Automatic Identification and Data Capture PDF

ELECTIVES REVIEWER 1. Optical. Most of these technologies use high-contrast graphical symbols that can Automatic Identification and Data be interpreted by an optical scanner. Capture...

ELECTIVES REVIEWER 1. Optical. Most of these technologies use high-contrast graphical symbols that can Automatic Identification and Data be interpreted by an optical scanner. Capture 2. Electromagnetic. The important AIDC - Automatic identification and data technology in this group is radio capture (AIDC) refers to technologies frequency identification (RFID), which that provide direct entry of data into a uses a small electronic tag capable of computer or other microprocessor- holding more data than a bar code controlled system without using a 3. Magnetic. These technologies encode keyboard data magnetically, similar to recording - A family of technologies that provide tape. direct entry of data into a computer or a. (a) magnetic stripe, widely used other microprocessor controlled system in plastic credit cards and bank without using a keyboard access cards, and b. (b) magnetic ink character AIDC Applications recognition, widely used in the ▪ Retail sales and inventory control banking industry for check processing. ▪ Material handling 4. Smart card. This term refers to small ▪ Factory operations plastic cards (the size of a credit card) imbedded with microchips capable of ▪ Othe containing large amounts of information. Components of AIDC 5. Touch techniques. These include touch screens and button memory. 1. Encoded Data - alphanumeric characters 6. Biometric. These technologies are are translated to machine-readable form utilized to identify humans or to 2. Machine reader or scanner - scanner interpret vocal commands of humans. reads the encoded data and converts it to Measures of AIDC Reading Accuracy alternative form, usually an electrical signal 1. First read rate (FRR). This is the 3. Decoder - electrical signal is transformed probability of a successful (correct) into digital data and finally back into original reading by the scanner in its initial alphanumeric characters attempt. AIDC Technologies - number of bar codes read over the - Optical number alternative over 100 percent - Electromagnetic 2. Substitution error rate (SER). This is - Magnetic the probability or frequency with which the - Smart Card scanner incorrectly reads the encoded - Touch Techniques character as some other character. - Biometric  Bar Code Technology Bar codes are of two basic types: 1. Linear (a) - in which the encoded data are read using a linear sweep of the scanner - see to customer goods - name, price, weight 2. Two-dimensional (b) - in which the encoded data must be read in both directions. Two-Dimensional Bar Codes Two forms of linear bar codes: ▪ First 2-D bar code introduced in 1987 1. Width-modulated ▪ Two basic types of 2-D bar code symbols ▪ Symbol consists of bars and spaces of 1. Stacked bar codes varying width ▪ Consists of multiple rows of conventional bar ▪ Most widely used (e.g., Universal Product codes stacked on top of each other Code) 2. Height-modulated ▪ Symbol consists of bars and spaces of varying height ▪ Used only by U.S. Postal Service for ZIP code identification. Bar code readers interpret the code by scanning and decoding the sequence of bars. The reader consists of the scanner and 2.. Matrix symbologies decoder. ▪ Consists of 2-D patterns of data cells that are Linear Bar Code Readers usually square and are colored dark or white Usually classified as: ▪ Advantage over stacked bar codes is 1. Contact capability to contain more data. - Contact bar code readers are handheld wands or light pens operated by moving the tip of the wand quickly past the bar code on the object or document. 2. Noncontact - Noncontact bar code readers focus a light beam on the bar code, and a photodetector reads the reflected signal to interpret the code. Radio Frequency Identification ▪ Much more data can be contained in the identification tag than with most AIDC RFID uses an identification tag containing technologies electronically coded data that is attached to the subject item. ▪ Data in read/write tags can be altered for historical usage purposes or to reuse the ▪ The tag consists of a memory microchip and tag an antenna, usually encased in a plastic container Disadvantages ▪ The tag is a transponder ▪ More expensive than most other AIDC technologies. Tag containing electronically coded data. Types of RFID Tags 1. Passive tags - Passive tags have no internal power source - smaller, less expensive, longer lasting, and have a shorter radio communication range. 