Chapter 2 – Manufacturing Operations INSY 4700 - Manufacturing Systems Design 2/27/2019 Chapter 2 – Manufacturing Operations John L. Evans, Ph.D. INSY 4700 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

Introduction to Assembly Systems INSY 4700 - Manufacturing Systems Design 2/27/2019 Introduction to Assembly Systems Definition of the term assembly The aggregation of all processes by which various parts and sub-assemblies are built together to form a complete, geometrically designed assembly or product either by an individual, batch, or continuous process. Assembly of manufactured goods accounts for: over 50% of total production time, 20% of the total unit production cost, and 33%-50% of labor costs 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

Types of Manufacturing Industries Aerospace Apparel Automotive Basic Metals Beverages Building Materials Chemicals Computers Construction Appliances Electronics Equipment Fab Metals Food Glass Machinery Paper Petroleum Pharmaceuticals Plastics Power Utilities Publishing Textiles Tire and Rubber Wood Furniture 2/27/2019 Assembly Systems

Processing and Assembly Operations Solidification Processes Casting and Molding Particulate Processing Pressing Powers and Sintering Deformation Processes Forging, Extrusion, Rolling, Drawing, Forming, Bending Material Removal Turning, Drilling, Milling, Gringing Material Finishing Heat Treatment, Cleaning, Surface Treatment Assembly Operations Welding, Brazing, Soldering, Adhesive, Rivets, Press, Threaded Fastners 2/27/2019 Assembly Systems

Product Assembly Virtually all end products go through some assembly process. Approaches Craftsman approach l Output = l parts/unit time 2/27/2019 Assembly Systems

Product Assembly Virtually all end products go through some assembly process. Approaches Craftsman approach l l l Output = 3l parts/unit time 2/27/2019 Assembly Systems

Product Assembly Virtually all end products go through some assembly process. Approaches Craftsman approach Assembly line 3l l l l Output = 3l parts/unit time Output = 3l parts/unit time 2/27/2019 Assembly Systems

INSY 4700 - Manufacturing Systems Design 2/27/2019 Example 3l l n1 m1 m2 m3 l = 2 parts/hour 3l = 6 parts/hour (each) n = 1/3l = 1/6 hour n2 l = 2 part/hour (each) 3l = 6 parts/hour m = 1/l = 1/2 hour n3 Craftsman approach: Craftsman  very little control over the cycletime. Need a skilled craftsman for each additional station (increase in demand) Line approach: Relies on the principles of interchangeability and division of labor Must be able to partition tasks – assumption here that n1=n2=n3 Assume m1=m2=m3=m Assume n1=n2=n3=n 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

INSY 4700 - Manufacturing Systems Design 2/27/2019 Assembly Line Each part moves sequentially down the line, visiting each workstation. Assembly (or inspection) tasks are performed at each station. 2 4 6 1 3 5 Tc is defined as the cycle time. At steady state, one unit is produced every Tc time units (i.e., TC = 1/required number of assemblies per unit time). Paced lines vs. unpaced lines Single product vs. mixed lines Flexible flow lines The line does not necessarily have to be straight – U-shaped or serpentine. How do we determine the cycle time? The pace of the slowest station dictates. General problems: Partitioning of tasks Assignment of tasks to stations Buffer allocation (if we consider variability) Part sequencing (for mixed lines) 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

Assembly Line Balancing INSY 4700 - Manufacturing Systems Design 2/27/2019 Assembly Line Balancing Assembly line balancing problems: ALB-1 - Assign tasks to the minimum number of stations such that the workload assigned to each station does not exceed the cycle time, TC. ALB-2 - Assign tasks to a fixed number of stations such that the cycle time, TC, is minimized. An assembly consists of a set of tasks. Task precedence relationships Precedence relationships are described by a graph G = (N, A) where njÎN represents task j, and aijÎA indicates that task i is an immediate predecessor of task j. For ALB-1, the required cycle time can be determined base on the demand. For example, Weekly demand: 3000 units 5 days, 1 shift/day, 8 hrs/shift  40 hrs/week 40 hrs/week / 3000 units/week = 0.0133 hrs/unit = 48 seconds/unit  Cycletime <= 48 seconds ALB-2 – assume that you already have a line configured or that you have a fixed number of stations. 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

Production Concepts and Models Production Rates TC= TO + Th + Tth Where TC = Operation Cycle Time TO = Time of Actual Processing Th = Handling Time Tth = Tool Handling Time For total batch processing time Tb = Tsu + QTc Where Q = Batch Quantity Tsu = Total Setup Time 2/27/2019 Assembly Systems

