Programmable Automation Technologies. Daniel Kandray
the increase in productivity may come from reduced labor costs, increased production rates, and reduction in scrap and rework. Optimizing material handling may involve a combination of mechanical technology systems, including conveyor systems, indexing units, and pick-n-place units, with robotic and PLC technologies.
Automate inspection
Product inspection determines if a product is within specifications. Often performed offline or outside of the process, inspection gives feedback about how a process is performing, and information gathered from inspection is typically used to adjust a process as needed. The feedback loop—make a part, inspect it, adjust process—can be rather long. Hence, products outside of specification (“off spec”) could be completed before the process that made them is adjusted. Automatic inspection is an attempt to minimize the feedback loop and thereby reduce scrap and rework. And, of course, a more consistent, higher quality product is produced. To sum up, raw material usage is reduced and output is increased, resulting in substantial productivity improvements. Automatic inspection systems may utilize material handling technology, including robotics, electronic vision systems, electronic sensors, actuators, and PLC technology.
Implement process control
To produce a high quality product it is necessary to have a consistent, repeatable, and reliable process. To achieve this, a process must be rigorously controlled. Programmable logic controllers are capable of providing this level of control, providing it over event-driven changes to the process. Based on the status of these events, the PLC will make decisions and take appropriate action on the system. This enables fast, reliable control of the process and greatly improves its efficiency. In addition to greater efficiency, process output and product quality are also improved.
Note that a particular automation project may focus on only one strategy or include all five. Keep in mind that not all processes can or should be automated. Some processes may be too technologically difficult to economically automate. For others, the product life cycle is so short that automation cannot be justified. In some cases it may appear that the cost of the automation is completely justified based on the anticipated productivity improvements, but later it may be discovered that is simply not the case. Thus, it is imperative one have a sound method of justifying where and when to use automation. The next chapter deals with this subject in detail.
Programmable automation technology is the combination of mechanical, electrical, and computer technology developed to have very specific automation capabilities. Programmable automation consists of three individual technologies that are linked together by their capacity to be programmed. These technologies include computer numerical control (CNC) technology, robotics technology, and programmable logic control (PLC) technology. These technologies are in use in almost all modern manufacturing facilities and together make up the technological foundation of automation.
Manufacturing converts a raw material into a more useful product that can be sold for a profit. The manufacturing operations that are necessary to produce a particular product include manufacturing processes, material handling, quality control, and manufacturing support. Manufacturing processes are the manufacturing steps that perform the actual physical conversion. They can be classified as shaping processes, property-enhancing processes, and assembly processes. A particular manufacturing process will follow a systematic sequence of operations called a program of instructions. The way in which the manufacturing operations and workers are organized defines the manufacturing system used by the facility.
The manufacturing system in use in a facility is dictated by the finished product’s product definition, which is determined by its complexity, variety, and quantity. Product complexity relates to the difficulty of its production process. Product variety refers to how many different product designs, versions, or models are to be produced within the facility. Product variety can be either hard or soft. Soft product variety indicates there are only subtle differences between product models. Hard product variety indicates vastly different products are to be produced.
The four standard manufacturing systems include fixed-position, process, quantity, and flow-line. Fixed-position manufacturing systems are used to produce large complex products. The process manufacturing system is used when product complexity is relatively low and there is hard product variety. The quantity manufacturing system and the flow-line manufacturing system produce mass quantities of products and are thus called “mass production systems.” The quantity manufacturing system is used with low product complexity and hard product variety. Flow-line manufacturing is for products with high product complexity and soft product variety.
Manufacturing support systems provide the management of the business operations of the facility and of the manufacturing system; they process information necessary to accomplish the conversion of the raw material into the finished product.
Automation is defined as the application of mechanical, electrical and/or computer technology to reduce the level of human participation in performing tasks. Fixed automation, programmable automation, and flexible automation are the three automation types. Fixed automation equipment typically consists of processing stations linked together with some form of material handling, which progressively moves the workpiece through the processing steps. Whereas fixed automation is “fixed” to a specific operation progression, programmable automation has the capability to alter both the type of operation to be performed and the order in which it is to be executed. Flexible automation possesses some of the features of both fixed and programmable automation with an added characteristic of no lost time for changeover between products. It is essentially a fixed automation machine that can process soft product variety with no setup.
CNC technology is one of the three distinct types of programmable automation that utilize a combination of mechanical, electrical, and computer technology to move a tool relative to a workpiece to perform some type of processing. Robotic technology is very similar to CNC technology in that it utilizes mechanical, electrical, and computer technology to move a manipulator in three-dimensional space. Whereas CNC and robotic technology provide motion control, PLC technology imparts automatic control over tasks and events through the use of electrical and computer technology. These three technologies are the foundation upon which modern automation is built.
The benefits of implementing automation come in many forms, each of which can almost certainly be expressed in terms of productivity improvement. The productivity of a manufacturing system is expressed as a ratio (%) of system output to system inputs. Productivity measure is perhaps the best indicator of when and where to use automation. Methods of improving productivity include increasing labor output, reducing labor input, reducing or eliminating labor shortages, reducing or eliminating routine manual and clerical tasks, improving worker safety, improving product quality, and reducing manufacturing lead time.
Some strategies to consider for implementing automation include minimizing manufacturing process steps, increasing process flexibility, optimizing material handling, automating inspection, and implementing process control.
assembly line manufacturing system
automation
batches
computer numerical control (CNC) technology
continuous products
conversion process
discrete process control system
discrete products
fixed automation
fixed position manufacturing system
flexible automation
flow-line manufacturing system
hard product variety
job shop manufacturing system
lead time
lot size
manufacturing