A machining process dimension chain calculation method based on dynamic tolerance chart
The method of calculating the process dimension chain using dynamic tolerance diagrams solves the problem of misjudging the acceptable range of component dimensions in the manufacturing of mechanical parts, achieving complete expression and cost savings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2022-11-01
- Publication Date
- 2026-05-05
AI Technical Summary
In the manufacturing and machining processes of mechanical parts, existing technologies cannot fully describe the acceptable range of the dimensions of the constituent rings, leading to misjudgment of scrap and resulting in economic losses.
A process dimension chain calculation method based on dynamic tolerance diagram is adopted. The independent acceptable area, maximum upper deviation and minimum lower deviation, dynamic upper deviation and lower deviation of the target ring are calculated by extreme value method. The dynamic tolerance zone diagram of process dimension chain is drawn to fully express the acceptable range of the constituent rings.
This avoids misjudging defective products during production, expands the range of qualified products, and reduces processing difficulty and production costs.
Smart Images
Figure CN115795707B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mechanical parts manufacturing and cutting process technology, specifically a method for calculating machining process dimension chains based on dynamic tolerance diagrams. Background Technology
[0002] In the manufacturing and machining processes of mechanical parts, some dimensions of the part structure can be linked together to form a machining process dimension chain. Most dimensions in this chain are directly obtained by machining according to the dimensional accuracy specified on the drawings. However, there is always one dimension that is naturally formed after the other dimensions have been machined; this can be called the closing loop. The dimension directly obtained through machining in the machining process dimension chain is called a component loop. Component loops are further divided into increasing loops and decreasing loops. When other component loops remain unchanged, increasing one component loop will increase the closing loop accordingly; this component loop is called an increasing loop. Conversely, when other component loops remain unchanged, increasing one component loop will decrease the closing loop; this component loop is called a decreasing loop.
[0003] In actual production, especially in mass production, if the design requires the dimensional accuracy of the closed loop, but there are problems such as difficulty in measurement, inability to be directly processed, or non-coincident references, it is necessary to calculate the dimensional accuracy of the constituent loops through the processing dimensional chain. By processing the dimensions of the constituent loops, the dimensional accuracy of the closed loop can be indirectly guaranteed.
[0004] Traditional methods for calculating the dimensional chain of a machining process mainly include extreme value method and probability method. However, the calculation results may show so-called "false scrap zone", which cannot fully describe the qualified range of the component dimensions. It is very likely that the part size will be in the "false scrap zone" and be "misjudged as scrap", resulting in economic losses. Summary of the Invention
[0005] Purpose of the invention: This invention provides a method for calculating the dimensional chain of a machining process based on a dynamic tolerance diagram. Its purpose is to determine the complete acceptable range in the calculated dimensional chain, avoid "misjudgment and scrap", and save production costs.
[0006] Technical solution:
[0007] A method for calculating machining process dimension chains based on dynamic tolerance diagrams, characterized by the following steps:
[0008] Step 1: Based on the initial conditions, calculate the independent qualified areas of the target ring using the extreme value method;
[0009] Step 2: Calculate the maximum upper deviation and minimum lower deviation of the target loop;
[0010] Step 3: Calculate the dynamic upper deviation and dynamic lower deviation of the target loop;
[0011] Step 4: Calculate the dynamic qualified zone of the target ring;
[0012] Step 5: Draw the dynamic tolerance zone diagram of the process dimension chain.
[0013] Preferably, step one involves calculating the independent qualified area of the target ring based on the initial conditions using the extreme value method. The specific process is as follows:
[0014] Calculate according to formulas (1), (2), and (3):
[0015]
[0016]
[0017]
[0018] In the formula: A0, Az, and Aj are the nominal dimensions of the closed loop, increasing loop, and decreasing loop, respectively; ES0, ESz, and ESj are the upper deviations of the closed loop, increasing loop, and decreasing loop, respectively; EI0, EIz, and EIj are the lower deviations of the closed loop, increasing loop, and decreasing loop, respectively; m is the number of increasing loops; and n is the number of decreasing loops.
