Flexible Manufacturing Systems

Transcription

1 Flexible Manufacturing Systems FMS is: Machine Cell used to implement the Group Technology Composed of Multiple automated stations Capable of Variable Routings (Type IIA) Integrate CNC, Computer Control, Automated Material Handling and Storage, and GT FMS can be applied to: Plant produces parts in batches or uses manned GT cells Portion of parts must be in part family Part similarity: parts belong to a common product and/or parts possess similar geometry Mid-volume, mid-variety production 5,000 75,000 parts / year <5,000: too expensive >75,000: dedicated line may be used 1 Enabler for the Flexibilities Ability to identify and distinguish among different part Quick changeover of operating instructions Quick changeover of physical setups Example: Is this Automated Manufacturing Cell FMS? CNC Machine Tool Robot CNC Machine Tool Parts carousel 2

2 Qualifying Test for Flexibility 1. Part Variety Test Can the system process different part styles in a non-batch mode? 2. Schedule Change Test Can the system readily accept changes in production schedule, and changes in either part mix or production quantities? 3. Error Recovery Test Can the system recover gracefully from equipment malfunctions and breakdowns, so that production is not completely disrupted? 4. New Part Test Can new part designs be introduced into the existing product mix with relative ease? 3 & 4: Softer requirements (sometimes not considered) 3 Detailed Type of Flexibility (1) Table 16.1 (P. 465) Machine flexibility Production flexibility Mix flexibility Product flexibility Routing flexibility Volume flexibility Expansion flexibility Not limited to Flexible Manufacturing Systems (can be applied to manned and automated system) 4

3 Detailed Type of Flexibility (2) Part Variety Part Variety Schedule Change New Part 5 Detailed Type of Flexibility (3) Error Recovery Schedule Change Schedule Change 6

4 Number of machines: Single Machine Cell Single machine cell One CNC machining center + part storage system Processing different part styles Responding to changes in production schedule Accepting new part Error recover (Criterion 3) cannot be satisfied 7 Flexible Manufacturing Cell Flexible manufacturing cell Two or three CNC workstations + part handling system Satisfies four criteria? 8

5 Flexible Manufacturing System Flexible Manufacturing System (FMS) Four or more CNC workstations + part handling + distributed computer system System include non-processing workstation (e.g. part washing stations, etc.) 9 Level of flexibility Dedicated FMS (Flexible transfer line) Part family is based on product commonality than geometric similarity Specially designed machine tools are used Random-order FMS New part can be introduced Production schedule is changed from day to day Trade-off between flexibility and productivity 10

6 FMS Components 1. Workstations / 2. Material Handling and Storage / 3. Computer Control / 4. People Workstation: Load/Unload stations Physical interface between FMS and the rest of the factory Raw workparts enter / finished parts exit By human operator (+ crane) Washing facility Must include data entry Machining stations CNC machining center Other processing Punching, Assembly Robot Programmable component placement machine (electronic assembly) Others Inspection (Coordinate measuring machines, visions, ) 11 Material handling and storage (1) Function of FMS handling system Random independent movement of workparts between stations To provide various routing alternatives Handle variety of workpart configurations Modular fixtures Temporary storage Queue Convenient access for loading and unloading Compatible with computer control Directly controlled by computer system 12

7 Material handling and storage (2) Equipment Material transport equipment In-line transfer mechanism Industrial robot Primary and Secondary Primary: Layout of FMS (See Table 16.5 Page 473) Secondary: Transfer device, Moves parts from primary to machine Accurate positioning Reorientation Buffer storage 13 In-line Layout Configuration Well-defined part progress sequence Two types: one-directional and bi-directional with secondary part handling 14

8 Loop Layout Configuration Usually flow in one direction Returning pallet is easy 15 Ladder and Open Field Layout configuration Ladder Increased possible ways from one machine to another Open field Good for large family of parts 16

9 Robot-Centered Layout Configuration Sometime used to produce round type part: Easy handling for part 17 Computer control Hierarchical control: Machine-level + System-level Control system Workstation control: CNC Distribution of control instruction to workstations: DNC to download CNC part programs Production control: Part mix and rate Traffic control: Transferring parts between workstations Shuttle control: Between primary and secondary material handling Workpiece monitoring: Status of each pallet and workpiece Tool control Tool location: Location of tool in storage Tool life: Tracking of time usage Performance monitoring and reporting Diagnostics 18

10 Computer control (cont.) 19 Human Resource 1. Loading raw workparts into the system 2. Unloading finished parts from the system 3. Changing and setting tools 4. Equipment maintenance and repair 5. NC part programming in machining systems 6. Programming and operating the computer system 7. Overall management 20