routercnc_MK3

[routercnc]

The saga continues!

On Sunday morning I managed to finish the last bit of basic wiring and set up all the motor tuning etc. Managed to achieve 2500mm/min - 3000mm/min jog speed before stalling, so settled on a safe 2000mm/min on X & Y to get it all going. Old machine ran at 1000mm/min so a great step forward.

I set out the machine to cut the 3mm aluminium front panel out to house all the controls. Fired up the spindle, hit cycle start and it started to cut the first circle. About 3 seconds into the cut there was a large bang and blue flash from the 60V 10A SMPS. This was the supply to the X, A and Y drivers (Z is only its own driver and supply).

After a bit of head scratch I realised that in my haste to get things going I'd left the 3off drivers on the factory default current setting of around 7.8A peak (5.6A RMS). As the power supply is rated at 10A I guess that was too much! Annoyingly the fuse inside the power supply was not blown, so I guess the whole thing is dead. I bought the PSU early last year, and I can't see another one of that spec on ebay, so that is that.

So, been doing a bit of research and will most likely build my own linear power supply for the X, A, and Y axes. Here is where I'm at with it:

Stepper motors - M60STH88-3008DF x 3off, 3.1Nm, 2.1A per phase (4.2 total), 5.46V
Drivers - DQ860MA 3off, 80V max

Toriod calculations
Nominal current draw = 3off x 2 phases x 2.1A per phase = 12.6A
Actual real draw = 0.7 x 12.6 = 9A
Required output to drivers = 68V (with margin for back EMF etc.)
Secondary voltage in coil = 68 / 1.4 = 48V AC
Toroid wired in series = 24 + 24
Power requirement = 48V x 9A = 432 Watts (432 VA)
Power with overhead in case of 4th axis = 750 Watts (750 VA)

Model selected: 750VA 230v to 2x24v CM0750224 from airlink at £48.00


Power regulator
For simplicity I'm looking at these power regulator boards at £29.00+£6.99 postage ebay. I know 60,000uF 100V is more than required but it was not much more than the 40,000uF 100V system.


Input fuse
I'm not completely sure on this but am looking at a 6A Type D MCB double throw fuse to switch the Live and Neutral into the toroid. Do I need to match the 9A real current draw or do I go lower? This 6A one is from Chalon at £7.18:


Output fuse
Is this required, and what would be the best type and rating to use?

Any thoughts on the above spec? thanks.