[0019] When the target ring is a decreasing ring, let the number be j1. The calculation result is: nominal size is Aj1, upper deviation is ES j1, lower deviation is EI j1. That is, the acceptable range of the actual size Aaj1 of the target ring j1 is: Aj1+EIj1≤Aaj1≤Aj1+ESj1, which can be expressed as EIj1≤Eaj1≤ESj1 in terms of deviation, where Eaj1 is the actual deviation of the target ring j1.
[0020] When the target ring is an increasing ring, let the number be z1. The calculation result is: nominal size is Az1, upper deviation is ESz1, and lower deviation is EIz1. That is, the acceptable range of the actual size Aaz1 of the target ring z1 is: Az1+EIz1≤Aaz1≤Az1+ESz1, which can be expressed as EIz1≤Eaz1≤ESz1 in terms of deviation, where Eaz1 is the actual deviation of the target ring z1.
[0021] The acceptable range of the target ring j1 or target ring z1 is independent of the dimensions of other component rings and the closing ring.
[0022] Preferably, the specific process for calculating the maximum upper deviation and minimum lower deviation of the target ring in step two is as follows:
[0023] When the target loop is a decreasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows:
[0024] Maximum upper deviation:
[0025] Minimum lower deviation:
[0026] In the formula, ES′j1 is the maximum upper deviation of the target loop j1, and EI′j1 is the minimum lower deviation of the target loop j1;
[0027] When the target loop is an increasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows:
[0028] Maximum upper deviation:
[0029] Minimum lower deviation:
[0030] In the formula, ES′z1 is the maximum upper deviation of the target ring z1, and EI′z1 is the minimum lower deviation of the target ring z1.
[0031] Preferably, the specific process for calculating the dynamic upper deviation and dynamic lower deviation of the target loop in step three is as follows:
[0032] When the target loop is a decreasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows:
[0033] Dynamic deviation:
[0034] Dynamic deviation:
[0035] In the formula, ESΣj1 is the dynamic upper deviation of the target loop j1; EIΣj1 is the dynamic lower deviation of the target loop j1;
[0036] When the target loop is an increasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows:
[0037] Dynamic deviation:
[0038] Dynamic deviation:
[0039] In the formula, ESΣz1 is the dynamic upper deviation of the target loop z1; EIΣz1 is the dynamic lower deviation of the target loop z1.
[0040] Preferably, the specific process for calculating the dynamic qualified area of the target ring in step four is as follows:
[0041] Relationship between the actual deviation Ea of the dimensions of the closed loop and the constituent loops Given the relationship EI≤Ea≤ES for each dimension, we can calculate:
[0042] When the target ring is a decreasing ring, the dynamic qualified area of the target ring j1 is:
[0043] E x -ES0≤E aj1 ≤E x-EI0
[0044] E x ∈[EI ∑j1 ES ∑j1 (13)
[0045] In the formula, Ex is the dynamic deviation variable;
[0046] When the target ring is an increasing ring, the dynamic qualified area of the target ring z1 is:
[0047] E x +EI0≤E az1 ≤E x +ES0
[0048] E x ∈[EI ∑z1， ES ∑z1 (14)
[0049] Preferably, the specific process of drawing the dynamic tolerance zone diagram of the process dimension chain in step five is as follows:
[0050] The dynamic tolerance zone diagram of the process dimension chain uses a rectangular coordinate system, with the horizontal axis representing the design dimension or dimensional deviation of the increasing link and the vertical axis representing the dimensional deviation of the decreasing link.
[0051] Let the sum of all increasing ring maximum values be ∑ESz, the sum of all increasing ring minimum values be ∑EIz, the sum of all decreasing ring maximum values be ∑ESj, and the sum of all decreasing ring minimum values be ∑EIj. These four values can form a rectangle, which is an independent qualified region.
[0052] On the dynamic tolerance zone diagram of the dimensional chain, each coordinate point corresponds to the size of the increasing and decreasing loops, so the size of the closed loop at that point can be calculated. Connecting the points with equal closed loop sizes forms a line, which is defined as the closed loop equal size line.
[0053] When the target ring is a decreasing ring, the size of the increasing ring is known, so the values of ∑ESz and ∑EIz are fixed. The ESj1 and EIj1 of the target ring j1 are calculated by the extreme value method.
