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THC Issue with Sheetcam and/or Mach3

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donniem70
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THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Thu Mar 29, 2018 4:52 pm

I have a home build CNC Plasma. I am Using the cutmaster 42 with the Proma 150 THC and the Gecko G540. I am using Mach3 and Sheetcam.
I have had the plasma running for a while until now. I am in the process of installing the Proma THC. I have it wired to the machine and the G540.
I added the settings in Mach3 for the THC. At least I think I have them all right.
The first issue I have is I turned every thing on and triggered the torch on to make sure the Proma is reading. It is. But, when I try to toggle the torch off it does not turn off. (yes, it worked before the changes).
I ran a couple of test cuts with the Plasma turned off to make sure it run though the code and it did. When I turn on the plasma, it touches off to set the height then it starts the torch. Then it does nothing. The torch is on but it will not lower to cut height or do anything. And the torch on/off will not cut the torch off.
I am stumped.
I am using the MP1000-THC post. I did try a different Post but it does the same thing. I don't know where to go from here. I am thinking it is something in my Mach3 setting, I just don't know what.
I am hoping someone here can help.

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Re: THC Issue with Sheetcam and/or Mach3

Postby tcaudle » Thu Mar 29, 2018 7:21 pm

FIRST: You make it cut with the THC off. If you can't setup , do a touch off , raise to pierce height , fire the torch , lower to cut height, get arc ok and release motion then you won't get it to work with the THC enabled. All that THC does is send simple UP and DOWN (jog) commands to MACH and it raises or lowers the Z. I don't think the Promo detects or uses Arc OK but MACH sure does. It has to have some kind of input on the THC ON input. You can "fool" it ans just set the polarity so it on all of the time. Not real great but at least you can cut. The MP1000-THC POST assumes a method of touch off and you have to put the SwitchOffset number in the POST if you have a floating torch holder (mechanical touch off) .

None of the pierce cycle is related in anyway to the THC.

Good Luck

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Thu Mar 29, 2018 9:19 pm

The machine does have a floating head. The Switchoffset is entered. The Promo does have and Arc okay Input. I had it connected to the output for the torch on at the G540. I did find when I unhooked it (the Arc Okay), the manual torch on/off function in Mach3 started working correctly again.
I did not try running it with the THC off. I will try that tomorrow and see what happens.
When I did run it with the THC on, the torch would touch off and come to correct pierce height and then start the torch. Then it would stop when it gets the the M03 line of code. With the Plasma OFF I could run the program. When it got to the point where it would stop (M03), I could hit the start function again and it would continue on with the program until it got to the M03 code again. With the plasma on, it would not go past the M03 code at all.
This is the first time I have ran the machine with the MP1000-THC post also. I will try running one of my old .tap files with the old post that I know worked and see what happens.

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Fri Mar 30, 2018 6:59 pm

Okay, update. I left everything set as it was. I turned off the THC and ran the file again. Worked perfect.
After checking and rechecking, I found that the wiring (pin out) for the G540 that I had was incorrect. At least for the unit I have. Once I located the correct one I moved one wire and changed the pin assignments in Mach3 it's working....kinda. lol. I believe now it is just a matter of fine tuning a few things.
Thanks for the help so far. I am sure I will need some more :)

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Tue Apr 03, 2018 8:33 pm

Another update, and issue.
After correcting the wiring and making a few adjustments in the settings I put the Proma in test mode and checked operation. Everything went up and down as it should. Up was up and down was down.
My issue now is. I have done a test circle to cut. When it cuts the smaller inner circle it works well. (It cuts between the slats of the table). When it starts to cut the outer part of the circle when it reaches a slat on the table, Z goes up to the safe height and stops.
I have read that I need to adjust the Anti-dive. I am not sure where that is. I do not see anything in my Mach3 setting that refer to the Anti-dive.
I also tried to install a THC plugin from Mach3's page but I cant get it to work. When i down load it, its an .M3P file not the .dll that the plugins need. Any suggestions on that too?

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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Wed Apr 04, 2018 10:02 am

I am very interested in the outcome of this thread. I have an almost identical setup (Mach3, G540, Proma THC-150, floating head torch mount, Everlast Powerplasma 60S c/w machine torch).

The Everlast cutter is not what I would have chosen, but it came with the table. It has very little in the way of suggested parameter settings info. I've also found that I have to set my THC voltage setting to about half what I've seen others using (60V) in order to keep the nozzle anywhere near the 0.06" cutting height. One good thing about this unit is it uses "Back striking ignition" instead of HF, so there is less EMF noise.

Up to now, I have been utilizing a ToM macro that I got from Adrian over at tamerisktechnicals.com It works just fine, but I think I will try one of the THC enabled posts (MP-1000) after reading this thread. I've also run the THC-150 in test mode and Mach seems to be reading and responding to the up/dn, Arc-OK signals as expected, so all my inputs appear to be correct.

My problem is the wildly inconsistent results I continue to get. Even when cutting straight lines on relatively flat material, I can observe the torch constantly moving up and down. I've tried changing various parameters to stabilize it, but can't get it where I feel it should be quality wise.

So, after all that my question(s) are, can someone please explain in detail what the following parameters do (what is their effect?), and what would be a reasonable setting for each?

THC-150:
volts = ? (as I stated above, I am operating in the 60v range, but most numbers I have seen from others say 100 to 120V)
HYS = ?
D-T = ?