2. Active tags - include their own battery power packs. - generally possess a larger memory capacity and a longer communication FLEXIBLE MANUFACTURING range (typically 10 m and more) SYSTEM Industrial Applications of RFID Manufacturing system – arrangement or logical arrangement and collection of equipment and ▪ Inventory management human worker. ▪ Supply chain management Flexible – it can accommodate different ▪ Tracking systems product. ▪ Warehouse control Product Variety ▪ Location identification - soft product variety – common process - hard product variety – no common ▪ Work-in-progress process A flexible manufacturing system (FMS) is RFID Advantages and Disadvantages a highly automated Group Technology (GT) Advantages machine cell, consisting of one or more processing stations (usually CNC machine ▪ Identification does not depend on physical tools), interconnected by an automated contact or direct line of sight material handling and storage system and 4. New Part Test. Can it accommodate controlled by a distributed computer system. introduction of new part designs? Group Technology – to identify and to group Types of FMS together the similar parts and processes. ▪ The ▪ Kinds of operations FMS relies on the principles of GT ▪ Processing vs. assembly ▪ No manufacturing system can produce an ▪ Type of processing unlimited range of products ▪ If machining, rotational vs. non-rotational ▪ An FMS is capable of producing a single part family or a limited range of part families ▪ Number of machines (workstations): Where to Apply FMS Technology 1. Single machine cell (n = 1) - consists of one CNC machining center ▪ The plant presently either: combined with a parts storage system ▪ Produces parts in batches or for unattended operation. - The cell can be designed to operate in ▪ Uses manned GT cells and a batch mode, a flexible mode, or a management wants to automate the cells combination of the two. ▪ It must be possible to group a portion of the parts made in the plant into part families ▪ The part similarities allow them to be processed on the FMS workstations ▪ Parts and products are in the mid-volume, mid-variety production range 5000 – 75000 per parts. 2. Flexible manufacturing cell (n = 2 Flexibility Tests in an Automated or 3) Manufacturing System -The cell can be designed to operate in To qualify as being flexible, a manufacturing a batch mode, a flexible mode, or a system should satisfy the following criteria combination of the two. (“yes” answer for each question): - The parts-handling system is connected to a load/unload station. 1. Part-variety test. Can it process different part styles in a non-batch mode? 2. Schedule-change test. Can it accept changes in production schedule? 3. Error-recovery test. Can it respond gracefully to equipment malfunctions and breakdowns?  3. Flexible manufacturing system (n = 4 or more). Workstations - has four or more processing stations connected mechanically by a common - The processing or assembly equipment parts-handling system and electronically used in an FMC or FMS depends on the by a distributed computer system. type of work accomplished by the system. - Loading and Unloading work station - Machine Station and Assembly stations ▪ Load and unload station(s) ▪ Factory interface with FMS ▪ Manual or automated ▪ Includes communication interface with worker to specify parts to load, fixtures FMS Types Level of Flexibility needed, etc. 1. Dedicated FMS Material handling and storage system ▪ Designed to produce a limited variety of part styles - This section covers the functions of the ▪ The complete universe of parts to be handling system, types of handling made on the system is known in equipment used in an FMS, and types of advance FMS layout. ▪ Part family likely based on product ▪ Functions: commonality rather than geometric similarity. ▪ Random, independent movement of parts 2. Random-order FMS between stations ▪ Appropriate for large part families ▪ Capability to handle a variety of part styles ▪ New part designs will be introduced ▪ Production schedule is subject to daily ▪ Standard pallet fixture base changes ▪ Workholding fixture can be adapted ▪ Temporary storage FMS Components ▪ Convenient access for loading and unloading 1. Workstation ▪ Compatibility with computer control 2. Materials handling and storage system ▪ Primary handling system establishes basic 3. Computer control system FMS layout; Function: 4. Human Labor Responsible for moving part to station to station ▪ Secondary handling system - functions:  ▪ Transfers work from primary handling system to workstations ▪ Position and locate part with sufficient accuracy and repeatability for the operation ▪ Reorient part to present correct surface for processing 2. FMS Loop Layout ▪ Buffer storage to maximize machine utilization Five Types of FMS Layouts ▪ The layout of the FMS is established by the material handling system ▪ Five basic types of FMS layouts ▪ One direction flow, but variations in 1. In-line processing sequence possible for different part types 2. Loop ▪ Secondary handling system at each 3. Ladder workstation 4. Open field 5. Robot-centered cell 3. FMS Rectangular Layout 1. FMS In-Line Layout ▪ Straight line flow, well-defined processing sequence similar for all work units ▪ Work flow is from left to right through the ▪ Rectangular layout allows recirculation of same workstations pallets back to the first station in the sequence after unloading at the final station ▪ No secondary handling system ▪ Linear transfer system with secondary parts handling system at each workstation to facilitate flow in two directions  4. FMS Ladder Layout FMS Benefits ▪ Loop with ▪ Greater responsiveness to change rungs to ▪ Reduced inventory requirements allow greater ▪ Different parts produced continuously variation in rather than in batches processing ▪ Lower manufacturing lead times sequence. ▪ Reduced labor requirements ▪ Higher productivity ▪ Opportunity for unattended production ▪ Machines run overnight ("lights out operation") 5. FMS Open Field MANUAL ASSEMBLY LINE Layout A production line