1) The manager sends the production information, NC program and so on to the production management system. The production management system calculates the number of tools needed in the whole process according to the production volume, the number of tools used in parts processing and the tool life.

2) According to the number of tools provided by the production management system, the operator measures the tool data on the tool regulator and automatically stores it in the tool holder chip (each tool holder has a unique ID identity).

3) The tool is loaded into the central tool magazine. The tool manipulator automatically reads the tool information through the chip and stores the tool information in the central tool magazine. The central tool magazine loads the tool into the corresponding tool magazine according to the instructions issued by the production management system. The machine tool automatically reads the tool information through the chip and stores the tool in the tool list of the machine tool.

4) In the process of using tools, the production management system needs to obtain real-time data of tool wear correction and tool life, and make information feedback on the use of tools according to the data;

5) According to the production plan, the operator loads the parts into the fixture in the loading and unloading station, loads the fixture into the tray and finds the parts.

6) The operator scans the tray chip (each tray has a unique ID identity) and stores the tray information in the production management system.

7) The production management system transfers the pallet information to the loading and unloading manipulator and the corresponding equipment. The loading and unloading manipulator automatically recognizes the pallet chip in the pallet storehouse, the equipment automatically opens the door, and the loading and unloading manipulator sends the pallet with the corresponding fixture to the corresponding equipment. The equipment automatically closes the door and feeds the information back to the production management system.

8) The probe for parts processing is used to collect information, and the clamping of parts is automatically corrected according to the collected information.

9) The tool wear in the machining process is automatically compensated by the on-line measurement of the tool setting instrument.

10) In the process of part machining, the tool breakage or fracture is detected online by the tool setting instrument in the machine, and the alarm information to be replaced is sent out. At the same time, it is fed back to the central control system, and the sister tool is preferred for machining, and the tool to be replaced is automatically withdrawn to the tool loading and unloading station.

11) The tool life has arrived in the process of parts processing. The alarm information that needs to be replaced is fed back to the production management system. The sister tool is preferred for processing, and the tool that needs to be replaced is automatically withdrawn to the tool loading and unloading station.

12) When the production management system receives the information of the end of the parts processing, the parts are rinsed and cleaned by the cleaning equipment, and the parts are detected by the online detection equipment, and the results are fed back to the production management system.

13) When the parts are qualified, the equipment door opens automatically, and the loading and unloading manipulator loads the tray into the tray library.

14) When the parts are not qualified, the production management system automatically determines whether manual intervention is needed according to the unqualified situation:

A,the need for manual intervention, the system automatically alarms, the device automatically opens the door, the loading and unloading manipulator will load the tray into the loading and unloading station, by manually removing the fixture in other equipment for supplementary processing;

B,without manual intervention, the system automatically adjusts the tool parameters according to the measurement results.

15) The automatic manufacturing process of the casing processing unit is completed.

1) Processing equipment. Because a large number of turning and milling processes are involved in the processing of Al-Mg casing parts, and the part surface is inclined with a certain angle⁶, when selecting the processing equipment, the first equipment to be determined is the five-axis machining center. Considering the processing experience, equipment precision and equipment price of similar equipment, this paper selects THM6363 IV precision horizontal five-axis machining center, JM50m turn-milling complex machining center is used as the main processing equipment to build the casing manufacturing cell.

2) Material transportation robot and guide rail. The aluminum magnesium casing parts produced by this manufacturing cell are about 10kg, plus the tray and tooling fixture, the robot load can reach up to 100kg. According to the determined size of the machining center, the working height range of the robot and the operational space range of the workpiece transportation, the robot is required to have a maximum operating radius of at least 1000mm on the x-axis, and the robot’s repeated positioning accuracy shall not be greater than ± 0.03mm. Considering the above conditions, the material transport robot finally selected in this paper is the LS500 robot. The robot is equipped with RFID reading and writing system, which can realize the reading and writing of tray information and the tray exchange between the tray warehouse and the equipment.

3) Loading and unloading station. A dual-station loading and unloading station can load and unload two parts at the same time. Four positioning sleeves are distributed on the loading and unloading platform for the positioning of pallets. The loading and unloading station is equipped with a dial gauge clamping bracket. The bracket is of three-section type, and the three sections can be flexibly adjusted. The length of the vertical bar (over the table) is 600mm, the length of the horizontal bar is 400mm, and the length of the small vertical bar is 500mm. The loading and unloading station has good dust isolation and sealing performance, which can prevent the impact of excess on the accuracy of the loading and unloading station. The loading and unloading platform surface is driven and rotated by the motor, and the operator can control the start and stop by the pedal.