Mach3:
THC Max = ?
THC Min = ?
Z Speed = ?
Antidive = ? (what is this function? I have pushed the button and the LED comes on, but I haven't detected any change in behavior.)

THC On/Off = ? (I have this button on my screen, but it seems to be disabled. Nothing happens when it is clicked. There is also a reset button next to it that also does nothing.)

Torch On = ? (This appears to work as expected. If the cutter is powered on, I can press this button and the torch will ignite. I don't use this very often so as to save tips, etc.)

I know this is a long winded post, but I wanted to included as much info as I could. Please, anyone. Help.

Thx. John

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Wed Apr 04, 2018 7:08 pm

John, where do you see the "Antidive" function. I have the others you listed on my screen, but I do not see an Antidive.
I am curious to see what the answers are to your questions also. I have been wondering about the same things.

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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Thu Apr 05, 2018 1:39 pm

donnie,

I too am interested to see a few answers, but it seems this thread has gone cold. Was it something I said?

As to your other inquiry, I am using a dedicated "plasma" screen set that I found over on the mach3 forum. Problem is, I can't remember exactly where I found it. I do, however, have a copy of the complete package I could send you if you will provide an email address you don't mind sharing on this forum. You can try searching that forum based on the name of the files: "plasma-ws4.zip" I don't know whether that will work, but, like I said, I do have that zip file heating on the grill if you want it. :D

john L.

jawneelogik
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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Thu Apr 05, 2018 1:46 pm

Donnie,

I went back, took a look and was able to find the original post. Go here:

http://www.machsupport.com/forum/index. ... w.html#new

There is a .jpg with a screen shot of the main screen. All the mach screens are included, but are accessed via a different, somewhat obscure set of buttons on the main screen. I like it because it has a quite large tool path window, but doesn't include a bunch of info that is irrelevant to plasma cutting.
enjoy, john

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Thu Apr 05, 2018 8:29 pm

Thanks John! I sent you a PM with my email info.

jawneelogik
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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Mon Apr 09, 2018 8:54 pm

Well Mr Donnie, It looks like we have fallen out of favor. I'm still interested in learning the function of the parameters I listed, but either they are a mystery to all or no one's talking.

BTW, did you have a look at that plasma screen set I pointed to?

John

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Thu Apr 12, 2018 8:10 am

Lol. I am use to falling out of favor when it comes to this stuff. Seems that I usually ask questions or have issues that no one else seems to come across.
I did take a look at the screen and I am going to try it. Haven't had time to get back to it as of yet though. Hopefully today or this weekend.

Maybe one day soon we will have an answer to these questions. :-)

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Thu Apr 12, 2018 7:00 pm

I am still at a loss. I believe the issue is in the post processor. I have tried a few different ones, but the only one that comes close to working is the MP-1000 THC
I have a simple washer that I have been using for a test file. It cuts the inside hole, but moves up and down very fast. Almost like its trying to saw though it. After it cuts it, it moves over to cut the out side circle, it touches off to find the height, starts the torch, pierces and immediately cut the torch off and raises up. That's it.
I have no idea where to go from here.

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Re: THC Issue with Sheetcam and/or Mach3

Postby AdrianH » Thu Apr 12, 2018 8:12 pm

I will try and give some input to you, not paid much attention to this thread as well you know what my THC is? 'The cheap one' so does not have settings in the THC it self.

but for the mach3 settings

THC Max = to what height do you want the maximum correction of the THC to move up to from zero.
THC Min = what height do you want the minimum correction height you want the THC to go down to

OK, so I work in metric, but deal with a lot of thin metal so I can get a lot of distortion at times with my slow machine so for THC max, I have about 12mm in here so if you use Inches try 0.5.
It just means as the THC tries to climb because of metal warping it will not go above 12mm or 0.5 inch.

The same for the THC min, if your normal cut height was say 1.5 mm or 0.06 inch then you may enter something like 0.5 mm or 0.02 inch to stop the THC taking the head lower and scraping the metal, but you need to have the touch off settings spot on the best you can.

Next Z speed = a percentage of your rapid Z speed that the THC will move in. There is no acceleration & deceleration in Z when it does this it jumps if you will, so to high a setting and it will simply miss steps or over jump, be too high then jump past, be to low jump high etc. For example my rapid Z speed is only 700mm per min approx 27.5 inches per min, but my THC speed I have set for 20 being 20% of 700mm per min, so quite low around there I find it does not hunt around the correct voltage, but can still get in the dead zone of the THC quite quickly.

Now on the right hand side of my screen there is another THC setting THC min speed, I basically have taken that as follows: I have mine set to say 70% so if the travel speed drops below 70% of the normal feed rate (this is cutting feed rate) then it turns the THC function off and no Z height adjustment happens.

When you are going into a corner the axis can not just continue at the same speed they have to slow down into the corner and speed out of a corner, the slowing down can mean that the width of the cut can increase as the arc has more chance to remove more metal. As the metal is cut away the volts go higher so the THC will try to adjust the height to bring the volts back to it's set level, hence the torch can dive when slowing, same happens on circles etc as it is constantly changing direction.

Now a bit of guesswork here as it's gone midnight for me so i am not downloading the manual for your THC and reading it, but, HYS I guess stands for Hysteresis, or dead zone as I call it, what amount can the voltage vary from the set voltage before it send either a move up or down command, suggest anywhere between +/-1 to +-2 Volts and see what happens 2 to 4 Volts.

