Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: AdrianH on November 23, 2016, 05:06:23 PM
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Mods if in the wrong place please move.
I am home brewing gear so sorry of the questions seem to be dumb, this is all new to me.
When using torch height control is there normally a 'dead' range that the head will not go up or down, hysteresis I guess it is called? So if you have your magic cutting height providing say 120 Volts into the controller, how many volts either side do you have before the controllers say move up or down?
I assume there is a hysteresis in controllers otherwise the Z axis would be constantly adjusting it self for even a minute variation.
I also assume that without the THCON input even if there is an input on Up or down the Z axis will not move until THCON is active?
If the last point is correct is there a requirement to send the X axis to a cutting height from pierce, or can this be left to THC control.
Cheers
Adrian
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Sorry the Topic should read
Question on Plasma THC control to users of this facility
I must have left it to long since posting and can not edit it now.
Adrian
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Usually something like 2-4v hysteresis or dead-band.
Generally Z axis is the height (you mention X ) and no it should not move on inputs if THC is off, providing it is all programmed to behave that way - you can set movements even if THC is off in ports & pins i believe.
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Thanks Dave for the feedback, yes should be Z I talk about not X was getting late.
Also thanks for the 2 to 4 volts dead band, that was an uncertainty for me. I guess it could be adjustable on some.
Adrian
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Usually is adjustable, even on the cheap Proma THC's there is a setting for it.
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Hi again Dave;
I have figured a way to change the dead band on what I am trying, quite easy when I stopped trying to think to hard.
I will explain what I am trying to do in very simplistic terms and please do not laugh as my set-up is purely as a hobby, keeping the grey cells active and a bit of fun.
I picked up one of the Chinese Cut40 plasma cutters, It is still at the limit of the mains supply in my garage and as my hobby is general metalwork I could not really justify a lot of hard earned.
After a few months I built a CNC frame for it, got a straight torch head for around £30 and started to have fun, the whole lot including plasma cutter probably cost me less than £500 and a far bit of time.
But I use it as a drag head across the metal, the Z axis has a floating section and the weight of the head keeps the drag tip on the work, but this slows every thing down, acceleration and top speed etc. It also means it will show any slop or flex in movement, my circles are not perfect circles etc.
So I have started to think how to improve it and the only way I could think of was to lift the tip off the work piece and for that I need THC, so ultra cheap THC control using a 4 input Voltage comparator project has started.
It would be ludicrous to go out and buy a £200 plus THC controller to work with a £180 Plasma cutter!
Adrian
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Sounds like your'e having fun, thats what matters :)
I guess you will have to start the cut as a drag then lift to move?
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I can pierce off the metal, only by a mm, two at most, so I tend to do that then drop after delay to in theory be 2mm under the top of the metal!
That way if the metal drops by up to 2mm it is still in contact, if the metal rises more then the torch floats up with it, but as I say at a cost.
thanks for your input it us appreciated.
Adrian
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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.
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Hi beefy;
I guess I like to play electronics, time is cheaper than money and I seem to learn a lot in the process. None of my stuff is for profit, just to help me make more things.
If at some point in the future I had a commercial thing to do it would be a different matter. I have a simple way to change my dead band, my travel speed is slow circa 900mm per min at the moment possibly up to 1200 or 1500 if I get this to work, still very slow in comparison to commercial equipment.
I enjoy the challenge also semi retirement helps.
If I get it to work I will try to do a video.
Adrian
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You need to consider hysterysis in terms of height....
1 volt is approx 0.5mm of torch height according to published material.... Hence 2v can be 1mm of torch height (act maybe a little more....) If your torch is flying around at 1.6mm above tge plate, that is only around 3 volts of height....
One of the failings of torch height controllers can be sampling speed in terms of input (sampled voltage) to output (up and down motion).... That is where the cheaper thcs can fail to match up when you are running higher ampage on thinner plate (higher feedrate required)
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Hello Robert, thanks for your input.
The figures you were quoting was something I have failed to find, so I can base my dead band initially from that.
