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1 What is an automated production line

The automated production line is similar to the previous manual assembly line, but the equipment is upgraded to automation, and then the workers are omitted, the use of robots, truss manipulators, etc. to realize the automatic loading and unloading of equipment, the use of conveyor lines, AGVs, etc. to achieve the connection of various processes and material transfer, the use of automatic three-dimensional warehouse to achieve the storage of materials, the goal is to achieve the full automation of all processes between raw material input and finished product output.

With the advancement of Industry 4.0 and the development of the Internet of Things, the functions of automated production lines are also expanding, in addition to the basic automation functions, but also added information content, such as the common SCADA, that is, data acquisition and monitoring control system, to automatically collect the process data and equipment parameters of the production line, and provide a large-screen display interface, real-time display of the production line running status.

2 Main parameters of automated production line

The main parameters of the automated production line are: product type, production capacity, production process, equipment specifications and quantity, process balance rate, layout, floor space, water and electricity consumption, personnel allocation, etc.

The automated production line is suitable for the production of a single variety and a large number of products, and the fewer product types are recommended, the better, because it involves tooling fixtures, etc., it is difficult to achieve multi-product compatibility, and in product changes, it may involve the replacement of tooling fixtures.

The production capacity is formulated by the company according to the market demand, and it has been determined at the beginning of the construction of the line, which is the basic parameter of the production line design, and the appropriate production process is selected according to the capacity demand.

After the production process is determined, it is necessary to select the appropriate equipment, determine the specifications and models of the equipment, determine the number of equipment according to the capacity requirements, calculate the balance rate of each process, and make a detailed process flow.

After the main equipment is determined, you can design the layout of the production line, select the appropriate loading and unloading device and logistics transfer scheme, determine the location of all equipment, and complete the layout design of the production line.

3 Automated production line cycle calculation method

3.1 Line balancing ratio

Before calculating the cycle time, it is necessary to understand the meaning of "process", in layman's terms, the process is what work is to be done in this position, and all the processes are grouped together to be a production process.

Figure 1 Process flow

The automated production line cycle time depends on the slowest process in the entire process, so the process cycle time is required to be the same as possible, but in fact it must be a slight deviation, this deviation is what we often call the line balance rate, if the production cycle of all processes is the same, the balance rate is 100%, if there is a process that is slow to dry, the efficiency of the entire production line will come down.

Line balancing rate = sum of all station time and / (bottleneck process time × number of operations)

A process can be 1 equipment, can also be several the same equipment, in order to achieve the same cycle time of each process, usually different processes need to configure different numbers of equipment, such as A process 1 equipment 2 minutes to complete, B process 1 equipment takes 4 minutes to complete, then B process can be arranged 2 equipment, so that A, B two processes of the cycle time match, there is no waste of resources.

After the process flow and the number of equipment are determined, the cycle time of the entire production line is determined, and it is necessary to consider how to realize the loading and unloading of each process and the connection between processes, such as robots, manipulators, conveyor lines, etc.

3.2 Cycle Time calculation considerations

First, find out which process and which robot has the longest action time, and directly analyze the longest cycle time of this equipment or robot.

Second, when analyzing the cycle time, be sure to stare at one machine (equipment or robot), not be influenced by other machines, list all the actions of this machine in a cycle, and calculate the time required for each action.

Finally, it is to compare the duration of other machines (equipment or robots) to see if they meet the requirements of the whole line cycle time.

3.3 Cycle Time calculation case

Let's take forging and machining as examples to illustrate how to calculate two very different cycle time calculation methods.

One of the main differences between forging and machining is the cycle time, such as crankshaft forging, the time of the forging press is only 2s, and the robot handling the workpiece time is 8.5s, the robot action time is relatively longer, so the focus is on calculating the cycle of the robot, and the crankshaft machining cycle 120s / piece, the machine tool is the bottleneck, so the key computer bed cycle time.

Case 1: Cycle time calculation of forging automated production line

Due to the fast cycle time of forging, forging generally uses one-handed claw loading and unloading.

For a specific process, the robot's beat is analyzed first, and then the press is checked.

Figure 2 Schematic diagram of the layout of the 2 forging unit

1# The cycle time of the robot to complete the feeding of the forging press (single process, single station) is 8.5s, while the time for the forging press to complete a cycle is 8.5s, and the beat of the entire production line is subject to the slow equipment, so the final beat of the production line is 8.5s.

Table 1 Forging timing

Case 2: Cycle time calculation of machining automated production line

Due to the long processing time of machine tools, machining generally uses two-hand claws to load and unload.

For a specific process, first analyze the cycle of the robot, and then find out the time when the robot loads and unloads the machine tool, plus the time of machining, which is the cycle beat of this process.

Figure 3 Schematic diagram of the layout of the machining unit

Total time of machining process = machining time + in-machine measurement time + machine tool opening and closing door time + clamping time + in-machine cleaning time + loading and unloading time.

The total time for the robot to complete a machine tool loading and unloading is 31s, of which the time of loading and unloading + tooling cleaning occupies 21s.

The effective machining time of the machine tool is 120s, plus the idle time of the machine tool 38s (machine closing time 12s, in-machine measurement time 10s, robot loading and unloading time 6s, tooling fixture cleaning time 10s), a total of 158s, so the cycle time of the machine tool is 158s, and the production cycle time of this process is 158s/piece.

Table 2 Machining timing diagram