Design and Fabrication of a Two Axis Benchtop Milling Table

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Design and Fabrication of a Two Axis Benchtop
Milling Table

• Presented By
• Corey Hoff, Taylor Groll,
• Thao Lai, and Rick Lopez
• EGR 367 Manufacturing Processes
• December 10, 2004

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Description of Need

• Translational motion in x and z axis
• Capable of machining plastic
• Dovetail type runner assembly
• Provide additional support for Engineering 101
  students
• Provide a wider range of travel than current GVSU
  benchtop milling machines

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Microkinetics Desktop CNC Milling Machine

• Hardware
• Motor Capacity
• 470 oz/in stepper motors
• 8.25in x 28.5in Table
• 17 in x-axis travel
• 7 in y-axis travel
• 5 in z-axis travel
• Cost
• Starts at 7,995.00

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MAXNC 15 Desktop CNC Milling Machine

• Hardware
• Motor Capacity
• 145 oz/in stepper motors
• 12.9 in x 13.9 in Table
• 10 in x-axis travel
• 10 in y-axis travel
• 12 in z-axis travel
• Cost
• Starts at 2,495.00

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ProLightTM 1000 Machining Center

• Hardware
• Motor Capacity
• 150 oz/in stepper motors
• 19.5 in x 6.25 in Table
• 12 in x-axis travel
• 6 in y-axis travel
• 9 in z-axis travel
• Cost
• Starts at 16,995.00

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Proposed 367 Milling Table Design

• Hardware
• Motor Capacity TBD
• 12.9 in x 13.9 in Table
• 16 in x-axis travel
• 10 in y-axis travel
• 10 in z-axis travel

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Existing Products and Design Comparison
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Material Selection

• Steel vs. Aluminum Considerations
• Weight of Milling Table
• Corrosion Wear Resistance
• Machinability
• Cost of Steel
• G.R. Central Iron Steel Supplier of Aluminum
  Alloy 6061-T6

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Design Calculations

• Machining time total 43.43 hours

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Pairwise Comparison Using Digital Logic Method
, n number of goals
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Decision Matrix
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Bill of Materials

• Aluminum Alloy 6061 Flat Stock

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Design Considerations

• Avoid use of round or tubular ways
• Eliminate Gibbs
• Utilize adjustable saddle ways for elimination of
  table slop
• Light weight
• Simplistic Design

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Previous Design
Adjustment Screws
Gibbs
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Proposed Design X-Z Milling Table
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Proposed Design - Saddle
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Proposed Design - Bed
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Gantt Chart
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Revised Design

• Less z-direction travel 10 inches
• Elimination of keyways
• Steel inserts
• Flat head hex bolts
• Lithium grease

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Revised Bed
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Fabrication Procedure

• Cut stock AA6061-T6
• Mill surfaces
• Drill holes
• Discrete fasteners
• Addition of lubrication

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Final Milling Table
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Final Milling Table
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Project Issues Encountered

• Tolerance stack-up
• Alignment of essential components
• Precision accuracy of milling machines
• Machine setup time
• Actual machining time 130 hours
• Complexity of design

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Test Results

• Force
• Static friction coefficient, µs 1.55
• Kinetic friction coefficient, µk 0.33
• Surface roughness, Ra 0.517 µm

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Future Considerations

• Ways base machined from single pieces of stock
  material
• Reconsideration of material choice
• Need a different method for adjusting amount of
  slop between the saddle and bed
• Address issue of single sided wear on x-axis
• Aluminum anodizing of wearing surfaces

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Questions?