hi there, i'm taking delivery next week of a used 3m x 1.5m plasma machine (servo driven) running off a burny 2.8 controller (apparently a 2.8 is just a 2.5 mounted in the same console as the servo drives and psu etc.)

It has a plate rider, ie no thc, and i'm wondering whether it's possible to retro-fit a thc to run off the burny. I don't have schematics for the burny (if anyone has, I'd be grateful for a scan!)

if the burny dies in the future i'd probably go the mach route rather than shell out big money on a repair, which would enable me to add the thc quite easily, but i'd rather just slot one in to the working system for now.

The plasma source is a hypertherm max 100 (100A o/p) with a machine torch. I heard that hypertherm do a thc, but i don't know whether it needs interfacing to the control.

Is anyone here a burny/hypertherm expert?

thanks for any advice

What machine is it?You should be able to download the manual from the Burny site.

gridley51 , thanks for the reply, I looked at the burny site, but you have to download a form, manually fill it in and then fax it back to them before they will let you download anything. I'll probably do it, but I gave up on fax years ago, so it's a bit of a pain.

The machine is an Esprit Lightning, I called Esprit and they said it wasn't worth adding a thc, presumably because they'd recommend a control replacement. I was hoping to find a reasonably-priced option.

Hypertherm has a couple THCs. Their Sensor THC is great. Simple. What type of Burny controller do you have? I can get a hold of all of the schematics. Also, what type of drive/motor combo are you using for the Torch(Z) axis?

Hypertherm has a couple THCs. Their Sensor THC is great. Simple. What type of Burny controller do you have? I can get a hold of all of the schematics. Also, what type of drive/motor combo are you using for the Torch(Z) axis?

hi justin, it's a burny 2.8 (see pic below, if I've done it right), which is just a 2.5 built into a case with all the drives.

as for motor/drive for the z axis, I was going to wait until I sourced the thc control and buy something that would be compatible. It would probably just be a gecko-stepper combo if i can get away with it.

85496

I have the maintenance/operator manual for the Burny DNC 2.8 plus and the maintenance manual for the Burny 2.5 as fitted to a Messer m/c.Messer told me it`s really a 2.8.They are on pdf`s if you want them.
BTW I was thinking about thc but from what I read on the forum here decided I`d wait and see how it went once the m/c was installed.

I have the maintenance/operator manual for the Burny DNC 2.8 plus and the maintenance manual for the Burny 2.5 as fitted to a Messer m/c.Messer told me it`s really a 2.8.They are on pdf`s if you want them.
BTW I was thinking about thc but from what I read on the forum here decided I`d wait and see how it went once the m/c was installed.

yeah, I asked the previous owner whether he'd had any problems with the plate rider, and he said it had been pretty good really- you just have to watch when leaving narrow strips between parts, or when doing small parts. If it does catch, you can lose a whole sheet if it gets dragged along.

I will be using it in its current state at first anyway, so I'll get a feel for it, but it does sound like the cut quality can be improved with the thc, as well as eliminating crashes. I've been reading about how the better ones work with the controller to compensate for the speed changes at corners etc, so the thc doesn't panic and dive the torch. That's why I was interested in the schematics to see whether there were pins on the controller for this purpose.

I'd be grateful for the schematic- I'm not too knowledgeable about forums- what's the best way of getting a copy from you?

thanks for taking time to respond http://www.cnczone.com/forums/images/icons/icon14.gif

Steve,if you click on my name above,you will be given the option of sending me a private message.Use that to send me your email address.That`s if you`re not a mile down the road from Broxburn.

The Hypertherm Sensor PHC height control is a great standalone THC system...it features ohmic and stall sense for finding the plate surface (necessary for good pierc height) as well as a very accurate arc voltage feedbeack process for real time height control. here is a link for more info:
http://www.hypertherm.com/en/Products_and_Services/Automation/Torch_Height_Controls/sensor_phc.jsp


Jim Colt Hypertherm

The Hypertherm Sensor PHC height control is a great standalone THC system...it features ohmic and stall sense for finding the plate surface (necessary for good pierc height) as well as a very accurate arc voltage feedbeack process for real time height control. here is a link for more info:
http://www.hypertherm.com/en/Products_and_Services/Automation/Torch_Height_Controls/sensor_phc.jsp


Jim Colt Hypertherm

thanks jim, that does look good, although it does require several connections to the cnc control to tell it when the arc is good etc- I'll have to check whether my burny has these i/o pins, and whether it needs any reprogramming or setting up to look for these inputs and send the outputs. Do you have any idea how much roughly they sell for? Or who the hypertherm agent is for london, i cant seem to find one with google. thanks.

