JP2005144563A - Making method of work manufacturing error model and making method of nc data for cutting work using work manufacturing error model made by this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily make a manufacturing error model of a work for cutting work in a short time. <P>SOLUTION: Moving locus data of the center of a tip surface of a first tool model is made when moving the tip surface of the semispherical first tool model having the tip surface having a predetermined radius R1 along a surface of a manufacturing error nonexistent model 11 by abutting on the surface of the manufacturing error nonexistent model 11 of the work. Next, the manufacturing error model of the work is made on the basis of a moving locus of a tip surface of a second tool model 13 when moving the semispherical second tool model 13 having a tip surface having a radius R2 (= R1-E) smaller by a manufacturing error E of the work than the predetermined radius R1 so that a moving locus of the center P2 of the tip surface of the second tool model 13, coincides with a central moving locus of the tip surface of the first tool model. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for creating a workpiece manufacturing error model necessary for considering the manufacturing error of a workpiece when the workpiece is cut using an NC machine tool, and cutting using the workpiece manufacturing error model created by the method. The present invention belongs to a technical field related to a method for creating machining NC data.

  In general, in machining by an NC (numerical control) machine tool, a workpiece is arranged on the tip side of a rotary machining tool such as an end mill that rotates about a central axis extending in a predetermined direction, and a predetermined path ( Cutting is performed by moving along the route according to NC data. At this time, the tool feed speed is normally constant and is set to a speed corresponding to the portion with the largest cutting load.

However, when the tool feed rate is constant as described above, there is a problem that the machining time becomes long. Therefore, conventionally, as shown in Patent Document 1, for example, it has been proposed to control the tool feed rate so that the cutting amount per blade of the tool becomes constant.
JP 2002-200540 A

  However, even if the tool feed rate is controlled as described above, there is a manufacturing error in the workpiece. Therefore, if the manufacturing error is not taken into consideration, the load increases rapidly while the tool is moving at a high feed rate. There is a possibility and there is room for improvement.

  Therefore, in order to consider the manufacturing error, a manufacturing error model is created that is enlarged by the manufacturing error as a whole with respect to the workpiece-free manufacturing error model. Using this manufacturing error model, the tool position on the tool movement path is set. It is conceivable that a corresponding cutting amount is obtained and the tool feed speed is set according to the cutting amount.

  However, although the above-mentioned model without manufacturing error can be easily obtained from data at the time of manufacturing the workpiece such as the cavity and dimensions of the mold for casting the workpiece, the manufacturing error model is usually manufactured using a CAD system. It is necessary to create each model of the error-free model by offsetting or transforming the solid model, and such work has a problem that it takes a lot of time.

  The present invention has been made in view of such a point, and an object of the present invention is to make it possible to create a manufacturing error model of a workpiece for cutting easily and in a short time.

  In order to achieve the above object, according to the first aspect of the present invention, a manufacturing error of a workpiece for cutting that is disposed on the tip side of a rotary machining tool that rotates about a central axis extending in a predetermined direction and is machined by the tool. A method of creating a workpiece manufacturing error model for creating a model, wherein the tip surface of the first tool model in which the tip surface forms a hemisphere having a predetermined radius is used as the tool model. Creating a movement trajectory data of the center of the tip surface of the first tool model when the model is brought into contact with the surface of the model and moved along the surface of the model without manufacturing error; A second tool model in which the tip surface has a hemispherical shape having a radius smaller than the predetermined radius by the manufacturing error of the workpiece, the movement locus of the center of the tip surface of the second tool model is the first tool model. Creating a manufacturing error model of the workpiece based on the movement locus of the tip surface of the second tool model when the tool model is moved so as to coincide with the center movement locus of the tip surface of the tool model. did.

  As a result, the tip surface of the first tool model is brought into contact with the surface of the workpiece-free model and moved along the surface of the model without the manufacturing error, whereby the center of the tip surface of the first tool model ( The movement locus of the center of the hemisphere is located away from the surface of the model with no manufacturing error by a predetermined radius, and the movement locus of the center of the tip surface of the second tool model is the center of the tip surface of the first tool model. Since the movement locus coincides with the movement locus, the movement locus of the tip surface of the second tool model is located away from the surface of the model with no production error by the production error, and the production error model is determined from this movement locus. can get. Such movement trajectory data can be easily obtained by using a CAM system, and each surface of a model with no manufacturing error can be offset using the CAD system (the work of connecting the offset surfaces is complicated). Compared to a method of creating a workpiece manufacturing error model by deforming a solid model, a workpiece manufacturing error model can be created easily and in a short time.

