Messages

421

General Mach Discussion / Re: 1st pierce is longer...

« on: August 15, 2014, 07:53:03 AM »

Nope - they're consistent here. Not accurate - but consistent.

I've never found G4 to be particularly accurate with small values. Your 0.1s actually gives 0.73s. HOWEVER - some of that is down to the delay of executing M3 and M5 because your M3 uses doSpinCW and presumably your M5 uses doSpinStop (you posted M4 rather than M5 so that's a guess). I replace these with direct signal activation/deactivation which makes the macros faster. That won't do anything for inconsistency though - don't know why your seeing that.

422

General Mach Discussion / Re: 1st pierce is longer...

« on: August 15, 2014, 03:47:41 AM »

Can't say I've seen this - post your gcode and the contents of your M3 and M5 macros.

423

General Mach Discussion / Re: THC Setting Issue?

« on: August 14, 2014, 10:48:10 AM »

I think that gives me a z axis travel of 0.93mm per second, and with the other axes possibly moving at 55mm/sec (3300mm/min) I can now see that I have a height change possibility of 0.93mm over a distance of 55mm.

I think that equates to a warp factor of 5.28mm halfway along a sheet of steel 625mm wide.

Correct - or to put it another way - a slope of 0.967977387 degrees i.e. just under 1 degree 

What I don't know is is that bad, useless, reasonable etc?

5mm of warp seems quite believable on a plate that size.

If I am correct on all of my assumptions above, maybe I have been testing it on too extreme of an incline??

If you can cut what you need to cut - then your THC is great - if you can't it isn't... 

424

General Mach Discussion / Re: THC Setting Issue?

« on: August 14, 2014, 08:14:12 AM »

@Dave - I was just attempting to get you to do the numbers so that you can actually predict what will happen. Every feedback loop needs smarts to cope with the delay. First approach should be to reduce the delay as much as poss but after that the longer the delay the more smarts are needed.

Back to the maths though for your system. That 5 in THC rate means max Z speed under THC will be 5% of what you have in motor tuning. So in your case 55mm/min. At (say) 3300mm/min feed just as an example, that means the max slope you could even hope for - all other things being ideal - is just under 1 degree.

@Brian - no worries.

425

General Mach Discussion / Re: THC Setting Issue?

« on: August 14, 2014, 04:28:27 AM »

Thanks Stirling.

I think the z axis is on a 2mm screw pitch, it was a pre-built z axis system, presumed it was "normal" ?

So just do the maths. How fast does your motor have to spin to handle the slope in the metal you want to handle at the XY feedrate you want to cut at.

426

General Mach Discussion / Re: THC Setting Issue?

« on: August 14, 2014, 03:57:49 AM »

Hi Brian

Never tried it on high def cutters but according to their manual (p246) the cnc interface on Hypertherm's high def cutters is completely different to their "standard" def cutters - so I'm pretty sure the answer is a no. TBH - if I were looking at high def - I'd be looking beyond ALL the "budget" THCs. Hypertherm's offering costs several grand for a reason.

427

General Mach Discussion / Re: THC Setting Issue?

« on: August 13, 2014, 12:10:51 PM »

Yes - the P45 is the lowest power/price Hypertherm system that has the machine interface which my THC is designed to use. Just note that if you decide to go that route you'll also need the machine torch. See www.razordance.co.uk/THC.htm for more details.

That said, I note from an xml you posted here ages ago that unless things have changed your Z axis isn't the fastest on the block so that's going to limit you to some extent whatever system you use.

428

General Mach Discussion / Re: THC Setting Issue?

« on: August 13, 2014, 03:38:19 AM »

There appears to be a belief with some THC manufacturers that Mach's internal THC functionality presents some sort of bottle-neck and hence they tout "standalone" as some sort of remedy to this. Some even blame Mach's "slowness" for causing "head bouncing". This is NOT the case. Mach's internal functionality simply responds to the up down signals sent by the THC hardware and it does this at KERNEL FREQUENCY so with even the lowest kernel of 25KHz it's responding within 40 MICRO seconds - orders of magnitude faster than any THC loop that I know of.

The problem is that SOME THCs are firstly slow and secondly not very smart or even smart at all in how they "condition" the signal. Mach will just do what it's told and if its not told very well it's hardly fair to blame Mach. It's "worrying" is it not, that some THC manufacturers out there clearly don't really understand how Mach's THC functionality works.

Note - this is not to totally dismiss "standalone" THCs - they have their uses - the main one being that they can more easily be made system independent - i.e. they'll work across say Mach3/4/LinuxCNC/whatever - but siting Mach's "slowness" is not one of them and is plain wrong. (I'm currently debating whether to do a standalone version of my system for this reason of system flexibility).

You can't use my system because your Hypertherm model doesn't support the Hypertherm robotics interface.

429

General Mach Discussion / Re: THC Setting Issue?

« on: August 12, 2014, 11:36:59 AM »

A THC loop of 150ms is pitifully slow. I can't see you getting much in the way of performance. All feedback loop systems operate behind the curve but apart from anything else - at 3300mm/s feed you're going to be a massive 8.25mm behind. I know you don't have the right system to use my THC but just to add perspective - at 3300mm/s feed mine would be just 0.055mm behind the curve (1 ms loop).

430

Promote and discuss your product / Re: Neuron.THC Torch Height Control (plasma)

« on: August 12, 2014, 11:29:00 AM »

Can I just correct something you've said about Mach3's internal THC functionality.

(The Neuron's) Servo cycle is 500 microseconds, it is 200 times faster than the internal logic of the THC Mach3.

...which means you're stating that Mach's THC loop period is 1/10th of a second.

This is absolutely wrong. You may be confusing it with Mach's screen update period or perhaps even Mach's macro-pump period.

The THC loop in Mach is at kernel speed so just 40 microseconds for the (slowest) 25KHz kernel.