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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. Description of Need. Translational motion in x and z axis Capable of machining plastic
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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
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
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
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 MAXNC 15 Desktop CNC Milling Machine
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
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
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
Design Calculations • Machining time total = 43.43 hours
Pairwise Comparison Using Digital Logic Method , n = number of goals
Bill of Materials • Aluminum Alloy 6061: Flat Stock
Design Considerations • Avoid use of round or tubular ways • Eliminate Gibbs • Utilize adjustable saddle ways for elimination of table slop • Light weight • Simplistic Design
Previous Design Adjustment Screws Gibbs
Revised Design • Less z-direction travel – 10 inches • Elimination of keyways • Steel inserts • Flat head hex bolts • Lithium grease
Fabrication Procedure • Cut stock AA6061-T6 • Mill surfaces • Drill holes • Discrete fasteners • Addition of lubrication
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
Test Results • Force • Static friction coefficient, μs = 1.55 • Kinetic friction coefficient, μk = 0.33 • Surface roughness, Ra = 0.517 μm
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