CNC3020T only comes with a configuration for Mach3, a Windows CNC controller software I’m not really interested in. Additionally, for some weird reason, its control block requires you to adjust spindle speed manually with a potentiometer.
Fortunately, all of that can be fixed; moreover, the control block is much more powerful than it seems.
The stepper board looks like this:
J9 correspond to axes X, Y, Z in that order.
IC part numbers and their functions:
|U6-U8||TB6560AHQ||stepping motor driver|
|U10, U11, U13||74HC140||hex inverting Schmitt trigger|
|black box below||B0505LS||isolating DC-DC converter|
As it can be seen, the board features quite a bit of unused functionality—it has unpopulated connectors for limit switches and spindle PWM, direction and cooling pump control. (I’ve soldered pinheads to them already.)
I didn’t trace the board completely, but it is built out of identical blocks.
I’ve drawn its input and output circuits (
VCCIO are provided by the
isolating DC-DC converter):
I’ve also mapped board functions to LPT pins:
(“Coolant Pump” is marked on board as
CP−, “Spindle Direction”
Miscellaneous machine parameters, gleaned from the attached “documentation” (a set of Mach3 screenshots in very poor resolution black&white):
|Step Time/Space||3000 ns|
|Direction Setup/Hold||1000 ns|
|Steps per revolution||400|
|Leadscrew pitch||2 mm/rev|
|Max. velocity X/Y||33.3 mm/s|
|Max. acceleration X/Y||200 mm/s²|
|Max. velocity Z||11.7 mm/s|
|Max. acceleration Z||100 mm/s²|
|Table travel X||0..200 mm|
|Table travel Y||0..300 mm|
|Table travel Z||−50..0mm|
Now the funny thing is, the stepper control board has a PWM output, and the spindle control board has a PWM input:
Pin 1 (rectangular) is positive, pin 2 is negative.
It would seem that obtaining software spindle speed control is as simple
as switching the
SW1 switch to position 2 (jumper adjacent to
and connecting the boards with a pair of wires. And it totally works!
I have no idea why didn’t they provide it out of the box.