The THC requires a plasma start output....and needs a avc disable..or corner output function that freezes the THC during cornering. Your Burny has these signals.

If you go to the Hypertherm website www.hypertherm.com you will find contact info for our European offices...they can direct you to dealers...our tech service department can assist you with proper connections to a Burny as well.

Jim Colt

It is easy to connect a THC to A Burny 2.8

The 3TB treminal strip (in the rear of the cabinet) is where you connect the THC (any type)

The Plasma Start Contacts are 15 & 16
The Height Freeze Contacts are 19 & 20 N.O. and 19 &18 N.C.

Cut Sense Input is 1 and for a 24 Volt Signal 2
120 Volt Signal 3
220 Volt Signal 4

You remove your plasma interface, connect the THC to the 3TB termionals and connect your plasma to the HTC per the mfg instructions.
Be careful with the Hypertherm THC's.
Their Cut Sense outputs are only rated for 24 Volts DC at 15 ma. You can destroy them easily. Most other brands use a relay contact output.
The Burny 2.8 input requires you supply 24VDC if using a Hypertherm THC for cut sense.
Most others with a relay output you can use any voltage (AC or DC) available.

I have attached a few pages I scanned from a Burny 2.8 Plus manual. That is the newer version, but the interface is the same.
You can request the manual from www.burny.com, or call Tech Support in Cleveland and they may have a copy of the 2.8 manual available as a .pdf.

Burny Division
7550 Hub Parkway
Cleveland, Ohio 44125-5794
Telephone: 216 / 524-8800
Fax: 216 / 642-2199
Be patient as it sometimes takes a while to get through to them.

Good Luck

wow, thanks alan and jim, that's exactly what i was after. It seems like it should be relatively straightforward to add a thc... in theory at least.

I did read in the manual (that gridley51 sent me earlier today) about using a relay for the cut sense with my max100, it draws quite a lot of current so will pop the thc logic if connected directly.

this forum is great! i'll let you know how i get on, thanks to everyone who has taken the time to reply :cheers:

Hi Steve

All the advice given so far sounds good, Alan and Jim know their stuff. I can't add much other than to say we are based up in the Leeds area and have a pile of bits for the Burny, diagrams etc and are happy to help over the phone. We have fitted a few different height sensors in the past and know most of the pitfalls.

Cheers

Mike

www.techserv.co.uk
www.techservcnc.com
www.bluemarlin.biz

Hi Steve

All the advice given so far sounds good, Alan and Jim know their stuff. I can't add much other than to say we are based up in the Leeds area and have a pile of bits for the Burny, diagrams etc and are happy to help over the phone. We have fitted a few different height sensors in the past and know most of the pitfalls.

Cheers

Mike

www.techserv.co.uk
www.techservcnc.com
www.bluemarlin.biz

Hi Mike, thanks very much for making contact, I'm sure you'll be getting a call as soon as I've got the machine up and running next week.. Do you supply thc units, or fit them for clients?

best wishes

steve

Hi Steve

We supply our own systems on new machines and for buy them in for retrofits.
A fairly simple thc can be built using a siemens logo mini plc and a voltage divider.

Cheers

Mike

Mike,

There is more than just a "plc and a voltage divider" to a properly functioning THC.

The THC is one of the more important components of a cnc plasma cutting operation....it can make the plasma produce better quality holes and fine features, as well as maintain proper edge angularity and minimal dross formation. Perhaps even more important....a good THC can extend the life of the plasma torch consumables dramatically...through accurate control of pierce height/timing. One pierce too close to the plate ruins the performance of a plasma torch nozzle.

