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  1. #1
    George has made a very good point, 3 phase motors tend to produce better torque with reduced speeds than with increased speeds, it might be better to set your vari-drive nearer to top speed and cover more range with reduction whilst still giving you some increase on the top end,
    Regards,
    Nick
    Last edited by magicniner; 21-05-2016 at 11:46 AM.
    You think that's too expensive? You're not a Model Engineer are you? :D

  2. #2
    Ah, so wind the head up to say 3000rpm and leave it there then use the VFD to give say 30% to 105% control ?

  3. #3
    See how it goes but if the motor runs smoothly on a VFD I think 120% should be do-able, do some test cuts to determine the bottom limit,
    Regards,
    Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  4. #4
    Eventful morning....

    Did some paying jobs, then started messing with the BP, it turns out I have the 1.5Hp / 1450rpm motor :( and top speed is 3500rpm although the vari-speed won't turn past 3000 or below 500 so I'm guessing something is wrong inside the head for a start.

    I tweaked the VFD a bit, luckily the front panel pot was still programmed as speed source - it was just set at 50Hz.

    After a few tests I finally set max to 100Hz and min to 15Hz, it was on default 25-75Hz.

    The head was then wound to 1450rpm so it was at 1:1 ratio. Using the VFD this gave me a range of 430-2860rpm in high and 52-346rpm in low.

    I made a test cut on one of the batch parts I was making earlier - these are moly steel and use I use a 1/2" HSS tool at 450rpm, I'd made loads so I knew what the machine sounded like when running them and there was no noticeable difference. With the tacho on the spindle while cutting the speed dropped from 450 to 420rpm but the chances are it did that anyway.

    There are some issues up top as the sheaves are flapping like hell at speed.

    I think a fixed conversion at 1:1 might be worth doing rather than repair the sheave bushes etc. At least that will give me the most of my meagre 1.5Hp at the spindle rather than lost in the pulleys.

  5. #5
    So, improvements... Is a servo motor torque really linear from zero to rated speed?? I.e. will a 1.5kw AC servo really give me 1.5kw or 2Hp at 100rpm AND at 3000rpm or have i read it wrong??


    Would I therefore be better off just fitting a 1.8kw AC servo motor for the drive and connecting at 1:1 ratio??


    If it was correct then I would have full power from 1 to 3000rpm at the spindle - sounds ideal.


    Would this play well with my upcoming CSMIO/A conversion - would Mach3 give speed control and correct rpm readout??

  6. #6
    A problem...

    On the top of the fine-feed screw at the side, there is a screw behind which i think should be a spring and a little bone-shaped object - this bone has broken and the end is jamming the screw in the head which needs to come out. Its well and truly jammed in there.


    Any suggestions here?

  7. #7
    Quote Originally Posted by Davek0974 View Post
    A problem...

    On the top of the fine-feed screw at the side, there is a screw behind which i think should be a spring and a little bone-shaped object - this bone has broken and the end is jamming the screw in the head which needs to come out. Its well and truly jammed in there.


    Any suggestions here?
    That is actually very common on Bridgeports. On my KRV it was hollow. I removed it be jamming a pin in but you need to wiggle the depth stop screw a bit to release it.

    Another option would be to magnetise a paperclip?
    https://emvioeng.com
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