D-T is typically delay timer before the THC stats to work after arc OK say 0.5 seconds and see how it goes, the idea is that it pierces, moves to cut height and starts to move cutting the metal, so it gives it 0.5 seconds before THC takes over again can save the torch diving in the metal recovering from to long a pierce delay or something.

The probable reason you need to set your voltage about 1/2 that of normal settings could be because the plasma has a resistor in series with the output of the arc voltage and this value is added to the potential divider in the THC, so the 50:1 divider of the THC becomes 100:1 some THC's have switchable divide ratios, I am not sure on yours.

Gone one in the early hours so I hope this helps, its sleep time for me.

Adrian
Last edited by AdrianH on Sat Apr 14, 2018 10:24 am, edited 3 times in total.

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Sat Apr 14, 2018 8:09 am

Adrian, Thank you so much for all this. You have really cleared up things for me. I can see that I definitely have some adjustments that need to be made.
This is a very good write up and explanation of the features in question.
I will take this and make some changes and let everyone know what the results are.

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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Sat Apr 14, 2018 6:10 pm

Looks like the system may have lost my last post. I was replying to Adrian H. last night, but it doesn't seem to be here.

Anyhoo, thx. Adrian for your detailed reply. I've already made a few adjustments based on the info you provided and tried them out. I'm still struggling with whole cutting voltage issue. Today I rigged up a little test apparatus that allowed me to stick a VOM meter across the gap between the cutting nozzle and the ground clamp thereby eliminating any internal voltage divider circuitry feeding my THC (The THC unit is and has been disabled-- no outputs. I've been using its voltage readout strictly for reference purposes only.) .

This morning while cutting 3/16" material @45A, moving @40ipm and a cut height of 0.062", I observed a voltage across the gap of between 55 and 60V. So, that leads me to believe that there is definitely something not right with this machine. It takes a certain amount of heat to melt steel at a certain rate. Heat equals watts and watts equal volts x amps. If the cutter unit is not maintaining high enough voltage across the gap for a given current, the heat of the plasma will be diminished and not perform as it should. What I'm trying to say is that, if the gap voltage were closer to 100V as I expect it to be then I would not need 45A to cut this relatively thin material at this slow speed (The advertised specs for this Everlast 60S state that it will achieve a "Quality cut of 1" @10-12ipm." I don't believe that, but I would expect it to cut 3/4" without struggling.).

All the specs and literature I have read regarding these units (plasma cutters in general, that is.) all state that, at a cutting height of 1/16" (.0625", 1.58mm), gap voltage should be about 110V regardless of the amperage setpoint. If the manufacturers would rate their products by Power instead of Amps, this would be a lot easier.

So, Adrian, if you wouldn't mind chiming in on the results of my little experiment, it would be most appreciated. Also, I noticed you didn't say anything regarding the Anti-dive and THC On/Off buttons. Are you able to comment on these?

Thx. again, John L.

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Re: THC Issue with Sheetcam and/or Mach3

Postby AdrianH » Sat Apr 14, 2018 8:11 pm

Unfortunately the Everlast is unknown to me, I use the Chinese Cut 40 but a quick check of the specs and I see 20-60A; 88-104V, so yes I would expect a higher voltage, but I would suggest that you could be measuring between the TIP in this picture and the work piece/clamp which I believe is the wrong place to take a measurement from.

I can not quickly find an exploded view of the CNC machine torch so will try with the hand held ipt 60 torch and hope it gives the correct idea.
body.png


If you connect at the tip i.e the MVU0661-08 and the work piece, that part is not where the cutting arc starts from, in fact it is insulated from the electrode and the electrode is the point you would need to connect to. Now that would be dam near difficult to achieve but you could connect to the torch body or to the pipe that goes into it and the ground clamp/workpiece. The torch body will in fact be negative with respect to the work.

I would suggest you are doing OK with the speed you mention. When I cut 5mm steel, granted I cut down at 30 Amps and I am only down at around 680mm/min or 27 ipm. At 45 Amps i would expect it to be around 40 ipm. Just by 27 ipm divide by 30 and mult by 40 to give a quick ratio?

These machines are not Hypertherm, they, typically can have a cutting voltage of around 135 Volts, not around 100 Volts so have a higher heat input than my Cut system or the Everlast. But they need a heavier supply to achieve it.

This section out of a Hypertherm cutting chart for 45 Amp shielded consumables
cutting.png


Shows 3/16 70 ipm 135 Volts for best quality, 108 ipm for production at 132 Volts, and I would think a lot of investment has gone into the Hypertherm consumables.

Say 100 Volts x 45 Amps 4,500 watts in the metal to cut. 135 Volts x 45 amps 6,075 Watts in the metal to cut.

On the last section the THC on off buttons and anti dive buttons, I did mention the settings used for these, but I do not switch them on/off via the screen, I have cut rules that do that for me. I must admit that I can not see a reason for turning anti-dive off, unless you want to see the effects of slowing down into and out of corners.

I also noted a mention of Post processor before, have you tried the Mach3 THC with scriber.scpost, you can switch off the scriber section by entering nil,

I use my own post as I migrated from a non THC cutter and have done things differently, I set height at every pierce, which slows things down to much for production work, but the Mach3 THC with scriber.scpost allows you to set say 250 mm or 500 mm travel before it does another set height on pierce. Do not use in in conjunction with my M800 macro, the settings for zero height setting are in the post itself so calling M800 is not required.