4) Pallet magazine. The tray silo adopts a steel frame double-layer structure, which can load 24 pallets. The size of a single tray silo is: long × wide × Height: 900mm × 900mm × 2000mm。The weight of a single tray library is 150kg, and it is equipped with a waterproof mechanism, which can collect the coolant into the water pan to keep the processing area clean.

5) Zero positioning tray. According to the aluminum magnesium casing parts and their clamps to be clamped, determine the size of the zero positioning tray as Φ 630mm, the tray accuracy is 0.01mm. The tray positioning mode is high-precision four-cone pin over-positioning, and equipped with an air blowing device for cleaning the cone pin positioning surface, which makes the positioning accuracy more accurate. In order to further improve the rigidity of the worktable, the tray uses the four-cone pin built-in cylinder locking mode, so that the locking point and the positioning point coincide.

6) Central tool magazine and tool loading and unloading station. The main body of the central tool storage adopts a truss structure, which is located on the upper part of the machine tool and can improve the transportation efficiency. There are 120 tools in the tool storage, and the specification of tool handle is HSK63A. The tool transport manipulator adopts a truss structure, which can transport one tool at a time. The tool transport manipulator is equipped with RFID reading and writing equipment to read and write tool RFID information.

7) Washer. The equipment includes washing host, 360-degree automatic spray cleaning system, liquid storage tank and circulating filtration system. It can remove impurities and machining residues on the surface of parts and meet the requirements of cleaning and drying of aero-engine casing.

8) Protective system. The cell is equipped with a fence to avoid accidental intrusion and accidents when the single material transport robot is carrying out transportation activities. A protective door is installed on the fence for solving problems in the production line and maintaining the production line. When the equipment breaks down or requires maintenance, personnel can enter the cell through the protective door.

After determining the number of processing equipment and stations in the cell, this section completes the selection of main equipment in the cell, including processing system, logistics system and auxiliary system. The determination of the model and quantity of equipment in the cell lays the foundation for the layout of facilities in the cell in the next step.

1) Objective function

The research object of this paper is the flexible manufacturing cell of aluminum-magnesium casing, and the workpiece transportation path in the cell is a straight line. Therefore, this paper chooses the minimum material handling cost as the optimization objective, and E represents the logistics cost, and the objective function expression is:

2) Constraints

The model built in this paper mainly considers hard constraints, including the following two aspects⁷:

Equipment coincident constraints. The equipment placed in a straight line should meet the minimum safety distance requirements to ensure that there is no interference between the equipment and avoid affecting the normal operation of the cell.

Shop size constraints. The casing production workshop contains more than one aluminum magnesium casing manufacturing cell, so it is necessary to complete the equipment layout within the given range, so that the overall size of the cell does not exceed the given space.

Minimum safety distance. The equipment in the cell must ensure the minimum distance, namely d_ij>0。

1) Coding and initial solution. In this paper, when solving the single-line linear layout model, the decimal sequence coding is used. The constructed cell includes 2 turn-milling compound machining centers, 2 horizontal five-axis machining centers, 1 dual-station loading and unloading station, 1 washer and 1 quality inspection station, a total of 7 stations, and the coding form is 1-2-3-4-5-6-7. The initial solution is determined by heuristic method.

2) Neighborhood structure and candidate solutions. When constructing neighborhood, neighborhood U is divided into two parts⁸: left neighborhood L and right neighborhood R: left neighborhood L is used to place excellent solutions and complete centralized search; The right neighborhood R is used to place random solutions for diversity search to avoid falling into local optimum. U=L∪R。

3) Fitness function

Since the objective function used in this paper is the maximum logistics cost, the optimization objective is to minimize the logistics cost. The fitness function constructed is shown in Formula 9:

4) Taboo object, Taboo table, Taboo length. The taboo object selected in this paper is to exchange the positions of two devices and put them in the taboo table. According to the scale of the problem studied in this paper, the tabu length T=7 is determined.

5) Flout the Code and terminate the Code. The contempt criterion used in this paper is the criterion of selecting fitness function. When all candidate solutions are tabu, release the best state tabu object in the tabu table to solve the optimal solution. The termination criterion used in this paper is the maximum number of iterations. When the maximum number of iterations is reached, the algorithm stops.