  In the invention of claim 2, as a method of creating NC data for cutting, a workpiece manufacturing error model created by the workpiece manufacturing error model creating method of claim 1 and a workpiece manufacturing error model created in advance for cutting the workpiece. When a workpiece having the same size as the workpiece manufacturing error model is cut by a tool that operates according to the initial NC data, based on the initial NC data including the moving path of the rotary machining tool and a constant feed speed, Obtaining a cutting amount corresponding to a tool position on the tool movement path, setting a tool feed rate at the tool position according to the cutting amount, and setting the tool feed rate of the initial NC data to the set tool feed rate A step of creating NC data for cutting by correcting to the speed.

  This makes it possible to easily and quickly obtain the optimum tool feed speed that takes into account the manufacturing error by using the workpiece manufacturing error model, and at the same time the tool is moving at a relatively fast tool feed speed. The cutting time of the workpiece can be shortened while preventing a sudden increase.

  According to a third aspect of the present invention, in the second aspect of the present invention, before the step of obtaining a cutting amount, the workpiece manufacturing error model is generated by a tool that operates according to the initial NC data based on the workpiece manufacturing error model and the initial NC data. The method further includes a step of performing a machining simulation when cutting a workpiece having the same size as.

  In this way, the interference between the workpiece and the tool can be checked by machining simulation. If there is an interference between the workpiece and the tool, the tool moving path of the initial NC data is changed and the cutting amount is calculated in the step. The cutting amount may be obtained based on the initial NC data after the change. Therefore, the operator of the machine tool becomes unnecessary, and cutting can be performed automatically.

  As described above, according to the present invention, it is possible to create a manufacturing error model of a workpiece easily and in a short time, and by using this manufacturing error model, an optimum tool feed speed considering the manufacturing error can be obtained. It can be obtained easily and in a short time, and the machining time can be easily shortened while preventing the load from rapidly increasing while the tool is moving at a relatively fast tool feed speed.

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

  FIG. 1 shows an NC machine tool that is arranged on the tip side of a rotary machining tool 2 (such as an end mill) that rotates about a central axis extending in a predetermined direction (in this embodiment, the vertical direction) and is cut by the tool 2. A cutting work 1 is shown. The workpiece 1 is a casting, and includes a rectangular portion 1a and a circular portion 1b provided on the upper surface of the rectangular portion 1a. And the cutting part 1c which is a part (upper part from the dashed-two dotted line shown in FIG. 1) of the upper surface side of the circular part 1b of the said workpiece | work 1 with the said tool 2 shall be cut. In addition, the workpiece | work 1 does not need to be a casting and what kind of thing may be sufficient as long as it can cut.

  Prior to the cutting process, a manufacturing error model of the workpiece 1 is created. This creation method will be described below.

  First, as shown in FIG. 2, a model 11 having no manufacturing error of the workpiece 1 (obtained from the shape data of the mold cavity for forming the workpiece 1) obtained from a CAD (computer-aided design) system, and the tool 2 As a model, a first tool model 12 (corresponding to a ball end mill having a tip tool radius R1) whose tip surface has a hemispherical shape having a predetermined radius R1 is the same position as when the workpiece 1 is cut by the tool 2. Arranged in the relationship, the tip surface of the first tool model 12 is brought into contact with the surface of the model 11 without manufacturing error and moved along the surface of the model 11 without manufacturing error. In this way, movement trajectory data of the center P1 (center of the hemisphere) of the tip surface of the first tool model 12 is created. As shown by the one-dot chain line in FIG. 2, this movement locus is located away from the surface of the model 11 without manufacturing error by a predetermined radius R1. Such movement trajectory data can be easily obtained by using a CAM (computer-aided production) system. That is, the movement trajectory data can be easily obtained from NC data when the cavity of the mold for forming the workpiece 1 is cut by the ball end mill having the tip tool radius R1. The predetermined radius R1 may be any value, but if the surface of the model 11 having no manufacturing error has a dent or a corner, the predetermined radius R1 can be made to contact the inner surface of the dent or the corner. A smaller value is preferable. However, it must be larger than the manufacturing error E described later.

  Subsequently, as shown in FIG. 3, as a model of the manufacturing error-free model 11 and the tool 2, the tip surface has a manufacturing error E of the workpiece (the maximum value of the manufacturing error that can occur (for example, 10 mm)) and a second tool model 13 (corresponding to a ball end mill with a tip tool radius R2) having a radius R2 (= R1-E) that is smaller by the same amount as that when cutting the workpiece with the tool. The second tool model 13 is arranged in a positional relationship, and the movement locus of the center P2 (the center of the hemisphere) of the tip surface of the second tool model 13 is the movement of the center P1 of the tip surface of the first tool model 12. Move to match the trajectory. A manufacturing error model 14 (see FIG. 5) is created based on the movement locus of the tip surface of the second tool model 13 at this time. That is, when the point on the innermost side (the model 11 side without manufacturing error) of the movement locus of the tip surface of the second tool model 13 is connected, the manufacturing error E (= R1−R2) is obtained with respect to the surface of the model 11 without manufacturing error. A surface separated by a distance (see the broken line in FIG. 3) is obtained, and this surface constitutes the surface of the manufacturing error model 14.

