JPH07260464A - Method and apparatus for judgment of assembling possibility of work - Google Patents

Abstract

PURPOSE:To obtain a method and an apparatus which can judge the assembling possibility of a work on the basis of actually measured data on the shape of the work, in accordance with a maximum entity tolerance system, at low costs, without being limited by the shape, a production quantity or the like and so as to be capable of grasping the capacity of a process. CONSTITUTION:A work assembling-possibility judgment system 100 receives theoretical shape data 7 and size tolerance data (including a geometrical tolerance) 4 from a CAD system 3 regarding a work as an object whose assembling possibility is to be judged, and it finds a size (an effective size) when an allowable condition is most stringent in the assembling operation of the work. On the other hand, the system 100 receives actual shape data 2 on the work from a coordinate measuring machine 1, and it finds a shape parameter on a body part including the tolerance of the work. The shape parameter is compared with the effective size, and the assembling possibility of the work is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work assembly possibility determination device, and more particularly to a method for determining whether a work can be assembled with a mating part based on actual shape data obtained by actually measuring the work. And equipment.

[0002]

2. Description of the Related Art In recent years, application of the maximum material tolerance method (JIS B0023-1984) has been rapidly progressing in the instruction of tolerances on mechanical drawings. In the conventional tolerance instruction system, there is a case where the assembly is not always possible even if the manufacturing is performed as instructed in the drawings due to a difference in interpretation, accumulation of errors, and the like. However, by adopting the maximum material tolerance method, it has become possible to assemble the parts and ensure compatibility with each other during mass production. Moreover, it is possible to strictly verify whether or not the component manufactured by this tolerance method can be assembled by a functional gauge (a gauge that simulates the most severe condition of the mating component to be assembled). The functional gauge is easy to operate and has high inspection efficiency, so it is very effective in mass production lines.

On the other hand, in the field of inspection, a coordinate measuring machine typified by a coordinate measuring machine has recently become popular. The reason for this is that compared to conventional calipers and micrometers, anyone can easily measure the size and shape of a wide variety of workpieces with high accuracy, and flexible automation can also be realized. That's why.

In the coordinate measuring machine, the surface of the work is sampled by a contact sensor using a touch trigger or a non-contact sensor using light as a medium, and is input to a computer as spatial coordinate data. In the electronic computer, the coordinate data is straight line, circle, plane, cylinder,
Substituting into the equations of the corresponding multidimensional shape elements such as cones and spheres, the shape parameters (for example, position, orientation, dimensions, etc.) are calculated by the method of least squares. For example, when a cylinder is considered as the shape element, the position is the coordinate of an arbitrary point on the central axis, the posture is the direction vector of the central axis, and the dimension is the radius. Geometric deviations such as squareness and parallelism can also be calculated from the shape parameters of a plurality of individually calculated shapes. It is determined whether or not the work can be assembled by comparing the results of these calculations with the dimensions and tolerances shown in the drawings.

In the future, it is expected that the coordinate measuring machine will occupy the mainstream of inspection due to the speeding up and cost reduction of electronic computers.

[0006]

The conventional techniques as described above have the drawbacks that the functional gauge has a high manufacturing cost and is difficult to manufacture in the case of a component having a complicated shape. Therefore, there is a problem in that the application is limited to parts having a sufficiently large production amount and a relatively simple shape. Further, the functional gauge inspection shows only the judgment result of goodness or badness, and it does not appear as a numerical value as to how good or bad. Therefore, the original purpose of the inspection is
It was extremely difficult to understand how the process capability of the manufacturing process is changing.

On the other hand, in the coordinate measuring machine, the method of judging the assembling possibility based on the maximum material tolerance method has not been sufficiently established. Therefore, even if the actual size obtained by the measurement is within the specified tolerance range of the drawing, there is a problem that it is not possible to immediately determine whether or not the component can be assembled with the mating component.

As described above, in the prior art, it was extremely difficult to judge the practical assembling ability in accordance with the maximum material tolerance method. Moreover, as described above, the function gauge and the coordinate measuring machine have their respective drawbacks, and both must be used together in order to make the inspection truly effective.
It was also a major obstacle in terms of inspection efficiency.

The present invention has been made in view of such problems, and is based on the actual measurement data of the work shape and is not limited to the shape, the production amount, etc. at a low cost in accordance with the maximum material tolerance method.
Moreover, it is an object of the present invention to provide a method and an apparatus for determining a workability of assembling a work capable of grasping process capability.

[0010]

According to the present invention, in the inspection using a coordinate measuring machine which has become mainstream in recent years, in order to truly achieve its effect, the maximum value is determined based on the actual shape data of the actually measured work. Recognizing that it is an important issue to judge the assembling possibility according to the substantive tolerance method, the result of earnest research,
The inventor of the present invention first discovered the method and completed the method.

That is, according to the method of the present invention, when determining whether or not the work can be assembled with the mating work to which the work is to be assembled, based on the actual shape data of the work obtained by actually measuring the work, The first step of calculating the effective size of the part from the size and geometrical tolerance specified for the part to be assembled with the mating work, and the part of the actual shape data specified as the datum feature in the geometrical tolerance. Of the actual shape data, the second step of calculating the shape parameter of the datum feature portion from the actually obtained shape data and the shape parameter obtained in the second step as constraint conditions Third step of calculating the shape parameter of the feature part with tolerance based on the actual shape data obtained by actually measuring the part designated as the feature with tolerance in the geometrical tolerance When, the effective dimensions obtained in the first stage and is characterized by comprising a fourth step of comparing the shape parameters obtained in at least the third stage.