I use a drag tip at the moment and these are really only cheep things so not made to any great spec, I will be using my lathe to modify these to remove the castelations and give more of a point to the nozzle to allow me to get a variation in height.
But first will run as standard with a few normal tips and measure arc volts if I can to see where it runs now, then try to set up with THC to get back around that same level.
Knowing the 1 volt per 0.5mm will help a lot.
I guess it will also depend on nozzle diameter, speed and width of cut/thickness of metal. Could you point me to the doc if possible.
At the end it may be a complete failure with my set-up and approach, but I am still having fun on the journey.
Adrian
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To avoid retyping a load of similar information, below is a link which provides a lot of the references you require, and provides guidance on published feedrates etc.
http://www.forum.cncdrive.com/viewtopic.php?f=4&t=168
HOWEVER, please note that this information may not be applicable to your specific application as I was discussing something specific here, to do with integrating THC with a motion controller, but the links and information should be off use (voltages and maximum expected feedrates referenced). Also your plasma cutter is not the same as a hypertherm as far as feedrates pierce and cut heights are concerned.
Plasma is all about power (Watts), and Watts = Volts x Amps..... hence although your plasma may say 40A.... that is 40A at what voltage?
I found this manual for the Cut40, although there are likley to be a tonne of similar manuals with machines that look different all called Cut40 from different factories in China... so bear with me a little (not being negative or sarcastic toward them at all)
http://www.bjhowes.com.au/CUT40.pdf
https://www.google.co.uk/search?q=Cut40&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=FIc5WOGdGu7W8gfL_rHICg#q=Cut40+pdf
The manual quotes 20 - 40A at 96V (hence at best you have 3840W).... there is also a power factor consideration at 0.93% .... possibly.... because although its suppose to be an IGBT plasma cutter if you have a look at the VERY basic schmatic you'll see there is a transformer dispite the quoting of PWM at 100kHz etc .... hence I'd say you probably have around 3571W of metal cutting power say 3.6kW.... note there is also an efficency of 85% quoted... hence there may be some more losses somewhere too
I had for many years (still have it, just not used) a hypertherm powermax 350, which could be probably used to provide comparable cutting tables for your CUT40 (at least something to start with), given the cut rating is 10mm.... similar to the cut40 manual posted above (but the power rating is only 27A at 91V so 2457W... hence you may be able to get better than the PMX350 (which is the same energy rating as the PMX380, both of which are "older" transformer technology although they are not scratch or HF start (they use blockback start).
https://www.hypertherm.com/Xnet/library/library.jsp?file=HYP104427&format=pdf
https://www.hypertherm.com/Xnet/library/library.jsp?file=HYP104478&format=pdf
You can browse the hypertherm manuals here for any model (including FULL service manuals, sign of a good manufacturer):
https://www.hypertherm.com/en-US/customer-support/documents-library/
Also reading the manual the plasma cutter uses HF (high frequency) plus requires "scratch start"..... never good with CNC because of noise and interfearence potential plus not sure how your'd going to do the "scratch start" operation as it requires your machine contacts with the plate then backs away for around 1mm (according to the ref'd manual), then begins cutting.
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my travel speed is slow circa 900mm per min at the moment possibly up to 1200 or 1500 if I get this to work, still very slow in comparison to commercial equipment.
Your feedrates are very (TOO) low.... plasma is all about acceleration too.... becuase the cutting current is constant and you need to change direction, you need to be able to have you machine accelerate and decelerate its axis as fast as possible. or you will end up with rounded corners and lots of dross.
How are you driving this plasma table?
What ampage stepper motors are you using?
What stepper drives are you using?
I started off with a load of ..... well not very good stuff and you end up buying twice to replace out the poor stuff to get the cut qulity where you want it.
Kind of like the old addage.... "measure twice, cut once"....... "design once, buy quality, never look back".
