Month: December 2016

Categories
Product Review Uncategorized

CNC Machine

I have had a MyDIYCNC Machine sitting around for a few years now. I was having some problems with the controller boards so I set it aside and am just getting back to take another look at it. I found that one of the boards that was sent to me was indeed bad but MyDIYCNC no longer sells machines or parts. I then decided to go to Amazon and pick out a controller board to try. I picked the SainSmart CNC TB6560 3 Axis Stepper Motor Driver Controller Board & Cable. This board seems to work quite well. I have been having a bit of a time getting it to work properly in LinuxCNC but I have got it to home and move but it seems to be at 1/2 scale. I am still tweaking with the settings to see if I can get it to work 100%.

A few notes about wiring and hardware. The MyDIYCNC instructions refer to the motor which moves the Z axis carrier as the Y axis. It appears that it should really be the X axis and the table should be the Y axis. If it were the Y axis, the home position would be in the wrong corner of the machine. I played with the configuration a bit to see if I could get it to work as expected but I had no luck. Finally when I decided to try to swap the X and Y axes did home line up in the correct corner. I could have swapped A & B around on the Y motor and that may have reversed the direction of the motor but I did not want to go there. Swapping the axes made the most sense.

Here is a short video of a test of the CNC. The spindle has a ink cartage in it and is simply running the default LinuxCNC project. The drawing should be 5.3 inches wide but is only half that size.

Here are the settings for LinuxCNC.

001
Base Information

  • Machine Name: MyDIYCNC_inches
  • Axis configuration: XYZ
  • Reset Default machine units: Inch
  • Driver type: Other
  • Driver Timing Settings (The Stepper Drive Timing page on linux.org states that 150,000 ns should be used for all values however the current version of LinuxCNC has a max value of 100,000.)
    • Step Time: 100000
    • Step Space: 100000
    • Direction Hold: 100000
    • Direction Setup: 100000
  • Base Period Maximum Jitter: 9000

002
Parallel Port 1

  • Outputs (PC to Mill):
    • Pin 1: Amplifier Enable (Invert)
    • Pin 2: X Step
    • Pin 3: X Direction
    • Pin 4: Y Step
    • Pin 5: Y Direction
    • Pin 6: Z Step
    • Pin 7: Z Direction
    • Pin 8: Unused
    • Pin 9: Unused
    • Pin 14: Spindle ON (Invert)
    • Pin 16: Unused
    • Pin 17: Unused
  • Inputs (Mill to PC):
    • Pin 10: Both Limit + Home X (Invert)
    • Pin 11: Both Limit + Home Y (Invert)
    • Pin 12: Both Limit + Home Z (Invert)
    • Pin 13: ESTOP In
    • Pin 15: Unused
  • Parport Base Address: 0
  • Output pinout presets: Sherline (The value here is not important. It is actually used with the “Preset” button to load values.)

003
Options

Selections here really do not matter. I have not figured out how to use these yet. I may look into it more in the future.

004
Axis X

  • Motor steps per revolution: 800 (Steppers included with MyDIYCNC are 50 steps per revolution. The TB6560 board has the switches set for 1/16 microstepping. 50 x 16 = 800)
  • Driver Microstepping: 2.0 (Someone posted that 2 meant that microsteping was being used. I had this set to 32 earlier.)
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0 (All axes are direct drive so they are all 1:1.)
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: 0.125 This took awhile to get. If using the limit switches as home switches as well, we need to back the machine off so that the limit switches are not active when at home position. I choose to back them off 1/8 inch on all axes.)
  • Table travel: 0.0 to 5.5
  • Home Switch Location: 0.0
  • Home Search velocity: -0.05
  • Home Latch direction: Same

005
Axis Y

  • Motor steps per revolution: 800
  • Driver Microstepping: 2.0
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: 0.125
  • Table travel: 0.0 to 8.0
  • Home Switch Location: 0.0
  • Home Search velocity: -0.05
  • Home Latch direction: Same

006
Axis Z

  • Motor steps per revolution: 800
  • Driver Microstepping: 2.0
  • Pulley teeth (Motor:Leadscrew): 1.0:1.0
  • Leadscrew Pitch: 20.0
  • Maximum Velocity: 0.4
  • Maximum Acceleration: 30.0
  • Home location: -0.125
  • Table travel: -4.0 to 0.0
  • Home Switch Location: 0.0
  • Home Search velocity: 0.05
  • Home Latch direction: Same

007
Almost Done

008
Do you want to quit?

Screenshot added for completeness

I plan to continue to look into what is going on with the scaling and settle on the correct settings or at least settings which will work.