Messages

11

General Mach Discussion / Re: Question on Plasma THC control to users of this facility

« on: November 25, 2016, 06:45:20 AM »

The dead band on my old Candcnc MP3000 is normally set at 0.5 volt for Finecut consumables or 1v for 40 amps and above nozzles. Have not had any issues with these settings and while watching the Z rotation during cutting you can observe it not rotating while it's in the dead band. So even 0.5 volts does not seem too sensitive, at least for my system.

However, the dead band is inter-related with the THC Correction Speed. If this speed is high then a small dead band allows the Z axis to "shoot straight through" the dead band. Then it corrects in the opposite direction, and on and on. Thus you get Z jack hammering. To get rid of that, you either reduce your THC Correction Speed or increase the Dead Band, or a mixture of the two.

I don't know if you've considered any sort of filtering of the measured voltage. The arc is not a nice smooth DC signal.

Paying $200 for a decent THC is not ludicrous if you put any value on your time. Unless the whole idea of doing everything as cheap as possible is worth more than $200 then go for it, but I wouldn't personally get locked into thinking that just because I got part A cheap, then I MUST also get part B cheap. Just a thought.

12

General Mach Discussion / Re: Controlling THC?

« on: May 09, 2016, 07:27:10 PM »

The way I look at it, once a hole is blown through (pierce delay), there's no need to hang about. Just get down to cut height ASAP and move into the leadin / cut.

I would hazard a guess that on thicker steel there could be some advantage to piercing with a mixture of pierce delay and slow plunge rate (the move from pierce height to cut height). For instance, on thick steel, as the pierce progresses the distance from torch to metal "surface" is increasing. On a 30mm plate let's say you start a pierce at say 5 or 6 mm then by the time the pierce has blown out metal half way through, the torch to metal distance is now about 20mm. Perhaps a slow plunge rate starting at that point is an attempt to get the torch a bit lower/closer to the metal "surface". Of course it can only go as low as the cut height.

Like I say though that's just a calculated guess as to how a slow plunge rate could have some use. Personally all I've ever done is blown a hole then moved to cut height at max Z speed (Sheetcam plunge rate).

Keith.

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General Mach Discussion / Re: Using DIR pin of unused axis for synchronous switching

« on: April 10, 2016, 07:04:23 AM »

Thanks Tweakie,

appreciate the input, but I don't think I'll be able to make that one work. I'm basically looking to have Sheetcam insert a certain command at particular points on the cut path and those commands activate an output at those points.

14

General Mach Discussion / Using DIR pin of unused axis for synchronous switching

« on: April 09, 2016, 11:57:48 PM »

The laser commands M10 M11 are normally used for switching an output at a specific point in gcode. In laser control it seems they are often used at the beginning and end of a cut to turn the laser at the exact moment in time the axis starts moving.

Another method of doing this has been to use the DIR pin of a "phantom axis" (unused axis).

Now this is my question - is there any way to use a DIR pin output DURING an XY move without affecting that XY move. Please don't suggest M10/11 for this, I have certain reasons I need to use the DIR pin for this and explaining why is just complicating matters.

So for instance, and to keep things simple, I want to move X to 5, then switch on my phantom DIR output at that point, then have X continue to 10, i.e. the X move from 0 - 10 is uninterrupted and the DIR pin is activated at the X 5 position.

Anyone know if that is possible.

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General Mach Discussion / Re: Mach3 driver doesn't restart after WinXP wakes up from sleep mode

« on: April 06, 2016, 02:11:00 PM »

Hi Michael,

how are you, last time we talked was at the manufacturing show.

I don't specifically know the answer to your question but I've never had that problem after leaving my machine just "sitting there" for some time.

All I can say is a go absolutely crazy with disabling anything I can possibly think of, that is not necessary for Mach3. Anything to do with power saving, screen power down, screen savers. I go through all Windows services and disable anything I THINK is not needed. I un-install any built in XP applications like Internet Explorer, etc

I even look in the BIOS and see if there's anything I can disable there, like networking, sound, etc.

