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Messages - Davek0974

2071
General Mach Discussion / Re: Physical buttons for plasma
« on: January 27, 2016, 01:30:26 PM »
HI Dave. Mach3 has anti corner dive built in. IF teh combined vel drops below the setting it locks out THCdown from working. You  still get the THC up function to prevent head collision. Most set it too low.

IF you set this too low teh head will dive due to teh THC trying to correct teh voltage as teh Vel slows down for a curve.  How far it will dive is a function of how slow teh Vel gets in that particular curve and where you have teh cutoff point set to.



Thanks, i did know that but maybe i need to revisit the settings, messing with sheet cam looks good on paper but i'm not convinced it even updates theTHC in time when running unless you switch THC off way in advance which is a bit pointless.

What sort of % is recommended in the anti-dive DRO?

Also, I gather there is no existing function that addresses my suggestion of stopping downward signals IF there is no corresponding fall in volts received???

2072
General Mach Discussion / Re: Physical buttons for plasma
« on: January 27, 2016, 12:50:43 PM »

What does everyone else do to turn THC on and off via gcode on the fly (I use sheetcam as I'm sure most probably do), before corners or small circles etc?


I've been messing a lot with this stuff lately, I have the CandCNC Mp3000-DTHC2 and I use Sheetcam rules to turn the tHC on and off all over the place as I've been messing with slowing down on corners and holes etc. I'm not convinced it makes any difference yet, need to run some tests with THC on and then slow down and see if it dives or not, I don't think i have ever had a true torch-dive yet! Normal reason for a dive for me is having the volts too low, especially on the 30A consumables as there is only 1.5mm gap to play with and a volt or three out and it will dive in on the run, sometimes you can catch it and bump the volts up but usually it catches me out.

Maybe it needs a "super anti-dive" feature whereby if it senses the THC being told to go down but the volts are not changing at all i.e. the torch is running along the plate, then it blocks further drop signals, maybe even lifts a bit until it sees a volt rise - don't know if any systems offer this but it sounds useful to me ;)

2073
General Mach Discussion / Re: Physical buttons for plasma
« on: January 27, 2016, 09:39:13 AM »

so Z moved at 1000 / 42.44131816 * 60 / 1000 m/min i.e. 1.4m/min.

Lets say then that it's cutting at 6m/min. It can therefore handle a slope of 6/1.4 = approx 13 degrees.


Any chance you can show the full workings of that sum please?
How you arrive at 13deg;)

2074
General Mach Discussion / Re: Physical buttons for plasma
« on: January 27, 2016, 07:48:20 AM »
I've been here before ;)

My answers were no and no :)

I think i calculated I can follow a warp of about 5-10mm across a distance of 1000mm on a good day.
Sounds bad but i don't cut corrugated and a 10mm warp is pretty bad i think, i gave up chasing some time back;)

2075
General Mach Discussion / Re: Physical buttons for plasma
« on: January 27, 2016, 02:42:43 AM »
Love this thread, great minds at work here:)

I have spent many (too many) hours messing with cut current on my PM45 the end result is that i just leave it at 45A! It really cuts poorly at lower amps on the 45A nozzle, the 30A nozzle works best only at 30A.

I have however discovered I can drop my speed by over 1000mm/min on aluminium and still get good cuts so the window for a nice cut is quite wide it seems, this helps my machine a lot, even though I took time to design it as rigid as possible it sill wobbles on fast moves which shows in the cuts.

BTW my THC rate is 20% with a max Z of 1300mm/min

2076
General Mach Discussion / Re: Physical buttons for plasma
« on: January 19, 2016, 03:19:53 PM »
I started off with a water tray on my first machine, PITA TBH.

I only cut occasionally 2-3 times a week. On the new table i fitted a large (350mm) duct extractor under the table making it a down-draught one. The fan exhausts through the garage wall, I have to open a window when cutting or the vacuum makes your ears bleed (well not quite but you get the idea), even with he water before, I would end up with the black-snot at the end of a day which was pretty worrying from a health point of view. With the extract, I can cut all day and not even smell it :)

If you do go with extract, make it down-draught as fitting the extract above is not as good.

2077
General Mach Discussion / Re: Z-Axis Dro - Odd behaviour?
« on: January 17, 2016, 02:42:32 PM »
IF you have ever watched a real comercial plasma cutter OR laser cutting thin sheet goods  they are WICKEDLY fast on Accelleration. Most use an Scurve planner that makes it not only wickedly fast but very smooth . Almost ALL runs servos. There are also designed with very low inertia Drives and gantries and are very rigid as well. 

Now that said A well planned Mach3 CNC plasma is a GREAT machine for the money and the normal useage for the average users.


Low inertia, high rigidity is the holy grail I think, very hard to do.

Personally I am very pleased with my table, for what it cost i think it's amazing, even more so when, after a couple of days messing around I have improved it ten-fold :)

2078
General Mach Discussion / Re: Z-Axis Dro - Odd behaviour?
« on: January 17, 2016, 02:13:04 PM »
Thanks

I did think of the switch falling into a hole but the arc it travels is very small and lands exactly where the torch would, I have been messing today and tried tight spacings, near-edge etc and all worked fine, if it would work with the torch, I think it will work with this. A true edge-start might be tricky, don't know yet, never done one.

The sliding Z is staying and i will be moving the limit switch wiring to the e-stop circuit as the limits do nothing when g28.1 is running, luckily I wired every switch with its own cable back to the control cabinet.


2079
General Mach Discussion / Re: Probably simple but...(G-Code help)
« on: January 17, 2016, 07:08:28 AM »
Everything working very nicely now, the new set origin button code is faster and does not mess the DRO's up :)
I also now have the Z rapid to slow position during a G28.1 move.

I think this thread has served its purpose well, thanks go to BR549 for all the help, and to any others who chipped in.

A short video of the final setup making a couple of cuts...
https://www.youtube.com/watch?v=FV6WpuQjFE0

2080
General Mach Discussion / Re: Z-Axis Dro - Odd behaviour?
« on: January 17, 2016, 07:02:00 AM »
Back to the topic, the new, reduced set-origin button works perfectly, setting "G28.1 No Initial Move" to OFF has made the Z rapid down to the Z value in the G28.1 command - brilliant.

A short video of the final setup making a couple of cuts...
https://youtu.be/FV6WpuQjFE0

That just leaves the fact that if the THC does not finish at zero as it started (which it never does) the difference between my 15.00mm safe height and the final THC adjustment is what shows in the Z DRO even though the machine was told to go to Z15.00 at the end.

Now, I have a theory -

The THC adjustments DRO is updating the Z DRO AFTER the machine has finished - the cut completes, the machine goes to Z15 as commanded but then the THC system adjusts the Z DRO to a wrong value.

I see no reason why  the THC should deb adjusting the Z DRO though, I will post this again on the CandCNC forum, probably won't get anywhere again though.