THC functions:

-Find the top surface of the plate, retract to manufacturers suggested pierce height (different for each material type and thickness). On thin materials....expect the material to deflect somewhat...so the plate sensing function must be quite accurate....often ohmic sensing between the torch shield and the plate is used for this. For situations where the surface of the plate is not conductive....or where the torch s cutting underwater...a backup method of surface sensing is used....often current sensing of the z axis drive is used for this.

- After succesfully reaching pierce height....the height control sends a start signal (either back to the cnc or directly to the plasma) firing the torch....motion is delayed for a period specified by the torch manufacturer (different for each type and thickness of material).

-Once this pierce delay time is complete....the thc indexes the torch rapidly to the manufacturers suggested cut height....this movement needs to be completed while the torch is on the lead-in of the cut...not after it is on the programmed cut path.

- THC interfaces to the cnc....whenever slowdown ocurrs as in corners or intricate detail...the z axis is frozen....so it does not react to changes in arc voltage that will ocurr when cut speed changes.

- THC should reconize kerf crossings and ignore them.....otherwise the torch will dive towards the plate.

- Many thc systems use ohmic contact to sense torch contact with the plate during steady state cutting.....this will cause the torch rise to 1/2 the programmed cut height rapidly to avoid colisions that could cause interruption of the cut.

- Better THC systems use proportial speed control...or have the ability for asychronous up/down speed adjustments.....often the down speed should be set slower than the up speed to help avoid plate collisions.

Along with a control system that can handle the above issues....a voltage divider (usually in the 50:1 range) is used to divide raw DC arc voltage and filter it....bringing it to a usable level for the feedback circuitry. A z axis motor and slide assemble is needed that is accurate, and will survive under plasma cutting dust and/or water splash from a water table situation. A torch breakaway that saves the torch in the event of a collision with a tipped up part...and stops machine motion is also a good feature on a torch height control system.

All of these things can certainly be done on a well designed system....but when you start adding up all of the costs and time involved with making all of the above work....it often makes the cost of the commercially available systems that were built with many years of field experience worth the price!

Best regards, Jim colt

Hi Steve

We supply our own systems on new machines and for buy them in for retrofits.
A fairly simple thc can be built using a siemens logo mini plc and a voltage divider.

Cheers

Mike

hi mike, what would be a ball-park kind of price for a commercial unit that could interface quite easily to my burny? I understand that you probably buy them wholesale, but if I were to buy just one unit through my (vat registered) company, what would I expect to pay roughly for a half-decent unit? I'm only asking because I've not got any idea what they cost whatsoever.

I was looking online at the bob campbell unit from america at $400 or so, they sell it as a mach-controlled unit, I might ask them whether the control signals could be utilised by other controllers, or if it really is mach-specific at a deeper level. If anyone here knows.....

Jim,

thanks for the description of the THC operation, but I kind of get mike's point- I'm not familiar with PLCs, or (obviously! THCs), but I do program PICS and build little interface circuits, and the processes you describe (lowering torch until a low-resistance path is detected, freezing z-axis (the cnc controller has output pins for that, it seems), pierce height and cut height setting etc are all pretty straightforward things to achieve in a few lines of code and a motor drive. Whether it's as straightforward to get it all working together is perhaps another matter (probably involving much hair-pulling), but in principle is do-able, which I think is Mike's point. You're absolutely right though, to actually make the thing, and make it work well, could easily outstrip the cost of just buying a well-honed system, particularly if the machine is meant to be making money and not a hobby project.

By the way, do you know how much Hypertherm charge for their system, roughly?

steve

ps the kerf-crossing detection is the one element that seems more of a challenge, I presume it could be detected as a rate-of-change in the arc voltage (sudden rather than gradual), but I think there could be a lot of tuning to get it to work reliably. Please enlighten me if there is a more obvious way to detect kerfs, I'm finding myself thinking about it instead of other stuff I'm meant to be thinking about!

I think the Hypertherm Sensor PHC is in the $5000 (US) range.....remember it is complete.....including an industrial quality z axis lifter and a magnetic torch breakaway device.....we also have more expensive THC systems that are designed for high definition class plasmas....these are more accurate, and have the ability to improve cycle to cycle times for better production rates. I realize that $5k is out of the price range for most hobby class user/builders......but I cannot stress enough the importance of a good working, full featured THC system.

