are merely illustrative of the technical content of the present invention to facilitate easier understanding by the reader, but do not imply that the implementation of the present invention is limited to these examples. Any technical extensions or re-creations made based on the present invention are protected by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A control method for automatic chip breaking using a long-period floating change strategy, applied to a CNC system controlling a CNC machine tool, wherein the CNC machine tool is 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, 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. 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 machining trajectory of the tool, and g(t) is the vibration trajectory; The spindle speed floating control adopts a long-period floating change control strategy, which can be expressed as equation (4) by combining equation (1) with the final machining of the spindle speed: F(t,x,s)=f(t,x,s)+g(t)... ...(4) Where s is the spindle speed.

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 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.

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