Integrated Scheduling Method Considering Reworked Workpieces

Abstract

A comprehensive scheduling method considering rework workpieces. The method of the present invention includes: First, calculate the lengths of each path including the standard path and the path where the quality inspection subtree is located, arrange the lengths of each path in descending order, and determine the path to be preferentially scheduled according to the order from high to low of the lengths of each path; improve the original process tree, set a virtual rework node after the quality inspection point to store the rework process, and when the quality inspection point is scheduled and rework is required, add the process in the virtual rework node to the set of schedulable processes; when the scheduled path is the path where the quality inspection subtree is located and there are multiple such paths with the same path length, arrange them in descending order from high to low according to the rework factor, and schedule the quality inspection subtree in this order; for different process attributes, schedule them according to the rework adaptive scheduling strategy; finally, arrange production according to the scheduling Gantt chart; the present invention is used for a comprehensive scheduling problem considering the existence of rework workpieces.

Description

Technical Field

[0001] The present invention relates to a comprehensive scheduling method considering the existence of rework workpieces. Background Art

[0002] Recently, there have been a large number of studies on various comprehensive scheduling problems. However, for the comprehensive scheduling problem considering the existence of rework workpieces, there are few research results and further research is needed. In actual production scheduling, there is often a situation where a class of unqualified workpieces need to be returned to the processing machine for reprocessing to become qualified workpieces. To solve this situation, quality inspection points are set at key workpieces. If the quality inspection fails, rework is required, and only after rework can the subsequent processes be processed. Summary of the Invention

[0003] The object of the present invention is to provide a comprehensive scheduling method considering rework. This method calculates the length of each path and schedules the processes with different attributes on its path in descending order of the path length. When there are multiple quality inspection subtree paths with the same length, the processing priority of the quality inspection subtree is determined through the quality inspection subtree selection strategy.

[0004] Through the rework adaptive scheduling strategy, it adaptively determines which method to use to schedule the processes with different attributes on the path, and finally determines the scheduling order of each process of the product.

[0005] The above object is achieved by the following technical solutions:

[0006] The characteristics are as follows: First, determine the length of each path, including the standard path and the path length with a quality inspection subtree. The path length with a quality inspection subtree is jointly determined by the length of the path immediately following the quality inspection point, the processing time of the quality inspection subtree, and the length of the long path of the subtree. Determine the path to be preferentially scheduled according to the sorting of each path length from high to low. Propose a rework factor and determine the processing priority of the quality inspection subtree according to the quality inspection subtree determination strategy. Set a virtual rework node to store the rework process. When the quality inspection point is scheduled and rework is required, add the process in the virtual rework node to the set of schedulable processes. For the processes on different paths, schedule them according to the rework adaptive scheduling strategy. Finally, arrange production according to the scheduling Gantt chart.

[0007] The comprehensive scheduling method for partially dynamic products with due dates considering the urgency index, the specific implementation steps of the scheduling method are as follows:

[0008] Step 1: Set the product process attributes, Pi / Mi / Ti / Bi / Li / Qi / Di, which are respectively: product process number / processing equipment / processing time / the process immediately following Pi / the quality inspection status of Pi / rework factor;

[0009] Step 2: Determine the path length of each path. The path length of the path with a quality inspection subtree is jointly determined by the sum of the processing times of the quality inspection subtree, the sum of the long paths of the quality inspection subtree, and the length of the immediate successor path of the quality inspection point.

[0010] Step 3: Compare the length of the current longest standard process path with the length of the path where the current longest quality inspection subtree is located. If the length of the standard process path is greater than the length of the path where the quality inspection subtree is located, jump to Step 6; otherwise, jump to Step 4.

[0011] Step 4: Determine whether the current longest path with a quality inspection subtree is unique. If it is, jump to Step 6; if not, jump to Step 5.

[0012] Step 5: Select the quality inspection subtree to be processed first according to the quality inspection subtree selection strategy.

[0013] Step 6: According to the different attributes of the process processing type, determine the process scheduling order according to the adaptive long-path scheduling strategy.

[0014] Step 7: If there are un-scheduled quality inspection subtrees, jump to Step 3; if not, jump to Step 8.

[0015] Step 8: Determine the scheduling order of the remaining processes according to the adaptive long-path scheduling strategy.