Best regards, Jim

"Commercial" THC's are typically stand alone systems (not integrated with the toolpath/control software, so need lots of extra "smarts" to do the listed functions. The CampbellDesigns THC has no preset capability (a knob is used while cutting to set arc gap) and it needs a 2nd parallel port in MACH for operation. Since it's MACH only it is not an option. Beginning pricing on stand-alone THC's is around $2400.00 and goes up from there.

The problem is with the Burndy controller; you won't be able to use MACH, so any of the lower cost solutions (non-standalone) are out.

If you were in the US you could replace the whole controller (including the motors) for less than a commercial THC is going to cost.

Our MP3000-DTHC when combined with SheetCAM and MACH has all of the features Jim listed plus some he didn't (Cut Profile operator assist listed by material, total analog isolation of arc volts, settable response and fault trigger points, etc) It's more of a control interface unit than JUST a THC, and supports all if the I/O from MACH to the downstream motor drivers, table switches, Arc OK feedback and more. Once again if you stick with the Burny controller the THC and Z operation has to be done as a separate control.

I did not post earlier because we don't sell our controls into the UK because of the numerous certifications and rules applied to imports.

I know designing a THC looks trivial but you need to have a very good grasp of hardware design (dealing with lots of noise and lots of power/voltage) and detailed understanding of how plasma cutting works. One assumption often made (by mistake) is that the plasma workclamp is ground and you can just throw a resistor divider across the Arc Gap voltage and interface that to a circuit that has a normal AC side ground reference. You have to pick a change of less than 1 volt out of a signal that is over a hundred volts and can have noise from the arc greater than the voltage you are trying to recover. Simple filtering can help but it throws delays in the feedback loop that alters the response time of the circuit and makes THC response fall to that of Jello.

You may want to go back and do some reading on the list about (first) the 10 dollar THC then the 100 dollar THC projects. The devil is always in the details.

TOM Caudle
www.CandCNC.com

Tom is pretty much right on with his comments.....an exception is that Hypertherm does have a couple of integrated THC's that work with our brand (Hypertherm Automation) PC based industrial cnc controller these integrated controls have all the funtionallity of the best THC's....but are driven as an additional axis output from the controller. Hypertherm has been manufacturing torch height control systems since 1976....so we are very aware of the needs of today's plasma process in terms of torch to plate distance! Hypertherm Automation CNC's are competitors to Burny's latest PC based controls.....and are often used as replacements for older style Burny's such as the 2.5, the 2.8, the 3 and the Burny5. These Burny controls are good quality microprocessor based controls...but do not have any where near the processing power of the newer PC based controls.

Don't take me wrong....you have a great machine there...and the Burny control is perfectly usable.....just be sure you don't sell yourself short on the THC end of it!

Best regards, Jim

Thanks for the comments, Jim and Tom.

I checked out your website Tom, your DTHC looks very good, at a good price. I did mention earlier that if/when the Burny dies, I would most likely move over to a mach setup. I have been retrofitting a small lathe and mill with mach, although I've not made much progress recently due to lack of time, so I should be pretty familiar with it in the not-too-distant-future.

Having said that, I guess a stand-alone system would work with any controller, so would be future-proof in that sense.

Hi Chaps,

My throw away comment about the PLC seems to have sparked a bit of interest!

Yes Jim you are right, we have integrated all the functions you describe into our own cnc controller, it works very well and gives us an accurate pierce height using ohmic sensing and following error sensing. We can hold the arc voltage to about +/-0.1volts. However this system uses a ballscrew actuator and fancy brushless drive, which costs us about £1500.
On our lower cost machines this degree of sophistication, and cost, is not nessesary so we select the simple height sense option in the software. The height sense now detects the plate using a torch mounted linear slide and switch, the pierce and initial cutting height are set by time delay ( this gives about .5mm ) arc voltage is by a very simple error loop ( actual arc voltage - set arc voltage x gain (with a bit of damping)= analog drive signal. Simple drive motor and amplifier with a rack and pinion drive. Good for the powermax systems.

