One of the most important application areas for robotic automation is industrial production. For many, automation means production automation.
Three types of production automation can be distinguished:
- stationary automation
- programmable automation
- flexible automation.
Fixed automation, also known as “hard automation”, refers to systems where the sequence of processing operations is fixed by the configuration of the equipment. That is, in those solutions where the programmed commands are contained in the machines in the form of cams, gears, wiring and other hardware that is not easily changed from one product to another. This form of automation is characterized by high initial investments and high production rates. It is therefore suitable for products made in large volumes. Examples of stationary automation include machining transfer lines found in the automotive industry, automatic assembly machines, and some chemical processes.
Programmable automation is a form of automation for producing batch products. Products are manufactured in batch quantities ranging from several dozen to several thousand units at a time. For each new batch, production equipment must be reprogrammed and modified to fit the new product style. Production rates in programmable automation are generally lower than in stationary automation, because the equipment is designed to facilitate product changeover rather than product specialization. A CNC machine tool is a good example of programmable automation. The program is encoded in the computer memory for each different product and the machine tool is controlled by the computer program. Anthropomorphic industrial robots are another example.
Flexible automation is an extension of programmable automation. The downside of programmable automation is the time it takes to reprogram and change production equipment for each batch of new product. This is lost production time, which is expensive. In flexible automation, the change of equipment can be done very quickly and automatically. Reprogramming of equipment in flexible automation is done offline; that is, programming is performed in a computer terminal without using the production equipment itself. Consequently, it is not necessary to group identical products into batches; instead, different products can be produced one after the other.
Automated production lines
An automated production line consists of a series of workstations connected by a transfer system to move the products being processed between the stations. Each station is designed to perform a specific machining operation, so components or products are built gradually as it progresses along the line. The raw components enter at one end of the line, proceed through each workstation and exit at the other end in the form of a finished product. In normal line operation, there is a processing part in each station, so that the products are processed at the same time and a finished part is produced with each cycle of the line. The various operations, part transfers and other activities that take place on an automated transfer line must all be sequenced and coordinated correctly for the line to function efficiently. Modern automated lines are controlled by programmable logic controllers, which are special computers that facilitate connections to industrial equipment and can perform the types of timing and sequencing functions needed to operate such equipment.
Assembly operations were traditionally performed manually, both on single assembly stations and on assembly lines with multiple stations. Due to the high labor content and high labor cost, more attention has been given in recent years to the use of automation for assembly work. Assembly operations can be automated using production line principles if the quantities are large, the product is small, and the design is simple (eg mechanical pencils, pens and lighters). Manual assembly is generally required for products that do not meet these conditions.
Automated assembly machines have been developed that operate in a similar way to processing transfer lines, with the difference that assembly operations, rather than machining, are performed at workstations. AA typical assembly machine consists of several stations, each equipped with a supply of components and a mechanism to bring the components into position for assembly. A workhead in each station performs the actual fastening of the component. Typical work heads include automatic screwdrivers, staking or riveting machines, welding heads, and other joining devices. A new component is added to the partially completed product at each workstation, thus building the product gradually as it progresses down the line. Assembly machines of this type are considered examples of stationary automation, because they are generally configured for a particular product made in high volume. The programmable assembly machines are represented by the component insertion machines used in the electronics industry, as described above.
Today, most robots are used in manufacturing operations; applications can be divided into three categories:
- material handling
- processing operations
- assembly and inspection.
Material handling applications include material transfer and machine loading and unloading. Material transfer applications require the robot to move materials or work parts from one place to another. Many of these tasks are relatively simple and require robots to pick up components from one conveyor and place them on another. Other transfer operations are more complex, such as placing parts on pallets in an arrangement to be calculated by the robot. Machine loading and unloading operations use a robot to load and unload parts on a production machine. This requires the robot to be equipped with a gripper capable of gripping parts. Usually the collet must be designed specifically for the particular geometry of the part.
In processing operations, the robot manipulates a tool to perform a process on the working part. Examples of such applications can be welding or painting. Spot welding of car bodies is one of the most common applications, the robot places a spot welder against the car panels and chassis to complete the assembly of the basic car body. Arc welding is a continuous process in which the robot moves the welding rod along the seam to be welded. Spray painting involves the manipulation of a spray paint gun on the surface of the object to be coated. Other operations in this category include grinding, polishing, and milling, where a rotating spindle acts as the robot’s tool.
The third area of application of industrial robots is assembly and inspection. The use of robots in assembly is expected to increase due to the high cost of manual labor common in these operations. Since the robots are programmable, one strategy in assembly work is to produce multiple styles of products in batches, reprogramming the robots between batches. An alternative strategy is to produce a combination of different product styles in the same assembly cell, requiring each robot in the cell to identify the product style as it arrives and then perform the appropriate activity for that unit.
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