[0016] Step 9: If the scheduling node is the root node, output the scheduling Gantt chart, and produce the products that meet the delivery date according to the scheduling Gantt chart.

[0017] For the product with rework, that is, for a certain product, quality inspection points are set at some assembly nodes. The quality inspection point is a special type of process used to detect the quality of workpieces and includes quality inspection time. Only when the quality inspection point scheduling is completed and the quality inspection is unqualified can the rework event be triggered; the subtree with the quality inspection point as the parent node is called the quality inspection subtree; after quality inspection, the workpiece may trigger a rework event and needs to be reprocessed. The rework needs to be carried out after the processing of its quality inspection point is completed, and its immediate successor process needs to start scheduling after the rework is completed.

[0018] The comprehensive scheduling method considering workpieces with rework is characterized in that: for the rework adaptive scheduling strategy, first determine whether the current longest path length is the standard path or the path with a quality inspection subtree; if it is the standard process, continue to determine whether there is a quality inspection subtree in the subtree. If there is, process until the length of the longest standard path is greater than the length of the current longest path with a quality inspection subtree, otherwise select the leaf node of the current path in descending order of path length; if it is the path where the quality inspection subtree is located, give priority to processing the quality inspection subtree completely.

[0019] Beneficial effects:

[0020] In view of the characteristics of products with rework, the present invention proposes an improved processing process tree with rework, fully considering the constraint relationship between the rework process, the quality inspection point and its subsequent processes, and converting the integrated scheduling problem with rework constraints into a general integrated scheduling problem.

[0021] According to the characteristics of rework and its impact on the completion time, the present invention proposes a rework factor, and determines the scheduling order of the quality inspection subtree according to the size of the rework factor, which shortens the maximum completion time of the product to a certain extent.

[0022] In view of the processes with different attributes on different paths, the present invention proposes a rework adaptive scheduling strategy, adopts different methods for processing processes with different attributes, takes into account the characteristics of rework constraints and the connections in the vertical and horizontal directions, and increases the opportunity for parallel processing. Brief Description of the Drawings

[0023] Attached Figure 1 is a flowchart of the scheduling algorithm considering rework of the present invention.

[0024] Attached Figure 2 is a flowchart of the adaptive scheduling algorithm of the present invention.

[0025] Attached Figure 3 is a legend of the processing process tree of product A of the present invention.

[0026] Attached Figure 4 is a legend of the improved processing process tree of product A considering rework of the present invention

[0027] Attached Figure 5 is for the present invention in view of the attached Figure 4 shown scheduling Gantt chart results of the process tree. Detailed Embodiments

[0028] Embodiment 1:

[0029] An integrated scheduling method considering workpieces with rework, characterized in that: the integrated scheduling method includes the following steps: first, determine the lengths of each path, including the standard path and the path length with a quality inspection subtree, where the path length with a quality inspection subtree is jointly determined by the subsequent path length of the quality inspection point, the processing time of the quality inspection subtree, and the length of the subtree long path, and determine the path to be preferentially scheduled according to the order from high to low of the lengths of each path; propose a rework factor, and determine the processing priority of the quality inspection subtree according to the quality inspection subtree determination strategy; set a virtual rework node to store the rework process, and when the quality inspection point is scheduled and rework is required, add the process in the virtual rework node to the set of schedulable processes; for the processes on different paths, schedule them according to the rework adaptive scheduling strategy; finally, arrange production according to the scheduling Gantt chart.

[0030] Embodiment 2:

[0031] Step 1: Set the product process attributes, Pi / Mi / Ti / Bi / Li / Qi / Di, which are: product process number / processing equipment / processing time / the immediate successor process of Pi / the quality inspection status of Pi / rework factor;

[0032] Step 2: Determine the path length of each path. The path length of the path with a quality inspection subtree is jointly determined by the sum of the processing times of the quality inspection subtree, the length of the longest path in the quality inspection subtree, and the length of the immediate successor path of the quality inspection point;

[0033] Step 3: Compare the length of the current longest standard process path with the length of the path where the current longest quality inspection subtree is located. If the standard process path length is greater than the length of the path where the quality inspection subtree is located, jump to Step 6; otherwise, jump to Step 4;

[0034] Step 4: Determine whether the current longest path with a quality inspection subtree is unique. If it is, jump to Step 6; if not, jump to Step 5;

[0035] Step 5: Select the quality inspection subtree to be preferentially processed according to the quality inspection subtree selection strategy.