When installing XP I go through the XP optimisation guide for Mach3 and install in "Standard PC" mode.

After all that if I don't get a fantastic driver test without glitches, or if I have any other issues, I try a different PC. I've found some PCs just don't work as good with Mach3.

Keith.

16

General Mach Discussion / Re: Mach3 suddenly stopped talking to the serial port.Help please

« on: April 05, 2016, 05:47:17 PM »

The fact you asked about losing your license if you re-install Mach3 tells me you probably haven't got your license file backed up somewhere safe. Your license file is in the main Mach3 directory. I'd copy and paste it to some other locations (including places other than that PC).

Likewise back up your profiles and any custom macros you have.

Then if re-installing Mach3 ever does cause a loss you just paste them back in.

Regarding the card you have coming. It sounds like it's a combined parallel/serial card. I'm sure I heard it recommended somewhere to used a dedicated parallel port card for Mach3, not a mixed one. I repeat though, that's just something I heard.

17

General Mach Discussion / Re: Physical buttons for plasma

« on: March 26, 2016, 06:42:37 PM »

Using two motors would add more weight to the gantry than a solid 30mm dia shaft would be anyway.

Hood

Yes, BUT with 2 motors you have twice the drive power / torque, which would much more than compensate for the extra weight. So with 2 motors your power to weight ratio would be much better.

18

General Mach Discussion / Re: Physical buttons for plasma

« on: March 26, 2016, 06:33:16 PM »

What I was planning was a rack and pinion at both sides and a tubular shaft running through the 4inch Alu gantry and belts from that to the pinions, the motor will drive one side of that shaft.

Hood

That's what I have right now but I want to change it for dual rack, dual motor when time / money permit.

One thing to consider is torsional twist, especially at higher cutting speeds with 180 degree direction changes. Seeing as you have a length of 3m you could do a torsion twist test. Get the torque specs of your motors (+ any gearing to factor in), and on the bench apply that torque to one end of the tube/bar while the other is held fixed. If that torque twists it, you will probably get that on your table during a cut, possibly leading to shaky oscillations and a scalloped edge cut.

Perhaps a thin wall high strength tube will be more rigid than a solid bar. I know aeroplanes and race car frames can be made from thin wall 4140.

I've messed up plenty with my first cheapy build so if I can help you avoid it, all the better.

Edit:
Oops, just realised Dave got there before me on the twisting matter. Great minds think alike Dave LOL.

19

General Mach Discussion / Re: Physical buttons for plasma

« on: March 26, 2016, 05:03:15 PM »

Got to back up what Dave said.

Let's do some maths to illustrate the problem. Assuming a cut speed of 6000 mm/min. That is 100mm per second. If you could write some test code that made you gantry move 5mm then reverse and come 5mm back, and repeat, the gantry would be changing direction and moving 5mm 20 times per second.

If you can picture that you can get an idea of the rigidity needed if you plan to do any thin stuff. Actually, if possible you also want to keep the gantry light so the inertia of fast direction changes doesn't try and move the table. I look at some of the gantries for plasma and they look heavy. That's OK if you don't need fast cut speeds.

A look at Hypertherm cut charts will show the cut speeds can get higher than that on thin stuff. I'm actually gobsmacked that Hypertherm are not realising this issue and coming out with a cutter that allows us to keep the cut speed down on thin stuff. We need low amps and a tiny cute little nozzle with a very narrow kerf. The Finecut nozzles just don't cut it and the speeds can get right up there.

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General Mach Discussion / Re: Difference between plasma and mill...

« on: March 21, 2016, 03:59:10 AM »

Hi Dave,

I had always ASSUMED the different was in the screensets and the functionality, e.g. in plasma you have the THC functionality, THC correction speed, THC max/min, anti-dive, etc.