Hybrid Layouts

Flexible Manufacturing Systems

(FMS)

Flexible Manufacturing Systems Manufacturing system that can produce a

large variety of items Low quantity automated manufacturing Group of machines

Capable of a variety of operations Integrated by an automatic transport facility

Automatic tool changing

FMS The Beginning Proposed in England 1960s: “System 24”

Automation vs. Reorganization Early FMS

Large & Complex Expensive Unpractical

FMS Current Trends Smaller version of traditional FMS As few as 2 CNC machines

FMS In Depth Mass production vs. Small batches Machines

Capable of a variety of operations Automatic transport facility Automatic tool changing mechanisms Built in sensing capabilities

FMS Constraints Variances

Task execution times Undeterminable arrival times Organization of multiple machines

Hierarchical Production Scheduling Model

Master Production Plan Specifies the set of products to be

manufactured Considers worst case production

times in order to guarantee requests

Conservative capacity analysis No sequencing

Production Flow Planner Distributes subassembly requests Requests material from storage Handles feedback from scheduling

level Controls part routing Monitors and adjust flow rates Compensates for free time

Workstation Scheduler Distributed among workcells Real time operation decisions

Available parts Priority

Uncertainties handled through gained time of over conservative estimates

Feed back Performance Produced subassemblies Gained time

FMS Layouts

Progressive FMS Parts follow identical progression Used for processing related parts

Closed-loop FMS Arranged in a general order Used for a large variety of parts Able to skip stations Able to move around the loop in

order to alternate sequence

FMS Ladder Layout Processed parts are not limited to

part families Parts can move through machines

in any sequence

Open Field Layout Most complex FMS layout Material is routed in any order Typically includes support stations

Tool interchange Pallet Inspections Chip/Coolant collection systems

Mitsubishi M-H4B Horizontal Machining Center Minimum cycle time for job completion Adaptive

Mass production Design changes in mid-production

Quick automatic tool changer (ATC) Simplistic programming centers Machine Flexibility

Mitsubishi Flexible Mass Production System

(FMPS) Same workpiece production runs from

750-12,000 units/month Runs 15 different workpiece families

on same production line ATC swaps tools in 1.33 sec. 6 sec. pallet changes

Mixed-Model Assembly Lines Problem

Higher demand Lower demand

Solutions Sophisticated forecasting techniques Mixed-Model Assembly Lines

Process more than one product model

Important Factors Line balancing U-shaped lines Flexible workforce Model sequencing

Line Balancing Variances in model completion

time Average time from all models Averages create periods of spare-

time (Flexible workforce)

U-Shaped Lines Workers assist other stations Communication Down time

Flexible Workforce Employees trained on multiple

machines Advantages

“Bottle Neck” can catch up Different model use different

machines Helps line adapt to varied task

lenghths

Model Sequencing Strategically ordering models sent

through the line Large runtime followed by shorter

runtime Uniform production