All good questions. One of the things that you don't mention is the type of cnc machine and Torch Height Control that you are using....these will make a difference in cut performance. Also....are you using a hand torch or a machine torch on your machine....if you are using a hand torch, make sure you use the machine torch consumables.
I'll try to answer your questions:
1. Anybody ever try the Thermal Dynamics IPM settings with their Hypertherm? Based on my cutting experience they appear to be much more real world settings.
The T-D torches and Hypertherm torches are quite different designs. If the T-D specs happen to work better, then those are the settings that you should use! In reality, with so many different alloys of aluminum, as well as so many different part programs and different machine acceleration rates and THC delays and calibration issues, especially on entry level cnc machines....you should consider the suggested settings in the Hypertherm manual to be good starting points. I guarantee that these setups will work on the laboratory machines (very accurate, perfect arc voltage calibration, industrial quality machines), however results will vary. Personally, I use the optimal speed settings as a starting point for all of my cutting...then do a little tweaking...and often end up with speeds that are 10 to 15% slower than optimal. The max speed settings are just that.....with a new nozzle, with no concern of cut edge angularity, the torch will cut at that speed...and I will stand behind that promise!
2. The arc volt listings in the Hypertherm charts, are they for the maximum settings or the optimum?
Once again...starting points. On our lab machines these settings are correct for the optimum speeds. Factors that affect the relationship between height and voltage: air pressure/flow, air purity, nozzle condition, electrode condition, THC calibration, cut speed, machine grounding. There may be a few others. Bottom line....start with the recomended voltage...then once you get your speed where you want it for a particular cut...tweak the voltage until the torch to work distance is correct...if the manual says to cut at .062" cut height...then the voltage required to maintain that height is the correct voltage for your particular machine.
3. Anybody have any REAL world setting for 1/4 , 3/8, and 1/2 aluminum with a Powermax 1250 or 1000?
I know what works on my PlasmaCam machine, and I'd be happy to share it, but as suggested above, it may not be the same on yours.
4. Why does Hypertherm still not list cutting charts for aluminum with Fine Cut consumables?
We do not have settings for aluminum with the FineCut consumables because our process engineers never tested aluminum cutting with the FineCuts during their development. I do not have a better answer! I have used them and developed my own parameters for up to 1/8", they workquite well in this range.
5. What are reasonable expectations for cut quality with a air plasma like the powermax 1250 or 1000 on thicker aluminum from 3/16 to 1/2?
Cutting aluminum is strictly a thermal (melting) process with plasma, as compared to the cutting of steel which is part thermal and part exothermic (reaction with the steel and oxygen content in air), therefore aluminum (and stainless) cannot be expected to cut with the edge quality and edge squareness that we expect with steel. On aluminum in the range you suggest (3/16" to 1/2") I would expect minimal dross formation, I would expect angularity in the range of 3 to 8 degrees from square, and I would expect a relatively rough, porous edge.
Remember I am talking here about air plasma systems on entry level (read low cost) cnc cutting machines. There is a whole different world of high definition class plasma cutting on precision industrial cnc machines. On these types of machines where motion, acceleration, following error, arc voltage calibration and gas flows are all very tightly controlled...you will see no tweaking. Input your CAD drawing into the CAM nesting software, select material type and power level, load plate on the table, ensure the correct consumables are in the torch...and push the cycle start button. These types of plasma/cnc machines start at 130 Amps and go to 800 Amps, have 100% duty cycle, and start at about $80k for a small (5 x 10) machine, and go to well over a million dollars for large machines with up to 4 torches and bevelling capability.
Best regards, Jim Colt Hypertherm