Cnc machining nm09/2
Types of manufacturing systems
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- 2.10 Special manufacturing systems
- 2.11 Manufacturing cells
- 2.12 Flexible manufacturing systems
- 2.13 Components of a CIM system
- 2.13.1 Machine tools and related equipment
- 2.13.2 Material handling systems
- Primary handling system
- Secondary handling system
- Robot — characteristics and applications
- Application areas for industrial robots
- 2.13.3 Computer control system
- 2.13.4 Human labour in the manufacturing system
2.9 Types of manufacturing systemsThe mid range shown, below as a Computer Integrated Manufacturing System, (CIMS) can be further divided into finer categories. These categories represent different levels of compromise between the objective versus production capacity. Generally these are referred to as:
Figure 2.14 Finer categories of CIMS 2.10 Special manufacturing systemsThe special manufacturing system is the least flexible Computer Integrated Manufacturing System. It is designed to produce a very limited number of different parts (perhaps two to eight) in the same manufacturing family. The annual production rate per part would typically lie between 1500 and 15,000 pieces. The configuration of the special system would be similar to the high production transfer line. The variety of processes would be limited, and specialised machine tools would not be uncommon. 
Figure 2.15 Special manufacturing system line 2.11 Manufacturing cellsAt the opposite end of the mid volume range is the manufacturing cell. It is the most flexible but generally has the lowest production rate of the three types. The number of different parts manufactured in the cell might be between 40 and 800 and annual production levels for these parts would be between 15 and 500. The highly integrated and in line flow is evident in the work part handling system shown below. This diagram also shows how the manufacturing cell might consist of several separate NC machines without an interconnecting materials handling system. 
Figure 2.16 Manufacturing cells 2.12 Flexible manufacturing systemsThe Flexible Manufacturing System covers the wide middle territory within the mid volume, mid variety production range. A typical FMS will be used to process several part families, with 4 to 100 different part numbers being the usual case. Production rates per part would vary between 40 and 2000 per year. A representative layout for a flexible manufacturing system is shown on the following page. Work parts are loaded and unloaded at a central location in the FMS. Pallets are used to transfer work parts between machines. Once a part is loaded onto the handling system it is automatically routed to the particular work stations required in its processing. For each different work part type, the routing may be different and the operations and tooling required at each work station will also differ. The coordination and control of the parts handling and processing activities is accomplished under command of the computer. One or more computers can be used to control a single FMS. 
Figure 2.18 Representative layout for a flexible manufacturing system 2.13 Components of a CIM systemA computer integrated manufacturing system consists of the following basic components:
2.13.1 Machine tools and related equipmentThe machine tools and other equipment that comprise a computer integrated manufacturing system include the following:
The selection of the particular machines that make up a CIMS depend on the processing requirements to be accomplished by the system. These processing needs also influence the design of the parts handling system. Some of the factors that define the processing requirements are the following:
2.13.2 Material handling systemsThe material handling system in a CIMS must be designed to serve two functions. The first function is to move work parts between machines. The second function is to orient and locate the work parts for processing at the machines. These two functions are often accomplished by means of two different but connected handling systems referred to as the primary handling system and the secondary handling system. Primary handling systemThe primary work handling system is used to move parts between machine tools or cells by way of an Automated Guided Vehicle CAGV). The requirements usually placed on the primary material handling system are:
Secondary handling systemThe secondary parts handling system must present parts to the individual machine tools in the CIMS. The secondary system generally consists of one transport mechanism for each machine. The specifications placed on a secondary materials handling system are:
Robot — characteristics and applicationsGeneral application characteristicsThere are certain general characteristics of an individual situation which tend to make the installation of a robot economical and practical. These general characteristics include the following:
Application areas for industrial robotsIndustrial robots have been applied to a great variety of production situations. Robot applications include:
Tools end effectorsThere are a limited number of applications in which a gripper is used to grasp a tool and use it during the work cycle. In most applications where the robot manipulates a tool during the cycle, the tool is fastened directly to the robot wrist and becomes the end effector. A few examples of tools used with robots are the following:
Robotic sensorsFor certain applications robots require more human like senses and capabilities in order to perform their functions in the most effective and efficient way. These senses and capabilities include abilities such as vision, hand/eye coordination and bearing. The figure below shows an adaptable programmable assembly system using robots and humans. This type of integration may lead to an assumption that robots can have some form of intelligence, this is not so. In this example we can assume that humans are capable of making decisions based on intelligent observations and reasoning, on the other hand, a robot is limited to the use of sensors which trigger a response when an object moves into the proximity field of the robots sensor. Robotic sensors are generally considered in three broad groups:
Figure 2.19 Robots on line 2.13.3 Computer control systemThe functions accomplished by the computer control system can be divided into seven categories. The following descriptions apply best to the case of the flexible manufacturing system. To a slightly lesser extent, they also apply to the Special System and the Manufacturing Cell. 1 Machine control. This is usually accomplished by Computer Numerical Control (CNC). The advantage of CNC is that it can be conveniently interfaced with the other elements of the computer control system. In some of the special systems which are dedicated to a limited part variety, CNC may be a sufficient control method for the system. 2 Direct numerical control (DNC). Most CIMS operate under DNC mainly because of its flexibility of functions, functions which include NC part program storage, distribution of programs to the individual machines in the system, post processing, and so on. 3 Production control. This function includes decisions on part mix and rate of input of the various parts onto the system. These decisions are based on data entered into the computer, such as desired production rate per day for the various parts, numbers of raw work parts available, and number of available pallets. 4 Traffic control. This term refers to the regulation of the primary workpiece transport system which moves parts between work stations. This control can be accomplished by dividing the transport system into zones. A zone is a section of the primary transport system (towline chain, conveyor, etc) which is individually controlled by the computer. 5 Work handling system monitoring. The computer must monitor the status of each cart and/or pallet in the primary and secondary handling systems as well as the status of each of the various work part types in the system. 6 Tool control. Monitoring and control of cutting tool status is an important feature of the computer system. There are two aspects to tools control:
7 System performance and reporting. The system computer can be programmed to generate various reports desired by management on system performance. 2.13.4 Human labour in the manufacturing systemThe Computer Integrated Manufacturing System is a highly automated production facility, however, human resources are required to operate the system. In the majority of CIMS installations, the individual machines are operated under CNC or DNC control (or a combination of these). The machines are not manually operated except in certain special operations, such as assembly. Personnel are required principally to manage, maintain, and service the CIMS. Personnel such as:
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