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with plasma, you will come across the name Jim Colt a lot across many forums, its worth reading his posts
http://www.cnczone.com/forums/archive/index.php/t-94386.html
here is some guidance on acceleration (although really it's a function of feedrate..... higher the feedrate, you'll need more than the 40miliG listed here in my opinion as 40miliG (0.04xG[9.81m/Sec/Sec *1000 = 393.2mm/sec/sec)
because if you were running a modest 100"/min (2,540mm/min) feedrate, the distance travelled is 2.3mm
but now at a 200"/min feedrate, the acceleration and deceleration distance is 4.6mm (which is probably the top end of your cut40 at a guess).
or at a top end (small scale) cutting feedrate of about 400"/min 10,160mm/min is 9.2mm.
you should get to know this formula well for your design:
Distance Travelled = Feedrate ^2 / (7200 x acceleration)
Distance travelled (in inches or mm)
Feedrate (cutting feedrate in inches /min or mm/min)
Acceleration (in in/s/s or mm/s/s)
http://www.engineeringtoolbox.com/acceleration-velocity-d_1769.html
note this is cutting feedrate (G1, G2 and G3 motion), but if you set the acceleration too high it will stall if you go for high rapid motion
There is a point when you wonder how fast do you really want your machine to go for rapid motion (g00).... depends on your pub... I'd go with knowing that you have good stable acceleration and your rapid feedrate is around your maximum cutting feedrate for a non-production enviroment (do you really need >600"/min??) as it won't save much time on a hobby if your maximum cutting feedrate is 400"/min.
a 4' traverse time will be less than 3 seconds saving ..... [4' (~1220mm), 600"/min (15240mm/min) = 4.8sec, excl accel + decel; 400"/min (10,160mm/min) = 7.2 sec; 200"/min (5,080mm/min) = 14.2 sec ...... bit slow for me though, but bread and butter for me is 2 to 6mm plate, occassional 1.5mm]
The generally accepeted rule is reduce feedrate to 60% for holes or radiused corners of less than 1" diameter (serves me well).
https://www.hypertherm.com/en-US/customer-support/faqs/how-can-i-cut-better-holes/
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Your feedrates are very (TOO) low.... plasma is all about acceleration too.... becuase the cutting current is constant and you need to change direction, you need to be able to have you machine accelerate and decelerate its axis as fast as possible. or you will end up with rounded corners and lots of dross.
How are you driving this plasma table?
What ampage stepper motors are you using?
What stepper drives are you using?
I started off with a load of ..... well not very good stuff and you end up buying twice to replace out the poor stuff to get the cut qulity where you want it.
Kind of like the old addage.... "measure twice, cut once"....... "design once, buy quality, never look back".
The 900mm per min is typically my G1 cut speed.
I just can not get a lot faster so it is not possible with my set-up size 23 steppers on X and y and type 17 on Z. Currents around 3 Amps X and Y and just under for Z, all from 24Volts supply and control max rating is 24Volts. Again Chinese set up cira £60 purchase.
I am aware it is cheap but it will have to do.
Table size is 760 by 460 ish mm. All home made and very, very budget.
I will have a read through the information you have provided, yes I have the manual for mine rated voltage is 100 Volts in the user guide.
The input is 4.7KVA at rated output of 40 Amps, so really wants a 22Amp supply but duty cycle is 60% at that those figures.
I need to run the machine under 25 Amps if I can reasoning is it is on a 13 amp socket.
220 Volts x 13Amps = 2860 KVA * 0.85% efficiency I have 2431 KVA available, 100 Volts rated so around 24 amps cutting current.
I can push a bit higher but the garage supply which is really only rated at 20 Amps has to power PC, lights and a compressor.
Thanks for the rest of the information I will read through the posts you have listed, thanks for that.
Adrian
p.s. even your modest feed rates are to fast for me, it is a case of do what I can for fun.
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the 24 volts power supply will be your problem to some degree....
What stepper drivers are you using (link, or picture?)
Be careful with TB6600's or their smaller brothers .... I killed a few of them at 42V (before moving onwards).... but they should be good for about 35/36V.... it can be the back EMF that can be the problem.
What / how are you driving your table? belts, rack & pinion...... not threaded rod please...
