edge quality

[tmbg]

I'm working on tweaking my edge quality from my powermax45 on my 4x4 table. 1/4" steel is looking pretty good, and I'm cutting around 10% under the recommended speed in the hypertherm manual. Book speed is 60ipm at 45A, I'm running 50ipm with good results.

Cutting 1/4" aluminum at book speeds results in a very rough edge with a fair amount of dross. Reducing travel to 50% book numbers (I think I was at 36ipm) results in a reasonably acceptable edge, almost no dross and quite square, squarer than steel even, but the edge is still "crumbly", almost like it was cut with a cheese grater. Is that just what you get with air plasma on aluminum, or is it possible to tweak it to a smoother edge? The mild steel edges are quite smooth.

[tmbg]

[jimcolt]

That is typical with air plasma on aluminum. It is more of a roughing cut with aluminum until you get into the larger plasma systems that can use more power and different gas combinations. I get some great results up through 3/16" with my 45, but above that the edge is similar to the one in your picture. When I need intricate holes....I cut them undersize and then drill them. Just not enough power....perhaps a 60 amp or 80 amp process would work better.

Aluminum and stainless are simply a thermal (melting) process, steel is two part, thermal and exothermic (chemical reaction with oxygen content in air).

Jim

[tmbg]

Thanks Jim,

I haven't tried it yet, but do you think I'll be able to get a fairly clean edge on 0.063" 2024-T3 alclad aluminum? One thing I want to be able to do with this machine is cut aircraft panels, and I'd hate to have to spend a week with a file cleaning up instrument holes.

[jimcolt]

You can do a pretty nice job on that material....assuming the cnc machine can handle speeds and your THC can maintain accurate height.

Jim

[tmbg]

The only thing I'm afraid of is up over 200ipm or so my lines start to get wavy. I know I can reduce feedrate as long as I either reduce current or increase torch standoff, but will running slower than normal with increased standoff mean I have to sacrifice edge quality and angularity?

[jimcolt]

You can reduce current, you can change feedrate.....but it is important to always maintain the recomended standoff. If the book specs recomend .062 " standoff....then do what you have to do to maintain that height. Increasing standoff will cause an increased edge bevel.

Jim

[super95awd]

I get beautifully smooth edges on anything up to 1/8" aluminum with my Powermax45. They require absolutely no prep before welding. My edges on 3/8" are substantially smoother than the 1/4" edges you have pictured, but I haven't cut any 1/4" aluminum unfortunately. Not a very common size for me.

On .090 I run at 135 IPM, 1/8" at 120 IPM, and 16 gauge at 180 IPM.

[sdubfid]

I get beautifully smooth edges on anything up to 1/8" aluminum with my Powermax45. They require absolutely no prep before welding. My edges on 3/8" are substantially smoother than the 1/4" edges you have pictured, but I haven't cut any 1/4" aluminum unfortunately. Not a very common size for me.

On .090 I run at 135 IPM, 1/8" at 120 IPM, and 16 gauge at 180 IPM.

What welding process are you using? I always have to clean the edges to remove the oxidation before tig welding.

[super95awd]

TIG... All I do sometimes is touch the top and bottom edge with a file, and I mean TOUCH.

[sdubfid]

Hmm if I don't sand the edge then I get lots of black pepper stuff in my welds.

This is the only example I have on 1/8" aluminum, any suggestions?

Uncleaned edges you can see the black around the tacks and the tacks themselves are dirty:


Pre-sanded with flapper wheel lightly before welding to remove oxidation

[super95awd]

This is with no edge preparation, the black pepper crap is an elusive little bugger. It's so inconsistent in my experience.

Nice beads BTW!