[desmo]

Hi,

I was asked to make a custom cookie mold/tray out of stainless steel that can bake 40 cookies at once. The cookie molds will be welded to the tray so that the baker can just place the cookie mold tray on an aluminum baking tray, fill the molds with dough, and after its done baking, he can just lift the cookie mold tray and the cookies stay in aluminum pan. The baker hopes to keep cookies consistent shape and size with this mold tray. I hope this makes sense, if not please refer to the pic I attached.

I'm thinking about using 16g 304 for the mold tray and 16g 304 for the cookie molds. I plan on using a 20 torch with gas lens/#7 cup .040 2% Thor or 2% Lanth and 308 rod. This has to be food grade so I need to purge this. I do not own a flow meter that has an extra line for purging or any purging devices. Can anyone please share any tips on how to I can run an extra line, flow of argon to the purge dam, any info is greatly appreciated.

Thanks

[ESENTI]

Dear Desmo , you can cannot use the same cylinder fro extra gas but i have seen doing it . Best is to use a square metal to put the whole thing in , like a champer. Argon is a lot heavier than air to get an idea is when you weld in areas like a cellar the argon form welding takes the place of the air gradually and
can choke you .Your mind must focus in a champer like thing put some agon gas in it and then weld it if you can do it in a cambinet like sand blaster is even better.Start with a little spot to see as test and then continue ...above all keep cool ...

Esenti

[Otto Nobedder]

Here's a topic on a dual-flowmeter I built, to purge and weld from the same bottle, with pictures.

http://forum.weldingtipsandtricks.com/v ... f=5&t=2092

Note, the pics are hosted, and one's been replaced... That's not my wife and kid..

Steve S

[desmo]

Thanks for the tips. So the described stainless I plan to use is good enough? I think Im just going to get another bottle of argon and hook up a flowmeter and use it for purging.
Thanks again

[Otto Nobedder]

Yeah, 304, with 308 filler, should be fine, since cookies are not highly corrosive. The back-purge and any other steps to maintain high purity and NO porosity will help maintain "food grade".

Steve S

[desmo]

Thanks for the help

[weldin mike 27]

Hey,

Stop me if this sounds whacked out, but would it be possible to make your own purge chamber? Like a open topped tub, filled with argon from your torch,( work out the volumes by calculations) and place the part in it and weld it in there. For this part or similar odd shaped parts. Or would the movement of your hands mess up the pool of argon??

Mick

[desmo]

Yes it is possible but I think your method sounds too complicated. From what I understand/know (I'm no expert) you can use any container that is air tight or somewhat airtight (depending on what you are welding). You need an intake (argon comes in) and an exhaust (atmosphere exits) port, once your container is purged, you have to maintain argon flowing at all times but at lower CFH. I used my friends harbor freight sandblast cabinet that he turned into a purge chamber to attempt to weld titanium and I had decent success. I think it all depends on how much the metal reacts to the atmosphere, I've seen Jody weld stainless with a backside purge cup and he had good success. I tried that with titanium and failed. lol So some metals don't require a purge chamber and can do with a purge cup, while others can't.

PLEASE CORRECT ME IF ANYTHING I STATED IS INCORRECT. I do not wish to misguide anyone.

Thanks

[krazziee]

i bought a Y valve from welding supply for purging different things, it was about $40. it has two adjustable valves on it, the one going to the welder stays wide open and i open the other one a little and have another valve ( ball valve ) near the end of the purge hose to shut off gas when weld is done to save gas without going to the bottle to turn off the valve there, i close the other valve when not needed. just go up on the gas a pound or two, works good for me and was cheap.

[Otto Nobedder]

krazziee,

I built a dual flowmeter for a fraction of that.

GEDC0359.JPG (199.05 KiB) Viewed 2014 times

I had the cost of two flowmeters and about $3 in brass in it. One flowmeter feeds the TIG at 20 CFH, the other feeds the backpurge at 5 CFH.

Steve S

[krazziee]

very cool steve,
and very cheap fix.
i did not have the another flowmeter or that is what i would have done.
i have only one right now and it is a regulator type. i think i would rather have the flowmeter type.
what do you think ? is the flowmeter better or the regulator type, i know they both pretty much do the same thing.

[Alexa]

A general question.
During your experience, has switching gases in flow meters, caused any difficulties?

Alexa

[Otto Nobedder]

The flowmeter (floating-ball) type will always be more accurate. I once had a "ball" flowmeter that could detect flow as low as 0.5 CC/hour. (Though this cost almost $100.) It was for leak-detection in valves.

Look on E-Bay. I'd considered selling all the flowmeters I just throw away, and they were going for less than $10, so I keep throwing them in the recycle bin.

I've discarded at least 50 perfectly good flowmeters.

Steve S

[krazziee]

thanks for the info,
i wish i had a good one, two would be better,
i will check around for a cheap used one.
thanks again,
Richard

[Otto Nobedder]

A general question.
During your experience, has switching gases in flow meters, caused any difficulties?

Alexa

I wouldn't put oxygen on one not rated for oxygen service, but other than that...

The ball height vs. flow is determined by the gas density. Helium, for example, will just barely lift the ball of an Argon flowmeter at 20 cfh, where on Argon it might be up an inch and a half.

My flowmeters at work are marked for 3 gasses-- Argon, 75/25, and Helium.

Steve

[Alexa]

Otto.

Tanks.
I enjoyed the explanation, particularly concerning the density ratings.

Alexa

[krazziee]

very good info
thanks again