Further, the apparatus of the present invention determines, based on the actual shape data of the work obtained by actually measuring the work, whether or not the work can be assembled with the other work to be assembled. , From the dimensions and geometrical tolerances specified for the part to be assembled with the mating workpiece,
First calculation means for calculating an effective dimension of the portion, input means for inputting actual shape data obtained by actually measuring the portion of the work, and of the actual shape data, as a datum feature at the geometrical tolerance. Second calculation means for calculating the shape parameter of the datum feature part from the actual shape data obtained by actually measuring the designated part, and the shape parameter obtained by the second calculation means as constraint conditions, Of the actual shape data, third calculation means for calculating the shape parameter of the feature portion with tolerance based on the actual shape data obtained by actually measuring the portion designated as the feature with tolerance in the geometrical tolerance, It is characterized in that it comprises an effective dimension obtained by the first arithmetic means and a judging means for comparing at least the shape parameter obtained by the third arithmetic means.

[0013]

According to the present invention, assembling of a work specified by the maximum material tolerance method from actual shape data measured using a coordinate measuring machine such as a three-dimensional measuring machine by an arithmetic means such as an electronic calculator. Possibility can be determined stably, accurately in a short time.

Therefore, as compared with the conventional function gauge, it is possible to judge the assemblability of any work accurately, at a much lower cost, and regardless of the complexity of the shape and the amount of production. Further, since the actual shape data obtained by the coordinate measuring machine is used, it is not necessary to use it together with the function gauge, and the efficiency of inspection can be improved. Further, since the judgment is made by comparing the effective dimension with the calculated actual dimension, the result can be understood as a numerical value, not just the quality, and the process capability can be grasped at the same time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a work assembly possibility determination method and apparatus according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the outline of the present invention. The CAD system 3 stores CAD data of a work whose assembly possibility is to be determined. From this, theoretical shape data 7 and dimensional tolerance data 4 of an assembly portion, which will be described later, are input to the system 100. When the drawing is only paper, it may be manually input by an input means such as a keyboard. The coordinate measuring machine 1 measures the assembly part of the work and inputs the result to the system 100 as the work actual shape data 2 represented by the data of the coordinate sequence, for example. In addition,
The coordinate measuring machine 1 may have any structure or sensor system. Any measuring device may be used as long as the coordinate data on the surface of the work can be digitally obtained. Based on the above input data, the system 100 determines whether the work can be assembled, and returns the result 6 to the measurer 5. Result 6 is
It shows not only good or bad, but also how good or bad it is as a numerical value.

The principle and method for realizing FIG. 1 will be described below with reference to specific examples. The target of the present invention is when the geometrical tolerances shown in Table 1 are specified.

[0018]

[Table 1]

As shown in this table, the geometrical tolerances to which the present invention is applied are roughly classified into posture tolerances and position tolerances. The geometrical tolerances include parallelism, squareness, and inclination. The tolerance includes position degree, coaxiality, concentricity, and symmetry. Due to space limitations, typical examples in the table will be described, but the same applies to cases other than those illustrated.

FIG. 2 shows an example of a drawing in which the posture tolerance is designated. In the work 10, the end face 11 is used as a datum (reference), and the squareness tolerance 13 is specified in the hole 12 which is a feature with tolerance by the maximum material tolerance method (indicated by a circle M). “⊥” indicates a squareness tolerance. Dimensions are added to the hole 12. In the example shown, the diameter φ is 40
Dimensions including upper and lower limit tolerances are specified, such as +0.1 mm to 40 +0.2 mm. This description of the squareness tolerance 13 indicates that the center line of the hole 12 should be included in a cylinder having a diameter of 0.3 mm which is perpendicular to the end face 11. The work 20 is a partner work that is assembled to the work 10. The dimensions and tolerances of the work 20 are omitted. In fact, the assemblability determination method of the present invention does not require data of the assembly target work. The end surface 11 and the end surface 21, and the hole 12 and the shaft 22 are portions that come into contact with each other during assembly. Therefore, the assembly portion of the work 10 is the end surface 11 and the hole 12.

FIG. 3 shows the principle of judging the assembling possibility based on the tolerance shown in FIG. (A) shows the effective state of the work 10 shown in FIG. The effective state is the limit state of assembling that is caused by the combined effect of geometrical tolerance and dimensional tolerance, and the dimension in this state is called the effective dimension.
In this example, φ39.8 indicated by reference numeral 13 is the effective dimension. Since this effective size is the size of the hole, the most severe condition in terms of assembly possibility is the lower limit of the diameter φ4.
An effective dimension of φ39.8 can be obtained by considering the squareness tolerance of φ0.3 with respect to 0 + 0.1. (B) is the work 10
The actual shape of is exaggerated. Reference numerals 14 and 16
Are actual shapes corresponding to the end face 11 and the hole 12 in FIG. 2, respectively.

