Hi all,
This might sound stupid, but what about a gas torch. If you have the right speed it should cut right without stopping.
Thanks. :)

There exists alot of CNC gas cutting tables, I just retrofitted one that uses 6 torches.
Al

Gas torches,I will assume you are refering to oxy/acetylene torches. they do a great job, especially on heavy plate. I change my plasma torch and oxy/acetylene back and forth on my table a lot depending on material thickness. One of the drawbacks to oxygen/acetylene cutting is that you are limited to mild steel. No stainless, aluminum, copper ect. It does a great job within it's limits.
Traveler

What about the preheating? And also, how do you guys start the cut? I know it's a little more difficult to start in the center than finding an edge and starting to cut.

Oh, yeah, is the cut nice and straight and smooth? I'm getting a little excited.
Thanks. :)

On a CNC machine, the gas is controlled by solenoid valves so after ignition, the preheat fuel solenoid is on for a the duration of the pre-heat timer,(this can also be manually overridden), then there is a creep time and creep speed after pierce option, before the torch goes into cut speed. It does a pretty decent job, it comes into its own on large material thickness.
Al

Is torch height control needed with an oxy. can i cut 1/4 steel an not use THC. also how intricate can you get with the work?

Good Question.
And also, what kind of software do you guys use for your solenoid valves, would the Xylotex board work for this? What kind of software for the toolpaths and what not?
Thanks. :)

I do not think automatic torch height control is as important on gas as with plasma, many of the machines I have converted have been older trace cutting machines where a trace head followed a full size drawing to control the machine, the conversion to CNC still allows for sharp corners and small curves. The system I have used so far is Acroloop's Acrocut (dos) software & motion card designed for plasma & gas cutting machines. programmed by G & M codes and will import DXF files and also has a library of size-definable shapes. Also has on screen graphic toolpath.
Al

Sounds perfect. :) Does any board work with this? Also, where did you get this software, and how much? Does it controll the solenoids?
Thanks. :)

Another question: How does plasma & oxy/acetylene compare price wise?

Klox

Originally posted by Sanghera
Sounds perfect. :) Does any board work with this? Also, where did you get this software, and how much? Does it controll the solenoids?
Thanks. :)
I purchased the s/w before Acroloop was taken over by Parker, It is a one time buy for the s/w, you have to use the Acroloop motion control card, I do not know if Parker are going to continue with the Acrocut for dos as they are bringing out a Win based s/w.
The thing I like about the Acroloop cards is they have all the I/O 24vdc isolated on board the card. i.e. all the control logic for the machine is done on board.
The Acrocut (DOS) mill package is not bad either, it has a couple of glitches, but does the job.
Al

So, the board is something like a parallel port that you plug your Xylotex in? Hmm... is it still even possible to get this software? How much (if you don't mind) did you pay?
Thanks. :)

No,it is a dedicated motion control card (like a Galil) , it is aimed at the comercial retrofit market, I purchased the software about 10 years ago for US$1,000.00. But you only purchase once. here is the present link. http://www.compumotor.com/products/Controllers__5380__30_80.html
Al

Oh, I was just looking at it as sort of a toy kind of thing. I wonder if you can just use turbocnc or Mach2, set the solenoids and striker as pumps or whatever, and run two paths, one for preheating and one for cutting. How does you software work when it makes a cut? How does the preheat work, and what if the torch stops cutting, does it have some sort of compensation?
Thanks. :)

The pre-heat works just like you would do it with a manual cutting torch, after you ignite the torch, the pre-heat fuel gas is held on together with the oxygen the torch is held in one place until the plate is heated through, the pre-heat fuel gas is then switched off and the torch remains on with almost a pure oxygen flame, this causes cut penetration and after a short delay the torch goes in to feed motion, on this software if the torch goes out, it has a reverse retrace feature, where the operator can back it up to the point of where it extinguished and relight and start at what point he choses.
Al

Is there a way to get around this without paying the $1000? I can sort of see a way of starting over. It would take a long time the way I would do it. I would either rewrite the G-Code or if my software allows it, to start from a specific G-Code near the stop point. Does TurboCNC Support this?
Thanks. :)

What software are all of you CNC Plasma and Gas Torch Guys using??
Thank you all very much for your help.
I really appreciate it. :)

What are you guys doing for preheat and what not other than paying the Big Bucks for the High End or even Medium End stuff.
Thanks. :)

Hello?
Thanks. :)

Remeber that oxy acetylene brings about some very serious fire risks.

