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