process engineering
DESCRIPTION
TRANSCRIPT
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
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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