Method for optimizing production line layout based on line balance rate

Abstract

The present invention relates to a method for optimizing the layout of a production line based on the line balance rate, belonging to the field of engineering assembly. On the basis of the process flow, the present invention disassembles all operations into the smallest work steps and constructs a binary tree model; structurally analyzes the work step man-hour library; operations that are adjacent work steps but cross different types of work cannot be merged, and operations that violate the operation sequence or cross work steps cannot be merged; traverses the binary tree model to query each combination relationship and its number of workstations, and uses the mapping relationship between work steps and man-hours to obtain the line balance rate of this combination; compares all combination results to obtain the optimal line balance rate, and then inversely solves the optimal tact time, the optimal workstations and their corresponding combination relationships; the maximum value of the line balance rate is the optimal target scheme. The present invention can reasonably arrange assembly, inspection, testing and other links on the same production line with the optimal tact time and the optimal number of workstations, realizing a cross-type work cooperation and flexible production line layout design.

Description

Technical Field

[0001] The present invention belongs to the field of engineering assembly, and particularly relates to a method for optimizing the layout of a production line based on the line balance rate. Background Art

[0002] Most production in the engineering assembly manufacturing industry adopts a streamlined operation of combining multiple working steps into one process and serial production of multiple processes. To avoid the accumulation or idleness of station operations caused by significant differences in working hours, it is necessary to reasonably layout the production line to ensure the balance of the production line rhythm, improve the line balance rate and the utilization rate of the production line.

[0003] Currently, the research on the production line balance problem mainly carried out on the premise of a given production line rhythm or the minimum number of workstations, and calculation methods such as the programming method, heuristic algorithm, genetic algorithm, etc. mainly have the following problems:

[0004] 1. The programming method has a large amount of calculation when calculating the optimal line balance rate, and it is difficult to construct a mathematical model;

[0005] 2. It is difficult for the heuristic algorithm to obtain the optimal solution, and it depends on production practice and experience;

[0006] 3. The genetic algorithm is prone to violate the operation sequence, and it cannot solve the production problem of multi-type cooperation;

[0007] 4. When the production line rhythm and the number of workstations are not given, a large amount of trial and error is required in the early stage to explore a more reasonable rhythm or the number of workstations, and then calculations are carried out on this basis, consuming a large amount of labor and time costs.

[0008] During the assembly process, inspection links often need to be interspersed, and the post-assembly test operation is essential. Therefore, arranging assembly, inspection and testing on the production line at the same time can effectively reduce product turnover and improve production efficiency. However, the current production line balance rate calculation method does not consider the production problem of multi-type cooperation, nor does it propose a corresponding solution. Summary of the Invention

[0009] (1) Technical Problems to be Solved

[0010] The technical problem to be solved by the present invention is how to provide a method for optimizing the layout of a production line based on the line balance rate to solve the problems of discontinuous production process and low production efficiency caused by product turnover in current multi-type cooperation production.

[0011] (2) Technical Solutions

[0012] To solve the above technical problems, the present invention proposes a method for optimizing the layout of a production line based on the line balance rate, and the method includes the following steps:

[0013] S1. Form a process step library and a man-hour library according to the minimum process steps and man-hours in the operation instruction manual; and establish the mapping relationship between the process step names and the man-hour durations in the program, that is, the unique corresponding relationship between [a1, a2, a3, …, an] and [t1, t2, t3, …, tn].

[0014] S2. Construct a binary tree for all process steps according to the operation sequence.

[0015] S3. Obtain all combination results of adjacent process step mergers by pre-order traversing the binary tree, and retain the traversal records of all combination results.

[0016] S4. Calculate the line balance rate for each combination result. The calculation formula is: line balance rate = total duration / (number of workstations × production line beat) × 100%, where the beat represents the production operation time of each workstation, and the production line beat represents the beat of the workstation with the longest production time on the production line.

[0017] S5. By comparing all calculation results, obtain the line balance rate with the largest value, that is, the optimal line balance rate. Query the combination result under this line balance rate, and then inversely solve the corresponding production line beat, number of workstations, and the combination relationship of each process step, which is regarded as the optimal production line beat and the optimal number of workstations.

