LinuxCNC conversion of Chinese 6040ZH Mach3 router

Hi

I'm new to CNC machines. I want to mill 3D aluminum on a smallish budget. That is the reason why I bough this used machine, my first one. Since I don't want to learn and buy end-of-life software and I like the power and flexibility that comes with open source projects like LinuxCNC the decision to convert it was easy.

It is a Chinese 6040ZH router, 60x40cm bed, 4 axis, rod rails on all axis, 1.5kw spindle, 57BYGH56-4011YD stepper motors (1.26Nm holding torque, 2.8A), 24V system, running mach3 with a USB connection.
Here is a link:  www.lygroupchina.com/gantry-cnc-router/h...c-machine-1500w.html

 

I' ve decided not to invest much into the machine because it has some mechanical design flaws and try to make the best out of it.

1. It has rod rails and not linear guides
2. The leaver arm on Y-axis to the rod rails is bigger than it needs to be. The rods could have been placed higher  

 

Since the controller board runs with a USB-Connection there is no way to run it directly with LinuxCNC. I wanted to know if its possible to reuse the electrical components and it seems so, the stepper motor controllers and the VFD for the spindle. Untested so far.
My plan is to use a MESA i796S board. If you have another suggestion let me know. Unfortunately they are out of stock currently.
  
The stepper motor controllers are 20 pin modules that stick on some kind of motherboard which also hosts the Mach3 controller, namely a Mach3-R-V1.3. With some reverse engineering I'm confident that I could figure out the function of the pins of the stepper motor controllers. The IC of the drivers seems to be a TB6600HQ or a clone. It has a voltage range of 8-42V, supports operating current of 4.5A, about 150w. It says www.shyidiao.com on them.
 

Front side from left to right (with the heat spreader remove from the IC. On the bottom left are two optocouplers):
GND, +5V, Pulse, Direction, Stepper RED, Stepper BLUE, Stepper GREEN, Stepper BLACK, +24V, +24V

 
Back side from left to right (reversed direction from above):
+24V, +24V, Stepper BLACK, Stepper GREEN, Stepper BLUE, Stepper RED, GND, GND, GND, GND

The soldering joints are very likely determining the microstepping of the drivers. If the configuration is from left to right: 1, 1/2, 1/4, 1/8, 1/16 and 1/32 then they are set to a reasonable 1/8.

 
The spindle driver runs independent of the 24V system. It has two ways to receive an input:

1. an analog input with voltage range 0-5V, currently wired to a potentiometer to manually control the spindle
2. three digital inputs, allowing for 8 fixed speeds

The VFD has the marking Inverter_B_v07. Its pins seem to be from top to bottom:
+12V, +5V, i5V (analog Input), SGND (signal ground), FWD (run forward), REV (reverse), BCD2, BCD1, BCD0, ErrB, ErrA

LinuxCNC can handle the TB6600HQ so if its correct they should run with it. Also the spindle can either be run with the analog input or the 3 bit digital one. I still have to decide which one to use. I like the possibility to run the stepper drivers and motors with 36V. That could be a nice upgrade from 24V.
I need a controller board that can handle 4 axis, this VFD, at least one limit switch, touch probe, automatic tool setting and in the future the possibility to attach sensors to close the loop (linear glass scale). The MESA i796S should be able to do that.

A question that is still open to me is how to physically connect the drivers to the MESA board?

1. Buy these 20 Pin sockets and make a board with them? Probably costly and time consuming
2. Solder the connections directly to the pins on the module and attach them somehow. Dirty, easy, quick, downside is, I can't plug them back in the motherboard
3. Solder the connecting wires to the motherboard and plug the drivers into the board. Could be neat because the machine could be back ported to Mach3. Possible unwanted side effects on the board. Of course I would unplug the Mach3 controller chip.

Feel free to correct me or give suggestions etc. I hope the MESA cards are back in stock soon.

Bes

Thank you for the interesting idea. I think it would not work to drive the stepper motor drivers from the blue Centronics connector because the drivers have each two Optocouplers, for STEP and DIR (see white frame on the front side of the driver board).

Below are some more pictures attached.

I think what I might try with that, would be to figure out which traces on the motherboard are step and direction for each axis. I would cut each trace on the motherboard somewhere between the I.C. and the blue card edge connectors in locations where I'd have a chance of bridging the cut with solder in case I later wanted to undo it. This would tend to be near the solder points where the blue card edge connectors are soldered in. This is to prevent the original I.C. from interfering with the signals from LinuxCNC.

Then I would solder maybe 24 AWG wires to the solder pins of each step and direction on the back side of the card edge connectors for wiring into a 4 or 5 axis parallel port bob that can be bought at low cost.

This would allow the power and motor connections to stay original. Spindle and e-stop signals I would wire direct to the bob. Make sure to connect bob's ground to a common ground on that motherboard.

Hope that helps.