A lot of commercial tables now feature flame management systems that actively watch the flame leaving the torch. Home users would probably not want to get involved with the added complexity and cost this would add to their table.

If you're not standing in the same room as your table, watching over it, there are a million and one horrible things that could happen. During piercing, the torch may blow back and start burning back along it's lines. Or flash back. This could turn the entire assembly into burning molten goo. It could also burn back into the tanks. Whilst flashback arrestors are designed to prevent this, they are not something you should be relying on to save the day. Even with them fitted, the flame will be able to burn into the mixing chamber of the torch.

Worst case, the flame could blow it's self out. Now you are left with the torch filling the room with an almost perfect combustion mixture. When it reignites, you loose your house and family.

In an industrial enviroment, there will always be at least one guy working somewhere near the machine. At home, you could get called away from it and forget it's running.

You absolutely must have a fire extinguisher and access to running water close to hand when working with gas cylinders. A hose with a misting gun is a good idea.

I have had first hand experience of using a fire extinguisher for real when my brother accidentally set his clothes on fire. He was making some extremely unpleasant sounds due to the shock of actually being on fire.

Unfortunately... the flames weren't quite hot enough to scar him, he survived and recovered 100%... :tired: :)

But seriously... gas cylinders... fire extinguishers!

The hand held size ones for cars and around the home are totally useless. Trust me.

Buy one of the waist height ones. CO2 or foam would be a good choice. The dry powder ones not only makes a lot of mess, but I don't like the way the powder dispenses. It's like slowly throwing talc at the flames. When the **** hits the fan, you want as much anti-fire stuff engulfing the flames as possible.

Also, read the instructions on the extinguisher a few times over, so you know precisely how to use it. Position it where you can reach out and have your hand on it - don't stack it behind anything. The burn from something like clothing that's on fire will go from nothing to deadly within a few seconds.

You might also want to consider running the table with natural gas from your mains. The gas company can fit a higher pressure line if you'd like to cut thicker material. Gas cutting is much easier than gas welding with natural gas. It's also much cheaper and you have a limitless supply of it on tap.

Thank you very much for all of that information. I really appreciate your input. I'm not so sure about this home gas torch cnc thing now.
Thanks. :)

Everything in moderation I'd say.

A lot of sites go over the top with safety, and nothing would ever get done if it was all followed. There is definitly a point were safety measures themselves become serious hazards.

I don't think running a gas torch table at home is a bad idea, but it will require a lot more respect that a plasma table.

If I was going to do it, I'd want...


Some way of quickly turning the gas off at the cylinders or mains. Nothing involving complicated keys or wrenches
A flash back arrestor on each gas line
A fire extinguisher sitting beside the table
A permanently on hose with a spray gun fitted that I could get to it in thirty seconds or less - so I'd just have to pick it up and squeeze the handle to have flowing water on hand


Apart from that, I don't think you'd need a great deal more.

You'd need to be aware of things like, were is the heat from the torch's preheat flame going? Is a lot of it rising up? Where will I put the gas lines to the torch? Will they sag down at all close to the table? Will the rising heat accelerate wear to or melt the hoses?

One easy way of adding some extra safety to the table would be to fit a thermocouple to some form of alarm on the controller. The couple could touch against the side of the flame or torch and trigger the alarm when it's temperature changes - suggesting that the flame has changed. I believe commercial tables use a UV sensitive diode of some kind.

