Processing method

Abstract

[Problem] To prevent relative positions of a first tool and a second tool from being shifted when the first tool and the second tool are made to face each other with a workpiece therebetween and unevenness is to be formed on the workpiece. [Solution] In the present invention, when forming unevenness on a workpiece P1 through incremental molding in a state in which a first tool 31 is disposed on a first side of the workpiece and a second tool 32 is disposed on a second side of the workpiece opposite to the first side, a processing point t1 on the first side and a processing point t2 on the second side are provided as a pair, and the movement speed from the processing point to the next processing point is set such that the arrival times of the two tools at the pair of processing points are the same time by using the difference between the movement distances of the first tool and the second tool.

Description

Processing method

[0001] The present invention relates to a processing method.

[0002] Parts such as vehicle body panels are produced not only by press working using a mold but also by a method that does not use a mold when producing only a small amount of parts like repair parts, and such a processing method can be called die-less forming (incremental forming).

[0003] Incremental forming is a method that applies sequential forming in which a plate material is gradually deformed by a tool attached to a robot or the like. In the prior art related to incremental forming, in the case of incrementally forming a plate-like workpiece with a front-side tool and a back-side tool, a step of generating data for the front-side tool, a step of generating data for the back-side tool, and a synchronization data generation step of synchronizing the front-side data and the back-side data are disclosed (see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2020-144513

[0005] When performing incremental forming on a plate material as in Patent Document 1, since the distances traveled by the front-side tool and the back-side tool are different when moving the front-side and back-side tools in an opposing trajectory via a plate-like workpiece (workpiece to be processed), it is difficult to move the two tools exactly opposite to each other.

[0006] An object of the present invention is to prevent the relative positions of the first tool and the second tool from shifting when forming concavities and convexities on a workpiece by opposing the first tool and the second tool via the workpiece to be processed.

[0007] One aspect of the present invention is a processing method. In this processing method, the first tool is arranged on the first side of the workpiece to be processed, and the second tool is arranged on the second side opposite to the first side with respect to the workpiece to be processed, and concavities and convexities are formed on the workpiece to be processed by incremental forming. The processing points on the first side and the processing points on the second side are provided in pairs. The moving speed from one processing point to the next processing point is set using the difference in the moving distances of the first tool and the second tool so that the arrival times of the two tools at the paired processing points are the same.

[0008] According to the above processing method, when forming irregularities on a workpiece by facing the first tool and the second tool across the workpiece, the relative positions of the first tool and the second tool can be prevented from shifting.

[0009] This is a block diagram showing the apparatus configuration of the machining method according to the embodiment. This is a side view corresponding to Figure 2, a perspective view showing the apparatus configuration of the machining method according to the embodiment. This is a schematic diagram showing a state in which the first tool and the second tool are arranged facing each other with the workpiece in between. This is a schematic diagram showing the machining paths of the first tool and the second tool at a certain height. This is a flowchart for setting the movement trajectories of the first tool and the second tool used in the machining method according to the embodiment. This is a flowchart for setting the movement speed of the first tool and the second tool used in the machining method according to the embodiment.

[0010] (Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. In the drawings, the same reference numerals are used for identical components, and redundant descriptions are omitted. In the drawings, the size and proportions of each component are exaggerated to facilitate understanding of the embodiments and may differ from the actual size and proportions.

[0011] Figure 1 is a block diagram showing the apparatus configuration of the processing method according to this embodiment. Figure 2 is a perspective view showing the apparatus configuration of the processing method according to this embodiment. Figure 3 is a side view corresponding to Figure 2. Figure 4 is a schematic diagram showing a state in which the first tool 31 and the second tool 32 are arranged facing each other with respect to the workpiece P1.

[0012] The processing method according to this embodiment can be used, for example, for large parts such as car body panels, when mass production of parts such as repair parts is not required. The sequential forming according to this embodiment can also be called incremental forming (die-less forming) because it forms the workpiece P1 without using a mold. By using incremental forming to form the workpiece P1 and suppressing springback, it is possible to manufacture relatively high-precision products at a relatively low cost. The material of the workpiece P1 is not particularly limited, but aluminum, which is prone to springback, can be used.

[0013] As shown in Figure 1, the apparatus configuration of the processing method according to this embodiment includes an input unit 10, a storage unit 20, a molding unit 30, and an apparatus control unit 40. Further details will be described below.

[0014] (Input Unit) The input unit 10 is used for operators to input and instruct the shape of the final product formed from the workpiece P1, the contents to be stored in the memory unit 20, the processing areas of the first tool 31 and the second tool 32 constituting the molding unit 30, and the control contents of the device control unit 40. The input unit 10 may include at least one of a mouse, keyboard, touchscreen, etc. Furthermore, the device used in the sequential molding method according to this embodiment may be able to communicate with the internet or the like, or be able to connect to storage media such as various disks or memory sticks, thereby enabling the acquisition of shape data such as drawings of the parts to be manufactured.