Production Concepts and Models (2) The Average Production Time for a Part (Batch) Tp = Tb/Q The Average Production Rate (pc/hr) Rp = 60/Tp For Job Shop Production Tp= Tsu + Tc For Mass Production – Q is very large making Rp ~ = Rc = 60/Tc Where Rc =Operation Rate of the Machine 2/27/2019 Assembly Systems

Production Concepts and Models (3) For Multiple Stations Dividing work evenly is not realistic Bottleneck Station is the “Gating” or limiting operation Tc = Tr + Max To Where Tr = time to transfer work between stations Max To = operation time at bottleneck operation Therefore the theoretical production rate is approximately Rc = 60/Tc 2/27/2019 Assembly Systems

Production Concepts and Models (4) Production Capacity is defined as PC = nSHRp Where n = number of work stations S = number of shifts per period H = hr/shift Rp= hourly production rate of each center Utilization is defined as U = Q/PC Availability is defined as A = (MTBF – MTTR)/MTBF Where MTBF is mean time between failure (hr) MTTR is mean time to repair (hr) 2/27/2019 Assembly Systems

Manufacturing Lead Time The Lead Time for Manufacturing a Product Through the Entire Operation is defined as MLTj = Sum of (Tsuij + QiTcji + Tnoji) i = 1 to oj Where Tsuji = Setup Time for Operation i Qj = Quantity of product j Tcji = Operation cycle time for operation i Tnoji = Nonoperation time with operation i 2/27/2019 Assembly Systems

Manufacturing Lead Time Lead Time for Job Shop – Q = 1 MLT = no(Tsu + Tc + Tno) Lead Time in Mass Production MLT = no(Tr + Max To) = noTc 2/27/2019 Assembly Systems

Work-in-Process Work-in-Process is the quantity of products currently in the process of production WIP = [ AU(PC)(MLT)] / SH Where A is Availability U is Utilization PC is Production Capacity MLT is Manufacturing Lead Time S is number of Shifts per Week H is the number of Hours per Shift 2/27/2019 Assembly Systems

Costs of Manufacturing Fixed and Variable Costs TC = FC + VC (Q) Where TC is the Total Cost FC is the Total Fixed Cost VC is the Variable Cost per unit Q is the Quantity 2/27/2019 Assembly Systems

Manufacturing Analysis Evaluate or Optimize Minimize Throughput Time Minimize Labor Minimize Capital Investment Maximize Capacity Minimize Operational Cost Minimize Cost Per Unit 2/27/2019 Assembly Systems

Types of Analysis Problems Capacity of Process Time Analyze Lead Time to Production “Optimize” Process Steps or Sequence Evaluate WIP Evaluate Cost of Operation “Optimize” Capital Investment Minimize Travel Time Minimize Floorspace 2/27/2019 Assembly Systems

Example Problem a b c d e 2/27/2019 Assembly Systems

Assembly Line Balancing INSY 4700 - Manufacturing Systems Design 2/27/2019 Assembly Line Balancing Problem (ALB-1): Assign tasks to workstations Objective: Minimize assembly cost f(labor cost while performing tasks, idle time cost) Constraints: Total time for all tasks assigned to a workstation can not exceed C. Precedence constraints between individual tasks. Zoning constraints Same workstation Different workstation Zoning constraints: Same workstations – specialized equipment, timing considerations, raw material usage, etc. Different workstations – safety, equipment conflicts, personnel (skill) concerns, etc. 2/27/2019 Assembly Systems AU - Industrial and Systems Engineering

Parameters / Inputs Parameters / Inputs P parts/unit time are required m parallel lines are to be designed (usually 1) C = m/P is the required cycle time ti is the assembly time required by task i, i = 1,…,N IP = {(u,v) | task u must precede task v} ZS = {(u,v) | tasks u and v must be assigned to the same workstation} ZD = {(u,v) | tasks u and v can not be assigned to the same workstation} S(i) is the set of successors for task i. 2/27/2019 Assembly Systems

Parameters / Decision Variables (cont.) k is the number of workstations required (unknown). cik is a set of cost coefficients such that: cik is the cost of assigning task i to station k 2/27/2019 Assembly Systems

Problem Formulation 2/27/2019 Assembly Systems

Solving the Problem Very difficult to solve optimally Integer variables Non-linear constraints Heuristic Solutions COMSOAL Ranked positional weight Enumeration Methods Tree Generation Niave approach Fathoming rules 2/27/2019 Assembly Systems

Example Problem 10 1 2 3 9 7 5 4 6 8 11 2/27/2019 Assembly Systems

Example Problem (cont.) 10 1 2 3 9 7 5 4 6 8 11 2/27/2019 Assembly Systems

Ranked Positional Weight Example C = 72 2/27/2019 Assembly Systems