[0036] Step 6: According to the different attributes of the process processing type, determine the process scheduling order according to the rework adaptive scheduling strategy;

[0037] Step 7: If there are unscheduled quality inspection subtrees, jump to Step 3; if not, jump to Step 8;

[0038] Step 8: Determine the remaining process scheduling order according to the adaptive long path scheduling strategy;

[0039] Step 9: If the scheduling node is the root node, output the scheduling Gantt chart and produce the products that meet the delivery date according to the scheduling Gantt chart.

[0040] Example 3:

[0041] For the product with rework, that is, for a certain product, quality inspection points are set at some assembly nodes. The quality inspection point is a special type of process used to detect the quality of workpieces, including the quality inspection time. Only when the quality inspection of the quality inspection point is completed and the inspection is unqualified can the rework event be triggered; the subtree with the quality inspection point as the parent node is called the quality inspection subtree; after quality inspection, the workpiece may trigger a rework event, and the workpiece needs to be reprocessed. The rework needs to be carried out after the processing of its quality inspection point, and its immediate successor process needs to start scheduling after the rework is completed.

[0042] For the rework adaptive scheduling strategy described above, first determine whether the length of the current longest path is the standard path or a path with a quality inspection subtree; if it is a standard process, continue to determine whether there is a quality inspection subtree within the subtree. If there is, continue processing until the length of the longest standard path is greater than the length of the current longest path with a quality inspection subtree. Otherwise, select the leaf nodes of the current path in descending order of path length; if it is a path where the quality inspection subtree is located, give priority to processing the quality inspection subtree until completion.

[0043] Example 4:

[0044] The above comprehensive scheduling method considering rework workpieces, as shown in the appendix Figure 1 is the product processing flow chart example of the present invention, which introduces the product processing process and the algorithms used:

[0045] The following will combine the product processing flow chart in the appendix Figure 1 to illustrate the specific execution process of this technology. As shown in the appendix Figure 3 and appendix Figure 4 , the number of processing steps of product A is 13, and each step has different attribute information. The rectangular boxes in the figure respectively represent: product process name / product process processing equipment name / product process processing time.

[0046] Example 5:

[0047] For the above comprehensive scheduling method considering rework workpieces, the following will use this scheduling method to perform scheduling on the improved processing process tree example of the product with rework shown in the appendix Figure 4 . In the appendix Figure 4 , q1 and q2 are respectively the two quality inspection points of this product. Virtual rework nodes are set after the two quality inspection points, and the corresponding quality inspection subtrees are placed in the rework nodes, and rework operations are performed at both quality inspection points during the processing.

[0048] First, calculate the lengths of each path. From left to right, they are 13 (including the quality inspection subtree q1), 7, 9, 15, 13 (including the quality inspection subtree q2). Since the current longest path is the standard path, according to the rework adaptive scheduling strategy, process 14 is selected. After the scheduling of process 14 is completed, the current longest paths are the two paths containing quality inspection subtrees. According to the quality inspection subtree selection strategy, the rework factors of the two are calculated. By comparing the magnitudes of the rework factors, the quality inspection subtree q2 is preferentially processed. After scheduling the quality inspection subtree q2 according to the rework adaptive scheduling strategy, the processes in the immediate successor rework virtual node of q2 are released. Select the current longest path again. At this time, it is the quality inspection subtree q1. Similarly, after scheduling the entire quality inspection subtree q1 according to the rework adaptive scheduling strategy, the processes in its immediate successor rework virtual node are released. Since there are no longer quality inspection subtrees in the remaining process tree at this time, the remaining standard processes are scheduled again according to the rework adaptive scheduling strategy, and finally the scheduling order of all processes is determined; according to the Figure 1 shown process, this scheduling method is used to schedule the product process tree shown in Appendix Figure 3 and Appendix Figure 4 until all processes are processed. The Gantt chart of the scheduling result is shown in Appendix Figure 5 as shown.

[0049] Example 6:

[0050] Analysis of the above comprehensive scheduling method considering rework workpieces, case analysis.