The best safety measure is to just stand beside it while it cuts.

I just retrofitted a 6 torch gas cutting gantry, this used large capacity torches and the pre-heat is usually only on for a short time, with a one inch plate on the test cut the pre-heat was in seconds not minutes. The length of a machine torch is such that the hoses are well out of the way. You also need some kind of torch height control to adjust the height when cutting. Most of the flame and slag is fired down into the table below.
Tables of this kind are also fitted with a master off switch that controls the solenoids and can cut the gas to all the torches if needed.
Al

Sanghera, I built almost exactly what you are looking for. I have a 2axis steel CNC gantry using an un-modified hand torch, a Xylotex board, TurboCNC, solenoid controlled air operated torch button and has a 30"x30" capacity. I need to do small runs of steel brackets, and this sure beats a hand torch. I have about $1200 invested in everything (including the PC & torch).
http://www.accuratepower.com/Torch/Machine.jpg
http://www.accuratepower.com/Torch/Y.JPG
http://www.accuratepower.com/Torch/Cut2.jpg
http://www.accuratepower.com/Torch/Bed.jpg
It was fun, and relatively easy. Enjoy, MIKE

Regarding interfacing the board and software; I use a parallel port pin (8) available on the Xylotex to activate an OMRON 24vdc relay. This energizes a 24v solenoid air valve, that operates an air cylinder, pushing the button. I throttle (needle valve) and regulate (70psi) this to control speed and pressure on the button. In TurboCNC, I configured "Coolant A" to be pin 8. I use an M07 in the code to push the button and an M09 to turn it off. I experimented with pauses (G04 "Dwell" with P* being pause in seconds, IE G04 P5.5 = 5.5second pause) and use 5.5sec in 3/16" steel. After the button is pushed, I pause again .5sec, and then go. It looks like this in code;
G00 X 1.00 Y 1.00
G04 P5.5
M07
G04 P0.5
G01 (first move of the part)
...
(last move)
M09
G00 X 0.00 Y 0.00
M02
To get started, I jog the torch off of the part, light it, and tune the "pre-heat" flame. Push "A" (in jog mode) to open cutting Oxygen and re-tune the "cutting" flame. I turn off "A", exit jog, and start the program. When it is done, I turn off the gasses.
A water tray is my next project, keep the dirt and smoke down. You will need to draw "lead ins" on your parts. I have to start about a 1/2' away from the part so the little puddle from pre-heating and piercing is not on the edge of the part. Also, I try to get the first G00 after the button is lifted to move the torch away from the part, so I don't get any secondary cutting from the (always on) pre-heat flame. (I was noticing little "J's" at the end of my cuts). Torch height is not an issue, seems to have a very wide acceptable range. I do clamp or tack the plate to the "bed" to minimize the sheet lifting. You can also arrange the cuts to move around on the plate so you don't heat it from one end to the other. I adjust the slats up and down (shims, different width material) for different thickness plate. Good luck, MIKE

Mike, Thats awesome, I've been planning on making a copy of your cutter ever since you posted it.. got the motors turning already, I just need some space to build the frame..

Since you are doing tube frame chassis work, how about adding an 'A' axis in one corner to hold tubing and rotate it, in conjunction with the 'Y' axis you could cut fishtails, perfect sinus holes, slots etc in tubing, sort of a CNC tube notcher. :)

I'll add some pics that give a rough idea of what I'm thinking, mentally add some sort of lathe chuck and belt 'n pulley arrangement to turn the tubing. the brassy thing is the torch.

cheers,
Adam.

Wow ! The 3-D renderings look great. I use the mill and big roughing endmills to notch, but I have thought about the CNC notcher. For a big hollow spindle, look at 4x4 front spindles. They have great bearings and ~1 1/2" bores. Bigger trucks have bigger bores. I have a few sitting around and was contemplating using one for a similar project. I'll be watching yours ! Good luck, MIKE

Yep, I use a 6" bench grinder for notching at the moment, but I was thinking more along the lines of this..