How are you driving your Z axis? with THC accelleration is disregarded hence the axis shoots up and down with technically near infinate acceleration, because the stepper motors do not ramp u to the feedrate set, hence you really want a very course threaded Z axis (2-3 turns per inch) .... yes you did read that right 9 to 12mm pitch ...
https://www.aliexpress.com/item/1pcs-T10-10mm-screw-length-400mm-picth-2mm-lead-10mm-trapezoidal-screw-with-1pcs-brass-copper/32659186417.html?spm=2114.30010308.3.140.s33IlW&ws_ab_test=searchweb0_0,searchweb201602_1_116_10065_117_10068_114_115_113_10000007_10084_10083_10080_10082_10081_10060_10061_10062_10056_10055_10054_10059_10099_10078_10079_10073_10097_10100_10096_10070_10052_10050_424_10051,searchweb201603_6&btsid=4169b973-4f52-4d3c-9886-bc20e58025db
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If you wish to see the project of building it then:
http://www.mig-welding.co.uk/forum/threads/cnc-plasma-cutter-start-of-bits-buying.52149/
The controllers are TB6560AHQ based the steppers on X and Y are 23HS9430B
X axis is 20 steps per mm, and Y, which is my problem is 100 steps per mm as I am driving a 4mm lead ball screw directly at 1/2 stepping, it was more reliable and faster than 50 steps per mm with full steps.
Yes my Z axis is threaded rod rather then try and get a ball screw which was 5 inch long.
Adrian
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Just found the information the Z stepper is NEMA 17 Stepper Motor JK42HS 1.8° 42x42mm [JK42HS40-1704]
Adrian
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Those drives don't have a good reputation at all on the mycncuk forum.
http://www.mycncuk.com/threads/1373-eBay-TB6560-Stepper-Motor-Driver-Boards
Ballscrews are unnecessary (and not good in my opinion) for plasma because of the amount of very hard abrasive swarf floating about even with good extraction over time).
Don't cut aluminium, stainless or galvanised (zinc) coated steel without extraction and good makeup ventilation as it is carcinogenic.
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I did have trouble with the controllers, I could blow then very easily, that was sorted by making my own filter network on the motor cables using back to back diodes, MOV's and caps. Also removing some earth loops I had placed on the system by trying to earth anything I could.
Not blown a chip since.
Not the same board as you link to there, but probably similar.
fuzzy picture here it sits in an extruded aluminium box.
Adrian
I have extraction, used for welding.
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I will have a read through the information you have provided, yes I have the manual for mine rated voltage is 100 Volts in the user guide.
The input is 4.7KVA at rated output of 40 Amps, so really wants a 22Amp supply but duty cycle is 60% at that those figures.
I need to run the machine under 25 Amps if I can reasoning is it is on a 13 amp socket.
220 Volts x 13Amps = 2860 KVA * 0.85% efficiency I have 2431 KVA available, 100 Volts rated so around 24 amps cutting current.
I can push a bit higher but the garage supply which is really only rated at 20 Amps has to power PC, lights and a compressor.
Thanks for the rest of the information I will read through the posts you have listed, thanks for that.
UK is 230v
100v(OP) x 40A(OP) = 4kW (OP)
4kW / 0.85 (%eff) = 4.7kW [so that checks out]
4.7kW / 230v = 20.4A
You can probably get away with a 16A BS60309 plug and socket [I do with my powermax 45 (45A @ 132V, 0.99 power factor = 5,940kW), 6kVA at 25A generator recommended]
http://www.toolstation.com/shop/Electrical/d190/Industrial+Connectors/sd2430/Industrial+Plug+IP44/p36175
http://www.toolstation.com/shop/Electrical/d190/Industrial+Connectors/sd2430/Industrial+Socket+IP44/p20698
advantage is that they aren't fused .... so have a bit more give than a 13A plugtop.
looking at another 3A per 1hp for the compressor (approx),
duty cycle is the operating time per 10 min duty cycle (hence 60% duty cycle means 6 mins run time, 4 mins cooloff).
on a 20A mcb, you can probably get away with around 30A maybe a little more at that duty cycle depending upon breaker or fuse type..... also you'll find that your actual cut time probably won't be 6 mins anyway (as that would be ~ 5m of cutting at your feedrate.... continious on a small table..... not really possible in my opinion
http://wiki.diyfaq.org.uk/images/d/d4/Curve-MCBTypeB.png
http://wiki.diyfaq.org.uk/images/thumb/d/d6/Curve-MCBTypeC.png/640px-Curve-MCBTypeC.png
I was told by a hypertherm technical person that as a guide (starting point) if you've got the feedrates for 40A, and reduce the ampage to say 32A (20% reduction), then your feedrate should drop by a corresponding percentage (roughly).
