Comet Mill

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Comet CNC Mill
Comet Overall.jpg
In the Metal Shop.

The Comet Mill is a CNC vertical mill in the Metal Shop. It is currently being repaired and refurbished.


The Comet mill is a Mighty MV-5 Mill. It consists of a Comet XT Mill, an Autocon Dynapath 50M controller, a Kurt PowerLock drawbar, and various modifications made by Mighty USA to incorporate ballscrews, servos, a control pedestal, and a control cabinet into the package.


Chorca (@Chorca on slack) is currently in the process of refurbishing this machine into a usable tool. Currently the controller is up and running and seems to be working properly after the replacement of two encoders on the servo motors. Coolant is non-operational. The front Y axis way-cover needs to be fixed, it is just a rubber mat at the moment. One vise is currently installed and trammed, and has aluminum jaws in it. The other needs to be mounted; Chorca will be making more t-slot nuts to install this onto the machine (or if someone wants to buy some and put it on, that's cool too). The monitor is just an LCD inside the box, @Circuit was working on producing a new front panel for the unit to handle an LCD screen while retaining the mounting ability of the keyboards and buttons. We probably need a postprocessor for Fusion 360 to talk to it. The mill is using a Dynapath 50M, but posts for the 40M, 50M, and 60M will probably work fine. Below that, there are different features and G-Codes and they may need modifications to work with our machine. The appendixes in the back of the Dynapath Manual has the accepted codes and formats needed to write a post.

Please contact @Chorca with any questions.



  • Motor: 5HP (30 min), 3.75HP (continuous)
  • Motor RPM: 1720 RPM
  • Speeds: Low gear: 94 - 580 RPM, High gear: 760 - 4700 RPM
  • Taper: CAT 40
  • Quill Travel: 5"


  • Size: 42 x 13"
  • T-Slot: 5/8", 4 slots, 2.5" pitch
  • Max Load: 1500LB
  • Max Travel:
  • Travel Speed: 250IPM


  • Servo: MTS3OU4-42 40in-lb
  • Gross Wt: 6400LB
  • Power Supply: 220/440V 60Hz 3PH


The mill uses an Autocon Dynapath 50M controller. This is an early CNC control system that uses a simple PC-based backplane combined with ISA cards that handle PLC and servo control. It is a 486 PC with 4MB of RAM, a 500MB HDD, and three ISA cards that comprise the machine control section. There is also an ISA VGA card used to provide display.

The control panel is able to be swung in and out; make sure it is out away from the bed before you start moving the bed around. The panel consists of a few buttons at the bottom, a keyboard to the right of the display, and a few soft buttons below the display.

The control can be programmed in its inbuilt conversational language, or externally via a serial port with CAM software.

There are controls below the screen for the machine's motion.

Comet front panel

Buttons on the panel

(Left to right, top to bottom)

  • Handwheel - Or MPG wheel, this is a wheel used on the Jog screen while moving the selected axis by .001" or .0001" increments.
  • Spindle - This switch allows turning the spindle on in the CCW or CW directions, off, or in automatic mode (controlled by the programming)
  • Feedrate Override - This knob allows controlling the speed at which the axis motion occurs. It allows overriding to slow (or stop when turned fully CCW until a click is heard/felt) or speed up the cut and rapid/travel rate. Important to use this while testing programs.
  • Tool Change Required - This lamp-only indicator is illuminated when an M06 - Tool Change command is executed in the software. It instructs the operator to change to the indicated tool. Pressing Cycle Start when the tool change is complete will continue the program.
  • Cycle Start - This is the go button on the panel. It commands the control to start or resume executing a program, sequence, command, etc. It lights up green when axis motion is occurring.
  • X/Y/Z - These jog dials allow for constant feed of the indicated axis when in the Slow, Fast, Rapid, or incremental jog modes. The speed is overridden by the Feedrate Override knob.
  • Coolant - Flood coolant is not currently connected, leave this set to Off
  • Retract - This button is for use in certain operations such as drilling or tapping. It will retract the cutter out of the hole for inspection or in case of breakage or other issue.
  • Motion Stop - This is similar to the Feed Hold button on other machines. it will stop motion but usually it can be resumed by pressing Cycle Start above. It illuminates when a motion stop has occurred in the program or when initiated by the operator.
  • Emergency Stop - This button stops all motion including spindle and servos. It disables power to the servo drive motors and the spindle motor, and also any other motors such as coolant and oil pumps.

Keyboard to the right

The keyboard consists of a sequential alphabet, followed by an Event Type button, four large buttons below, and a numeric keypad with -, . Enter and Clear buttons. At the bottom there is an Inc and a Mode Select button.

The Mode Select button is one of the most important, it allows you to change between modes in the user interface. The Reset button at the bottom is very important also, it allows you to recover from an error or emergency-stop button press, to start the machine after power on, and clear any errors from programming after they have occurred. It also allows stopping the program after a Motion Stop button press, resetting the program back to the beginning.

Mode TM1 should always be enabled on the 5 - Set Up page. This allows the Feedrate Override knob to also control rapid events and will help allow sufficient time to identify and prevent programming errors when running a program for the first time or testing an event. If it's not set, press Mode Select, then 5 to get into the setup screen. Then press T-M-1 and press Enter. TM2 may be used when trying to verify X/Y programming without actually performing cuts by disabling the Z axis. This will also disable the motion in Jog mode, so keep that in mind if Z is not moving but the numbers on the display are changing, verify TM2 is not set.

Parameters must be entered by typing the first letter of the axis or preceding letter on the setting to be set. For the tool tables, you would set Diameter 5 by pressing D005 Enter followed by X .5902 Enter. If you don't press X, the input will be invalid.

Drip Feed

The control supports drip feeding via serial port. Refer to the manual for how to enable this.

External Links

Experts & Contacts