Gone one again so good night from me.
Adrian

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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Sun Apr 15, 2018 10:13 am

Adrian. Again, I thank you for responding. I only hope I too can help some noob in the future as I progress in my increasing level of knowledge.

"If you connect at the tip i.e the MVU0661-08 and the work piece, that part is not where the cutting arc starts from, in fact it is insulated from the electrode and the electrode is the point you would need to connect to. Now that would be dam near difficult to achieve..."

I agree that the tip makes no "direct" contact with the electrode, but when the main arc is established, the plasma jet is streaming through the orifice and IS in contact with the nozzle. Granted, there may well be some reduction in voltage potential due to the overall resistance of the plasma compared to a straight copper-copper connection, but I refuse to believe there would be a 40V or even 60V reduction. Everlast tech support were kind enough to share a copy of this "unofficial" chart. He (Brett K.) kept saying it was an old document whatever that means. The chart's title clearly states it is for the 60S (Actually it includes sheets for both the 60S and the 80S.) Please take a look at the chart and see the voltage they expect to see.

Everlast Powerplasma 60s CNC CUTTING SPECS.xlsx


When you shifted to using watts, everything comes clear to me . If you do the math on my cutter (in its current state of functionality: 55V x 45A = 2475W), this unit is NOT putting out the power that is needed to cut a given material at published specs. Right now I'm only trying to gather sufficient evidence of machine malfunction (or not) before I make the monumental decision to lay out $5k to $6k for a machine that is guaranteed to perform at the needed rate. I was foolish enough (maybe lucky enough?) to enter into a commercial obligation before I knew everything I needed to know to meet that obligation. However, according to Everlast's advertised specs for this machine, I should be able to cut material at the rates I've promised my customer.

Everlast 60S, 80S specs.PNG

As things are right now, I can barely get half-way there. And, just to be clear, I didn't choose this Everlast box. It was included with the used table I bought. At the time, I didn't know shyte-from-shinola about plasma cutters and what separates the men from the boys!

"On the last section the THC on off buttons and anti dive buttons, I did mention the settings used for these, but I do not switch them on/off via the screen, I have cut rules that do that for me. I must admit that I can not see a reason for turning anti-dive off, unless you want to see the effects of slowing down into and out of corners."

Let me restate that I have been operating with my THC Up/Dn signals physically disconnected. I'm cutting on new, flat sheets, so there is not a huge variation in height for the torch to deal with. I've been attempting to get a baseline voltage reading which I can then use to set the controller. I've tried running with Anti-dive both on and off. I have not detected a difference in performance between On and Off. That doesn't mean it isn't working, it just means I can't see the difference. I'm reasonably certain that I am the problem, not the system.

So, are you saying that, if I did have my Proma hooked up, the anti-dive function would be doing something based on the parameters we discussed earlier? (THC Min/Max/Z Speed, etc. That is, assuming I had them set properly.) Could you possibly elaborate a little more on how that whole Mach3 THC with Anti-dive is intended to function?

I will, indeed, go and investigate the other post(s) you mentioned, but probably not until I've ironed out this voltage issue. In one of my earlier posts that seems to have gone missing, I tried to send you a thank you and complement re your M800 macro. It works great for my current needs. In fact, it has never failed to find ToM. I have inserted it into a non-THC post, so that is the only code in there relating to THC. Perhaps, now that I think on it, that is the reason I see no response from Anti-dive?

I'm going to end this here. It's 9AM and the Mrs. is reminding me that there is grass that needs cutting etc. Thanks again for all your input. Cheers, John L.

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Re: THC Issue with Sheetcam and/or Mach3

Postby jimcolt » Sun Apr 15, 2018 11:19 am

Just to clarify a few things:

-Arc voltage as listed in the Hypertherm mechanized cut charts is a direct DC measurement between the Electrode (negative) and the Workpiece (work cable connected to metal being cut). Both of these connections can be made inside any plasma power supply rather easily.

-If you cut a piece of metal at a fixed cut speed (straight line) at a fixed current and a fixed height (material is perfectly level and torch stays exactly the same distance from metal)....you will be able to read a fairly stable DC voltage in the power supply from - to + with a digital voltmeter.

-If you cut at the exact specs listed in the Hypertherm manual, using a new set of consumables at the listed physical cut height, current, cut speed and material thickness....then you will read the same voltage listed in the manual if you connect a DVM to the + , - output of the power supply.

- Arc Voltage based torch height controls have been on the market since 1976 (Hypertherm had the first one). The ones that work have a lot of technical built in features such as kerf crossing detection (ability to recognize voltage anomalies of kerf crossing to prevent diving) as well as good integration with the CNC velocity (to sense slowdown in corners and fine cut details) to eliminate diving without having to write machine code for each feature that causes slowdown. The designers and manufacturers of these THC systems are likely not going to share all of their technology with the builders of the (half dozen or so) low cost THC systems on the market today.

-In my opinion (which is based on 40 years of mechanized plasma cutting) the best THC's are integrated as another axis in the cnc control (Z) and works intimately with the velocity loop and timing of the plasma, the CNC, and in some cases the CAM software.