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Uk is in theory 240 Volts + 6% and - 10%, http://www.schneider-electric.co.uk/en/faqs/FA144717/ (http://www.schneider-electric.co.uk/en/faqs/FA144717/)
but the voltage drop along my garage supply run gives me around 220 to 225 Volts when I have the plasma going and compressor running as well, it is not attached to the house. The supply has two 20 Amp breakers in line, one in the house and another in the garage and yes I can trip it out. especially when I have the plasma up at around 40 amps cutting, lights on in the garage and the compressor kicks in (2HP)
Max time running was when I was cutting a butterfly out and that was 13mins run time in 2mm steel, granted not all cutting I know.
(http://www.mig-welding.co.uk/forum/attachments/dscf0942-jpg.67788/)
So I try to keep the cutting amps down, no matter what calcs you wish to run. ;)
I need to visit the local electronics shop in the morning and pick up some multi-pin sockets and 1mH inductors and drill/fit to the plasma, then I can box that back up and get it back in the garage.
I will run a modified G-code file and have a play with the home made THC driven from a PSU just to simulate things before I get too adventurous.
Adrian
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Nice butterfly, you did that with a cut40?
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Yes that is with my cut40 and cnc.
Approx 270mm wide 220mm tall.
Adrian
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Just had a quick scan through the thread on mig-welding. Are you the Adrian H who happened to sell a rapid cycle Harrison mill a number of years ago?
The basic older TB drivers are not great. They're ok if you don't push them near their limits, but lots of implementations have woeful heatsinking, which compound their limitations. For not much more money, I'd buy some newer individual TB6600 drives (search ebay for TB6600 - there are plenty options), which use far better chips, and would allow you to run a higher voltage power supply. You also get the benefit that if you do blow one up, you only need to replace that one.
For plasma, you need speed, and the main way to get speed from steppers is by increasing the power supply voltage.
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Yes to the first question, a Mill I bought not really knowing what it was, Had the switches but no feed motor if my memory is correct. I had, and still have a Harrison manual mill. So went back to the manual mill. far less of an issue, only just getting it power driven now!
Why did you buy it from me?
I will have to stick to the controller for the time being it is all built in a box an all with a dedicated 24Volt PSU.
Adrian
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I was going to convert it to CNC, but after much deliberation, I got the chance of a CNC lathe, then an even bigger mill, which led to another CNC lathe, which led to a ready to run CNC mill, and am currently retrofitting yet another mill.
In amongst that, the mill I bought from you got sold (I think I still have the wiring diagram from when I worked out exactly how the rapid cycle worked). I still have my original Harrison mill, which is currently setup to do second ops.
You could increase the supply voltage to your existing driver, however you really want to be using a linear supply.
I suspect the real reason you kept blowing controllers, was under deceleration, the drive dumps energy back into the power supply. Switch mode power supplies generally don't like that and have little capacity to absorb it, with the result you see a voltage surge, which and the TB chips just don't handle going over their rated voltage. Linear supplies on the other hand, with a reasonable sized capacitor will quite happily absorb the surge.
The other option is to add in a reverse energy dump, which will dump any energy from the drive into an external resistor (check the stepper motor basics guide over on gecko drive for examples)
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Highly recommend adam at http://www.vigortronix.com/
http://www.vigortronix.com/Toroidal.aspx
Buy direct from a manufacturer... you'll see their products resold via a numner of outlets (farnell, maplin, etc etc).
Adam is very helpful (and works odd hours.... I asked him a question on night at about 11, and after 4 emails till about 1am, transformer was bought and arrived next day....)