[0018] S6. Apply the finally solved combination result to the production line to achieve the consistency of the production line beat.

[0019] Furthermore, establishing the mapping relationship between the process step names and the man-hour durations in the program includes: establishing the mapping relationship between the process step names and the man-hour durations, that is, randomly searching for the process steps and man-hours among them, and being able to accurately find the corresponding man-hours and process steps.

[0020] Furthermore, in step S2 when constructing the binary tree, the sequence of process step operations should be satisfied.

[0021] Furthermore, constructing the binary tree in step S2 includes: regarding the first process step as the root node a1, and its left and right nodes respectively represent not merging with the first process step, denoted as (, a2), and merging with the first process step into the same workstation, denoted as (+a2), that is, represented as [a1, a2], [a1 + a2], and so on for subsequent process steps.

[0022] Furthermore, when constructing the binary tree, operations of adjacent process steps but across different job types cannot be merged, and operations that violate the operation sequence and cross process steps cannot be merged.

[0023] Furthermore, the pre-order traversal method includes: starting from the root node, following the principle of preferentially traversing all left nodes and then traversing the right node of the previous node, and recording each traversal process.

[0024] Further, after the step S3 and before the step S4, it further includes: obtaining the number of workstations and the production line beat of all combination results.

[0025] Further, if all production line operations are of the same type of work, a complete binary tree is formed, and there are 2n - 1 combinations in total, where n is the total number of work steps. It is necessary to exclude the situation where all work steps are combined at the same workstation, that is, all operation contents are completed by a single person.

[0026] Further, the number of workstations and the production line beat in the line balance rate are two independent variables, which are solved in the binary tree traversal. On this basis, the line balance rate is calculated, and the optimal line balance rate is obtained by comparison. Furthermore, the optimal beat, the optimal workstation and their corresponding combination relationships are solved inversely.

[0027] Further, given the production line beat or the number of workstations, among all the results of the binary tree traversal, all combination results corresponding to the production line beat or the number of workstations are solved, and the optimal solution is obtained among all the combination results.

[0028] (III) Beneficial effects

[0029] The present invention provides a production line layout optimization method based on the line balance rate. The beneficial effects of the present invention are as follows: On the premise of satisfying the sequence of work step operations, an algorithm for traversing a binary tree is innovatively adopted to quickly query all combination results of work step combination and multi-type work cooperation, solve the optimal line balance rate and its corresponding production line beat and the number of workstations, and ensure the continuity of the production process and high production efficiency. The time and space complexity of the algorithm is O(N), and the operation efficiency is high. Using the present invention can effectively solve the problem of preliminary workstation configuration according to experience and practice at the initial stage of receiving a new production order. The present invention can be applied to the production line layout design and has a broad application prospect. Description of the drawings

[0030] Figure 1 It is a schematic diagram of the binary tree model for multi-type work cooperation on the production line of the present invention;

[0031] Figure 2 It is a schematic diagram of the complete binary tree model for single-type work assembly on the production line;

[0032] Figure 3 It is an example of the binary tree algorithm for assembling printed circuit boards with multi-type work cooperation on the production line;

[0033] Figure 4 It is an example of the binary tree algorithm for assembling connectors with single-type work assembly on the production line. Specific implementation manners

[0034] To make the objectives, contents and advantages of the present invention clearer, the following further describes the specific implementation manners of the present invention in detail with reference to the drawings and embodiments.

[0035] The present invention discloses a production line layout optimization method based on the line balance rate, which can reasonably arrange assembly, inspection, testing and other links on the same production line with the optimal beat and the optimal number of workstations, so as to realize the cross-occupational cooperation and flexible production line layout design. The main method is to decompose all operations into the smallest work steps on the basis of the process flow and construct a binary tree model; structurally analyze the work step man-hour library; operations that are adjacent work steps but cross occupations cannot be merged, and operations that violate the operation sequence and cross work steps cannot be merged; traverse the binary tree model to query each combination relationship and its number of workstations, and use the mapping relationship between work steps and man-hours to obtain the line balance rate of this combination; compare all combination results to obtain the optimal line balance rate, and then inversely solve the optimal beat, the optimal number of workstations and their corresponding combination relationships; the maximum value of the line balance rate is the most target solution.