-Different plasma torches with different consumable designs will have different arc voltage characteristics when they are producing the best cut quality. Hypertherm torches using the shielded consumables will have higher arc voltage as compared to older technology "exposed nozzle" design. Note....the nozzle is the part that constricts the arc....in one of the above graphics the nozzle is called a "tip", (which is a takeoff term from a "contact" tip in a mig welder I suspect). Note that the torch style used in the Everlast is a copy of a 30 year old torch design from an Esab plasma....really old torch tech!

-Most modern THC's read their arc voltage in either a "divided" form (most often 1/50th, though Hypertherm systems also have dip switch selectable ranges of 1/20th, 1/30th, 1/40th as well), or in a digital signal for better accuracy on large industrial machines. The divided voltage is divided for safety reasons to meet CSA and CE certifications worldwide. Raw DC arc voltage can be as high as 350 VDC in open circuit conditions.

- I am not a Mach 3 guy. Never used it.....as I am a fan of software for plasma cutting that eliminates the need for the operator to have to even see machine code. We have been using excellent CAM software for about 25 years in the plasma cutting industry....don't want to take a step back!

_ My experiences in working with a few thousand end users with the low cost THC imports is.....they work better than no THC, but not nearly as well as the better designs integrated into the CNC controls on many machines in uses today. I like to nest a few hundred parts on my cnc plasma and push the start button....then walk away while the machine does the cutting. This cannot be done unless the THC maintains the correct pierce height, cut height all the time without operator intervention, including compensating for electrode wear (auto voltage sensing / calibration).

Jim Colt Hypertherm

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Re: THC Issue with Sheetcam and/or Mach3

Postby AdrianH » Sun Apr 15, 2018 4:13 pm

jawneelogik wrote:I agree that the tip makes no "direct" contact with the electrode, but when the main arc is established, the plasma jet is streaming through the orifice and IS in contact with the nozzle. Granted, there may well be some reduction in voltage potential due to the overall resistance of the plasma compared to a straight copper-copper connection, but I refuse to believe there would be a 40V or even 60V reduction.


Well I feel I must disagree with the everlast guy there, when cutting the arc is formed from the Electrode Tip and the workpiece, the arc plasma is restricted by a circulating high pressure column of air as it passes through the 1 to 1.2 mm hole in the tip, it is insulated to a degree by this air all around the plasma, if it was not the tip would quickly be destroyed in my view.

In fact with my very cheap system, that same tip is connected to ground by a 15 Ohm 300 watt resistor, I can measure 96 Volts at my electrode by my THC and a meter when cutting has commenced, but the current that flows through the resistor is in the fraction's of an amp range where if it was connected to the column of plasma one would expect a current flow of 6.4 Amps at 96 Volts, it just does not happen.

You may well have a faulty plasma cutter, but I do not believe what you are measuring would prove it. Is it not possible to put the negative of the meter into the housing of the torch and connect to the metal torch body?

The maximum cutting current you have is 60 amps at 104 Volts so that is 6,240 watts, the effective input wattage full power is 7,776 watts, around 85% efficiency should give 6,610 Watts, but one also has to allow for cooling fan, solenoids control circuits etc so I tend to think the figure would stack up from that point. I tend to think that at 45 amps you should be reading some where in the region of 97 to 100 Volts.

jawneelogik wrote:So, are you saying that, if I did have my Proma hooked up, the anti-dive function would be doing something based on the parameters we discussed earlier? (THC Min/Max/Z Speed, etc. That is, assuming I had them set properly.) Could you possibly elaborate a little more on how that whole Mach3 THC with Anti-dive is intended to function?

With the THC being disconnected then the Mach 3 settings and buttons for THC on, off, anti-dive will not have any effect what so ever. The only signal it would need is arc OK to get it moving in the first place.

John, I have dumbed this down a bit, not for you, but in the hope any non-technical reader can find it useful.

Think of the plasma column as a variable resistor. Let me make a few descriptive assumptions for aid of clarity.

    1) The electrode is 2 mm up from the end of the tip and you are cutting at a tip height of 2 mm, so the total column height from electrode to metal is 4 mm.
    2) The plasma cut voltage is measured at 80 Volts (all nice round figures).
    3) The current has been set for 40 Amps and similar to a Tig welder the machine is going to try it's very best to keep the amps constant at 40 Amps.
    4) The resistance of the plasma column is basically 80 Volt / 40 Amps = 2 Ohms, or, said another way the resistance is 0.5 Ohms per mm distance.

So if 2 mm is the preferred cut height you set 80 Volts on the THC and have a hysteresis of +/- say 2 Volts so can be between 78 and 82 Volts.

Now due to a warped bit of metal the 2 mm tip gap drops to 1.5 mm, the plasma column drops to 3.5 mm the resistance of the column drops to (3.5 x 0.5) = 1.75 ohms, but the plasma cutter is going to maintain 40 amps cut current with its own loop control and the only way it can maintain 40 amps similar to any TIG welder is to reduce the applied voltage down to 40 amps x 1.75 Ohm = 70 Volts.

But hang on, the THC is set for 80 +/- 2 Volts so it has dropped below it's limits so all that happens is it closes a contact that is read by Mach3 to move the Z height up a bit and again and again until the voltage once again measured by the THC sits within the range of 78 to 82 Volts when it does nothing all up or down contacts are open no signals to do anything.