[0054] ESj1 is calculated from the top left corner of the independent qualified area rectangle. At this time, the closed loop is at the lower deviation EI0. Draw the closed loop equal dimension line from the top left corner of the independent qualified area rectangle to the upper right at a 45° angle, so that it intersects the line where ∑ESz is located at a point to form a triangle, which is the upper condition qualified area.
[0055] EIj1 is calculated from the lower right corner of the independent qualified area rectangle. At this time, the closed loop is at the upper deviation ES0. Draw the closed loop equal dimension line from the lower right corner of the independent qualified area rectangle to the lower left at a 45° direction, so that it intersects the line where ∑EIz is located at a point to form a triangle, which is the lower condition qualified area.
[0056] When the target ring is an increasing ring, the size of the decreasing ring is known, so the values of ∑ESj and ∑EIj are fixed. The ESz1 and EIz1 of the target ring z1 are calculated by the extreme value method.
[0057] ESz1 is calculated from the lower right corner of the independent qualified area rectangle. At this time, the closed loop is at the upper deviation ES0. Draw the closed loop equal dimension line from the lower right corner of the independent qualified area rectangle to the upper right at a 45° angle, so that it intersects the line where ∑ESj is located at a point to form a triangle, which is the right condition qualified area.
[0058] EIz1 is calculated from the top left corner of the independent qualified area rectangle. At this time, the closed loop is at the lower deviation EI0. Draw the closed loop equal dimension line from the top left corner of the independent qualified area rectangle to the lower left at a 45° angle, so that it intersects the line containing ∑EIj at a point, forming a triangle, which is the left condition qualified area.
[0059] Beneficial effects: This invention provides a method for calculating the dimensional chain of a machining process based on a dynamic tolerance diagram. It describes the dimensions of the constituent rings in the form of dynamic tolerances, which can completely express the entire acceptable range of the constituent rings. By implementing this invention, "misjudgment and scrap" in production can be avoided, thus preventing economic losses. At the same time, the expanded acceptable range reduces machining difficulty and lowers production costs.
[0060] The initial condition for implementing this invention is that the size and tolerance of only one component loop ("target loop") in the size chain need to be calculated, while the size and tolerance of the remaining component loops and the closing loop are known. The calculation method adopts the extreme value method.
[0061] Compared with the prior art, the beneficial effects of the present invention are: 1. It fully expresses the entire qualified range of parts; 2. It avoids "misjudgment and scrap" in production, thereby avoiding economic losses; 3. It expands the qualified range, reduces processing difficulty, and thus reduces production costs. Attached Figure Description
[0062] Figure 1 This is a schematic diagram of the dynamic tolerance of the process dimension chain when the target loop is a reduction loop;
[0063] Figure 2 This is a schematic diagram of the dynamic tolerance of the process dimension chain when the target ring is an increasing ring;
[0064] Figure 3 This is a schematic diagram of the process dimensions for an application example;
[0065] Figure 4 This is a schematic diagram of the processing positioning for an application example;
[0066] Figure 5 This is a dimension chain diagram of an application example;
[0067] Figure 6 This is a schematic diagram of the dynamic tolerance of the process dimension chain (dimension deviation representation) as an application example;
[0068] Figure 7 This is a schematic diagram of the dynamic tolerance of the process dimension chain (limit dimension representation) as an application example. Detailed Implementation
[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0070] Please see Figure 1-2 This invention provides a technical solution: a method for calculating process dimension chains based on dynamic tolerance diagrams, comprising the following steps:
[0071] Step 1: Based on the initial conditions, calculate the independent qualified areas of the target ring using the extreme value method;
[0072] Step 2: Calculate the maximum upper deviation and minimum lower deviation of the target loop;
[0073] Step 3: Calculate the dynamic upper deviation and dynamic lower deviation of the target loop;
[0074] Step 4: Calculate the dynamic qualified zone of the target ring;
[0075] Step 5: Draw the dynamic tolerance zone diagram of the process dimension chain.