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Adrian, how are you doing the THC (long term interest of mine.... better thc.... some people chase divots... I seem to chase THCs....)
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Couple of things
Moray? is that correct. 2003'ish is that correct?
It is a transformer based psu rather than switched it is a 24 Volt 12 amp Lamda PSU I had spare. The blowing of the chips was when I was arcing up or, more when I can to the end of the cut I had an arc away from the cut edge and a dwell time to the plasma cutter was trying to arc into thin air and the HF would blow an axis. Put it this way I have spare units and chips now sat on my shelves just in case.
Robert, noted on the transformers if ever needed.
Not quite sure what you mean by how am I doing the THC, or perhaps I do I have not mentioned what I am using have I ???
I will copy what I have on another thread again in Mig welding
And as there some other like minded souls on here I thought I would share my thoughts so they can be picked over and comments raised.
When playing with my cut40, so I will assume very similar to cut50 etc. I found then when not cutting, i.e. the torch switch is off, the voltage at the terminals sits around -24 Volts ground to torch.
When cutting, the voltage can vary depending I guess on height, nozzle, speed etc on mine from around -85 Volts to -110 volts. The manual says it can go to 250 volts and I assume that is when it is trying to cut but the arc is broken and lastly on mine the manual says the rated voltage is 100 Volts.
So I read from that that I really want to keep the cutting voltage at 100 Volts, and that from what I have measured and assume, if I get less then 75 Volts I am probably driving the nozzle into the work piece and if the voltage was to go higher then say 125 volts I run the risk of breaking the arc.
I hope in my assumptions are OK so far ?
If I have read it correctly, THC controllers seem to provide 3 outputs: THC ON or ARC OK, move up, move down.
From my readings and figures above, I would say that if I can measure a voltage across the terminals of between 75 to 130 Volts, it must mean that the ARC is OK, in that it has an arc between torch and metal.
Then further to THC on, if the voltage goes above 101 Volts move the torch down and if the voltage goes above 99 Volts move the torch up. Guessing at a level of hysteresis here.
I would not like to be messing with anything that can reach over 100 Volts DC let alone the no load level of 250 Volts DC. So the output will get tapped with a resistive divider. To get me down to a respectable level I will probably consider a 10 to 1 divider, so 250 volts becomes 25 volts 110 to 10 etc.
Bring the voltage out of the plasma unit to a 4 way voltage comparator with relay outputs and set it up to provide THC on at a range of voltages between 7.5 Volts and 12.5 Volts.
Down at 10.1 Volts and up at 9.9 Volts.
I have a board from Ebay that looks like it may do the task
This is from the Ebay add.
(http://www.mig-welding.co.uk/forum/attachments/s-l1600-jpg.95797/)
and cost less tan £10 delivered, has 4 inputs and drives relay outputs which means I should be able to keep things isolated.
It has a common ground between all inputs, has a 12 Volt input which provides an internal voltage of 31 Volts for the devices so can measure up to 30 volts.
Initial tests suggest it could work, but the idea is open to your thoughts.
So that above is what I looked at doing and I am part way through. The psu for the comparator is a plugtop 12 volt unit that is fully isolated, from my junk box, the board was less than £10 and I have just bought a plastic box to fit it in so I do not short out on my welding bench, wires and most of the other parts I have.
If it does not work then less than £20 wasted, just time.
If it helps make the cut40 and CNC that little bit better because I have a bit more control and I am not dragging the tip all the time then that will be a reward.
Adrian
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Around 2003 would probably be about right.
Your plan sounds reasonable.
I suspect you'll need to add a bit filtering/smoothing to the input, otherwise your up/down relays will likely do nothing but chatter.
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Hi;
I have some very simple filtering in there at the moment just to really stop HF, but yes I think you are correct in that I need to slow the readings from the arc voltage.
I am considering just a simple Resister/Capacitor time delay/filter 5K Ohm and 20uF just to give around 100ms.
I am also wondering about pierce delay as I believe from reading posts that I will loose the pierce delay in Sheetcam as soon as the THCON signal is present.