Same thing when the height increases above the 2 mm tip gap to say 2.5mm, the plasma column goes up to 4.5 mm to maintain the 40 Amps the applied voltage has to increase to 40 x 4.5 x 0.5 = 90 Volts, which is now higher than the 78 to 82 Volt range, so a closing contact is made telling Mach 3 to move Z down a bit and repeat until we hit a figure within the range of 78 to 82 Volts. If the movement is to fast, or goes to far one ends up sawing up and down passed the set voltage range hence starting off with a low Z THC speed say 10% and slowly going up in small steps until to you find a point where it does it quickly without over shooting the volts.

I am going to stick a comment in here with respect to Jim's Colts post.

I am going to agree with everything you have said and if anyone wanted the best solution, was not interested in technicalities, how it works etc then for flat out production with simple drawing transfer from computer to table, I would think you would struggle to beat a full Hypertherm solution.

My solution is definitely not the best it is the cheapest way I could ever go, my stuff is pure hobby, experimenter for the type of person that likes to understand and work it all out for themselves.

The cutter and software side of thing is the main part to any system, The table to me is second and good support is essential when things go wrong or when setting up in the first place, hence why many will buy a ready made system from a manufacturer with support.
The difference between it all can range from tens of thousands of dollars to around 10,000 dollars with a range of supplier solutions between the two. You make your choice dependent on depth of pockets and the business case.

Adrian

donniem70
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Re: THC Issue with Sheetcam and/or Mach3

Postby donniem70 » Mon Apr 16, 2018 10:20 pm

Adrian I also thank you again for you input and clarifications.

Here is what I ran across today. I know everything is different and I a not asking for a solution. I am just kind of thinking out loud and bouncing things around a bit.

So I decided I really didn't (don't) know enough about my machine (Thermal Dynamics Cutmaster 42) as it does not have any mechanized cut charts like the Hypertherm units others are using.

I made 4 (4" long .300 wide with radius's at each end) cuts on .125 mild steel and 4 cuts on .1875 with the THC disabled. I cut at different amp settings and heights to find the best quality. The manual that came with my plasma says cut height should be between 1/8" to 3/8" I found .090 to have the cleanest cut with the least flame distortion. All cuts I was getting a reading for approx 132 volts on the .125 and 138 volts on the .1875. I was thinking that was a little hi, but they were all consistent. On both, the volts would increase by almost 10 volts in the radii. Which I kind of expected from you explanation earlier on the radii cuts.

I set my Proma 150 THC for 138 volts (for the .1875) with the hysteresis of 2.
When I reactivated the the THC and started the cut, the voltage reading on the THC is way off. It was reading 158 volts.
Not sure why my Volts have gone so hi. I adjusted the Proma to the new volts and tried again. This time it would cut the straight line, until the voltage would go above or below the +/-2 then z would move up and down fast and then set a Softlimit fault. (this was all before reaching the radius cut area) What seems odd is I have the THC min set to -.500 and the softlimit is actually below the top surface of the .1875 material I was cutting.
I got frustrated and quit.....LOL
If anyone has any input, AWESOME.....if not, thats cool too. Thats just where I am right now. Hopefully I will have a few more ideas to try tomorrow.

beefy
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Re: THC Issue with Sheetcam and/or Mach3

Postby beefy » Tue Apr 17, 2018 2:29 am

jawneelogik wrote:I agree that the tip makes no "direct" contact with the electrode, but when the main arc is established, the plasma jet is streaming through the orifice and IS in contact with the nozzle.
John L.


I think that's a bit of an assumption.

What happens when ANY metal is in contact with the plasma jet ????????????

It's very quickly melted / vapourised and blasted away. What exotic space age material would the nozzle (tip as it's often called) need to be made of to be practically unaffected while in long term contact with a plasma jet at how many 1000s of degrees Celcius above the melting temperature of most (all ??) metals/alloys.

As has already been stated, my guess would be the plasma jet has practically zero contact with the nozzle orifice, and instead, is insulated from it by the high velocity swirling air stream, which I believe also serves the secondary purpose of shaping/concentrating the plasma jet.
8 x 5 water table
Powermax 1250 with Duramax torch
UCCNC controller, UC400-ETH & UC300-ETH motion controllers.
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AdrianH
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Re: THC Issue with Sheetcam and/or Mach3

Postby AdrianH » Tue Apr 17, 2018 3:33 am

How about this for a starter to help with your cut speeds. http://eagleplasma.com/cutters/cut-chart-cm42.pdf It actually seems to be the 52 but may help?

The hardest issue I think, was for me was going as fast as the machine can. Most of the testing I did without THC similar to what you have done but lots of straight lines from one end of the metal to the other. As you have seen as it slows down for corners the higher the volts, so are you going fast enough to provide the absolute thinnest cut, like for each thickness at what speed would you not cut through reliably, then back off say 10%

This bit is just a suggestion. In Sheetcam I have a 'tool' for each thickness of metal I cut. I called the tools 1.6 mm, 2 mm, 4 mm and 5 mm. They all have their own pierce delay, Pierce height (stays much the same), cut height and speed etc. So for each thickness set your cut height as the chart so it starts at the correct height.

If you are getting rapid movement of the Z axis then I think your THC speed is still to high, slow it down further. A lot of this will depend on what your Rapid Z speed actually is set at and how many steps per inch you have. On the THC if you have hysteresis at 2 that is probably +/-1 volt , so give it a chance make it say 6 Volts for +/- 3 volts until you can fine tune it.