[0051] Next, the scheduling method of the present invention will be analyzed by example. At the start time of the product, the current longest path is the path where process 14 is located, with a length of 15. After the scheduling is completed, the length of the remaining paths is the longest for the paths containing quality inspection subtrees. Processing starts according to the adaptive strategy. According to the quality inspection subtree selection strategy, it is determined that the rework factor of the q2 quality inspection subtree is larger. After scheduling the q2 quality inspection subtree, the rework processes in its virtual node are released. Similarly, after scheduling the entire quality inspection subtree q1 according to the rework adaptive scheduling strategy, the processes in its immediate successor rework virtual node are released. Finally, the remaining processes are scheduled by the adaptive scheduling method; this method takes into account the characteristics of rework constraints and the vertical and horizontal connections of the process tree, and at the same time enables the two immediate successor virtual rework nodes of q1 and q2 to be released as early as possible, which also increases their parallelism with other processes.

[0052] Therefore, the comprehensive scheduling method proposed by the present invention can better solve such problems.

Claims

1. An integrated scheduling method considering the existence of reworked workpieces, characterized in that : The integrated scheduling method includes the following steps: First, determine the lengths of each path, including the length of the standard path and the path length with a quality inspection subtree. The path length with a quality inspection subtree is jointly determined by the length of the immediate successor path of the quality inspection point, the processing time of the quality inspection subtree, and the length of the long path of the subtree. Sort the paths in descending order of their lengths to determine the paths to be scheduled first. Propose a rework factor and determine the processing priority of the quality inspection subtree according to the quality inspection subtree determination strategy. Set up a virtual rework node to store the rework processes. When the quality inspection point is scheduled and rework is required, add the processes in the virtual rework node to the set of schedulable processes. For the processes on different paths, schedule them according to the rework adaptive scheduling strategy. Finally, arrange production according to the scheduling Gantt chart. The specific implementation steps of the scheduling method are as follows: Step 1: Set the product process attributes, Pi / Mi / Ti / Bi / Li / Qi, which are respectively: product process number / processing equipment / processing time / immediate successor process of Pi / quality inspection status of Pi / rework factor; Step 2: Determine the path length of each path. The path length with a quality inspection subtree is jointly determined by the processing time of the quality inspection subtree, the sum of the lengths of the long paths of the quality inspection subtree, and the length of the immediate successor path of the quality inspection point; Step 3: Judge the size of the current longest standard process path length and the path length of the subtree where the current longest quality inspection subtree is located. If the standard process path length is greater than the path length of the subtree where the quality inspection subtree is located, jump to Step 6; if not, jump to Step 4. Step 4: Judge whether the current longest path with a quality inspection subtree is unique. If it is, jump to Step 6; if not, jump to Step 5; Step 5: Select the quality inspection subtree to be processed first according to the quality inspection subtree selection strategy; Step 6: According to the different attributes of the process processing type, determine the process scheduling order according to the rework adaptive scheduling strategy; Step 7: If there are unscheduled quality inspection subtrees, jump to Step 3; if not, jump to Step 8; Step 8: Determine the scheduling order of the remaining processes according to the adaptive long path scheduling strategy; Step 9: If the scheduling node is the root node, output the scheduling Gantt chart and produce the products that meet the delivery date according to the scheduling Gantt chart.

2. The integrated scheduling method considering rework workpieces according to claim 1, characterized in that: For the product with rework, that is, for a certain product, set quality inspection points at some assembly nodes. The quality inspection point is a special type of process used to detect the quality of workpieces and includes the quality inspection time. Only when the quality inspection point is scheduled and the quality inspection is unqualified can the rework event be triggered; The subtree with the quality inspection point as the parent node is called the quality inspection subtree; After quality inspection, the workpiece will trigger a rework event and needs to be reprocessed. The rework needs to be carried out after the quality inspection point is processed, and its immediate successor process needs to start scheduling after the rework is completed.

3. The integrated scheduling method considering rework workpieces according to claim 1 or 2, characterized in that: For the rework adaptive scheduling strategy, first judge whether the current longest path length is the standard path or the path with a quality inspection subtree; if it is the standard process, continue to judge whether there is a quality inspection subtree in the subtree. If there is, process it until the longest standard path length is greater than the current longest path length with a quality inspection subtree, otherwise select the leaf nodes of the current path in descending order of path length; if it is the path where the quality inspection subtree is located, give priority to processing the quality inspection subtree completely.

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