[0076] Step one describes the calculation of the independent qualified area of the target ring based on the initial conditions using the extreme value method. The specific process is as follows:
[0077] Calculate according to formulas (1), (2), and (3):
[0078]
[0079]
[0080]
[0081] In the formula: A0, Az, and Aj are the nominal dimensions of the closed loop, the increasing loop, and the decreasing loop, respectively; ES0, ESz, and ESj are the upper deviations of the closed loop, the increasing loop, and the decreasing loop, respectively; EI0, EIz, and EIj are the lower deviations of the closed loop, the increasing loop, and the decreasing loop, respectively; m is the number of increasing loops; and n is the number of decreasing loops.
[0082] When the target ring is a decreasing ring, let the number be j1. The calculation result is: nominal size is Aj1, upper deviation is ES j1, lower deviation is EI j1. That is, the acceptable range of the actual size Aaj1 of the target ring j1 is: Aj1+EIj1≤Aaj1≤Aj1+ESj1, which can be expressed as EIj1≤Eaj1≤ESj1 in terms of deviation, where Eaj1 is the actual deviation of the target ring j1.
[0083] When the target ring is an increasing ring, let the number be z1. The calculation result is: nominal size is Az1, upper deviation is ESz1, and lower deviation is EIz1. That is, the acceptable range of the actual size Aaz1 of the target ring z1 is: Az1+EIz1≤Aaz1≤Az1+ESz1, which can be expressed as EIz1≤Eaz1≤ESz1 in terms of deviation, where Eaz1 is the actual deviation of the target ring z1.
[0084] The acceptable range of the target ring j1 or target ring z1 is independent of the dimensions of other component rings and the closing ring, and is defined as an independent acceptable area.
[0085] Step two involves calculating the maximum upper deviation and minimum lower deviation of the target loop, and the specific process is as follows:
[0086] When the target loop is a decreasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows:
[0087] Maximum upper deviation:
[0088] Minimum lower deviation:
[0089] In the formula, ES′j1 is the maximum upper deviation of the target loop j1, and EI′j1 is the minimum lower deviation of the target loop j1;
[0090] When the target loop is an increasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows:
[0091] Maximum upper deviation:
[0092] Minimum lower deviation:
[0093] In the formula, ES′z1 is the maximum upper deviation of the target ring z1, and EI′z1 is the minimum lower deviation of the target ring z1.
[0094] Step three involves calculating the dynamic upper and lower deviations of the target loop, and the specific process is as follows:
[0095] When the target loop is a decreasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows:
[0096] Dynamic deviation:
[0097] Dynamic deviation:
[0098] In the formula, ESΣj1 is the dynamic upper deviation of the target loop j1; EIΣj1 is the dynamic lower deviation of the target loop j1.
[0099] When the target loop is an increasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows:
[0100] Dynamic deviation:
[0101] Dynamic deviation:
[0102] In the formula, ESΣz1 is the dynamic upper deviation of the target loop z1; EIΣz1 is the dynamic lower deviation of the target loop z1.
[0103] Step four involves calculating the dynamic qualified area of the target ring, and the specific process is as follows:
[0104] Relationship between the actual deviation Ea of the dimensions of the closed loop and the constituent loops Given the relationship EI≤Ea≤ES for each dimension, we can calculate:
[0105] When the target ring is a decreasing ring, the dynamic qualified area of the target ring j1 is:
[0106] E x -ES0≤E aj1 ≤E x -EI0
[0107] E x ∈[EI ∑j1 ES ∑j1 (13)
[0108] In the formula, Ex is the dynamic deviation variable;
[0109] When the target ring is an increasing ring, the dynamic qualified area of the target ring z1 is:
[0110] E x +EI0≤E az1 ≤E x +ES0
[0111] E x ∈[EI ∑z1，ES ∑z1 (14)
[0112] Step five, drawing the dynamic tolerance zone diagram of the process dimension chain, is as follows:
[0113] The dynamic tolerance zone diagram of the process dimension chain uses a rectangular coordinate system, with the horizontal axis representing the design dimension or dimensional deviation of the increasing link and the vertical axis representing the dimensional deviation of the decreasing link.