I think I need to change config/ports and pins/spindle set up/CW Delay spin Up to be my pierce delay, but time will tell I guess.
I have posted a bit more on the Mig welding forum as I have modified a few tips and test run the THC and Mach3, just doing another post processor now and a cad file to cut out three 15mm by 300mm slots in sheet for tomorrow.
I will either have some success or smash things up with a hammer!
Adrian
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Adrian,
Make sure you use the proper hammer!
As far as you have gotten you wouldn't want to make a mistake now ;D
Mike
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Sounds like your'e having fun, thats what matters :)
I guess you will have to start the cut as a drag then lift to move?
Well you were correct on this I was definitely wrong, I could only start the arc when tip grounded with a drag tip and then move up, The tips I modified to remove the castelations would not work, not sure if I restricted the hole a bit with the lathe work, so until I get a Plasma with pilot arc, that is the way it will have to be.
There was a method I tried once that grounded the tip through high wattage resisters, may need to try that again to see if it makes a sort off pilot arc.
What it would do to the arc volts is anyone guess.
Adrian
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Some success
https://www.youtube.com/watch?v=uongcUZbv6Y (https://www.youtube.com/watch?v=uongcUZbv6Y)
Adrian
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Looking good :)
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I thought I would add a quick update.
I have got Probing to work on my home made rig, using the torch position so I have no X and Y offsets to deal with only Z height offset.
I am very new to this so I have questions on my Macro as follows
' Find Zero
' Initial try
' APH
Code ("G31 Z-30 F200")
' Wait for movement to complete
While (IsMoving())
' Sleep, so other threads can run while we wait
Sleep(80)
Wend
Code ("G92 Z-1.4")
Sleep(80)
GotoSafeZ
' Wait for movement to complete
While (IsMoving())
' Sleep, so other threads can run while we wait
Sleep(80)
Wend
' End
So mainly using what I see in the Macro guide and I can understand, one question is do I need to have the following after the GottSafeZ
' Wait for movement to complete
While (IsMoving())
' Sleep, so other threads can run while we wait
Sleep(80)
Wend
Should I use SetOemDRO(802,-1.4) rather than
Code ("G92 Z-1.4")
Sleep(80)
Do I need that last Sleep there.
It all works and in my post processor to generate G-Code I have an opening option set of G21 and G90 which sets milli-meters and machine co-ordinates if that makes a difference to this.
Tomorrow is trying to get it all working together.
Adrian
Perhaps I should say using a micro-switch on a parallel port pin pulled up with a low'ish value 2K2 Ohm resistor, when the probe is active it opens the switch and allows the pin to get pulled to 5 Volts, seems safer then relying on a closing contact to always work.
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I'd suggest using sleep 100, as macros run at 10hz, 100msec.
G92 z-*********x is correct.
If you have a motion command, yes you need to use while is moving to let the motion complete before the next item.
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Hi Robert thanks for the information I assumed the 100 was just arbitrary I will put it back to 100 from 80.
I was not sure about sleep after the Code ("G92 Z-1.4") as it is not a motion command just a change to the DRO as such?
Adrian
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100th of a second wait after g92 is not a lot of time to wait.
It is 1 macro loop cycle at 10 hz, you can take it out, but now you run the risk of the machine setting g92 as fast as its running for z safe.....
I'd leave it in....
If you upgrade to an ohmic probe, I use one input and a relay to test which triggered, and set the appropriate offset.
I find my offset with a piece of paper.....
Probe the z, and then back off one step at a time until the paper slides out, redo it and test again a few times if it's borderline, if you miss the point, don't jog the other way, back off say 10mm and re run, so that the pressure applied be the floating head is correct (reflective of normal operation).....
If that important... Subtract paper thickness..... But really.... Once the torch fires, and starts moving, it's just a starting point for the thc....
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Again thanks for the information Robert.
I have been very surprised with something in Mach3, In the Macro I had the Feed rate on Z slowed down so as to have minimal travel when the micro-switch opened, I had a sudden thought that I had to discover what the feed rate was before going into the Macro and set it again when I left, but no it all just seemed to work, someone must have put a lot of thought into it.
Adrian