consisting of a sequence ▪ Multiple loops and of workstations where assembly tasks are ladders, suitable for performed by human workers as the large part families product moves along the line ▪ Organized to produce a single product or a limited range of products ▪ Each product consists of multiple components joined together by various assembly work elements 6. Robot- ▪ Total work content - the sum of all work Centered elements required to assemble one product unit on the line Cell ▪ Factors favoring the use of assembly ▪ Suited to the lines: handling of rotational parts and turning ▪ High or medium demand for operations. product ▪ Identical or similar products ▪ Total work content can be divided into work elements  ▪ It is technologically impossible tasks on each work unit within a certain or economically infeasible to automate cycle time, which paces the line to the assembly operations maintain a specified production rate. ▪ Most consumer products are Manual Assembly Line assembled on manual assembly lines - is a production line that consists of a sequence of workstations where assembly tasks are performed by human workers, as depicted - Configuration of a manual assembly line with n manually operated workstations Why Assembly Lines are so Assembly Workstation Productive - A designated location along the work ▪ Specialization of labor flow path at which one or more work - Called “division of labor” by Adam Smith elements are performed by one or more (Historical Note 15.1), this principle workers asserts that when a large job is divided into small tasks and each task is assigned to one worker ▪ Interchangeable parts - In which each component is manufactured to sufficiently close tolerances that any part of a certain type can be selected for assembly with Work Transport Systems its mating component. ▪ Workflow principle ▪ Two basic categories: - which involves moving the work to the ▪ Manual worker rather than vice versa. Each work unit flows smoothly through the ▪ Mechanized production line, traveling the minimum distance between stations. ▪ Line pacing Manual Work Transport Systems - Workers on an assembly line are usually required to complete their assigned ▪ Work units are moved between stations by the workers without the aid of a powered conveyor Types of Mechanized Work Transport ▪ Types: ▪ Continuous transport ▪ Work units moved in batches ▪ Conveyor moves at constant ▪ Work units moved one at a time speed ▪ Problems: ▪ Synchronous transport ▪ Starving of stations - is the ▪ Work units are moved situation in which the assembly operator simultaneously with stop-andgo has completed the assigned task on the (intermittent) motion to next stations current work unit, but the next unit has not yet arrived at the station ▪ Asynchronous transport ▪ Blocking of stations - means that ▪ Work units are moved the operator has completed the independently between workstations assigned task on the current work unit ▪ Queues of work units can form in but cannot pass the unit to the front of each station downstream station because that worker is not yet ready to receive it. Mechanized Work Transport Line Pacing Systems ▪ A manual assembly line operates at a certain cycle time - On average, each ▪ Work units are moved by powered worker must complete his/her assigned conveyor or other mechanized task within this cycle time apparatus ▪ Pacing provides a discipline for the ▪ Categories: assembly line workers that more or less ▪ Work units attached to conveyor guarantees a certain production rate for ▪ Work units are removable from the line conveyor ▪ Several levels of pacing: ▪ Problems 1. Rigid pacing ▪ Starving of stations 2. Pacing with margin ▪ Incomplete units 3. No pacing Rigid Pacing ▪ Allow worker to move beyond station boundaries ▪ Each worker is allowed only a certain fixed time each cycle to complete the No Pacing assigned task ▪ No time limit within which task must be ▪ Allowed time is set equal to the completed cycle time less repositioning time ▪ Each assembly worker works at his/her own pace ▪ Synchronous work transport system provides rigid pacing ▪ No pacing can occur when: ▪ Manual transport of work units is used ▪ Undesirable aspects of rigid pacing: ▪ Work units can be removed from the ▪ Incompatible with inherent conveyor to perform the task human variability ▪ An asynchronous conveyor is used ▪ Emotionally and physically Coping with Product Variety stressful to worker ▪ Single model assembly line ▪ Incomplete work units if task not (SMAL) - produces only one product in large completed quantities. Every work unit is identical, so the task performed at each station is the same for all products. Pacing with Margin ▪ Batch model assembly line ▪ Worker is allowed to complete the task (BMAL) - are designed to produce two or within a specified time range, the upper more products or models, but different limit of which is greater than the cycle approaches are used to cope with the model variations. time ▪ Mixed model assembly line (MMAL) - ▪ On average, the worker’s average task are designed to produce two or more products time must balance with the cycle time of or models, but different approaches are used the line to cope with the model variations. ▪ How to achieve pacing with margin: ▪ Allow queues of work units between stations ▪ Provide for tolerance time to be longer than cycle time