Hmm... Is there a kind of relay or stuff that can control the flame torch on off? Eg. automatic ignition for oxy/acet. ...

Hi Mike,

Just one question. How long did you take to build and assemble all these things into a working piece? I'm curious.

Pre-heat flame stays on all of the time. I move the torch off of the work, light & tune the flame and start the program. It moves to the first pierce and pre-heats for the time programmed. Then the relay energizes the air solenoid, pushing the oxy (cut) lever via a small cylinder. At the end of a cut, the oxy is turned off. Pre-heat flame stays on as the torch rapid moves to the next pierce. (And so on). I used no (expensive) gas/oxy solenoids. I have to turn on/off the gasses when I am ready to cut. The pre-heat staying on during rapids has little effect. I do sometimes move away from the part before heading for the next one. If not, you may get a little secondary cutting (notch) if the pre-heat flame crosses a recently cut area. It took around 6mos of on & off work to build it. I never worked too hard (I built it for "fun"). Could have been done in a week or so. Enjoy, MIKE

Is it possible to post some plans for an entire machine? This will be my 1st machine build and while it looks simple enough, I'd benefit from some more guidlines.

I think I have it figured. Well almost. This looks like what I need.
Will it cut 1" steel?
I think Oxy is dangerous, so I'll do a bit of research on the safety parts.

I really like the simple design of this table. Thanks for posting the pics!

Here is a link to a Flashback Arrestor, this will save you're house from exploding.

http://www.koike.com/products/gasapparatus/a_sentflashback.asp?CatID=203%7Csentinelflashback

Hey accurateMike,
I was wondering what kind of solenoid you used. Did you need two? Also, where can you get this and how much does the solenoid cost. My machine is built, it is mainly designed as a router, but I might make the bracket for a torch to come off to the side to a separate water based table.
Sanghera

I use an air/electric solenoid to operate a small cylinder that pushes the torch button. I operate the gases manually.
RE: Flashback arrestors, they are included in my (& most) torch kit. I have had an oxy/acetylene rig in the shop for 19yrs. The only new part for me is the CNC table. MIKE

Has anyone make a automatic torch igniter that works perfect everytime?

torch igniter that works ?
A 12 volt automotive ignition coil with a spark plug wire leading to an electrode directed at the O.A. torch tip, close to it's end works.

Your PSU can feed the coil & the software fire it as required for ignition.

Don't touch the electrode when activated unless you want both eyes WIDE open! ;)

So you used a solenoid that controls the air coming into the torch? Or did you use a solenoid that simply pushes or turns the contols on the torch? Are the controls proportional, or are they simply on- off? How much is this solenoid worth?
Thank you.
Also, could you use a bbq lighter, it wouldn't be electronically controlled by your computer, but you could light it when you want to. The new bbq's come with an ignition system which runs on 1.5 volt battery. so, maybe you could hook this up to a relay. Not sure.
Thank you.
Sanghera

My machine uses a plain, garden variety, hand torch. I use the regulators on the bottles and the knobs on the torch, the old-fashioned way. My solenoid and cylinder uses shop air pressure to actuate the cut button on the torch. A torch button is on-off. I use a Bic lighter for ignition.
Goes like this:
1) manually jog the torch off of the plate
2) turn on and adjust the regulators
3) turn the acetylene on at the torch
4) light the acetylene with the Bic
5) tune the acetylene for proper flame
6) turn on the pre-heat Oxygen at the torch
7) adjust the Oxygen for proper flame
8) manually open the cutting Oxygen valve (from the jog menu, using the CNC control)
9) adjust the cutting flame, using the knob on the torch
10) manually turn off the cutting Oxygen (from the jog menu)
11) start the code and watch it cut
12) turn off the gasses when it is done
My usual cutting job is just a few minutes of actual work. It is easier than it sounds. The solenoid, relay, regulator, needle valve and cylinder were less than $30 for all. The solenoid was $7.
The cylinder pushes the button, the relay is triggered from a parallel port pin, the solenoid controls the cylinder with 24v from the relay, the regulator controls the force on the button, the needle valve regulates the speed that the cylinder opens the button. Once again, easier than it reads. Hope this helps. MIKE

Remeber that oxy acetylene brings about some very serious fire risks......A hose with a misting gun is a good idea....