  More specifically, as shown in FIG. 4, the model 11 without manufacturing error is a rectangular parallelepiped model 15 (so-called Z-map model) that is composed of a large number of line segments extending in the vertical direction and is larger than the manufacturing error model 14. The first tool model 12 is replaced with the second tool model 13, and the cuboid model is used as the second tool model 13 by using NC data when the cavity of the mold for forming the workpiece 1 is cut. 15 is scraped off. What remains is the manufacturing error model 14 (see FIG. 5).

  Next, using the manufacturing error model 14, cutting NC data for cutting the workpiece 1 is created. This creation method will be described with reference to FIG.

  That is, in the first step S1, the data of the model 11 without manufacturing error of the workpiece 1 and the shape data after cutting the workpiece 1 are taken from the CAD system into the CAM system, and the tool movement path is calculated. Subsequently, in step S2, the calculated value is converted into a format suitable for the NC machine tool to create initial NC data. The initial NC data includes a fixed tool feed speed in addition to the tool movement path.

  In the next step S3, based on the manufacturing error model 14 and the initial NC data created in step S2, the work 1 having the same size as the manufacturing error model 14 is cut by the tool 2 operating according to the initial NC data. Processing simulation is performed. That is, the model of the tool 2 is moved on the display screen, and the interference check between the workpiece 1 and the tool 2 is performed.

  In the present embodiment, such interference does not occur. For example, the cutting portion 21a (the portion above the two-dot chain line) of the workpiece 21 having a shape as shown in FIG. 7 (b), in the manufacturing error model 24 of the workpiece 21, the vertical wall portion 21b of the workpiece 21 It can be seen that the part of the tool 22 without a blade interferes. In FIG. 7B, 26 is a model of the tool 22, and 27 is a model with no error of the workpiece 21.

  If there is such interference, the tool moving path is changed to create new initial NC data. In the case of the example in FIG. 7, the tool moving path is changed so that the standing wall 21 b is cut first while the tool 22 is moved downward, and then the cutting portion 21 a is cut.

  In the next step S4, a tool feed speed optimization process is performed. Specifically, first, based on the manufacturing error model 14 and the initial NC data (if there is interference, new initial NC data after changing the tool movement path), the initial NC A cutting amount (cutting volume) corresponding to the tool position on the tool movement path when the workpiece 1 having the same size as the manufacturing error model 14 is cut by the tool 2 operating according to the data is obtained. Then, the tool feed speed at the tool position is set in accordance with the cutting amount, and the NC feed data for cutting is created by correcting the tool feed speed of the NC data to the set tool feed speed.

  In this embodiment, assuming that the tool 2 is moved in the horizontal arrow direction from the side of the cutting part 1c of the workpiece 1 to cut the cutting part 1c, as shown in FIG. And the cutting amount is obtained from the tool model 16 which is a model of the tool 2. That is, as shown in FIG. 8B, the cutting amount is zero until the tool model 16 comes into contact with the manufacturing error model 14, and the cutting amount as the tool model 16 moves from the contact position. From the point of movement of the tool model 16 from the contact position, the amount of cutting is constant. As a result, as shown in FIG. 8 (c), the tool feed speed is made relatively fast (the speed is slightly slowed just before the contact) until the tool model 16 comes into contact with the manufacturing error model 14. As the tool model 16 moves from the contact position, the speed is gradually decreased, and from a position moved from the contact position by the diameter of the tool model 16, a relatively slow constant tool feed speed is set. Then, the same operation as that of the tool model 16 is performed on the tool 2 to actually machine the workpiece 1.

  As another example of cutting, the tool 32 is moved in the direction of the arrow (downward) in the cutting part 31a (the part surrounded by a two-dot chain line) of the workpiece 31 having a shape as shown in FIG. 9B, if the workpiece 31 has the same size as the manufacturing error model 34 of the workpiece 31, as shown in FIG. 9B, before the cutting portion 31a is cut, It is necessary to cut the standing wall 31b of 31. Therefore, the tool feed speed is made relatively high until the tool model 36 which is a model of the tool 32 comes into contact with the manufacturing error model 34 (the portion corresponding to the standing wall portion 31b) (the speed is slightly reduced just before contact). ) The tool model 36 is set to a relatively slow constant feed speed until the tool model 36 contacts the upper surface of the portion corresponding to the cutting portion 31a of the manufacturing error model 34 from the contact position. Therefore, a slower constant tool feed speed is set.

