Second CNC table build, here we go again....

**Davek0974** · 11-09-2015

CandCNC advised me to up the pulse width to 5us and that seems to have sorted it out, all drives now running the same way.

**JAZZCNC** · 11-09-2015

Originally Posted by Davek0974

CandCNC advised me to up the pulse width to 5us and that seems to have sorted it out, all drives now running the same way.

So you were just on the wrong side of the pulse edge then. Could only really be this or the BOB inverting signals really.! Changing the pulse width doesn't always work thou unfortunately so you've been fortunate.!

**Davek0974** · 11-09-2015

Yes its an oddity i think,

A Mach guru has just pointed out that the BOB has opto isolated outputs and the drives have opto isolated inputs so i am driving an opto with an opto, he seemed to feel that was not a good idea generally.

**JAZZCNC** · 11-09-2015

Originally Posted by Davek0974

Yes its an oddity i think,

A Mach guru has just pointed out that the BOB has opto isolated outputs and the drives have opto isolated inputs so i am driving an opto with an opto, he seemed to feel that was not a good idea generally.

Nah not at all it's common as muck with Just about every BOB worth it's salt having opto's has will any decent drives and there'll be few machines that don't run with both.!

Unfortuantlly it's more a sign of poor drive or BOB with slow opto's.!!

**cropwell** · 11-09-2015

If every bit and bob and driver has opto isolation why not cut out the middle man and have a fibre optic connection ? I'll bet there are some machines with bespoke electronics that do it.

**Davek0974** · 11-09-2015

Originally Posted by cropwell

If every bit and bob and driver has opto isolation why not cut out the middle man and have a fibre optic connection ? I'll bet there are some machines with bespoke electronics that do it.

Probably purely a cost issue, this stuff is not really found on the high-end machines, I have no doubt those ones would have fibre where needed.

:)

**Davek0974** · 11-09-2015

Ok, we have action

Mixed bag of results, sort of exciting and disappointing all at the same time.

The good parts...
It works, speed is no issue,
The ripple effect in my cuts has disappeared,
It does not shake and wobble all over the place,

The bad parts...
The voltage is still way off of book specs, no change,
Can't get a clean cut on aluminium yet,
Need to work on divots,

Here we go...
Pierce & Cut heights are all as per book and this was checked several times by stopping mid cut and measuring the gap.

35mm washer, 45A 107v, 4000mm/min. Nasty divot as no cut rules yet just perpendicular lead in and no lead out.

Add a 2mm overburn and turn torch off 2mm before end - divots now pretty good.

Same speed, acceleration as listed, small shape again - 35mm sq. Same 2mm overburn etc but divot is terrible again????? There is a marked improvement between the 1st and 2nd cuts but little change between 2nd and 3rd so i set the acceleration at 1500mm/s/s. I can improve the internal corners a bit by setting Mach to stop CV on angles > 89 degrees but don't know if that is a good idea or not??/

3mm aluminium - 6400mm/min 45A 106v, lots of top dross, tried slower but made little difference. Had better cuts on old machine

1.2mm stainless is not too bad, 7900mm/min 45A or 4800mm/min 30A 109v

10mm steel, 0.9s delay, 117v, 500mm/min 45A.

Had one nozzle blow out completely, was getting poor cuts and found the orifice practically missing, no idea how that happened at all, as i'm testing I have been very careful of wrong pierce heights etc.

So, as i said, a mixed bag really. The divots are concerning, I need to get that bit nailed as well as the aluminium.

If anyone wants to chime in with some useful settings, please do. Is there a group test file that those with some spare minutes could cut for comparison???