Tool Magazine Slot Assignment Using Greedy Feeder Scheduling
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Solution Overview
Problem
Existing methods for assigning tools to locations in a machine tool's tool magazine are inefficient, leading to prolonged waiting times for the machine tool due to the feeder's movement times, especially when processing sequences with varying tool distances and times.
Innovation Solution
A method using a greedy algorithm to iteratively select and assign tools to locations in the tool magazine, minimizing feeder trips and waiting times by prioritizing tools with shorter processing times and optimizing tool placement based on feeder transport times, which can be implemented on a standard computer for practical use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mixed integer programming is used to optimize tool assignment, then the optimality of the solution is improved, but the processing time becomes unacceptable for practical problem sizes
Solution Approach 1:
The patent segments the tool assignment problem into smaller subproblems by grouping tools into tool groups and processing them separately. This decomposition allows the system to handle large problem sizes (500 work steps, 100 tools, 250 locations) efficiently while still achieving near-optimal solutions, avoiding the computational intractability of applying mixed integer programming to the entire problem at once.
Solution Approach 2:
The patent applies local optimization by focusing on optimizing tool assignments within specific tool groups and their associated work steps rather than attempting global optimization across all tools simultaneously. This local quality approach enables practical processing times while maintaining solution quality for each local group.
2Quantity of substance
If tools are placed in locations far from the transfer point, then more tools can be stored in the tool magazine, but the feeder movement time increases causing machine tool waiting
Solution Approach 1:
The patent performs preliminary assignment of tools to specific locations in the tool magazine based on their usage patterns and processing times before actual machining operations begin. By pre-optimizing the spatial arrangement of tools according to their operational characteristics, the system ensures that frequently used tools with short processing times are positioned closer to the transfer point, minimizing feeder movement time while maintaining high storage capacity.
Solution Approach 2:
Different locations in the tool magazine are assigned different qualities based on their distance from the transfer point. Tools are strategically placed in locations with appropriate qualities matching their processing requirements - tools with short processing times are placed in locations closer to the transfer point, while tools with longer processing times can be placed farther away, optimizing both storage capacity and retrieval efficiency.
3Loss of time
If the feeder transports tools to locations closer to the transfer point, then waiting time is reduced, but the effective storage capacity of the tool magazine decreases
Solution Approach 1:
The patent implements a dynamic tool assignment strategy where tool locations are not fixed but are optimized based on the specific sequence of work steps to be executed. The system dynamically determines the optimal assignment of tools to locations considering the actual usage patterns, allowing the effective storage volume to be maximized for each specific production scenario while ensuring that tools required for upcoming operations are positioned to minimize waiting time.
Data Source
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AI summary
The invention relates to a machine tool which is designed to carry out a specified sequence of work steps. A tool and a processing time is assigned to each work step. A tool magazine is designed to keep a number of tools ready for the machine tool and comprises a feeder for conveying tools from and to a transfer point for the machine tool. In a method for assigning tools to spaces of the tool magazine, a number of work steps are determined from the sequence, the respective processing time of each work step being shorter than a specified cycle time of the tool magazine. A work step is iteratively selected from the number of work steps; a previously used tool and a subsequently used tool are assigned spaces of the tool magazine; and the work step is removed from the number of work steps. The tools are assigned spaces such that the machine tool must not wait on the feeder if possible when transitioning from one work step to the following work step. The selection of the work step from the number of work steps is carried out according to a greedy algorithm such that by assigning spaces to the previous tool and to the subsequent tool, as many movements as possible which are required as part of other work steps of the number of work steps are determined anew.