Soft limt is different to the THC min and Max, that is based and used with home limit switches generally to slow things down when you approach the axis limits of your machine, basically for when you are using a mill or lathe so you do not go at full speed into your limit switches, so if you have home switches or limit switches on your machine especially on the Z axis and still have a soft limit set, are you now asking it to go lower than it's soft limit?

Watch this youtube https://www.youtube.com/watch?v=ma7lMocQbv0 Please consider this is talking about a Mill not plasma where the Z operates differently as Z is work surface and not home top of Quill travel on a mill.
Then check what you have in your own set-up screens for soft limits.

One day I will fit limit switches to my table.

My last bit of advice, when getting frustrated, is go away have a brew or what ever you need to take a step back, then try and approach it again looking for why it happens, it is typically some default settings somewhere or not quite understanding a setting in the manual, so have a printed copy with you.

When it does finally click in place the feeling is good, you stand back and say, I did that!

Adrian

You have just given me an idea for my next video, now where are those opto sensors I bought?

jawneelogik
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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Tue Apr 17, 2018 7:35 pm

beefy wrote:
jawneelogik wrote:I agree that the tip makes no "direct" contact with the electrode, but when the main arc is established, the plasma jet is streaming through the orifice and IS in contact with the nozzle.
John L.


I think that's a bit of an assumption.

What happens when ANY metal is in contact with the plasma jet ????????????

It's very quickly melted / vapourised and blasted away. What exotic space age material would the nozzle (tip as it's often called) need to be made of to be practically unaffected while in long term contact with a plasma jet at how many 1000s of degrees Celcius above the melting temperature of most (all ??) metals/alloys.

As has already been stated, my guess would be the plasma jet has practically zero contact with the nozzle orifice, and instead, is insulated from it by the high velocity swirling air stream, which I believe also serves the secondary purpose of shaping/concentrating the plasma jet.


Yes, as Adrian has already pointed out, mine was an erroneous assumption and I have moved on from there. After much 'back-and-forth' discussion, I decided to open the Green box and take some voltage readings directly off the electrode and work clamp terminals as they exit the front of the unit. I ran a couple of cutting jobs that I knew would cut more-or-less straight and true without any possibility of upset. This is what I learned:

On each pierce, the initial voltage spiked up to almost 150v after main arc was initiated then as the metal was pierced it settled down to right around 100v as the torch began to move laterally at the cut height of 0.0625" (1/16"). I was cutting 1/4" plate at 30ipm and the edges were decent. I did NOT have my Torch Height Controller enabled so the correct cutting height was not maintained and started to change after about 1-2" of cut. This was reflected in the voltage readings which varied between about 88v up to 105v depending on whether the tip was too close or too far away.

Based on my observations, I no longer believe there is a fault in the machine. It is not broken. However, I now have come to believe that Everlast has dramatically oversold the capabilities of this machine. I'm stating this because I have empirical evidence that it will not "in a million years" cut the thickness of material that is stated in Everlast's literature.

I'm now in discussion with Hypertherm about their best option form my situation, and that part of this saga can be put to bed.

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Re: THC Issue with Sheetcam and/or Mach3

Postby jawneelogik » Tue Apr 17, 2018 8:45 pm

AdrianH wrote:
jawneelogik wrote:I agree that the tip makes no "direct" contact with the electrode, but when the main arc is established, the plasma jet is streaming through the orifice and IS in contact with the nozzle. Granted, there may well be some reduction in voltage potential due to the overall resistance of the plasma compared to a straight copper-copper connection, but I refuse to believe there would be a 40V or even 60V reduction.


Well I feel I must disagree with the everlast guy there, when cutting the arc is formed from the Electrode Tip and the workpiece, the arc plasma is restricted by a circulating high pressure column of air as it passes through the 1 to 1.2 mm hole in the tip, it is insulated to a degree by this air all around the plasma, if it was not the tip would quickly be destroyed in my view.

In fact with my very cheap system, that same tip is connected to ground by a 15 Ohm 300 watt resistor, I can measure 96 Volts at my electrode by my THC and a meter when cutting has commenced, but the current that flows through the resistor is in the fraction's of an amp range where if it was connected to the column of plasma one would expect a current flow of 6.4 Amps at 96 Volts, it just does not happen.

You may well have a faulty plasma cutter, but I do not believe what you are measuring would prove it. Is it not possible to put the negative of the meter into the housing of the torch and connect to the metal torch body?

The maximum cutting current you have is 60 amps at 104 Volts so that is 6,240 watts, the effective input wattage full power is 7,776 watts, around 85% efficiency should give 6,610 Watts, but one also has to allow for cooling fan, solenoids control circuits etc so I tend to think the figure would stack up from that point. I tend to think that at 45 amps you should be reading some where in the region of 97 to 100 Volts.

jawneelogik wrote:So, are you saying that, if I did have my Proma hooked up, the anti-dive function would be doing something based on the parameters we discussed earlier? (THC Min/Max/Z Speed, etc. That is, assuming I had them set properly.) Could you possibly elaborate a little more on how that whole Mach3 THC with Anti-dive is intended to function?

With the THC being disconnected then the Mach 3 settings and buttons for THC on, off, anti-dive will not have any effect what so ever. The only signal it would need is arc OK to get it moving in the first place.