In order to determine whether or not it is possible to assemble, first, the parameters (position, orientation, etc.) of the plane 15 are calculated from the actual shape data obtained by measuring the actual shape 14 corresponding to the end face 11. Next, a constraint condition that is perpendicular to the obtained plane is given to obtain the real shape 16 corresponding to the hole 12.
The diameter of the cylinder 17 is calculated from the actual shape data of In this case, since it is a hole, the cylinder 17 is calculated as the maximum inscribed cylinder, but in the case of an axis, it may be calculated as the minimum circumscribed cylinder. Also, shapes with dimensions other than cylinders (keyways, etc.)
Is similarly calculated. The same applies to cases other than this example.

If the diameter 18 of the cylinder 17 obtained at this time is not less than the effective dimension 13, it can be determined that this work can be assembled. Furthermore, since the dimensions (in this case, the diameter 18 and the effective dimension 13) are obtained as numerical values, it is possible to easily grasp how good or bad they are.

FIG. 4 shows an example of a drawing in which the posture tolerance is similarly given. However, it differs from FIG. 2 in that the maximum substance tolerance is also given to the datum. Reference numeral 30 is a sectional view of the work, and reference numeral 39 is a front view. The hole 31 is a datum and is given a dimension 32. With the hole 31 as a datum (reference), the parallelism tolerance 35 is specified by the maximum material tolerance method in the hole 33 that is a feature with tolerance. Hole 3
Dimension 34 is given for 3.

FIG. 5 shows the principle of judging the assembling possibility from the tolerance shown in FIG. (A) shows the effective state of the work shown in FIG. In this example, the effective dimensions of the datum 31 and the tolerance feature 33 of FIG. 4 are the values indicated by reference numerals 48 and 47, respectively. Effective size 47
Is the lower limit of the diameter dimension 34 shown in FIG.
Is reflected. (B) is a figure which shows the shape of an actual work. Reference numerals 41 and 42 are actual shapes corresponding to the datum 31 and the tolerance feature 33 of FIG. 4, respectively.
In order to determine whether the assembling is possible, first, the parameters (position, posture, dimensions, etc.) of the cylinder 43 are calculated from the actual shape data obtained by measuring the actual shape 41. In this case, since it is a hole, it is calculated as the maximum inscribed cylinder. Next, the dimension of the maximum inscribed cylinder 44 is calculated from the actual shape data of the actual shape 42 by giving a constraint condition such that it is parallel to the obtained cylinder. Again, if it is a shaft instead of a hole,
Similarly, it may be calculated as the minimum circumscribed cylinder. The diameters 45 and 46 obtained by the above are effective dimensions 48 and 47, respectively.
If it is above, it can be determined that this work can be assembled. Furthermore, it is easy to understand how good or bad it is.

FIG. 6 shows an example of a drawing in which the position tolerance is designated. A position degree tolerance 66 in which the datums are planes 61, 63 and 64 is designated in the hole 65 (62 in the right side view) in the plan view. Note that, by definition, datums have a priority order, in this case 61, 63, 64. A dimensional tolerance 67 is specified for the hole 65.

FIG. 7 shows the principle of judging the assembling possibility from the tolerance shown in FIG. 6A shows the effective state of the work shown in FIG. In this example, the effective dimension of the feature 62 with tolerance shown in FIG. 6 is 9.8 as a result of reflecting the position tolerance 66 on the lower limit of the diameter dimension 67 of FIG.
However, this cylinder is at a right angle to the plane 61 of FIG. 6 and must be in a predetermined dimensional position from the planes 63 and 64.

(B) is a diagram showing an actual work. Reference numerals 71, 72, 73 and 74 are reference numerals 61 and 61 in FIG. 6, respectively.
It is a real shape corresponding to 62, 63, and 64.

To determine whether or not the assembly is possible, first, the parameters of the plane 75 are calculated from the actual shape data obtained by measuring the reference numeral 71. Next, a constraint is given so that the plane 75 becomes a right angle, and the parameters of the plane 77 are similarly calculated from the actual shape data of reference numeral 73. further,
Similarly, the above 7
The parameters of the plane 78 are calculated from the real shape data of No. 4. In this way, the parameters of all the planes forming the datum can be obtained. Next, the diameter 79 of the maximum inscribed cylinder 76 having an axis that is perpendicular to the plane 75 and is at a distance of 30 from the plane 77 and a distance of 20 from the plane 78 is calculated. The diameter 79 obtained by the above is the effective size φ
If it is 9.8 or more, it can be determined that this work can be assembled. Furthermore, it is easy to understand how good or bad it is.

The principle of the present invention has been described with reference to some examples. In any case, it is important to calculate the maximum inscribed dimension or the minimum circumscribed dimension from the actual shape with some restrictions on the position and orientation. Conventionally, it has been extremely difficult to stably and quickly obtain the maximum inscribed dimension and the minimum inscribed dimension under such constraint conditions. In view of this problem, the present inventors have considered a method and apparatus for measuring shape parameters of a multidimensional shape (Japanese Patent Application No. 5-66).
No. 439), and a method and apparatus for measuring shape parameters of a constrained multidimensional shape (Japanese Patent Application No. 5-224293). The method of obtaining the maximum inscribed dimension and the minimum circumscribed dimension under stable conditions in a stable and short time will be described below with reference to these prior inventions.