[0015] (Memory Unit) The memory unit 20 is configured to store information such as the physical properties of the workpiece P1 input and instructed by the operator and the application required for incremental molding, the shape of the final product, molding information from the molding unit 30, and control content from the device control unit 40. The memory unit 20 may include RAM (Random Access Memory) or ROM (Read Only Memory). The memory unit 20 can store point cloud data obtained by converting CAD (Computer-Aided Design) data input by the input unit 10, position information data modified from said data, tool speed data, etc. The memory unit 20 can store drawing data, part shape data as design data, and tool trajectory data calculated by the device control unit 40, etc.

[0016] (Forming Unit) The forming unit 30 is configured to form the workpiece P1 under the control of the device control unit 40 based on the tool trajectory stored in the memory unit 20. The forming unit 30 may include, as an example, a multi-axis robot with a rod-shaped tool or the like attached to its tip.

[0017] The molding section 30 includes a first tool 31 positioned on one side (first side) of the workpiece P1, as shown in Figure 3, and a second tool 32 positioned on the opposite side (second side) of the workpiece P1 from the first tool 31. The first tool 31 and the second tool 32 can be configured as rod-shaped tools attached to the tip of an NC (Numerical Control) machining center.

[0018] Furthermore, as shown in Figure 2 and other figures, the molding unit 30 may include a multi-axis robot, a fixing base 33 for fixing the workpiece P1, a jig 34 for fixing the workpiece P1 to the fixing base 33, and the like.

[0019] In this embodiment, when forming an uneven shape on a workpiece P1, the first tool 31 can be a processing tool positioned inside the uneven shape as shown in Figure 4, and the second tool 32 can be a support tool.

[0020] (Device Control Unit) The device control unit 40 includes a CPU (Central Processing Unit) and is configured to control the input unit 10, the storage unit 20, and the molding unit 30. The device control unit 40 can perform incremental molding on the workpiece P1 using the molding unit 30 based on information such as the material, thickness, and shape of the workpiece P1, as well as the tool trajectory, which is stored in the storage unit 20 via the input unit 10.

[0021] The incremental molding process performed by the device control unit 40 on the workpiece P1 can be stored as a program in the storage unit 20.

[0022] Here, when machining the workpiece P1 using the first tool 31 and the second tool 32, the first tool 31 and the second tool 32 move around the workpiece P1 in accordance with the shape to be formed (see Figure 4). However, the distance required to form a predetermined shape differs between the tool located on the inside and the tool located on the outside. Therefore, if the first tool 31 and the second tool 32 are to be moved along the same trajectory, it is not possible to position the first tool 31 and the second tool 32 at the corresponding positions required to form a predetermined shape at each given time interval.

[0023] Therefore, the inventors conceived of using the difference in travel distance between the support tool and the machining tool to set the two tools to arrive at the next (paired) machining point at the same time from a given machining point. This makes it possible to move the first tool 31 and the second tool 32 in correspondence so that they align without deviating from their predetermined positional relationship, and to stably and accurately reproduce a predetermined shape.

[0024] Here, we will explain the program for setting the movement trajectories and speeds of the first tool 31 and the second tool 32. First, we will explain the movement trajectories of the first tool 31 and the second tool 32. Figure 5 shows the machining points t1 and t2 of the first tool 31 (machining tool) and the second tool 32 (support tool) at a certain height. Figure 6 is a flowchart for setting the movement trajectories of the first tool 31 and the second tool 32. Figure 7 is a flowchart for setting the movement speeds of the first tool 31 and the second tool 32.

[0025] In this program, CAD data is first output as CAM (Computer-Aided Manufacturing). For example, CAD data composed of surfaces is converted into point cloud data. Then, machining paths for the first tool 31 and the second tool 32 are created on the workpiece P1 (S11 in Figure 6). Here, the destination coordinates of the first tool 31 and the second tool 32 included in the machining path are called machining points t1 and t2. Machining points t1 and t2 can be set as a pair on the support side and the machining side (see Figure 5).

[0026] Then, the machining paths of the first tool 31 and the second tool 32, which form recesses in the workpiece P1, are divided in the height direction into one rotation at the same height coordinate in each rotation (S12). Then, machining points in the divided machining paths that fall within a certain error range are omitted (S13).

[0027] Here, machining points are omitted using the Douglas-Peucker method to ensure the required precision. The Douglas-Peucker method involves plotting the start and end points, connecting them with a line, searching for points that are more than a certain tolerance away from this line, plotting the furthest points, connecting the points that are plotted, and repeating the above process. By processing in this way, machining time can be reduced and speed increased by reducing the number of machining points while maintaining precision. The coordinate space can be defined as a Cartesian coordinate system. Also, the spaces between points can be interpolated with straight lines or curves.

