Process Engineering

i-Design Lab.

Contents

3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision

Trees3.3 Process-Capability Analysis3.4 Basic Machining Calculations3.5 Process Optimization3.6 Conclusion

i-Design Lab.

3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision

Trees3.3 Process-Capability Analysis3.4 Basic Machining Calculations3.5 Process Optimization3.6 Conclusion

i-Design Lab.

• Process capability is historic and scientific knowledge for each process (≠machine tools)

Introduction

• Manufacturing• Raw material → Finished product

Process

historic

Scientific knowledge

Process

Capability

• Process capability = machine tools ??

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Process Capability

• Important parameters• The shapes and sizes• The dimensions and geometric tolerances• The material removal rate• The relative cost• Other cutting characteristics/constraints

Universal-level

Shop-level

Machine

-level

• Three levels of Process Capability

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3.0 Introduction

3.1 Experience-Based Planning

3.2 Decision Tables and Decision Trees3.3 Process-Capability Analysis3.4 Basic Machining Calculations3.5 Process Optimization3.6 Conclusion

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Experience-Based Planning

"The accumulation of experience is knowledge "

• Problem of Experience-Based• requires a significant period of time to accumulate• represents only approximate, not exact knowledge• is not directly applicable to new processes or new systems

• Machinist Handbooks• has long been a standard manufacturing practice

i-Design Lab.

3.0 Introduction3.1 Experience-Based Planning

3.2 Decision Tables and Decision Trees

3.3 Process-Capability Analysis3.4 Basic Machining Calculations3.5 Process Optimization3.6 Conclusion

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Decision Tables and Decision Trees

• Describing the actions associated with conditions• Help systematize decision making• Translate each other• Difference

• Ease and elegance of presentation and programming when a computer is used

Stub Entries

Condition

Action

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Decision Table

Limited-entry Decision Tables

Extended-entry Decision Tables

Mixed-entry Decision Tables

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Decision Table

• When constructing, consider factors• Completeness, Accuracy, Redundancy• Consistency, Loops, Size

• Merge

Merge

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Decision Table

• Table splitting and parsing

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Decision Tree

• Single root, Node, Branch• Branch – ‘IF’, branches in series – ‘AND’

Root

Node

Branch

i-Design Lab.

3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision Trees

3.3 Process-Capability Analysis

3.4 Basic Machining Calculations3.5 Process Optimization3.6 Conclusion

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Information Required to Make the Decision

Power Consumption

Cutting Force

Surface Finish

Tolerance

Size Limitation

Shape

Capability

Limitation

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Process Boundaries

• One way to represent process capability• Limiting size, tolerances, surface finish• System-dependant

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3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision Trees3.3 Process-Capability Analysis

3.4 Basic Machining Calculations

3.5 Process Optimization3.6 Conclusion

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Feed and Feed Rate

• Feed• The relative lateral movement between the tool and the

workpiece during a machining operation (= thickness of the chip)

• Feed in turning and drilling• The advancement of the cutter per revolution of the workpiece

(turning) or tool (drilling)• Unit - ipr (inch per revolution)

• Feed in milling• The advancement of the cutter per cutter-tooth revolution• Unit - inch per revolution per tooth

• Feed rate - ipm (inch per minute)• Equation (3. 17)

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Machining

• Cutting Speed• The maximum linear speed between the tool and the

workpiece• Equation (3. 18)

• Depth of cut• Width of the chip• Equation (3. 19)

• Metal-Removal Rate• How fast material is removed from a workpiece• Equation (3. 20) ~ (3. 28)

MRR is Large ( )Short processing time

Short the life of cutter

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Machining Time

• Total amount of time

• Parameter• The length of the workpiece• Overtravel of the tool for clearance• The number of passes required to clear the volume

• Equation (3. 29) ~ (3. 31)

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Tool Life

• Erosion (Wear)• Crater wear

• High Temperature

• Flank wear• Friction

• Breakage (Catastrophic Failure)

• F. W. Taylor• Tool-life Equation• Relation of Tool life and Cutting speed

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Machining Force and Power Requirements

• Important considerations in selecting process parameters(feed, speed, and depth of cut)

• Not limiting values

• Machining force• Equation (3. 35) ~ (3. 37)

• Cutting power• Equation (3. 38) ~ (3. 39)

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Process Parameters

• Feed, Speed, Depth of cut

• Process selection becomes an iterative procedure• Process Selection• Machining parameters are adjusted to accommodate the

system constraints• Parameters affects the time and cost

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3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision

Trees3.3 Process-Capability Analysis3.4 Basic Machining Calculations

3.5 Process Optimization3.6 Conclusion

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Process Optimization

• Tool has been worn → Replace

• Trade-off between increased machining rate and machine idle time

MRR is Large ( )Short processing time

Short the life of cutter

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Single-Pass Model

• Assume that only one pass to produce the required geometry

• The depth of cut is fixed• Constraint

• Spindle-speed constraint• Feed constraint• Cutting-force constraint• Power constraint• Surface-finish constraint

• Equation (3. 40) ~ (3. 47)

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Multipass Model

• Assumption of single-pass model is relaxed• Can be reconstructed into a single-pass model• The depth of cut is a control variable• Constraint

• Spindle-speed constraint• Feed constraint• Cutting-force constraint• Power constraint• Surface-finish constraint• Depth-of-cut constraint

• Equation (3. 63) ~ (3. 67)• No general solution method

i-Design Lab.

3.0 Introduction3.1 Experience-Based Planning3.2 Decision Tables and Decision

Trees3.3 Process-Capability Analysis3.4 Basic Machining Calculations3.5 Process Optimization

3.6 Conclusion

i-Design Lab.

Conclusion

• Information of process-planning system• Design knowledge – Chapter#2• Process knowledge – This Chapter (Chapter#3)

• Process planning• Procedure that matches the knowledge of the processes

with the requirements of the design

• Process Capability• Decision logic