Replacing control boards, XP to Windows 10. Mach3 to Mach4.

[erikdunn]

Hello!

I'm pretty much a "noob" in this CNC world and was hoping I could find some help here. I've recently came into the possession of a built DIY CNC and it's using this board: https://www.steppermotorcanada.ca/db25-1205f.pdf

Though I'm wanting to update to Mach4 to be able to use a computer I plan to 3D model on using Fusion 360 which is Windows 10. The CNC came with an uninstalled SmartBOB-IsoUSB PMDX-424 board. The drivers used are: https://www.makerlab-electronics.com/product/stepper-motor-driver-dq860ma/

Is this possible? I wasn't able to find a wiring diagram, maybe it's supposed to be straight forward.. hah.

[12strings]

Should be pretty easy to switch over.  Your existing board is just a simply isolated parallel port breakout board - 1 screw terminal for each signal on the PC parallel port.

For your stepper motor drivers, see:
https://faq.pmdx.com/index.php?solution_id=1010
and follow the suggested connection scheme for the SmartBOBs "Ground Common".  Also see the linked article about connecting the ENA signals.

For each motor, take the wires from the existing breakout board and connect them to the PMDX-424:
P2/P3 to Motor0 Step and Dir respectively
P4/P5 to Motor1 Step and Dir
P6/P7 to Motor2 Step and Dir
(if you have a 4th motor) P8/P9 to Motor3 Step and Dir

If you have any of the P1, P14, P16 or P17 terminals with wires connected, figure out where the wires go and I can give you an idea of where to connect them.  The PMDX-424 has only 3 general purpose outputs, with a 4th output controlling the on-board relay.

If you have an EStop signal, connect the EStop switch between the "EStop" and "Gnd' terminals on J14 (if the EStop switch is normally closed).  If the EStop switch is normally open (not usually the case) then connect it between the "Fault" and "Gnd" terminals.

For the other input signals on P10, P11, 12, 13 and 15, move them to the PMDX-424's isolated inputs 1 to 4 on J16 (and/or 5-8 on J17), with the GND leads all tied to the GND terminals on J16 and/or J17 - NOT the "gnd" pin on any other connector.

In Mach4 - I suggest making a copy of the PMDX-supplied sample PMDX-424 profile.  Start the Mach4 loader, click once on the "PMDX-424-Sample" profile to select it then click the "Copy Profile" button.  Name it whatever you like, and leave the "screen set" line blank.  Now open up the profile that you just created.  It should already have the X/Y/Z axis mapped to Motor0/1/2 respectively and the EStop configured.  You will have to play with the motor tuning to set the actual steps/inch or steps/mm, plus max speed and acceleration.

You will also need to figure out what limit and/or home switches are connected to which inputs, and configure them in Mach4.  Go to the Mach4 "configure" menu then select "Control".  Click on the "Input Signals" tab and scroll until you see things like "Motor0 Home", "Motor0 ++" (positive limit switch), "Motor0 --" (negative limit switch), etc.  If you have both a positive and negative limit switch for an axis wired to a single input, set both of those entries in Mach4 to the same PMX-424 input.  Or you might have the positive limit switches for all axis to a single input pin, and all negative limit switches to another input pin.  If so, map Motor0++, Motor1++ and Motor2++ to the same input pin, and Motor0--, Motor1-- and Motor2-- to the other input.

If this general advice gets too confusing, post a list of all the connections to your current breakout board and tell us a bit more about your machine.  For example, 3 axis?  4 axis?  Is there an axis with 2 motors driving it?  Is there a spindle motor under PC control?  If so, it is simply on/off?  Or is there a speed control of some kind.  How are your limit and home switches configured?  Any other inputs or outputs (coolant pump signals, etc.)?

[erikdunn]

The CNC has three axis, the spindle is controlled by an external Chinese VFD though I'd like to see if it's possible to control the spindle through Mach4. There are no limit-switches or home-switches on the machine, I have switches available to be used but they aren't installed.(If you're careful with your gcode, do you even need them?)

It seems on the parallel port board, the PUL+5V and DIR+5V are attached to terminals P2-P7, then everything else is tied up into a wire nut with two wires going to GND. It seems like that's all removed because I just take the PUL- and DIR- and put the two wires into the one "com" port.

[12strings]

Yes, PUL- and DIR- tie together into a single COM terminal for each motor.

The PMDX-424 should be able to control your VFD if you add a PMDX-407.  It plugs into the ribbon cable header on the board and gives you one solid-state relay to turn the spindle on/off, and generates the speed control voltage (using a voltage reference from the VFD, usually 10V).

Limit switches aren't for when things are working, they are for when things AREN'T working.  If your machine has mechanical stops that prevent damage to the machine should it try to move too far, you may be able to get by without them.

[erikdunn]

I just might do that, there's a little bit of worry in me about the spindle not being able to be turned off through the master-switch in case something goes wrong. For right now though I've made a little setup where the VFD is right next to the operator.