I have to finish machine about 8-10 pieces each of 2 different parts that will be plasma cut from .375 and .125 mild steel plate. I remember reading that the edges of plasma cut steel can be very hard and I was wondering if anyone here has ever had to finish machine some parts like these and if so how did you do it and what can I expect?
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Machining Plasma Cut Blanks
- Thread starter micro
- Start date
- Replies 18
- Views 5,163
Limy Sami
Diamond
- Joined
- Jan 7, 2007
- Location
- Norfolk, UK
Generally IME it's harder than a whores heart and murder on cutters,........... hopefully you've left enough to get ''under the skin'' of the cut edge.
If it is mild steel you will have know trouble. The 1/8 thick plate will be the problem depending on what operation your doing on it. I turn plasma cut blanks all the time with both HHS and insert style cutters. If its high carbon steel then thats a different storie but is doable. Ron
IAMATT
Stainless
- Joined
- Aug 3, 2009
- Location
- LAS VEGAS, NV
Carbide cutters and do not climb mill into the edge.
ARB
Titanium
- Joined
- Dec 7, 2002
- Location
- Granville,NY,USA
+1
About the only time I don't climb is when I cut burnouts.
cncprogman
Cast Iron
- Joined
- Jul 24, 2007
- Location
- Temple, Texas, USA
+2
And use variable pitch endmills if you have them.
And use variable pitch endmills if you have them.
mori lover
Plastic
- Joined
- Feb 10, 2010
- Location
- republic mo
cutting flame cut
build a fire and turn it red and come back tomorrow cuts like butter
build a fire and turn it red and come back tomorrow cuts like butter
jimcolt
Cast Iron
- Joined
- Oct 3, 2007
- Location
- Hanover NH
If you have any control of the plasma cutting process for these blanks....make sure it is a high definition class plasma using oxygen as the plasma gas and air as the shield. This combination of a high energy density arc, along with oxygen as the plasma gas virtually eliminates the chemically induced hardening that many air and oxygen plasma systems produce.
Air plasma, and conventional oxygen plasma systems allow nitrogen to impregnate the molten cut face.....this puts a nitride finish on the edge....which is extremely hard. The Hypertherm HPR series plasma is designed to minimize the plasma hardening effect....by keeping the N2 away from the edge. Attached is a picture of a 5/16" hole cut with an HPR260 plasma on 3/8" A-36 steel.....the hole was then tapped using a $3 Craftsmen tap.....
Jim Colt Hypertherm
Air plasma, and conventional oxygen plasma systems allow nitrogen to impregnate the molten cut face.....this puts a nitride finish on the edge....which is extremely hard. The Hypertherm HPR series plasma is designed to minimize the plasma hardening effect....by keeping the N2 away from the edge. Attached is a picture of a 5/16" hole cut with an HPR260 plasma on 3/8" A-36 steel.....the hole was then tapped using a $3 Craftsmen tap.....
Jim Colt Hypertherm
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jdj
Diamond
- Joined
- Oct 22, 2007
- Location
- detroit,mich.
Be very happy that you don't have to cut 304 or 316 that has been plasma cut. That shit is brutal!
Jeff
Jeff
Jim. I've seem hi def plasma and it's pretty amazing. What I've seen rivals lasers. These blanks are already cut so there is little I can do about that this time. However I plan on bringing CNC plasma cutting to my list of available capabilities (just bought a Hypertherm Porwemax 45 with this in mind), but there is no way I could afford nor justify hi def.
What about cutting with 02 and shielding with Ar or CO2?
yep i will secound that its the plasma gas that makes the diffrence. Air assist cutters leave a very hard nitrided like edge. Oxygen bassed cutters leave a lot softer edge. Still not as soft as a drilled hole but theres a night and day diffrence bettwen the 2!
jimcolt
Cast Iron
- Joined
- Oct 3, 2007
- Location
- Hanover NH
There actually are plasma process gases for SS that will have minimal hardness impact on the cut edge. Hypertherm's HPR systems can use F5 (95% nitrogen, 5% hydrogen) as the plasma gas, and nitrogen as the shield gas to cut this material with a weldable, machineable edge....the F5 process works on materials to about 3/8" thick. Above 3/8" we use H35 (65% argon, 35% hydrogen) as the plasma gas and nitrogen as the shiled gas.