FIG. 8 schematically shows the principle for obtaining the shape parameter of the multidimensional shape element forming the work shape based on the actual shape data obtained by actually measuring the work. Consider preparing real shape data composed of N measurement points and a corresponding theoretical shape, and aligning the theoretical shape with the actual shape data. The position vector of the i-th measurement point of the actual shape data is Mi, the position vector of the corresponding theoretical point on the theoretical shape before alignment is Mthi, the unit normal vector of the theoretical shape at that position is ni, and the alignment is performed. The position vector of the theoretical point on the subsequent theoretical shape is Mopt. A screw vector (described later) from Mthi to Mopt is set as DMthi.

Here, the amount related to the alignment (translation amount, rotation amount, etc.) is minute, and the theoretical point M before the alignment is
It is assumed that the unit normal vector ni on thi and the direction of the unit normal vector on the theoretical point Mopt after alignment do not change. Under this assumption, the error amount ei between the basic theoretical shape after alignment and the measurement point is expressed by the following equation.

[0033]

[Equation 1]

Here, the symbol ".multidot." In the equation represents the inner product of two vectors.

Further, assuming that the reference position (position vector) of the theoretical shape is A, DMthi of the equation 1 can be expressed as follows.

[0036]

[Equation 2]

Here, VMA is a vector from the theoretical point Mthi to an arbitrary reference position A. DA is a vector representing the translation amount at A, and R is a vector representing the rotation amount at A. The symbol "x" in the equation (2) represents an outer product of two vectors.

The two vectors DA and R are collectively called a screw vector (Dmthi in FIG. 2). In a three-dimensional space, these two vectors can also be expressed as the following equation.

[0039]

[Equation 3]

Here, dx, dy and dz are coordinate components of the translation vector in the three-dimensional space, and u, v and w are respective coordinate components of the rotation vector.

By substituting the equation 2 into the equation 1, the following equation 4 is obtained. Here, VAM is a vector obtained by inverting the vector VMA.

[0042]

[Equation 4]

In other words, the equation (4) represents the amount of error between the measurement point and the basic theoretical shape after alignment. By applying this equation (4) to all the measurement points, DA and R are unknown variables (the total number of elements in the three-dimensional space is six, and in the following, the three-dimensional space is assumed). Then, N simultaneous linear equations are obtained. Therefore, according to this theoretical formula, if there are at least 6 measurement points, each element of the unknown variables DA and R can be determined.

When the number of measuring points is 6, DA and R are uniquely determined by directly solving the simultaneous linear equations. However, if the number of measurement points is more than 6,
By applying various evaluation functions when solving the simultaneous linear equations, various solutions according to the evaluation functions can be obtained.

Here, for the purpose of aligning the measurement point and the theoretical shape, it is considered to minimize ei in the equation (4) as an evaluation function. There are various methods for minimization, but the two methods of maximum inscribed method and minimum circumscribed method will be described as an example. In addition, an example of an evaluation function representing these two methods will be described below taking a case of a circle or a cylinder as an example. In the case of a multi-dimensional shape having a dimension other than a circle or a cylinder (such as a key groove), the formula of the evaluation function is slightly different, but the same idea can be applied.

(1) In case of maximum inscribed method

[0047]

[Equation 5]

(2) In case of the minimum circumscribed method

[0049]

[Equation 6]

Here, r represents the radius of the circle. Also min
() And max () mean a function for finding the minimum and maximum values of variables in parentheses. The above is the basic theory for aligning the measurement point and the theoretical shape.

However, when the actual shape measurement and its evaluation are considered, the assumption that "the amount relating to the alignment (the amount of translation and the amount of rotation) is minute", which is a precondition of the above theory, generally does not hold. . Therefore, in the invention of the prior application, by applying the method of linear approximation and iterative calculation to the theory of calculation of shape parameters, which should originally be a nonlinear simultaneous equation, and systematizing it as a new methodology, not only the least squares method but also the conventional method We achieved stable and short-time determination of shape parameter measurement by the maximum inscribed and minimum circumscribed methods, which was impossible. Furthermore, instead of simply solving the simultaneous linear equations of Equation 4, a theory and method for giving arbitrary constraint conditions to translational movement and rotational movement obtained as a result of solving the simultaneous linear equations were devised.

The theory and method will be described below. There are roughly two methods for giving the required constraints to the simultaneous equations obtained as the equation (4). The first is to eliminate unnecessary unknown variables (which may be arbitrary combinations of constrained translational movement components or rotational movement components) in the equation (4) or fix them to 0. The second is a method of directly transforming the equations, and the second is a method of adding equations that give necessary constraint conditions to the simultaneous equations of the equation 4 and solving them as new simultaneous equations.

First, in the former method of directly transforming the equation, if only movement is not performed, DA in the equation 4 is used.
It can be realized by the following formula by deleting the term of (or fixed to 0).

[0054]

[Equation 7]

Alternatively, when only rotation is not performed, the following equation can be realized by deleting (or fixing to 0) the term of R in the equation (4).

[0056]

[Equation 8]

Further, since DA and R have elements of each coordinate axis component as expressed by the equation (3), the variables of these constrained components should be deleted (or fixed to 0) respectively. Thus, it is possible to arbitrarily suppress translational movement or rotational movement for each coordinate axis component.