[0114] Let the sum of all increasing cycle maximum values be ∑ESz, the sum of all increasing cycle minimum values be ∑EIz, the sum of all decreasing cycle maximum values be ∑ESj, and the sum of all decreasing cycle minimum values be ∑EIj. These four values can form a rectangle. Figure 1 and Figure 2 The rectangle ABCD in the diagram is an independent qualified area.
[0115] On the dynamic tolerance zone diagram of the dimensional chain, each coordinate point corresponds to the dimensions of the increasing and decreasing loops, thus allowing the calculation of the closed loop dimension at that point. Connecting points where all closed loop dimensions are equal creates a line defined as the closed loop equal-dimensional line. For example... Figure 1 and Figure 2 AA′, DE, FB.
[0116] See Figure 1 When the target ring is a decreasing ring, the size of the increasing ring is known, so the values of ∑ESz and ∑EIz are fixed. The ESj1 and EIj1 of the target ring j1 are calculated by the extreme value method.
[0117] ESj1 is the dimension chain located at the top left corner of the independent compliance area rectangle. Figure 1 The value is calculated from point D in the diagram. At this point, the closed loop is at the lower deviation EI0, starting from the upper left corner of the independent qualified area rectangle ( Figure 1 Draw a closed loop of equal dimensions from point D in the middle at a 45° angle to the upper right, intersecting the line containing ∑ESz. Figure 1 The line BC in the middle intersects at a point ( Figure 1 Point E in the middle), forming a triangle ( Figure 1 The triangle DCE in the diagram represents the qualified area for the upper condition.
[0118] EIj1 is the dimension chain located at the lower right corner of the independent compliance area rectangle. Figure 1 The value is calculated from point B in the diagram. At this point, the closed loop is at the upper deviation ES0, starting from the lower right corner of the independent qualified area rectangle ( Figure 1 Draw a closed loop of equal dimensions from point B in the middle at a 45° angle to the lower left, intersecting the line containing ∑EIz. Figure 1 The line DA in the middle intersects at a point ( Figure 1 Point F in the middle), forming a triangle ( Figure 1 The triangle BAF in the diagram represents the qualified area for the lower condition.
[0119] At this point, the acceptable area of the dimensional chain is a parallelogram. Figure 1 The parallelogram BFDE in the dimension chain is defined as the dynamic qualified zone. When the coordinate point (∑Eaz, ∑Eaj) formed by the sum of all decreasing deviations ∑Eaj and the sum of all increasing deviations ∑Eaz in the dimension chain falls inside the parallelogram BFDE and on each side, the closed loop deviation Ea0 is always qualified.
[0120] See Figure 2 When the target ring is an increasing ring, the size of the decreasing ring is known, so the values of ∑ESj and ∑EIj are fixed. The ESz1 and EIz1 of the target ring z1 are calculated by the extreme value method.
[0121] ESz1 is the dimension chain located at the bottom right corner of the independent compliance area rectangle. Figure 2 The value is calculated from point D in the diagram. At this point, the closed loop is at the upper deviation ES0, starting from the lower right corner of the independent qualified area rectangle ( Figure 2 Draw a closed loop of equal dimensions from point D in the middle at a 45° angle to the upper right, intersecting the line containing ∑ESj. Figure 2 The line BC in the middle intersects at a point ( Figure 2 Point E in the middle), forming a triangle ( Figure 2 The triangle DCE in the diagram represents the right-hand condition-compliant area.
[0122] EIz1 is the dimension chain located at the top left corner of the independent compliance zone rectangle. Figure 2 The value is calculated from point B in the diagram. At this point, the closed loop is at the lower deviation EI0, starting from the upper left corner of the independent qualified area rectangle (…). Figure 2 Draw a closed loop of equal dimensions from point B in the middle at a 45° angle to the lower left, intersecting the line containing ∑EIj ( Figure 2 The line DA in the middle intersects at a point ( Figure 2 Point F in the middle), forming a triangle ( Figure 2 The triangle BAF in the diagram represents the qualified area on the left.
[0123] At this point, the acceptable area of the dimensional chain is a parallelogram. Figure 2 The parallelogram BFDE in the dimension chain is the dynamic qualified zone. That is, when the coordinate point (∑Eaz, ∑Eaj) formed by the sum of all decreasing deviations ∑Eaj and the sum of all increasing deviations ∑Eaz in the dimension chain falls inside the parallelogram BFDE and on each side, the closed loop deviation Ea0 is always qualified.
