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Sample Package v1.3

Purchase list

  1. Copper rod stock

    Superconducting 101 copper rod, Diameter = 1.5"

    https://www.mcmaster.com/8965k75

  2. Screws for fastening (4 for each)

    #4-40 Brass socket head screw, Length = 5/8"

    https://www.mcmaster.com/93465a111

  3. Screws for mounting (2 for each)

    #4-40 Brass Pan Head Phillips Screws, Length = 1"

    https://www.mcmaster.com/94070a115

  4. Nuts for mounting (2 for each)

    #4-40 Brass hex nut, Width = 1/4", Height = 3/32"

    https://www.mcmaster.com/92671a005

  5. Screws for thermalization (1 for each)

    #4-40 Brass socket head screw, Length = 1/4"

    https://www.mcmaster.com/93465a106

Milling procedures

These G-code files are generated in a certain order. Particularly, I assume that the milling procedures are performed before the drilling ones.

The way I name the files:

  1. The first letter:

     x: Stands for the top part
 y: Stands for the bottom part

  2. The second letter:

     t: Stands for the topside of the part
 b: Stands for the bottomside of the part

  3. Letter "c" indicates that this file is for center drills

  4. The numbers indicats the tool to use.

Top, Topside

  1. Pockets: 3/32" End Mill

     xt332.txt

  2. Center Drills

     xtc43.txt (Z = -0.015")
 xtc32.txt (Z = -0.135")
 xtc3mm.txt (Z = -0.135")

  3. #4-40 tapped holes: #43 Drill Bit

     xt43.txt (Z = -0.620")

  4. #4-40 close fit: #32 Drill Bit

     xt32.txt (Z = -0.620")

  5. #4-40 mounting holes: 3mm Drill Bit

     xt3mm.txt (Z = -0.620")

Top, Bottomside

  1. The pocket: 3/32" End Mill

     xb332.txt

Bottom, Topside

  1. Open pocket: 3/8"" End Mill

     yt38.txt

  2. Pockets: 3/32" End Mill

     yt332.txt

  3. Center Drills

     ytc45.txt (Z = -0.015")
 ytc43.txt (Z = -0.055")
 ytc2p3.txt (Z = -0.105")
 ytc3mm.txt (Z = -0.055")

  4. Post pockets: #45 Drill Bit

     yt45.txt (Z = -0.0667")

  5. #4-40 tapped holes: #43 Drill Bit

     yt43.txt (Z = -0.300")

  6. Coaxial holes: #42 Drill BIt

     yt40.txt (Z = -0.300")

  7. #4-40 mounting holes: 3mm Drill Bit

     yt3mm.txt (Z = -0.300")

Bottom, Bottomside

  1. Pockets: 3/32" End Mill

     yb332.txt

Guidelines for CNC machining (Bridgeport EZTrak)

Workflow

  1. Design the part using SolidWorks.

  2. Generate the toolpaths using the built-in SolidWorks CAM.

  3. Generate the G-code files using a post processor named "EZTRAK_G.ctl". One G-code file corresponding to one toolpath only (without tool change operations).

  4. Use the python scripts to modify the generated G-code files.

Compatibility

The machine is old, which means certain G-code commands are not recognized by this machine. The known examples include:

  1. Drilling commands like G81, G83

  2. Tool radius compensation commands like G40, G41

In order to bypass these commands, we use python scripts to modify the G-code files generated by the default "Drill" and "Center Drill" operations in SolidWorks CAM.

Milling

We do both roughing & finishing procedures.

  1. Spindle

     Spindle Speed = 2400 rpm

  2. Feedrates:

     XY Feedrate = 8 in/min

 Z Feedrate = 4 in/min
 
 Leadin Feedrate = 4 in/min

  3. Side parameters:

     Allowance = 0.01 in
 
 Stepover = 80%

 Wedge Machining: True

  4. Depth parameters:

    a. For roughing

     Bottom Allowance = 0 in

 Island Allowance = 0 in

 First Cut Amount = 0.02 in

 Max Cut Amount = 0.02 in

 Final Cut Amount = 0.01 in

    b. for finishing

     Allowance = 0 in

 First Cut Amount = 10 in

 Max Cut Amount = 10 in

 Final Cut Amount = 0 in
 
 (The value "10 in" can be as large as possible)

  5. NC

     CNC Compensation: OFF
 
 (This prevents the program from producing G40 and G41 codes.)

Drilling

We do centering before drilling. G-code file for both procedures are modified by the python script "modify_gcode.py". Spindle and feedrate parameters are the same as used in the milling procedures.

  1. Center Drill

     Center Drill Depth = 0.015 in

  2. Drill

     Add Tip Length: True

  3. Pecking (This parameter is defined in the python file "gcode-tools.py")

     Pecking Depth = 0.050"

Related projects

  1. A new sample rack and a new copper bucket for our new fridge