Rebuilding gantry type Suregrave engraver - advice needed!

[GordonB]

Just a quick response to JAZZCNC, thanks very much indeed, plenty to digest there but I think I'd go for the AXBB board, looks like it would do what I want and the cost is offset by the lower cost of the software, about £80 less than Mach 3 I think. For stepper drivers I was considering these, partly for cost, partly because they have decent reviews, and they will easily cope with 36V 2.8A/phase supply to the steppers, which is what they are rated at.
https://www.amazon.co.uk/TB6600-Step...p_pl_dp_2&th=1

The power supply within the existing engraver controller is a large toroidal transformer with a rectification and smoothing circuit board. I've checked the outputs and it provides 36V for the steppers, 5V for controllers etc, and 24V for the spindle. All works fine and I don't see any need to use anything else. I'll post a photo tomorrow.

The spindle spec sheet is shown below, the one installed is 24V brushed dc, but it's rated at 17.4A. Needs a PWM controller I presume but I'm not sure what to go for. There might be a PWM circuit in the existing controller but I think it's part of the stepper driver board, which is completely unmarked as to what each connection is, which is a bit of a bummer as I might have been able to use it. From my discussions with Mervyn White at Microwhite (he's a Suregrave guru) the main controller boards were somewhat unreliable and not capable of being repaired. More tomorrow!

[JAZZCNC]

For stepper drivers I was considering these, partly for cost, partly because they have decent reviews, and they will easily cope with 36V 2.8A/phase supply to the steppers, which is what they are rated at.

Complete and utter junk I wouldn't use them on a printer let alone a CNC machine. If you run them at 36v, even thou rated at 42V they won't last long.
If you buy those you will regret it take my word for it. Even if they stay alive long enough the difference is motor smoothness and performance alone is worth paying the extra.

Don't make the classic mistake made by many new CNC users and buy cheap electronics, they are cheap for a reason none of which make for a good or reliable machine.

Regards the speed controller then you will need something that can accept 0-5 or 0-10v analog input for the speed reference because I don't think the Axbb provides a PWM output, I could be wrong so ask CNC drive first or go to there forum and ask.

You can also get BDC controllers that have stand-alone PWM built into them and control the spindle speed with a Pot.!

To be honest I don't do a lot with BDC controllers as Brushed spindle motors are not common on CNC machines these days.