[0124] In summary, regardless of whether the target loop is an increasing or decreasing loop, the parallelogram BFDE can completely represent the acceptable area of the process dimensional chain. The "false scrap area" often mentioned in production is actually the area between triangles EDC and FBA, i.e., the conditionally acceptable interval. Within these two areas, the acceptable range cannot be simply represented by upper and lower deviations; instead, the relationship between the actual dimensions of the increasing and decreasing loops must be used to determine whether it is acceptable. The acceptable area has been expanded from rectangle ABCD to parallelogram BFDE, thus increasing the acceptable range, reducing processing difficulty, and saving production costs.
[0125] Application examples;
[0126] See Figure 3 The processing requirements for the workpiece are as follows: (1) First, use surface 3 as the rough datum to process surface 1, and then use surface 1 as the fine datum to process surface 3, to obtain dimension A1 = 30 -00.2mm; (2) Process surface 2 to obtain dimension A2, while ensuring that the dimension A0 from surface 2 to surface 3 is 10 ± 0.3mm. A1, A2 and A0 constitute a dimension chain. A1 and A2 on the workpiece are obtained through processing, and A0 appears naturally after A1 and A2 are processed. The processing sequence is to process A1 first, and then process A2.
[0127] See Figure 4 When machining surface 2, surface 1 is used as the positioning reference, and machining can only be carried out according to dimension A2. Therefore, A2 must be calculated before machining.
[0128] See Figure 5 Preparatory work: Draw a dimension chain diagram. Analysis shows that A0 is a closed loop, A1 is an increasing loop, and A2 is a decreasing loop.
[0129] See Figure 6 The process of calculating process dimension A2 using the method of this invention is as follows:
[0130] Step 1: According to formulas (1), (2), and (3); substituting the data, we have: 10 = 30 - A2, +0.3 = 0 - EI2, -0.3 = -0.2 - ES2; calculating, we get: A2 = 20mm, EI2 = -0.3mm, ES2 = +0.1mm; thus, we can obtain This is an independent qualified area.
[0131] Step 2: Calculate the maximum upper deviation and minimum lower deviation of the target ring: A2 is the reducing ring. Substitute the data into equations (4) and (5), and we have ES′2=ES1-EI0=0-(-0.3)=+0.3mm, EI′2=EI1-ES0=-0.2-(+0.3)=-0.5mm;
[0132] Step 3: Calculate the dynamic upper deviation and dynamic lower deviation of the target ring: Substitute the data into equations (8) and (9), and we have ESΣ2=0mm; EIΣ2=-0.2mm;
[0133] Step 4: Calculate the dynamic acceptable zone of the target loop: According to formula (13), the dynamic acceptable zone of the actual deviation Ea2 of A2 is Ex-0.3≤Ea2≤Ex+0.3, Ex∈[-0.2,0], that is Ex∈[-0.2, 0].
[0134] Step 5: Draw the dynamic tolerance diagram of the process dimension chain. The dynamic acceptable range is parallelogram BFDE, meaning that Ea0 is always acceptable when the actual dimensions of Ea1 and Ea2 fall within or on any side of parallelogram BFDE. Limit dimensions can also be used here; see [link to relevant documentation]. Figure 7 .
[0135] After processing A1, if A1 is the minimum value of 29.8mm, i.e., Ea1 = -0.2mm, then Ex = -0.2mm, and the acceptable range for A2 is... That is, you can press Size processing A2, corresponding Figure 6 and Figure 7 After processing line segments FD and A2, A0 is obtained simultaneously. A0 has a maximum value of 10.3mm at point F (actual deviation Ea0 = +0.3mm) and a minimum value of 9.7mm at point D (actual deviation Ea0 = -0.3mm).