[0036] The purpose of the present invention is to provide a production line layout optimization method based on the line balance rate, to solve the problems of discontinuous production process and low production efficiency caused by product turnover in the current multi-occupational cooperation production, and at the same time, to provide a technical solution for quickly solving the optimal line balance rate on the premise that both the production line beat and the number of workstations are unknown.

[0037] The line balance rate calculation method provided by the present invention includes the following steps:

[0038] S1. According to the smallest work steps and man-hours in the operation instruction book, form a work step library and a man-hour library; and establish the mapping relationship between the work step name and the man-hour duration in the program, that is, the unique corresponding relationship between [a1, a2, a3,..., an] and [t1, t2, t3,..., tn];

[0039] S2. Construct a binary tree for all work steps according to the operation sequence;

[0040] S3. Obtain all combination results of adjacent work step mergers by pre-order traversing the binary tree, and retain the traversal records of all combination results;

[0041] S4. Calculate the line balance rate for each combination result. The calculation formula is: line balance rate = total duration / (number of workstations × production line beat) × 100%, where the beat represents the production operation time of each workstation, and the production line beat represents the beat of the workstation with the longest production time on the production line;

[0042] S5. By comparing all calculation results, obtain the line balance rate with the largest value, that is, the optimal line balance rate, query the combination result under this line balance rate, and then inversely solve the corresponding production line beat, the number of workstations and the combination relationship of each work step, which is regarded as the optimal production line beat and the optimal number of workstations;

[0043] S6. Apply the finally solved combination result to the production line to achieve the consistency of the production line beat.

[0044] Among them, after forming the work step library and the work time library according to the minimum work step and work time of the work instruction, the work step library and the work time library are used as the original data for constructing the binary tree. A mapping relationship between the work step name and the work time duration is established, that is, any search for the work step and work time can accurately find the corresponding work time and work step, avoiding the situation where the work step cannot be accurately located due to the same work time duration.

[0045] When constructing a binary tree, the order of the work steps should be met. Figure 1 As shown in the figure, the first work step is regarded as the root node a1, and its left and right nodes represent not merging with the first work step (, a2), merging with the first work step into the same work station (+a2), that is, [a1, a2], [a1+a2], and the subsequent work steps are analogous. In addition, the operation instructions must be strictly followed. Adjacent work steps but cross-type operations cannot be merged. Operations that violate the operation sequence and cross-step operations cannot be merged. Figure 1 The order of a1 and a2 cannot be changed, and a2 and b1 cannot be combined into the same workstation.

[0046] Among them, the pre-order traversal method is adopted, starting from the root node, with the principle of traversing all left nodes first and then traversing the right node of the previous node, and recording each traversal process. Figure 1 There are 4 combinations of all the work steps in the binary tree, namely [a1,a2,b1,b2,c1], [a1,a2,b1+b2,c1], [a1+a2,b1,b2,c1], [a1+a2,,b1+b2,c1]; "+" means that different work steps form a process and are merged into the same work station, and "," means that the work steps will no longer be merged and the operation will be completed by the next work station. Get the number of work stations and production line rhythm of all combination results. The number of work stations for the 4 combination results is 5, 4, 4, and 3 respectively; a, b, and c represent different types of work, such as assembly, inspection, and testing.

[0047] Among them, if the production operations of the production line are all the same type of work, a completely binary number is formed, and there are 2n-1 combinations in total, where n is the total number of work steps. It is necessary to exclude the situation where all work steps are combined in the same workstation, that is, all operations are completed by a single person.

[0048] Among them, the number of workstations and production line rhythm in the line balance rate are two independent variables, which are solved in the binary tree traversal, and the line balance rate is calculated on this basis. The optimal line balance rate is obtained through comparison, and then the optimal rhythm, optimal workstation and their corresponding combination relationship are reversely solved.

[0049] Among them, when a production line cycle or the number of workstations is given, all combination results corresponding to the production line cycle or the number of workstations can be solved among all the results of the binary tree traversal, and the optimal solution can be obtained among all the combination results.