The constraint in this method is a constraint for each axial direction of the coordinate system in which the equation (4) is defined. Before establishing the simultaneous equations in the equation (4), the measurement point is set in the desired coordinate system in advance. It is also possible to give a restriction to an arbitrary direction by transforming the coordinates of or by selecting the coordinate axis of the reference coordinate system when creating the equation 4 so as to face a predetermined direction.

The above is how to give a constraint by the method of transforming the simultaneous equations. In the latter method, the simultaneous equations of Equation 4 are not touched and an equation (constraint) that newly means a constraint is added. Explain the method by adding (conditional expression).

As described above, constraining the translational movement or the rotational movement means constraining DA and R obtained from the simultaneous equations of Formula 4, respectively. There are various constraint methods for giving this constraint, such as a method of limiting the direction of translational movement or rotational movement to a designated direction, and a method of allowing translational movement or rotational movement only in the designated direction. An example of this constraint condition expression is shown below.

[0061]

[Equation 9]

The above equation is a method for restricting translational movement within a designated plane, and Np in the equation is a unit surface normal vector of the plane that constrains movement. “·” In the formula means the dot product of the vectors. This expression allows the resulting translational motion vector DA to move only in the plane designated by Np, because the motion component in the Np vector direction is suppressed.

Two numbers 9 which are not parallel to each other
When the equation (the plane represented by the equation 9 has a line of intersection) is added, the constraint condition by the two equations is satisfied at the same time, so that the translational movement is possible only on the line of intersection of the two planes. It becomes a constraint to say.

Furthermore, when three equations (9) which are not in parallel with each other are added, the constraint condition of perfect position fixing is given, and no movement is performed at all.

Next, in the case of restricting the rotational movement, like the translational movement, it can be realized by adding the following equation to the original simultaneous equations.

[0066]

[Equation 10]

The above formula is a formula for limiting the rotational movement around an arbitrary axial direction. In the formula, Cd is a unit vector representing the direction of the rotation axis, and “x” in the formula means the outer product of the vectors. To allow the rotational movement only around the designated axis means in other words that the rotational movement vector becomes parallel to the designated axis direction vector. However, it is difficult to solve as simultaneous equations as it is, so transform this equation as follows,

[0068]

[Equation 11]

It is assumed that However, θ is an arbitrary variable representing the rotation angle. It is possible to obtain the rotation component vector R in which the rotation direction is restricted around the designated axial direction by replacing R in the equation 4 by using this equation 11 and solving θ as a variable of the new rotational movement component. become.

Alternatively, the rotation axis direction vector C is previously set.
When Cv can be obtained as an arbitrary unit vector that is orthogonal to d, replace Equation 10 with the following equation,

[0071]

[Equation 12]

You may add as. However, “·” in the equation means the inner product of the vectors. In this case, the outer product calculation is not included in the formula, so there is no need to perform variable conversion and calculation is easier.

FIG. 9 shows an outline of a method of measuring a constrained shape parameter according to the invention of the prior application. In the invention of the prior application, the above theory is used as a theory for alignment.

First, in the first step, the shape type, the actual shape measurement data, the theoretical shape data, the geometrical tolerance information, the datum shape data, etc. are input. At this time, if there is no theoretical shape data from CAD or the like, the initial theoretical shape is obtained from the shape type and the measurement data. This theoretical shape need only be a shape that is reasonably close to the measured data, and may not satisfy the assumptions of the above theory.

As a second step, an equation of constraint condition is created from each input data. The constraint expression created here is different depending on the type of geometrical tolerance and the shape of the target, but basically it is a combination of the above-mentioned conditional expressions that constrain translation or rotation. Become.

As the third step, the simultaneous equations shown by the equation 4 are prepared from the theoretical shape data and the measurement data according to the above-mentioned alignment theory. The simultaneous equations are combined with the constraint condition expressions created in the second step to form one simultaneous equation. Either of the order of the second stage and the third stage may come first.

As the fourth step, the simultaneous equations previously obtained are solved to obtain the translational movement amount and the rotational movement amount. The translational movement amount and the rotational movement amount obtained here are values satisfying the conditions constrained in the second step.

In the fifth step, the theoretical shape is moved / rotated in accordance with the translational movement amount / rotational movement amount thus obtained. Obviously, this is not a correct solution because the above assumption is not satisfied. However, the solution obtained here is closer to the correct solution than the state of the theoretical shape before moving and rotating.

Therefore, the translational movement amount / rotational movement amount and the like obtained in the sixth step are compared and determined with preset numerical values. If the calculated value is smaller than the set value, it means that the correct solution has been obtained, but if not, by repeating the second to sixth steps as the seventh step, the theoretical shape is determined. It is possible to gradually get closer to the correct solution.

The above-mentioned prior invention makes it possible, for the first time, to practically calculate the maximum inscribed dimension or the minimum circumscribed dimension of a multidimensional shape whose position and orientation are restricted. Next, how to use the method to realize the principle illustrated in FIGS. 2 to 7 will be described.