[0136] After processing A1, if A1 reaches its maximum value of 30mm (i.e., Ea1 = 0mm), then Ex = 0mm, and the acceptable range for A2 is... That is, you can press Size processing A2, corresponding Figure 6 and Figure 7 After processing line segments BE and A2, A0 is obtained simultaneously. A0 has a maximum value of 10.3mm at point B (actual deviation Ea0 = +0.3mm) and a minimum value of 9.7mm at point B (actual deviation Ea0 = -0.3mm).
[0137] After A1 is processed, if A1 is in When A1 is within the acceptable range, the acceptable range for A2 is affected by the actual size of A1. It is the range of the perpendicular line segment between line segments DE and FB that corresponds to the coordinate of A1 (Ea1). For example, after machining A1, if A1 = 29.9 mm, then Ea1 = -0.1 mm. Figure 7 ) or Ea1 = -0.1mm ( Figure 6Draw a perpendicular line upwards from the x-axis, intersecting line segment DE at H and line segment FB at G. Then the y-coordinate corresponding to line segment GH is within the acceptable range of A2, meaning A2 can be...
[0138] This example demonstrates that, according to the traditional extreme value method, A0 is only qualified when A1 and A2 are inside or on the edge of rectangle ABCD. However, with the implementation of this invention, A0 is also qualified when A1 and A2 are inside or on the edge of parallelogram BFDE, thus expanding the qualified range. Calculated proportionally by area, the qualified range of the dynamic qualified area BFDE is expanded by 50% compared to the independent qualified area ABCD. In actual production, this can reduce "false rejections" and lower processing difficulty, both of which are significant for reducing production costs.
Claims
1. A method for calculating machining process dimension chains based on dynamic tolerance diagrams, characterized in that: The method includes the following steps: Step 1: Based on the initial conditions, calculate the independent qualified areas of the target ring using the extreme value method; Step 2: Calculate the maximum upper deviation and minimum lower deviation of the target loop; Step 3: Calculate the dynamic upper deviation and dynamic lower deviation of the target loop; Step 4: Calculate the dynamic qualified zone of the target ring; Step 5: Draw the dynamic tolerance diagram of the process dimension chain; Step one describes the calculation of the independent qualified area of the target ring based on the initial conditions using the extreme value method. The specific process is as follows: Calculate according to formulas (1), (2), and (3): （1） （2） （3） In the formula: A 0 、A z 、A j These are the nominal dimensions of the closing ring, the increasing ring, and the decreasing ring, respectively. ES 0 ES z ES j These are the upper deviations of the closed loop, the increasing loop, and the decreasing loop, respectively. EI 0 EI z EI j , respectively, represent the lower deviations of the closed loop, increasing loop, and decreasing loop; m is the number of increasing loops; n is the number of decreasing loops; When the target cycle is a decreasing cycle, let the number be... j1 The calculation result is: the nominal size is A j1 Upper deviation is ES j1 The lower deviation is EI j1 , i.e., target ring j1 Actual size Aa j1 The acceptable range is: A j1 + EI j1 ≤Aa j1 ≤A j1 + ES j1 , expressed as deviation EI j1 ≤Ea j1 ≤ES j1 ， in Ea j1 For the target ring j1 The actual deviation; When the target ring is an increasing ring, let the number be... z1 The calculation result is: the nominal size is A z1 Upper deviation is ES z1 The lower deviation is EI z1 ; that is, the target ring z1 Actual size Aa z1 The acceptable range is: A z1 +EI z1 ≤Aa z1 ≤A z1 + ES z1 ， Expressed as deviation EI z1 ≤Ea z1 ≤ES z1 ,in Ea z1 For the target ring z1 The actual deviation; The above target ring j1 or target ring z1 The acceptable range is independent of the dimensions of other component rings and the closing ring; Step two involves calculating the maximum upper deviation and minimum lower deviation of the target loop, and the specific process is as follows: When the target loop is a decreasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows: Maximum upper deviation: (4) Minimum lower deviation: (5) In the formula ES′ j1 For the target ring j1 The maximum upper deviation, EI′ j1 For the target ring j1 The minimum lower deviation; When the target loop is an increasing loop, its maximum upper deviation and minimum lower deviation are calculated as follows: Maximum upper deviation: (6) Minimum lower deviation: (7) In the formula ES′ z1 For the target ring z1 The maximum upper deviation, EI′ z1 For the target ring z1 The minimum lower deviation; Step three involves calculating the dynamic upper and lower deviations of the target loop, and the specific process is as follows: When the target loop is a decreasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows: Dynamic deviation: (8) Dynamic deviation: (9) In the formula ES Σj1 For the target ring j1 Dynamic deviation; EI Σj1 For the target ring j1 Dynamic deviation; When the target loop is an increasing loop, its dynamic upper deviation and dynamic lower deviation are calculated as follows: Dynamic deviation: (10) Dynamic deviation: (11) In the formula ES Σz1 For the target ring z1 Dynamic deviation; EI Σz1 For the target ring z1 Dynamic deviation; Step four involves calculating the dynamic qualified area of the target ring, and the specific process is as follows: Actual deviations in the dimensions of the closed loop and the constituent loops E The relationship of a Available in every size EI≤Ea ≤ES The relationship, calculated as follows: When the target cycle is a decreasing cycle, the target cycle is... j1 The dynamic qualified zone is: （13） In the formula Ex For dynamic deviation variables; E aj1 The actual deviation of the target ring j1; When the target ring is an increasing ring, the target ring z1 The dynamic qualified zone is: （14） In the formula E az1 This represents the actual deviation of the target ring z1.