[0050] The present invention will be described in detail below in conjunction with embodiments and the accompanying drawings. This embodiment is implemented through the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments. It should be noted that improvements and modifications made on the basis of the present invention all fall within the protection scope of the present invention.

[0051] The method for optimizing the production line layout based on the line balance rate provided by the present invention includes the following steps:

[0052] In the first step, read the minimum work steps and working hours in the operation instruction book to form a work step library and a working hour library. In this embodiment, it includes links such as assembly, inspection, and testing, as shown in Table 1:

[0053] Table 1

[0054]

[0055]

[0056] Establish the mapping relationship between the work step name and the working hour duration in the program. Represent the work step names [install steel sleeve, lay the PCB board flat, fasten the PCB board, inspect the size, take pictures, insulation test] with a sequence: [a1, a2, a3, b1, b2, c1]; represent the working hours [10, 5, 15, 20, 15, 25] with a sequence [t a1 , t a2 , t a3 , t b1 , t b2 , t c1 , so that the work step name and the working hours are bound in the program to avoid the situation where it is impossible to distinguish between fastening the PCB board a3 and taking pictures tb2 when the working hour values are the same: t b2 = t a3 = 15s.

[0057] In the second step, on the premise of satisfying the sequence of work step operations, construct a binary tree model. In this embodiment, according to the process flow and following the principle that operations of adjacent work steps but across work types cannot be merged, and operations of the same work type but across work steps cannot be merged, construct a binary tree, as Figure 3 shown.

[0058] In the third step, adopt the pre-order traversal method to traverse the binary tree constructed in this embodiment, with a total of 8 combination results, as shown in Table 2:

[0059] Table 2

[0060]

[0061] In the fourth step, the line balance rate calculation formula in this implementation is: η = T / (M × Pt max ) × 100%

[0062] Among them, η is the line balance rate (generally reasonable above 85%, and the balance loss rate should be controlled below 5% - 13%), Pt max is the production line tact time (the working hours of the longest workstation), T is the total production duration, and M is the number of workstations. In this embodiment, the total production duration is t a1 +t a2 +t a3 +t b1 +t b2 +t c1 =87s. The line balance rates of the 8 combination results are respectively: 66%, 50%, 80%, 62%, 79%, 62%, 73%, 97%. It can be seen from the results that the line balance rate of the 8th combination result is the best, and the combination relationship is [a1 + a2 + a3, b1 + b2, c1]. Installing the steel sleeve, laying the PCB board flat, and fastening the PCB board are combined into one workstation, inspecting the size and taking pictures are combined into one workstation, and the insulation test is in a separate workstation. A total of 3 workstations are required, and the bottleneck tact time is 30s.

[0063] Step 5 In this embodiment, on the premise of giving the production line tact time or the number of workstations in advance, for example, if the number of production line workstations is required to be 5, a total of 3 combinations can be obtained: [a1, a2, a3, b1 + b2, c1], [a1, a2 + a3, b1, b2, c1], [a1 + a2, a3, b1, b2, c1]. The line balance rates are respectively 50%, 80%, 79%. From this, the optimal line balance rate can be obtained as 80%, and the combination relationship: installing the steel sleeve is in a separate workstation, laying the PCB board flat and fastening the PCB board are combined into one workstation, inspecting the size is in a separate workstation, taking pictures is in a separate workstation, and the insulation test is in a separate workstation. The production line tact time is 22s.

[0064] Step 6 If the production line is a single assembly type of work, including installing the shielding pad, installing the connector, component insertion, and fastening the components, the working hours and work steps are shown in Table 3:

[0065] Table 3

[0066] Type of work Name of work step Man-hour / s Assembly 1 Install shielding gasket 7 Assembly 2 Install connector 25 Assembly 3 Mate components 13 Assembly 4 Fasten components 27

[0067] Establish the mapping relationship between the work step names and the working hours in the program. Represent the work step names [installing the shielding pad, installing the connector, component insertion, fastening the components] with a sequence: [a1, a2, a3, a4]; represent the working hours [7, 25, 13, 27] with a sequence [t1, t2, t3, t4]. On this basis, construct a full binary tree model, as Figure 4 shown. Using the pre-order traversal method, traverse the binary tree constructed in this embodiment. There are a total of 8 combination results, as shown in Table 4:

[0068] Table 4

[0069]

[0070] In this embodiment, the total production time is t1 + t2 + t3 + t4 = 72 s. It is necessary to exclude the situation where all work steps are combined at the same work station, as shown in item 8 of Table 4. The line balance rates of the combination results in 7 are: 67%, 60%, 63%, 55%, 75%, 90%, and 80% respectively. It can be seen from the results that the line balance rate of the 6th combination result is the best, and the combination relationship is [a1 + a2, a3 + a4]. Installing the shielding pad and the connector are combined into one work station, and the device insertion and fastening components are combined into one work station. A total of 2 work stations are required, and the bottleneck beat is 40 s.

[0071] The above method has high operation efficiency, can ensure the continuity of the production process during multi-type cooperation, has high production efficiency, and can further improve the production capacity.

[0072] Embodiment:

[0073] The production line layout optimization method based on the line balance rate of the present invention includes:

[0074] According to the minimum work steps and working hours in the operation instruction book, a work step library and a working hour library are formed, and a mapping relationship between the work step name and the working hour duration is established in the program, that is, the unique corresponding relationship between [a1, a2, a3,..., an] and [t1, t2, t3,..., tn]; all work steps are constructed into a binary tree according to the operation sequence, and all combination results of adjacent work step combinations are obtained by traversing the binary tree; the line balance rate is calculated for each combination result, and the calculation formula is: line balance rate = total duration / (number of work stations × production line beat) × 100%; by comparing all calculation results, the optimal line balance rate is obtained, and then the optimal beat, the optimal work station and their corresponding combination relationships are solved reversely; the optimal combination result is applied to the production line to achieve optimal beat production.

[0075] Furthermore, according to the minimum work steps and working hours in the operation instruction book, a work step library and a working hour library are formed, and the work step library and the working hour library are used as the original data for constructing the binary tree. And a mapping relationship between the work step name and the working hour duration is established, that is, randomly searching for the work steps and working hours therein can accurately find the corresponding working hours and work steps, avoiding the situation where the work steps cannot be accurately located due to the same working hour duration.

[0076] Furthermore, when constructing the binary tree, the sequence of work step operations should be satisfied, and the operations should be strictly performed according to the operation instruction book. Operations of adjacent work steps but across different types of work cannot be combined, and operations that violate the operation sequence and cross work steps cannot be combined. For example Figure 1 the order of a1 and a2 cannot be changed, and a2 and b1 cannot be combined into the same work station.

[0077] Furthermore, the preorder traversal method is adopted to traverse Figure 1All the process step combination results of the binary tree are 4 types, namely [a1, a2, b1, b2, c1], [a1, a2, b1 + b2, c1], [a1 + a2, b1, b2, c1], [a1 + a2, b1 + b2, c1]; where "+" means different process steps form a process, merged in the same work station, and "," means the process steps are no longer merged and the operations are completed by the next work station. The number of work stations for the 4 combination results are 5, 4, 4, and 3 respectively; a, b, and c represent different job types, such as assembly, inspection, testing, etc.

[0078] Furthermore, if all the production operations on the production line are of the same job type, a complete binary tree is formed, and there are 2n - 1 combinations in total, where n is the total number of process steps. As Figure 2 shown, all the situations where all process steps are merged in the same work station need to be excluded, that is, all the operation contents are completed by one person.

[0079] Furthermore, the number of work stations and the production line cycle time in the line balance rate are two independent variables, which are solved in the binary tree traversal, and based on this, the line balance rate is calculated. The optimal line balance rate is obtained through comparison, and then the optimal cycle time, optimal work stations and their corresponding combination relationships are solved inversely.

[0080] Furthermore, given the production line cycle time or the number of work stations, all the combination results corresponding to the production line cycle time or the number of work stations can be solved among all the results of the binary tree traversal, and the optimal solution can be obtained among all the combination results.