FIG. 10 is an example of a preferred flow chart for implementing the present invention with an electronic computer. First, in step 110, various data required for assembly possibility determination is input. In this step, theoretical shape data, dimensional tolerance data and corresponding actual shape data of the target work assembly portion are input. As the theoretical shape data, the theoretical shape type (plane, cylinder, sphere, cone, etc.) of the datum and the feature with tolerance, and the shape parameter of the theoretical shape are input. The dimensional tolerance data includes inner dimensions, distinction between holes (for holes) and outer dimensions (for shafts, bosses, etc.), dimensional values and tolerances specified for the dimensions, types of specified geometric tolerances, and geometric The tolerance value of the tolerance and whether or not the maximum material tolerance method is applied are entered. As shown in the example of FIG. 6, there are a plurality of datums, and when configuring a datum system, it is also necessary to input the priority order thereof. These data are C
If design data created at the time of design by the AD system or the like exists, necessary data may be extracted from the design data and input by a data file or the like. You may input directly by input means such as. The parameter of the theoretical shape is used as the initial theoretical shape for the above-described alignment, but it can be calculated from the actual shape data and thus can be omitted. The actual shape data is shape data obtained by actually measuring the datum and the feature with tolerance, and is generally composed of a plurality of measurement coordinate values.

Next, in step 120, the datum,
Since the processing differs depending on whether the feature with tolerance is a shape type having dimensions, four cases as shown in Table 2 are performed, and a discrimination flag is set for each case. This flag is appropriately referred to in each subsequent step.

[0083]

[Table 2]

The flag 3 corresponds to the example of FIGS. 2 and 6.
The flag 4 corresponds to the example of FIG. An example corresponding to flag 2 is not shown.

Next, at step 130, flag discrimination is performed. If the flag is 1, that is, the datum,
If the shape with tolerance is a shape type that does not have dimensions, no processing is performed and the process proceeds to the end. If the flag is other than 1, proceed to the next step.

Next, in step 140, the effective dimension of the assembly portion is calculated. FIG. 11 shows a procedure in which this step is further detailed. Step 14 of FIG.
In 1 it is determined whether the flag is 3 (whether it is a shape type having only dimensions with a tolerance), and if so, the process proceeds to step 145. Otherwise, step 1
At 42, it is determined whether the size of the datum is the inner size or the outer size. If it is the inner dimension, as shown in step 143, if it is the outer dimension, the effective dimension of the datum is calculated and stored as in step 144, and the routine proceeds to step 145.
In step 145, it is determined whether the flag is 2 (whether the shape type has dimensions only in the datum), and if so, this step 140 ends. If not, a determination is made in step 146 as to whether the dimensions of the feature with tolerances are inner or outer. If it is the inner dimension, as shown in step 147, if it is the outer dimension, the effective dimension of the feature with tolerance is calculated and stored as shown in step 148, and this step 140 is ended. The effective dimensions illustrated in FIGS. 3, 5, and 7 are calculated by such a procedure.

Next, in step 150 (FIG. 10), the shape parameters of the datum are calculated from the actual shape data of the datum. A procedure showing this step in more detail is shown in FIG. This shows the case of a single datum as shown in FIGS.

When a datum system is composed of a plurality of datums as shown in FIG. 6, the shape parameters of the lower datums are calculated by using the shape parameters of the actual shape data of the datums of high priority as a constraint condition. However, the method is similar to the next step (160 in FIG. 10).
In step 151 of FIG. 12, it is determined whether the flag is 3 (whether the shape type has only dimensions with a tolerance). If so (in the case of FIG. 2), the shape parameter is calculated and stored by the least square method as shown in step 152. Otherwise (Fig. 4
In such a case), it is determined whether the inner dimension or the outer dimension (step 153), and in the case of the inner dimension, the shape parameter is calculated and stored as the maximum inscribed shape (step 154). In the case of the outer dimension, the shape parameter is calculated and stored as the minimum circumscribed shape (step 155). With the above, step 150 is completed. Regarding the method of calculating the shape parameter by the least squares method, the maximum inscribed method, and the minimum circumscribed method, the invention of the prior application (Japanese Patent Application No. 5-66439).
Method may be used.

Next, in step 160 (FIG. 10),
In step 150, the shape parameter of the feature with tolerance is calculated under the constraint conditions of the position and orientation data of the datum calculated and stored. A procedure showing this step in more detail is shown in FIG.

In FIG. 13, first, step 161.
Then, it is determined whether or not the flag is 2 (whether or not the shape type has dimensions only in the datum). If so, this step 160 ends. If not, the process proceeds to step 162, and it is determined whether the inner dimension or the outer dimension. In the case of the inner dimension, the shape parameter is calculated and stored as the maximum inscribed shape with the shape parameter of the datum calculated in step 150 as a constraint condition (step 163). In the case of the outer dimension, the shape parameter is similarly calculated and stored as the minimum circumscribed shape (step 1
64). The calculation method of steps 163 and 164 may use the principle and procedure (FIG. 8) of the above-mentioned prior invention. With the above, step 160 ends.

Next, in step 170, the effective dimensions calculated in step 140 and the steps 160, 17
A comparison of the actual dimensions calculated with 0 is performed.

FIG. 14 shows a decision tree when the assembling is possible. If the result of the comparison corresponds to any of the decision trees, as a determination result, it is possible to assemble, but if not, the assembling is output together with the actual size. With the above, step 170 ends, and FIG.
All the processes indicated by 0 are completed.

