[steve_p]

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

[gridley51]

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

[steve_p]

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.

[justinhosley]

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?

[steve_p]

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.

[gridley51]

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.

[steve_p]

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

[gridley51]

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.

[jimcolt]

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/Product...sensor_phc.jsp


Jim Colt Hypertherm

[steve_p]

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/Product...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.

[jimcolt]

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

[Alan Bradford]

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

[steve_p]

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:

[cowleym]

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

[steve_p]

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

[cowleym]

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

[jimcolt]

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

[steve_p]

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.....

[steve_p]

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!

[jimcolt]

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