I just wanted to say something regarding this.

1) Hose with a misting gun is a very good precaution but not by itself (Which I know johnuk didn't suggest but worth re-iterating). If a large amount of metal goes on fire such as was being suggested, some metals burn too hot that they will evaporate misted water before contact. Also if you set one of these up remember at all times NOT to use it if any oil based products are alight. If you have a lot of oil type containers lieing around, might be better off giving this a miss just in case.

2) When buying tools everyone always tries to go to the max that they can afford, its similar with fire equipment but more important. A CO2 extinguisher is a good idea for any workshop, but get a 5kg one for about $100, not a crappy small one. DONT hold the body of a CO2 extinguisher when using it or your skin will freeze to it...not pleasant. Just hold the handle. It'll work for almost everything, but not for light materials like paper, with paper it'll just blow the fire all around the room.

3) Whats more important and Im sure few home workshops have them is a Class D extinguisher specifically for burning metal. These are quite expensive thats probably why, but if your using a cnc gas cutting setup, or any other metal cutting/welding for that matter its a useful precaution. About $300. Specially formulated powder for the high temps of burning metal. Messy to cleanup but thats a small price to pay. If your getting one they usually come in 9kg so no worries there.

4) If you want one all round extingguisher a dry powder is the one, but if you need to use it, again the cleanup is messy and it doesn't cover a large area quickly to put out a large fire like CO2. But buy a 9kg one if your getting one.

5) Water is crap and generally a waste of space! Its horrible to see how many people buy a crappy little water extinguisher in their local store and put it in the kitchen where it cant be used on anything! If your insisting on buying a wet type extinguisher for whatever reason, at least buy foam.

6)Remember when you buy the extinguisher/s to take 20min and mount them somewhere easily accessible. Dont be a lazy git and sit them somewhere, use the hooks that are included in the box and put them on the wall. Regulation height is the handle 1m off the floor to allow any height person to use them. Beside a door is usually a good place because your less likely to put crap leaning against them. Please dont leave them sitting on the ground or a counter (Pet Peeve :) ). Apart from the amount you paid for them if they get damaged, if you spill something corrosive and it eats into the extinguisher it'll be nasty when you use it. People have been killed when they used extinguishers in these circumstances, the base rots and explodes off when you press the handle, the extinguisher shoots up into the bottom of your jaw breaking your neck! (And yeah, hold it away from you at arms length when using), likewise if the neck of the extinguisher corrodes. Look at it once a week for 20sec to check if theres any damage/corrosion. Its a good idea to get it serviced once a year (Legal requirement for a business).

The amount of money most people spend on equipment you think they'd be willing to spend a few hundred on good fire precautions. Especially if you work from or at home as a hobby or otherwise, think of your family and neighbours and dont skimp and buy a crappy small extinguisher.

Remember that burning metal gives off toxic fumes and if the fire is bad when you notice it your extinguisher will be useless so dont risk your life. Oh yeah....get a damn smoke alarm and keep fresh batteries in it! Even if you only use it at night due to smoke/fumes when your working.

Whatever extinguisher/s you get, buy a small fire blanket aswell. Saves the mess of an extinguisher if its a small manageable fire.

Last Point: :) Too many people, businesses especially, do go overboard on safety nowadays. No need for that, but not taking simple precautions like buying an extinguisher is just plain stupid.

------------------------------------------------
The opinions expressed in this post do not constitute professional advice. Any persons buying or using fire safety equipment should seek professional competant training. ;)