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  1. #1
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    Question Tool Steel (D2,A2,4140)

    Does anyone have any experience with cutting tool steel on an 1100? When you calculate your speeds and feeds, how much of the available 1.5hp do you aim to use?

  2. #2
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    For any 3-phase motor with VFD "available" HP varies with speed. Below the motors rated base speed (the RPM @ 60Hz frequency), the motor is essentially constant torque, which means HP reduces linearly with decreasing RPM - at 30Hz, you'll have full torque, but only about half the HP. Above base speed, it's constant power, which means torque reduces linearly with increasing RPM - at 120 Hz, you'll have only 1/2 the torque you have at 60 Hz, but the HP will be the same. This all needs to be taken into account when picking RPM and feedrate. You're sometimes better off deviating from "ideal" RPM and feedrate to accommodate the motors characteristics.

    Regards,
    Ray L.

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    Do you know if there is a graph or other information regarding the "available" hp at certain speeds? Or an equation I can use to figure it out?

  4. #4
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    Some good information posted by 'Keen' in these threads. Haven't seen him on here in while though.

    http://www.cnczone.com/forums/tormac...teel_k600.html

    http://www.cnczone.com/forums/tormac...ned_steel.html

    http://www.cnczone.com/forums/tormac...ugh_steel.html


    I'm cutting a bit of P20 tomorrow, so I might chip in with what I find as well.

  5. #5
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    Thanks Peter, that is some good information. Please let me know how you make out with the P20 and, if you are willing, the speeds and feeds you used.

  6. #6
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    Quote Originally Posted by adamboon View Post
    Do you know if there is a graph or other information regarding the "available" hp at certain speeds? Or an equation I can use to figure it out?
    Like I said, both relationships are linear. I don't know the specs for the Tormach motor, but let's assume 1.5HP, with a base speed of 3600 RPM @ 60Hz.

    Below 60 Hz/3600 RPM:
    HP = 1.5 * RPM / 60HzRPM
    Torque = HP * 5252 / 3600

    Above 60 Hz/3600 RPM:
    HP = 1.5
    Torque = 1.5 * 5252 / RPM

    At 3600 RPM, you'd have:

    Power: 1.5 HP
    Torque: 2.18 ft-lbs

    At 2000 RPM, you'd have:

    Power: 1.5 * 2000 / 3600 = 0.83HP
    Torque: 2.18 ft-lbs

    At 5000 RPM, you'd have:

    Power: 1.5 * 3600 / 5000 = 1.08 HP
    Torque: 1.08 * 5252 / 5000 = 1.13 ft-lbs

    Regards,
    Ray L.

  7. #7
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    Thanks for that Ray. Now I just need to find out the specs for the Tormach motor. I couldn't find it in the manual I downloaded, maybe somebody out there knows what it is. Now I can better calculate if my pretend speeds and feeds are within the capabilities of the Tormach.

  8. #8
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    Hi Adam

    From the tech sheet on the Tormach web site
    100-5,100 RPM
    110ipm in x and y
    90ipm in z

    Max power 1.5hp

    Peter

  9. #9
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    You're trying to eat the elephant from the wrong end.

    Horse power calculations are very approximate. Horse power at the cutting tool is not the same horse power as at the motor. Whether you can use the available horse power depends on other factors not included in the calculator. Horse power calcs are only good for telling you if you are way outside or inside your limit. Constant torque to rated rpm and constant hp above rate rpm is more than close enough for your calcs considering all the other uncertainties. Hence the reason you can't find what you are looking for is because it is of low interest.

    Don't forget to allow for the speed difference between the motor and the milling spindle.

    Phil

    Quote Originally Posted by adamboon View Post
    Thanks for that Ray. Now I just need to find out the specs for the Tormach motor. I couldn't find it in the manual I downloaded, maybe somebody out there knows what it is. Now I can better calculate if my pretend speeds and feeds are within the capabilities of the Tormach.

  10. #10
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    Constant horsepower calculations don't mean squat if you're cutting D2. If your spindle speed is too fast, you'll fry your cutter in about 6 turns.

    A2 is a little more forgiving, and with the right tools, 4140 in an annealed condition and with the right tools can be at some fairly high feeds and speeds.
    You can buy GOOD PARTS or you can buy CHEAP PARTS, but you can't buy GOOD CHEAP PARTS.

  11. #11
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    Went quite well, posted the pics/info in a different thread to avoid hijacking this one.

    Quote Originally Posted by adamboon View Post
    Thanks Peter, that is some good information. Please let me know how you make out with the P20 and, if you are willing, the speeds and feeds you used.

  12. #12
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    Quote Originally Posted by HimyKabibble View Post
    Like I said, both relationships are linear. I don't know the specs for the Tormach motor, but let's assume 1.5HP, with a base speed of 3600 RPM @ 60Hz.
    Just for completeness on the motor topic:

    The motor is 1.1 KW, 230 V, 60 Hz, 1715 RPM, Delta config.

    I had a spectrum analyzer hooked up to mine to check unbalance, and the motor to pulley ratio was 1.26 (from the response peaks), on the high speed ratio.

    Tormach designed it to overdrive to ~140 Hz with the VFD. 1715 RPM * (140/60) * 1.26 = 5042 RPM.

    Regards,

    Geo

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