2. The method for calculating the machining process dimension chain based on a dynamic tolerance diagram according to claim 1, characterized in that: Step five, drawing the dynamic tolerance diagram of the process dimension chain, is as follows: The dynamic tolerance diagram of the process dimension chain uses a rectangular coordinate system, with the horizontal axis representing the design dimension or dimensional deviation of the increasing link and the vertical axis representing the dimensional deviation of the decreasing link. Let the sum of the maximum values of all increasing cycles be ∑ ES z The sum of all minimum values of increasing cycles is ∑ EI z The sum of the maximum values of all decreasing rings is ∑ ES j The sum of all minimum values of decreasing rings is ∑ EI j These four values can form a rectangle, which is an independent qualified area; On the dynamic tolerance diagram of the dimensional chain, each coordinate point corresponds to the size of the increasing and decreasing loops, so the size of the closed loop at that point can be calculated. Connecting the points with equal closed loop sizes forms a line, which is defined as the closed loop equal size line. When the target cycle is a decreasing cycle, the size of the increasing cycle is known, so ∑ ES z and ∑ EI z The value is fixed, and the target ring is calculated using the extreme value method. j1 of ES j1 and EI j1 ; ES j1 The dimensional chain is calculated from the upper left corner of the independent qualified area rectangle, at which point the closed loop is in the lower deviation position. EI 0 Draw a closed loop of equal dimensions from the upper left corner of the independent qualified area rectangle at a 45° angle to the upper right, so that it coincides with ∑ ES z The lines intersect at one point, forming a triangle, which is the qualified area for the upper condition; EI j1 The dimensional chain is calculated from the lower right corner of the independent qualified area rectangle, at which point the closed loop is in the upper deviation position. ES 0 Draw a closed loop of equal dimensions from the lower right corner of the independent qualified area rectangle at a 45° angle to the lower left, so that it coincides with ∑ EI z The lines intersect at one point, forming a triangle, which is the area where the lower condition is met; When the target ring is an increasing ring, the size of the decreasing ring is known, so ∑ ES j and ∑ EI j The value is fixed, and the target ring is calculated using the extreme value method. z1 of ES z1 and EI z1 ; ES z1 The dimensional chain is calculated from the lower right corner of the independent qualified area rectangle, at which point the closed loop is in the upper deviation position. ES 0 Draw a closed loop of equal dimensions from the lower right corner of the independent qualified area rectangle at a 45° angle to the upper right, so that it coincides with ∑ ES j The lines intersect at a point, forming a triangle, which is the qualified area on the right. EI z1 The dimensional chain is calculated from the upper left corner of the independent qualified area rectangle, at which point the closed loop is in the lower deviation position. EI 0 Draw a closed loop of equal dimensions from the top left corner of the independent qualified area rectangle at a 45° angle downwards to the left, so that it coincides with ∑ EI j The lines intersect at a point, forming a triangle, which is the qualified area on the left.