When cutting 16-20 ga are you starting from the center?

[glgsales]

I want to cut some bigger art work here at the school ,so to be sure i don't melt and warp the metal too much before i cut I usually try to cut from the center out.
I can't afford to waste any ... like anyone else can.. anyway before I cut it out what are your opinions, on say the wolves cut out .
there are some close pieces and many smaller ones..
Thanks
Gary
Prior Lake High School
Industrial Technology Dept.

[plain ol Bill]

Gary if you do not have a water table skipping around is your best bet to prevent as much warpage as possible. You might also use a hand spray bottle and keep spraying the material while cutting - that will help. You might also delay cutting whenever you start to see any signs of warpage and let the material cool off.

[elkriverfab]

glgsales,

Plain ol bill is right about jumping around on the detailed cuts.

I have drawn and cut a lot of highly detailed pieces that would have bowed all over the place if i was to cut it all at once.

I have built a down draft table that sucks air (dust) down and out from the table, that helps at times by pulling a draft through the cuts.

I have also installed a fan that blows down onto the table, that helps also.

But cutting one section and than moving to a different area helps more than anything.

I have cut a lot of detail without having to much trouble but.......thin material will always bow if a lot of material cut out of it.
It will bow no matter what you do (just my experience)........

I have never tried the spry bottle before but I am sure it would help.

If I was cutting the material you are wanting to cut and get the detail out of it, I would cut and cool -cut and cool -cut and cool.

It may take a little time but it will be worth it.

I have cut detail out of steel and watched it bow bad, gave it time to cool and it went right back down without any problem.
Continue cutting a shape or two and let it cool again.

I have learned to do this with the plasmacam on thin material........Nothing like cutting and having the material bow, catch your torch and watch it pull the entire sheet out of place. Good luck putting it back in the same position so you can resume, not going to happen

Hope this helps

[glgsales]

Thanks guys
We just picked up a load of scrap steel from Continental Machine here in the area. They make the do-all machines, they give us scrap every year to use .So I can try some stuff out before investing in bigger sheets. They are hurting as well sales are down so scraps are down...

I will try to do what you all have said ,it's not like we are in a hurry at school to get all these jobs out like most of you. We have plenty of time...

Well I mean there is only 1 metals class this trimester...and they are the basic class of welding and sheet metal so they are not going into the plasma cam on their own. So i have time to cut and cool and let it sit over night if need be.

Thanks again guys

Gary

[hobbyrobbie]

Well, wish I had read this post before now. I was cutting the Happy Thanksgiving that Jason posted out of 16 ga this afternoon and was 42 seconds to completion. Yep, the material warped, torch hit the metal, moved it and took off across the left corner. I just shut everything down and went to the house.

Just happened to go to the Cut Quality section tonight and found out it has happened to some of you also. Started out fresh with another sheet and WOW, it worked! I am still sooooo new at this, but thanks to all of you and your wonderful advice and tips, slowly but surely I am learning.

Robbie

[K stylz]

I tried to cut a big sheet into 16 moto riders in one shot... to test the limits of our machine (and a lil push from my boss!), found out the hard way about extreme heat transfer!!

Those are some good idea's you guys listed

[geo4932]

The problem of warping on thin gauge is minimized if you use the correct Cut Height, Cut Speed, Amperage and nozzle.
If the Cut Height is too high, the arc is spread out and heats a large area.
If the Cut speed is too slow the metal heats up too much.
If the amperage is too high the metal warps.
Use the right nozzle. If you have a Hypertherm, use the "FineCut" nozzle.

george

[elkriverfab]

George,

I have found the metal I buy is already warped from the supply shop a lot of the time.
I am guessing they don't unroll it properly?? Not sure.

When I place a warped sheet on my plasmacam, I place it with the bulge side up.
After I cut several shapes out, it relaxes the sheet and it pops down rather then up to the torch.

Now the sheet is flat on the table and I don't have any trouble with pop up.
I still watch the entire cut of the project just in case a piece hangs up without falling through.

It really is worth for me to stop the machine if I see a piece that may bugger up and catch the torch.

Just thought I would mention this so if future cutters are looking for solutions.

If anyone does end up with a bulge in the sheet from the supply shop,just place it with the warp up.
Sometimes the sheet will want to flatten as you set it on the table giving you a false sense of security.......Pop it back up. It will be worth it.

I do use fine cut nozzles on my hypertherm and it makes a huge difference.
I have had so many people tell me it wont matter but with any kind of art or intricate piece, it really does.

If I am cutting plate for parts or heavy weld on pieces, I use the regular nozzles, as I don't see a huge difference in cut quality on heavy plate. I am going to weld and grind on it anyway.

I will mention I did notice a difference with warping after I added a refrigerated air dryer to the supply line (less warping all around).

Maybe thats just my imagination but I think it did help.

Just thought I would share