FIG. 15 is a block diagram showing a preferred embodiment of the device according to the present invention. In FIG. 15, a CAD system 3 is a computer-aided device for designing a work, to which CAD data composed of shapes, dimensions, tolerance data and the like is input by a designer. The first storage unit 220 stores the CAD data created by the CAD system 3.

The measuring machine 1 is a device for actually measuring the shape of a work by using, for example, coordinate values. The second storage means 260 stores the actual shape data obtained by actual measurement by the measuring machine 1 as a datum,
It stores as a plurality of coordinate data groups for each feature with tolerance.

The CAD data input means 271 fetches the theoretical shape data and the dimension tolerance data of the target work assembly portion from the CAD data of the first storage means 220, and outputs the third data.
It is stored in the storage means 272. As theoretical shape data,
The theoretical shape type (plane, cylinder, sphere, cone, etc.) of the datum and the feature with tolerance, and the shape parameter of the theoretical shape are input. Inner dimension as dimension tolerance data (for holes)
Whether it is the outer dimension (in case of shaft, boss, etc.), the dimension value and the tolerance specified in the dimension, the specified geometric tolerance type, the tolerance value of the geometric tolerance, whether the maximum material tolerance method is applied, etc. Is entered.

When there are a plurality of datums as shown in FIG. 6 and the datum system is constituted, the priority order thereof is also input. C
When there is no AD data, the theoretical shape data and the dimensional tolerance data are directly input by the input means 240 such as a keyboard or a mouse and stored in the third storage means 272.

The actual shape data input means 274 takes in the actual shape data from the second storage means 260 and stores it in the fourth storage means 274.

The first computing means 275 reads the data of the third storage means 272, calculates the effective dimension of the assembly portion according to the procedure shown in FIG. 11, and stores it in the sixth storage means 281.

The second calculation means 276 is the third storage means 27.
2 and the data in the fourth storage means 273 are read, and the data in FIG.
It is in charge of arithmetic processing (calculation of shape parameters without constraints) of the flowchart shown in FIG. Error messages during calculation are sent to the display means 230,
Is displayed. The calculation result is stored in the fifth storage unit 279.

The constraint condition setting means 280 reads the data in the fifth storage means 279, sets the constraint condition equations according to the equations 7 to 12, and sends them to the third computing means 277.

The third calculation means 277 is the third storage means 27.
2. Read data from the fourth storage unit 273 and read the constraint condition expression from the constraint condition setting unit 280,
It is in charge of arithmetic processing (calculation of shape parameters with constraints) of the flowchart shown in FIG. Error messages during the calculation are sent to the display means 230 and displayed. The calculation result is stored in the fifth storage unit 279.

The judging means 278 reads the data of the sixth storing means 281 and the fifth storing means 279 and judges whether or not the assembly is possible according to the decision tree shown in FIG. The result is sent to the display means 230 together with the actual size and displayed.

The CAD data input means 2 described above
71, measured shape data input means 274, third storage means 2
72, fourth storage means 273, first calculation means 275, second
Computing means 276, third computing means 277, fifth storage means 2
79, a sixth storage means 281, a constraint condition setting means 280,
The determination unit 278 constitutes the apparatus main body 100 which is an embodiment of the work assembly possibility determination apparatus according to the present invention. In addition, it is desirable that the apparatus main body 100 be configured by an electronic computer. The electronic computer can realize each of the above means by causing the central processing unit to execute the program stored in the main storage device.

[0104]

[Effect] As described above, according to the present invention, the actual shape data obtained by measuring the work specified by the maximum material tolerance method by using the coordinate measuring machine such as the coordinate measuring machine is calculated by the calculating means such as the electronic calculator. Therefore, the possibility of assembling the work can be accurately determined in a stable and short time.

Therefore, as compared with the conventional function gauge, the assembling possibility of any work can be accurately determined at a much lower cost, regardless of the complexity of the shape and the amount of production.

Further, since the actual shape data obtained by the coordinate measuring machine is used, it is not necessary to use it together with the functional gauge, and the efficiency of inspection can be improved.

Further, since the judgment is made by comparing the effective dimension with the calculated dimension, the result can be understood as a numerical value, not just the quality, and the process capability can be grasped at the same time, which is extremely effective.

Although it has been known that the maximum material tolerance method has an extremely great advantage such as cost reduction, the reason why it has not spread widely is that the correct function gauge evaluation cannot be performed by the coordinate measuring machine. According to the present invention, this large obstacle is removed, and as a result, it greatly contributes to the spread of the maximum material tolerance method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention.

FIG. 2 is an example of a drawing for explaining the principle of the present invention,
It is explanatory drawing which shows the case where the squareness is instruct | indicated by the maximum substance tolerance system as a posture tolerance.

3A and 3B are diagrams for explaining the principle of determining the assembling possibility from the tolerances shown in FIG. 2, where FIG. 3A is an effective state of a work, and FIG. 3B is an actual work shape and the shape thereof. It is an explanatory view showing a multidimensional shape element (plane, cylinder).

FIG. 4 is an example of a drawing for explaining the principle of the present invention,
It is explanatory drawing which shows the case where the parallelism is instruct | indicated by a maximum substance tolerance system as a posture tolerance (a case where the maximum substance tolerance is given also to the datum).