[0028] Then, from among the machining points of the second tool 32, which is the support side, the point whose polar coordinate Θ is closest to the machining point of the first tool 31, which is the machining side, is selected and the path of the support tool in terms of its height coordinate is determined (S14). The path creation of the second tool 32 is performed for all height coordinates Z of the first tool 31 (S15: NO). Note that the position in polar coordinates can be defined by coordinate transformation in the space of the Cartesian coordinate system. Once the path creation of the second tool 32 is completed for all height coordinates Z of the first tool 31 (S15: YES), the program is terminated.

[0029] Furthermore, when the machining point is provided by a set of first tool 31 and second tool 32, the machining points on the machining side and the support side can be selected from those whose polar coordinates Θ are closest to the centroid of their respective circumferences. By configuring it in this way, the amount of positional displacement between the first tool 31 and the second tool 32 can be minimized.

[0030] Next, we will explain how to set the speeds of the first tool 31 and the second tool 32. First, the speed of the second tool 32 is set to the maximum speed of the NC machining center (S21 in Figure 7). Then, the operating speed of the NC machining center on the first tool 31 side, where the second tool 32 and the first tool 31 arrive simultaneously, is calculated from the difference in the path length when the second tool 32 and the first tool 31 are moved to the next machining point (S22).

[0031] Here, the movement speeds of the first tool 31 and the second tool 32 can be set such that the second tool 32, which has a longer movement path, operates at the maximum speed of the NC machining center, while the speed of the first tool 31, which has a shorter movement path, is set lower than that of the second tool 32. By configuring it in this way, the first tool 31 and the second tool 32 can be synchronized while circling around a certain height coordinate Z as quickly as possible.

[0032] Furthermore, the movement speeds of the first tool 31 and the second tool 32 can also be calculated by solving an algebraic equation, such as a linear equation, based on the difference in the movement distances of the first tool 31 and the second tool 32 and the operating speed of the NC machining center. This configuration enables synchronous operation of the NC machining center.

[0033] Furthermore, the movement speeds of the first tool 31 and the second tool 32 can be calculated by solving a linear programming problem based on the difference in the movement distances of the first tool 31 and the second tool 32 and the operating speed of the NC machining center. By configuring it in this way, the amount of synchronous deviation of the NC machining center up to the next machining point can be minimized over the entire rotation.

[0034] The process described above determines the operating path of the first tool and the operating speed of the NC machine at each point, and these results are used to create a program for the NC machine for the entire rotation (S23). After the program for the entire rotation is completed, the two NC machines are set to simultaneously start the program operation for the next rotation (S24). By configuring it in this way, the operations of the first tool 31 and the second tool 32 can be synchronized to form the workpiece P1 into the intended shape.

[0035] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. In the above explanation, the program is divided into units of a certain height coordinate, and the simultaneous start of the next program by the machining side and the support side tools marks the beginning of a lap. However, the unit of program division is not limited to the same height; the machining path may be divided into several laps of the same height, and the support side and the machining side tools may be started simultaneously for each divided unit.

[0036] Furthermore, the following embodiments are also included in the scope of the present invention: the processing method according to claim 1 having the features of claim 2; the processing method according to claim 1 or claim 2 having the features of claim 3; the processing method according to any one of claims 1 to 3 having the features of claim 4; the processing method according to any one of claims 1 to 4 having the features of claim 5; the processing method according to any one of claims 1 to 4 having the features of claim 6; and the processing method according to any one of claims 1 to 4 having the features of claim 7.

[0037] 31 first tool, 32 second tool, P1 workpiece, t1, t2 processing points.

Claims

1. A machining method in which, when forming irregularities on a workpiece by incremental molding with a first tool positioned on the first side of the workpiece and a second tool positioned on the second side opposite to the first side of the workpiece, the machining points on the first side and the machining points on the second side are provided as a pair, and the speed of movement from one machining point to the next machining point is set using the difference in the travel distance of the first tool and the second tool so that the two tools arrive at the paired machining points at the same time.

2. The machining method according to claim 1, wherein the program for the trajectory in which the first tool and the second tool orbit is divided into one orbit consisting of coordinates of the same height, and after the programmed operation of the first tool and the second tool is completed, the program for the next orbit is started simultaneously.

3. The machining method according to claim 1 or claim 2, wherein the machining points on the first and second sides are selected from those whose polar coordinate θ is closest to the centroid of their respective circumferences.

4. The machining method according to claim 1, wherein the machining point on the first side is omitted using the Douglas-Peucker method to satisfy a predetermined accuracy.

5. The machining method according to claim 1, wherein the speeds of the first tool and the second tool are calculated by solving an algebraic equation based on the difference in travel distance between the first tool and the second tool and the operating speed of the NC machining center.

6. The machining method according to claim 1, wherein the speeds of the first tool and the second tool are calculated by solving a linear programming problem based on the difference in travel distance between the first tool and the second tool and the operating speed of the NC machining center.

7. The machining method according to claim 1, wherein, if the travel distance of the second tool is longer than the travel distance of the first tool, the second tool is operated at the maximum speed of the NC machining center and the speed of the first tool is reduced.

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