John, I have dumbed this down a bit, not for you, but in the hope any non-technical reader can find it useful.

Think of the plasma column as a variable resistor. Let me make a few descriptive assumptions for aid of clarity.

    1) The electrode is 2 mm up from the end of the tip and you are cutting at a tip height of 2 mm, so the total column height from electrode to metal is 4 mm.
    2) The plasma cut voltage is measured at 80 Volts (all nice round figures).
    3) The current has been set for 40 Amps and similar to a Tig welder the machine is going to try it's very best to keep the amps constant at 40 Amps.
    4) The resistance of the plasma column is basically 80 Volt / 40 Amps = 2 Ohms, or, said another way the resistance is 0.5 Ohms per mm distance.

So if 2 mm is the preferred cut height you set 80 Volts on the THC and have a hysteresis of +/- say 2 Volts so can be between 78 and 82 Volts.

Now due to a warped bit of metal the 2 mm tip gap drops to 1.5 mm, the plasma column drops to 3.5 mm the resistance of the column drops to (3.5 x 0.5) = 1.75 ohms, but the plasma cutter is going to maintain 40 amps cut current with its own loop control and the only way it can maintain 40 amps similar to any TIG welder is to reduce the applied voltage down to 40 amps x 1.75 Ohm = 70 Volts.

But hang on, the THC is set for 80 +/- 2 Volts so it has dropped below it's limits so all that happens is it closes a contact that is read by Mach3 to move the Z height up a bit and again and again until the voltage once again measured by the THC sits within the range of 78 to 82 Volts when it does nothing all up or down contacts are open no signals to do anything.

Same thing when the height increases above the 2 mm tip gap to say 2.5mm, the plasma column goes up to 4.5 mm to maintain the 40 Amps the applied voltage has to increase to 40 x 4.5 x 0.5 = 90 Volts, which is now higher than the 78 to 82 Volt range, so a closing contact is made telling Mach 3 to move Z down a bit and repeat until we hit a figure within the range of 78 to 82 Volts. If the movement is to fast, or goes to far one ends up sawing up and down passed the set voltage range hence starting off with a low Z THC speed say 10% and slowly going up in small steps until to you find a point where it does it quickly without over shooting the volts.

I am going to stick a comment in here with respect to Jim's Colts post.

I am going to agree with everything you have said and if anyone wanted the best solution, was not interested in technicalities, how it works etc then for flat out production with simple drawing transfer from computer to table, I would think you would struggle to beat a full Hypertherm solution.

My solution is definitely not the best it is the cheapest way I could ever go, my stuff is pure hobby, experimenter for the type of person that likes to understand and work it all out for themselves.

The cutter and software side of thing is the main part to any system, The table to me is second and good support is essential when things go wrong or when setting up in the first place, hence why many will buy a ready made system from a manufacturer with support.
The difference between it all can range from tens of thousands of dollars to around 10,000 dollars with a range of supplier solutions between the two. You make your choice dependent on depth of pockets and the business case.

Adrian


Adrian, this is why, IMHO, you are the perfect forum member. You haven't forgotten where you came from. You're humble about what you know and always understate that, yet yours is always a detailed, methodical analysis of the problem. Thank you.

Now, back to my questions/concerns. I would like to revisit the questions re various Mach3 parameters/functions

First off, I am quite certain that all my wiring is correct re the THC device. I can open, have opened, the diagnostic page and observed the 3 signals (Arc-OK, Torch-Up, Torch-Dn) coming from the Proma 150 while it runs in demo mode. On the screen set that I use which is a hybridized 'Plasma' only affair, I have a set of buttons and parameters that I personally am unclear as to their meaning/functionality/effect whatever!

(Before we begin, assume that my Proma Compact 150 is hooked up and all signals are reporting.)

- I have a button c/w LED called THC. It appears to me that this button does nothing because the LED never changes state.
- I have a button c/w LED called Torch On. This button triggers the torch on and off and it works. LED lights when clicked.
- I have a label c/w LED called Arc OK. The LED changes state and seems to correspond to the same signal on the Proma.
- I have a label c/w DRO called Pierce Delay. I can enter a number, but it has no effect nor does it seem to reflect the delay injected into the gcode which Sheetcam produces. I.e. if I have specified a pierce delay in SC of 1s, it is not displayed in the DRO on screen, and if I put any number other than zero into the DRO, there is no observable effect on program execution. So, what is it?
- I have a button c/w LED and DRO called Anti Dive. I have never observed any effects from this. If I click the button, the LED changes state, but nothing else seems to happen and I have entered various values into the DRO with no observable effect. What is the internal logic for this button/function?
- I have a label c/w DRO called Z speed. I have been told that this value limits Z movement to a percentage of max Z speed, but I have entered values into the DRO and observed no visible effect.
- I have labels c/w DROs called THC Max/Min. I have been told that these values represent the min and max Z travel values that are permitted under THC. I have entered what I consider reasonable values for these, but, again, I have no sense of whether they are doing anything.

That is all I wish to know for now. I realize it is a lot, but I would be eternally grateful if I could get a salient, clear explanation of the logic involved in these buttons/label/dros, etc. I.e. Don't tell me what I should be doing. Please just explain what these do. If you can do that, I can probably solve my own problem(s) and not bother anyone further.

thank you, john


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