Hakan Gultekin1 A Synthesis of Decision Models for Tool Management in Automated Manufacturing

Hakan Gultekin 2 Scope of the Paper Evaluates tool management approaches Identifies operational tradeoffs Analyzes models developed to address management decisions involving tooling Accounts for 25% to 30% of both fixed and variable costs of production in automated manufacturing

Hakan Gultekin 3 Management Decisions Involve Selecting optimal machining parameters Most economic processing rate for a particular operation Loading of tools and jobs on machines Determination of optimal tool-mix inventories needed for a particular production schedule

Hakan Gultekin 4 Tool Management Requires A tool monitoring strategy: To coordinate tooling inventory, tool tracking, tool loading/unloading To ensure that the appropriate tools are available in the right time in the right quantities To account for tool availability and tool changes To coordinate tool transfers between machines and tool cribs To identify and react to unexpected tool wear and breakage A control strategy: A scheduling strategy: A planning strategy: A design strategy:

Hakan Gultekin 5 Classification Tool management can be classified into: Tool-level Machine-level System-level issues Decisions at one level constrain those at lower levels, information from lower levels feeds back to higher level decisions

Hakan Gultekin 6 Integration of Tool Management and Other Basic Production Functions Better tracking and cost accountability of tooling Due to minimizing number and types of required tools Due to reduced tools’ stockouts and setup delays Increase in productivity Reduction in production costs Improvements in part and routing flexibility

Hakan Gultekin7 Order Delivery Schedule Process Planning and Part Programming Machine Sequencing Scheduling Machine Grouping Capacity Requirements Planning Tool Requirements Planning Master Production Planning Process Monitoring Individual Tool Monitoring Tool Placement in Magazine Tool Allocation to Machines Machine Loading Tool Inventory Control Tool Replacement

Hakan Gultekin 8 Tool Specific Issues Number and types of tools Tool speed rates Tool feed rates Technology used to monitor and control machining and tooling conditions TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 9 Level of integration necessary between the various production functions Greater capital and time involved in developing hardware, software and technical support for automated manufacturing Tool Specific Issues More critical in automated manufacturing than manual operations because of: TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 10 Tool Specific Issues TOOL LEVELMACHINE LEVELSYSTEM LEVEL Spindle speed Depth of cut Feed rate

Hakan Gultekin 11 Major tool management concerns: Tool life Cutting tool economics Tool standardization Information requirements Tool Specific Issues TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 12 1-Tool Life Useful life depends on: Machining environment (speed, feed rate…) Material composition of the part and the tool Depth of the cut TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 13 1-Tool Life Taylor: VT n = k Extended tool life equation: V t =C/d x f y Expected tool life Cutting speed Emprical constants (depends on m/c conditions and material composition) Cutting speed for a given tool life Depth of cut Feed rate Empirical constants TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 14 2-Cutting Tool Economics Economic tool life: optimal time interval between planned tool replacements. Tradeoff: As machine speed increases, tooling expenses rise exponentially vs Throughput rates increases Machine speed should be controlled TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 15 2-Cutting Tool Economics Cook’s formula: Y=(Y o +nG)/(n+1) Y: mean tool usage cost Y o =initial cost of the tool n: number of times a tool is reground G: cost of a single regrind Economic tool life is found where Y is minimized TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 16 2-Cutting Tool Economics Objectives include: Production rate, profit rate, variable cost, surface roughness. Decision variables: Speed, feed rate, spindle revolution rate. Multiple shallow cuts vs fewer deeper cuts More realistic cases: tool life is treated as a random variable TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 17 2-Cutting Tool Economics Using same tool for a mixture of part types: Minimizes the # of tool changes Minimizes the # of tools required Increases part routing flexibility However, existing tool life models are unable to provide reliable predictions of tool life under these conditions TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 18 3-Tool Standardization Hundreds of tool types and thousands of tools in inventory Done either by redesigning the part or process, or assigning more operations to similar tool types Substantial savings in tool inventories, data management and improved system reliability TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 19 4-Information requirements Common tool management database Data record should be linked to vendors, part types, machines… Extensive information requirements both for planning and monitoring tooling TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 20 4-Information requirements Tools must be monitored for wear to permit planning for replacement and regrinding. Continuous monitoring: Adaptive control to adjust m/c speed and feed rates appropriately Off-line monitoring: Increase non- productive m/c times and may result in workpiece damage. TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 21 4-Information requirements Sophisticated information systems to: coordinate delivery of the proper tools to specific m/c’s in time provide location information correlate the # of tools needed for the quantity of parts to be produced offer acceptable substitutes when needed TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 22 4-Information requirements Bar-code labelling of tools or tool cabinets or memory chips are used to track tools and collect real time data TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 23 Tool Management at the Machine Level Loading and placing a set of tools in the machines’ magazine Determining the part input sequences to meet certain magazine constraints Establishing tool replacement strategies TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 24 Tool Management at the Machine Level Tool Magazine Work table Part Stored Tools Empty Storage Slot Active Tool Tool Change Arm TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 25 1-Equipment Selection Specifications of a tool magazine and an automatic tool changer include: Tool storage capacity Type of accessing system Whether tool loading is manual or automatic Tool standards used Maximum tool diameter, length, weight TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 26 2-Sequencing on a Flexible Machine Total number of tools required is usually larger than the available magazine storage capacity Required tool may be absent and a tool change must occur before that operation can begin TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 27 2-Sequencing on a Flexible Machine Objectives include: Min # of group tool change instances Min # of individual tool changes Min tool setup, tool replacement and m/c times TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 28 3-Tool Placement in a Magazine Many tools of various sizes Placement of individual tools determine magazine capacity (large tools) Weight balancing Tool search time TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 29 3-Tool Placement in a Magazine One copy of each tool to save magazine capacity or multiple copies because of short life or often use Open research question: Determination of the optimal # of copies of each tool TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 30 4-Tool Replacement Tool replacement strategy is two-fold: When to replace a particular tool due to wear or failure Which additional tools to change early, given a tool change must take place. TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 31 4-Tool Replacement Non-bottleneck machines: Tool change may not result in lost system throughput Bottleneck machines: Change several tools early when one tool fails. TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 32 System Management Tooling issues arise in: Production planning Scheduling Spare tool management Tool inventory management TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 33 1-Master Production Planning Effective planning models must take into account: Tool magazine sizes Tool commonalities Tool changing times Tool lives TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 34 1-Master Production Planning Tool management issues are particularly visible in: Part type selection Machine grouping Loading problems TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin Part-Type Selection Two approaches: Batching approach: Partition the part types into batches, machine each batch individually, change all the tools Flexible approach: Select the part type to be produced next, machine according to ratios that balance the workload TOOL LEVELMACHINE LEVELSYSTEM LEVEL 1-Master Production Planning