  Here, if the manufacturing error is not taken into account using the manufacturing error model 14 (34) as described above, the load abruptly comes into contact with the workpiece 1 (31) while the tool 2 (32) is moving at a high speed. It can grow. However, since the manufacturing error model 14 (34) is created and the manufacturing error is taken into account as in this embodiment, such a problem is eliminated and cutting is always performed with an appropriate load. Processing time can be shortened. Further, by performing a machining simulation using the manufacturing error model 14 (24), it is possible to check the interference between the workpiece 1 (21) and the tool 2 (22), eliminating the need for a machine tool operator, and automatically Cutting can be performed.

  Then, the manufacturing error model 14 (24, 34) as described above creates movement locus data of the center of the tip surface of the first tool model 12, and the movement locus of the center of the tip surface of the second tool model 13 is the above-described movement locus data. The CAD system can be easily created based on the movement locus of the tip surface of the second tool model 13 when moved so as to coincide with the center movement locus of the tip surface of the first tool model 12. The manufacturing error model of the workpiece 1 (21, 31) can be obtained by offsetting each surface of the model 11 without manufacturing error (complicating the operation of connecting the offset surfaces to each other) or by deforming the solid model. The manufacturing error model 14 (24, 34) of the workpiece 1 (21, 31) can be created easily and in a short time compared to the method of creating.

  The present invention is useful when, for example, a tool feed speed is made variable according to a cutting amount corresponding to a tool position on a tool movement path when a workpiece is cut using an NC machine tool.

It is a perspective view which shows an example of the workpiece | work for a cutting process which produces a manufacturing error model with the workpiece manufacturing error model preparation method concerning embodiment of this invention. It is a figure which shows the point which produces the movement locus data of the center of the front end surface of a 1st tool model. It is a figure which shows the point which produces the manufacturing error model of a workpiece | work based on the movement locus | trajectory of the front end surface of a 2nd tool model. It is a figure which shows the state before scraping off the rectangular parallelepiped model comprised by many line segments extended in an up-down direction with a 2nd tool model. It is a figure which shows the state which scraped off the rectangular parallelepiped model with the 2nd tool model, and the manufacturing error model was completed. It is a flowchart which shows the procedure which produces the NC data for cutting for cutting a workpiece | work. It is a figure which shows an example of a process simulation. It is a figure which shows the relationship between a tool position, a cutting amount, and a tool feed rate. It is a figure which shows the other example of a cutting process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work 2 Tool 11 No manufacturing error model 12 1st tool model 13 2nd tool model 14 Manufacturing error model 21 Work 22 Tool 24 Manufacturing error model 31 Work 32 Tool 34 Manufacturing error model

Claims (3)

A workpiece manufacturing error model creation method for creating a manufacturing error model of a workpiece for cutting that is disposed on the tip side of a rotary machining tool that rotates about a central axis extending in a predetermined direction and is cut by the tool,
As the model of the tool, the tip surface of the first tool model whose tip surface has a hemispherical shape having a predetermined radius is brought into contact with the surface of the model without manufacturing error of the workpiece, and the surface of the model without manufacturing error. Creating movement trajectory data of the center of the tip surface of the first tool model when moved along
As a model of the tool, a second tool model in which the tip surface has a hemispherical shape having a radius smaller than the predetermined radius by the manufacturing error of the workpiece, a movement locus of the center of the tip surface of the second tool model is used. Creating a manufacturing error model of the workpiece based on the movement trajectory of the tip surface of the second tool model when the tool is moved so as to coincide with the center movement trajectory of the tip surface of the first tool model; A method for creating a workpiece manufacturing error model, comprising: An initial NC including a workpiece manufacturing error model created by the workpiece manufacturing error model creating method according to claim 1 and a moving path of a rotary machining tool and a constant feed speed created in advance for cutting the workpiece. A cutting amount corresponding to a tool position on the tool movement path when a workpiece having the same size as the workpiece manufacturing error model is cut by a tool operating according to the initial NC data based on the data; ,
Creating a cutting NC data by setting a tool feed speed at the tool position according to the cutting amount and correcting the tool feed speed of the initial NC data to the set tool feed speed. A method of creating NC data for cutting, comprising: In the preparation method of NC data for cutting of Claim 2,
Before the step of obtaining the cutting amount, based on the workpiece manufacturing error model and the initial NC data, a machining simulation in which a workpiece having the same size as the workpiece manufacturing error model is cut by a tool that operates according to the initial NC data The method for creating NC data for cutting, further comprising the step of

Images