[0081] The beneficial effects of the present invention are as follows: On the premise of satisfying the sequence of process step operations, the algorithm of traversing the binary tree is innovatively adopted to quickly query all the combination results of process step merging and multi-job type cooperation, solve the optimal line balance rate and its corresponding production line cycle time and number of work stations, and ensure the continuity of the production process and high production efficiency. The time and space complexity of the algorithm is O(N), and the running efficiency is high. Using the present invention can effectively solve the problem of preliminary work station configuration based on experience and practice exploration at the initial stage of receiving new production orders. The present invention can be applied to the production line layout design and has a broad application prospect.

[0082] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A production line layout optimization method based on the line balance rate, characterized in that The method includes the following steps: S1. Form a process step library and a man-hour library according to the minimum process steps and man-hours in the operation instruction book; and establish a mapping relationship between the process step names and the man-hour durations in the program, that is, the unique corresponding relationship between [a1, a2, a3, …, an] and [t1, t2, t3, …, tn]; S2. Construct a binary tree for all the process steps in the operation sequence; S3. Obtain all the combination results of adjacent process step merges by pre-order traversing the binary tree, and retain the traversal records of all the combination results; S4. Calculate the line balance rate for each combination result. The calculation formula is: line balance rate = total duration / (number of workstations × production line beat) × 100%, where the beat represents the production operation time of each workstation, and the production line beat represents the beat of the workstation with the longest production time on the production line; S5. By comparing all the calculation results, obtain the line balance rate with the largest value, that is, the optimal line balance rate. Query the combination result under this line balance rate, and then inversely solve the corresponding production line beat, number of workstations, and the combination relationship of each process step, which are regarded as the optimal production line beat and the optimal number of workstations; S6. Apply the finally solved combination result to the production line to achieve the consistency of the production line beat; Among them, In step S2, constructing the binary tree includes: regarding the first process step as the root node a1, and its left and right nodes respectively represent not merging with the first process step, denoted as (, a2), and merging with the first process step into the same workstation, denoted as (+a2), that is, represented as [a1, a2], [a1 + a2], and so on for the subsequent process steps.

2. The production line layout optimization method based on the line balance rate according to claim 1, characterized in that, Establishing the mapping relationship between the process step names and the man-hour durations in the program includes: establishing the mapping relationship between the process step names and the man-hour durations, that is, randomly searching for the process steps and man-hours among them, and being able to accurately find the corresponding man-hours and process steps.

3. The production line layout optimization method based on the line balance rate according to claim 1, characterized in that, In step S2, when constructing the binary tree, the sequence of process step operations should be satisfied.

4. The production line layout optimization method based on the line balance rate according to claim 1, wherein When constructing the binary tree, operations of adjacent process steps but across different types of work cannot be merged, and operations that violate the operation sequence and cross process steps cannot be merged.

5. The production line layout optimization method based on the line balance rate according to claim 1, wherein, The pre-order traversal method includes: starting from the root node, following the principle of preferentially traversing all the left nodes and then traversing the right node of the previous node, and recording each traversal process.

6. The production line layout optimization method based on the line balance rate according to claim 1, wherein, After step S3 and before step S4, it also includes: obtaining the number of workstations and the production line beat of all the combination results.

7. The production line layout optimization method based on the line balance rate according to any one of claims 1-6, characterized in that, If all the production operations on the production line are of the same type of work, a complete binary tree is formed, and there are 2n - 1 combinations in total, where n is the total number of process steps. The situation where all the process steps are merged into the same workstation, that is, all the operation contents are completed by a single person, needs to be excluded.

8. The production line layout optimization method based on the line balance rate according to any one of claims 1-6, characterized in that, The number of workstations and the production line beat in the line balance rate are two independent variables, which are solved during the binary tree traversal. On this basis, the line balance rate is calculated, and the optimal line balance rate is obtained by comparison. Then, the optimal beat, optimal number of workstations, and their corresponding combination relationships are inversely solved.

9. The production line layout optimization method based on the line balance rate according to any one of claims 1-6, characterized in that, Given the production line beat or the number of workstations, among all the results of the binary tree traversal, solve all the combination results corresponding to the production line beat or the number of workstations, and obtain the optimal solution among all the combination results.

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