5A and 5B are explanatory views showing the principle of judging the assembling possibility from the tolerance shown in FIG. 4, in which FIG. 5A is an effective state of a work, and FIG. 5B is an actual work shape and the shape is calculated from the shape. It is explanatory drawing which shows a multidimensional shape element (cylinder).

FIG. 6 is an example of a drawing for explaining the principle of the present invention,
It is explanatory drawing which shows the case where the degree of position is instructed by the maximum substance tolerance method as a position tolerance.

7A and 7B are explanatory views showing the principle of determining the assembling possibility from the tolerances shown in FIG. 6, in which FIG. 7A is an effective state of the work, FIG. 7B is an actual work shape and the shape is calculated from the shape. It is an explanatory view showing a multidimensional shape element (plane, cylinder).

FIG. 8 is a schematic diagram showing a principle for obtaining a shape parameter of a multidimensional shape element from actual shape data obtained by actually measuring a work.

FIG. 9 is a schematic diagram of a method of measuring a constrained shape parameter according to the invention of the prior application.

FIG. 10 is an overall view of a flowchart when a method according to an embodiment of the present invention is implemented by an electronic computer.

FIG. 11 is a flowchart illustrating a more detailed procedure of step 140 that constitutes the overall flowchart shown in FIG.

FIG. 12 is a flowchart illustrating a more detailed procedure of step 150 which constitutes the overall flowchart shown in FIG.

FIG. 13 is a flowchart for explaining a more detailed procedure of step 160 which constitutes the overall flowchart shown in FIG.

FIG. 14 is an explanatory diagram showing a decision tree that serves as a determination criterion when determining the assembling possibility in step 170 of FIG. 10 (conditions for determination are shown in a rectangular frame, and the determination condition is shown from the left side; It can be assembled if all the conditions in the route are satisfied by following the decision tree).

FIG. 15 is a block diagram showing a configuration of a main part of an apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 100 ... Device main body 271 ... CAD data input means 272 ... Third storage means 273 ... Fourth storage means 274 ... Measured shape data input means 275 ... First calculation means 276 ... -Second calculation means 277 ... Third calculation means 278 ... Determination means 279 ... Fifth storage means 280 ... Constraint condition setting means 281 ... Sixth storage means

Front Page Continuation (72) Inventor Izumi Izumi 3-2 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation (72) Inventor Kenshi Kishinami 2-3-3-20 Moiwashita, Minami-ku, Sapporo-shi, Hokkaido

Claims (6)

[Claims] 1. A method for determining whether or not assembly is possible with a mating work to which the work is assembled, based on actual shape data of the work obtained by actually measuring the work. The first step of calculating the effective dimension of the portion from the dimensions and geometrical tolerances designated for the assembled part, and measuring and obtaining the portion of the shape data designated as the datum feature in the geometrical tolerance. The second step of calculating the shape parameter of the datum feature part from the actual shape data, and the geometrical tolerance of the actual shape data in the geometrical tolerance with the shape parameter obtained in the second step as a constraint condition. A third step of calculating a shape parameter of the tolerance-added feature portion based on actual shape data obtained by actually measuring a portion designated as the attached feature, and the first step 4. A method of determining the assemblability of a work, comprising: the effective dimension obtained in the above step; and a fourth step of comparing at least the shape parameter obtained in the third step. 2. If the datum feature has dimensions, the shape parameter obtained in the second step is also compared in the fourth step with the effective dimension obtained in the second step. 1. A method of judging the assembling possibility of a work according to 1. 3. In the first step, the calculation of the effective dimension is performed by reflecting the geometrical tolerance on the dimension so that the strictest condition for assembly is possible. 1. A method of judging the assembling possibility of a work according to 1. 4. The effective dimension is calculated by subtracting the geometrical tolerance from the dimension at the lower limit of the dimension tolerance when the dimension of the feature with tolerance is an inner dimension so that the dimension of the feature with tolerance is outside. 4. The method according to claim 3, wherein, in the case of a dimension, the workability is determined by adding the geometrical tolerance to the dimension at the upper limit of the dimension tolerance. 5. In the second or third step, when the shape parameter has a dimension, the shape parameter is calculated by the maximum inscribed method when the dimension is an inner dimension, and the dimension is an outer dimension. The method for determining the assemblability of a work according to claim 1, wherein the method is performed by a minimum circumscribing method at a certain time. 6. An apparatus for determining whether or not the work can be assembled with a mating work to which the work is assembled based on actual shape data of the work obtained by actually measuring the work. First calculation means for calculating the effective dimension of the part from the dimensions and geometrical tolerances specified for the part to be measured, and actually measured shape data input means for inputting actual shape data obtained by actually measuring the part of the work. A second calculation means for calculating a shape parameter of the datum feature portion from the actual shape data obtained by actually measuring a portion of the actual shape data designated as a datum feature in the geometrical tolerance; With the shape parameter obtained by the second calculation means as a constraint condition, the portion of the shape data designated as the feature with tolerance in the geometrical tolerance is actually measured. Based on the obtained actual shape data, a third calculation means for calculating the shape parameter of the tolerance-added feature part, an effective dimension obtained by the first calculation means, and at least the third calculation means. An assembly possibility determination device for a work, comprising: a determination unit that compares the obtained shape parameters.