Hakan Gultekin 36 Flexible approach: More frequent tool changes but the time to change tools is much less More uniform utilization of machines and setup personnel Decreased order leadtime and increased productivity More duplicate tooling and more sophisticated tool transport system TOOL LEVELMACHINE LEVELSYSTEM LEVEL 1-Master Production Planning

Hakan Gultekin Machine Grouping and Loading Machine grouping problem: Partition machines into groups so that each machine in a group is tooled to be able to perform same set of operations Loading problem: Allocate the operations and required tools among the machine groups subject to technological and capacity constraints TOOL LEVELMACHINE LEVELSYSTEM LEVEL 1-Master Production Planning

Hakan Gultekin Machine Grouping and Loading Can be considered jointly, separately or iteratively Many studies in the literature TOOL LEVELMACHINE LEVELSYSTEM LEVEL 1-Master Production Planning

Hakan Gultekin Manual vs Automatic Tool Handling Tool transporters requires large investment in tools, magazines, setup and delivery system, causes additional scheduling problems Some setup time on the magazines is reduced No formal characterization of operational tradeoffs. TOOL LEVELMACHINE LEVELSYSTEM LEVEL 1-Master Production Planning

Hakan Gultekin 40 2-Machine Sequencing and Process Monitoring Tools are resources that must be scheduled and controlled along with parts. Few scheduling models fully consider the implications of tooling constraints Machine, operation and routing flexibilities increases complexity of scheduling TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 41 3-Process Planning for Economic Production Rates Improved scheduling performance can be based on a production rate/tool wear tradeoff Once a throughput target is set processing times can be manipulated to reduce cost and increase tool lives Slow down noncritical machines TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin Spares Management Tool handling system Ability to substitute non-identical tools Need to provide alternate part routes # of identical tools required Tool magazine capacities Tool life distributions Tool costs TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin Tooling Inventory Management Operational flexibility requires many tool types At least 3 duplicate tools: one in tool magazine, one as backup, one in preparation # of types in storage increases over time Determination of the appropriate # of tools to be purchased TOOL LEVELMACHINE LEVELSYSTEM LEVEL

Hakan Gultekin 44 Custom tools are more expensive but can shorten processing times Optimal reorder points and safety stock levels are not studied The tradeoff between tool availability, manufacturing capacity, tool reorder points and the overall investment in tooling stocks TOOL LEVELMACHINE LEVELSYSTEM LEVEL 5- Tooling Inventory Management

Hakan Gultekin 45 TOOL LEVEL DESIGNPLANNINGCONTROL -Standardization of Tool Types (3) -Tool Tracking Technology (3) -Tool Information Requirements (5) - Assignment of Tool Types to Operations (2) - Economic Process Planning (21) -Tool Life (13)

Hakan Gultekin 46 SINGLE MACHINE LEVEL DESIGNPLANNINGCONTROL -Monitoring and Control Technology (0) -Tool Magazine Capacity (0) -Tool Changing Technology (0) -Tool Replacement Strategy Due to Expected Tool Wear (5) -Sequencing Parts/ Scheduling Tools (8) -Sequencing Operations/ Assigning Tools to Slots (4) -Tool Replacement Strategy Due to Actual Wear (2) -Adaptive Control at One Machine (1)

Hakan Gultekin 47 SYSTEM LEVEL DESIGNPLANNINGCONTROL -Number and Type of Machines (0) -Tool Loading & Handling Technology (0) -Loading Duplicate Tools (0) -Production Planning (2) -Part Type Selection (7) -Cell Grouping & Facility Loading (14) -Tool Change Times and Detailed Scheduling (6) -Processing Rate Determination & Bottleneck Control (6) -Spares Levels (0) -Allocation of Spares (7) -Tool Inventory Control (4) -Adaptive Control Strategies (2)

Hakan Gultekin48 Questions?