The issue on stainless is with oxidation.....by using the above gas mixes the oxygen content on the cut face is dramatically reduced....leaving a clean, shiny, metalugically good edge. This technology was developed by Hypertherm and has been in use for a number of years!
Air plasma cuts on stainless as well as non high definition cuts will harden the edge of most stainless steels.
Jim Colt
The issue on stainless is with oxidation.....by using the above gas mixes the oxygen content on the cut face is dramatically reduced....leaving a clean, shiny, metalugically good edge. This technology was developed by Hypertherm and has been in use for a number of years!
Air plasma cuts on stainless as well as non high definition cuts will harden the edge of most stainless steels.
Jim Colt
SteveinAZ
Stainless
- Joined
- Aug 20, 2007
- Location
- Snowy Arizona
Micro, I second the conventional over climb cutting (I presume you are milling). Where I used to work we used to mill quite a few Oxy-Act burnouts and lost a ton if inserts and a few tool bodies before figuring that one out. Two part problem, inexperienced operators not recognizing that BANG-BANG-BANG-BANG is followed by KABOOM and just loading in new tools or insert doesn't solve the problem, and me not recognizing that the edges were not even cleaned up a bit (still had some slag!).
A quick program change of direction and tools lasted pretty well, hopefully you have enough meat to get under the hard edge.
Steve
A quick program change of direction and tools lasted pretty well, hopefully you have enough meat to get under the hard edge.
Steve
jimcolt
Cast Iron
- Joined
- Oct 3, 2007
- Location
- Hanover NH
Often...on a plasma cut part (especially air cuts) you can run a grinder over the edge and take off about .005" to .007".....this is the thickness of the chemically induced nitride hardening that ocurrs on steel from the nitrogen content of air. Machining will normally be fine after this is done....better yet, use the best plasma technology (Hypertherm HPR systems) to do the cutting and go directly to machining operations.
High Definition class plasma systems are expensive to buy......but by far are the least expensive to use when you consider cut quality, accuracy and secondary operations (machining, welding and forming) that must be done on the part after cutting.
I watch so many that shop for the lowest price when buying a plasma......when often the lowest price cannot be calculated until after the parts you are producing are finished!
Jim Colt
High Definition class plasma systems are expensive to buy......but by far are the least expensive to use when you consider cut quality, accuracy and secondary operations (machining, welding and forming) that must be done on the part after cutting.
I watch so many that shop for the lowest price when buying a plasma......when often the lowest price cannot be calculated until after the parts you are producing are finished!
Jim Colt
mori lover
Plastic
- Joined
- Feb 10, 2010
- Location
- republic mo
plasma blanks
Quit the wa wa and put the heat to them and get the job done on one hss
endmill
Quit the wa wa and put the heat to them and get the job done on one hss
endmill
i_r_machinist
Titanium
- Joined
- Apr 12, 2007
- Location
- Dublin Texas
Jim,
Would 95/5 argon work?
thanks
i_r_
Would 95/5 argon work?
thanks
i_r_
Limy Sami
Diamond
- Joined
- Jan 7, 2007
- Location
- Norfolk, UK
Micro,......... like hows it going? you making chips or trashing cutters.?
jimcolt
Cast Iron
- Joined
- Oct 3, 2007
- Location
- Hanover NH
It might....however the process and consumable parts were designed using 95% nitrogen/5% hydrogen......so I guess I cannot answer for sure. We have 15 engineers with PhD's......I suspect there must be an arguable reason as to why they chose the gas mix that they did!
Jim
Jim
The pieces got to the shop today but I'm out with the flu. When I get back Ill let you know how it went. It can't be any worse than the 316 parts that were driving me nuts on Monday.
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