In the past we have supplied retrofit plasma and height sense kits for Burny systems, for these we have used a Siemens logo plc, this can handle the plate detection, pierce height, cutting height, arc voltage control, corner slow down etc with ease. Ok its not as accurate or complex as the precision control we and others sell but its fine for a small air plasma and certainly better than plate riding roller (which we can also supply).

It all really depends on what you want to achieve from your plasma machine, how much budget you have and how much time you are prepared to put in. All of our machines go to industrial users who want maximum productivity and accurancy for a moderate cost and we tailor the machine to suit their end product, bit silly for a ducting company to use a hi def.

To Steve, yes we could supply you with a system, I think that the cost (labour, travel etc) would start to build up to the point where a Hypertherm system would be cheaper. From your comments I suspect that you could sort most of it out yourself, we are happy to talk you through it and can supply a copy of the plc programme we wrote & a circuit if you have the time to play..

Kerf detection = rate of change.

Give us a call if you want any info or prices

Cheers

Mike

Sounds like you can supply the necessary THC components! I see many claims for THC systems on this and other sites.....any electronics guy can design a circuit that will sample DC voltage, compare it to a known voltage and then issue a drive command to move the torch away...or closer to the plate. There are , however a lot of other important functions involved with Plasma torch height control.....handled correctly...the plasma cutting process will be more accurate and will provide a low cost of operation. I have seen many cnc plasma machines with no THC.....or one that does not work well!

Best regards, Jim

That's right Jim
we sold several machines and fitted the kaliburn innova height sense unit, they worked very well. We then used the innova as a benchmark for our own system.
It is interesting to see how much the thc has improved since the early days when we used to fit the hypertherm thc2 systems. Pierce and cut height the same with relay raise/lower control, the advent of hi def plasma has introduced higher standards of performance and control.

Mike

Before HyDefinition Plasma Systems, the good old THC-2(Hypertherm) was all that was needed for conventional Plasma (20,000 V/SqIn)
Innerligic(Kaliburn) introduced the RSVP 100 series. It did nit sense the pate any better but it did reduce the cycle time for a fully automatic system.
The 300 Series along with the Hypertherm Command THC was the first big leap in THC sensitivity to make the precision plasmas (60,0000 V/SqIn) look even better. Thye had a more precise motion control lifter and could adjust to 1/2 to 1 volt.
If you dont have HyDef (or any other precision plasma) you dont need that kind of accuracy.
Each usesr will have to determine how much control is needed for their needs, plasma system and required cut quality.

As far as using a PLC or Microcontroller I have built them with both.
The hardware is cheap, just get a PLC, A/D conveerter module, and a properly filtered Voltage Divider. Fine tuning, and polishing up the code is whats time consuming. Labor does cost money, the same as components.
Replacing burned up parts is also expensive. There still isnt any free lunches.

As far as crossing the kerf, it is a simple calculation.
Monitor the arc voltage, and if it rapidly raises above a predetermined limit, freeze the motion. When the voltage recovers to the previous value continue torch height adjusting.
If you are spending the money on a precision plasma, buy the matching precision THC. In the long run it will save money.
If you have a conventional plasma, and you have lots of time, can afford to cut up lots of metal developing cut height specs, and dont need to pay any bills, then have a ball designing a THC
For a 1 of a kind system it is expensive.
If you are going to make lots of them then it is worthwhile.

Thanks for that balanced comment alan, it helped me make a decision- I got
quotes for the modern self-contained units mentioned above, and they were both more than I paid for the entire machine with plasma source, computer and software. So, based on your info about the non-hydef applications not requiring such fine control, I found a thc2 for sale, to which I'll add my own initial height sense unit. This way, I get the cutting height control out of the box, and the easy bit to self-build I can add and fiddle about with as time allows.

Thanks for all your input, this forum is really good.

Thanks for that balanced comment alan, it helped me make a decision- I got
quotes for the modern self-contained units mentioned above, and they were both more than I paid for the entire machine with plasma source, computer and software. So, based on your info about the non-hydef applications not requiring such fine control, I found a thc2 for sale, to which I'll add my own initial height sense unit. This way, I get the cutting height control out of the box, and the easy bit to self-build I can add and fiddle about with as time allows.

Thanks for all your input, this forum is really good.