[MNFIC] CNC Lathe

CNC Lathe

We aim to have a functional CNC Lathe in the year 2020. The following are the components which we intend to use:

1. Mach 3 CNC board
2. Linux CNC OS and an old computer
3. DC Spindle motor (upgradable to a VFD Spindle motor)
4. Stepper motors for the x and z axis
5. Rhino stepper motor drivers (equivalently Bholanath)

Linux CNC supports such an endeavour directly and it is hoped that we can begin with a simple machine tool to fabricate brass and plastic items.

About Linux CNC and Mach3

Hardware Requirements:

1. Mach3 Breakout Board
2. Parport card
3. Board/PC with parport card slot
4. Parport cable

Software requirement
LinuxCNC OS

G-Code generator. (e.g. dxf to gcode)
https://cnc-code-generator.soft112.com/
https://sourceforge.net/projects/dxf2gcode/
https://sourceforge.net/projects/genericcam/
https://sourceforge.net/projects/caelinux/
https://camotics.org/download.html (milling, drilling simulator)
https://ultimaker.com/software/ultimaker-cura (3D print)
https://slic3r.org/ (3D print)

Connection:




*robu.in


Software setup (for basic CNC machines):

1. Open terminal and type: “lspci -v”.
2. Search for parport address
3. Type “latency-test” in terminal. Let it run for a few minutes and load the pc wit background apps during test. Record the max jitter value (with units).
4. Select the motor maximum speed and acceleration from motor’s characteristic curves.
5. Right click on the desktop.
6. Search for “step config” in CNC in applications.
7. Fill the fields accordingly. Put port address and max jitter speed (careful of units) in the asked fields.

Important links
Documentation: http://linuxcnc.org/docs/html/
Plasma CNC:
http://linuxcnc.org/docs/devel/html/plasma/plasma-cnc-primer.html
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?GantryPlasmaMachine


LinuxCNC Alternatives:

Fanuc, Siemens, Chinese knock off
Pros: Robust, heavy duty
Cons: Expensive

GRBL

Pros: Easiest to use and install, freeware.
Cons: Slow and serial use. Prone to frequent problems due to use of development board.

MACH3 Software

Pros: Easy to set up. Based on windows. Reasonable price.
Cons: Not freeware. Cannot make changes/adapt. Requires Windows OS.

About the Stepper motors and drivers

There is nothing sacrosanct about the nature of the driver and motors. In general we choose the readily available nema 17 series stepper motors.


Edit: 3-1-2020

Issue: Spindle motor does not work with Mach3 from the output pins designated on m3

Solution:
Use Rhino PWM 20A 40V motor driver
Assign B axis as Spindle PWM and put it into the pulse pin
Calibrate the pulse pin by modifying the configuration file to have the same PWM pulse rate as desired by the motor driver. Otherwise the motor simply wiggles.

Edit: 7-1-2020

We were able to get the VFD motor running. The brand of VFD was Delta EL series rated for 1 hp. The vfd setting manual was looked up and was set in such a way that 02.00 and associated entries were 1. This essentially implies that the vfd is set to run not through the built in controls but with the help of the terminal block inputs and input signals from the computer. The vfd connections are rather straightforward from that point onwards since the AVi pin expects a voltage signal. The DCM and FOR or REV pins are attached to the ground and relay pin of the mach3 board. The relay pin is essentially controlled by means of pin 17. Once this is done, we can also increase the peak rpm of the board to achieve top speeds.