BPort Series I and VFD questions


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Thread: BPort Series I and VFD questions

  1. #1
    Registered NeoMoses's Avatar
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    Question BPort Series I and VFD questions

    I'm looking at buying an older series I bridgeport and I have a few questions. First off, I've noticed that the J-head machines tend to be considerably cheaper than the 2J heads.

    If I'm correct, you must manually change belt positions on the J head, and the 2J has the adjustable knob with a Hi and Low range, right?

    I don't have 3-phase available, so I will need a phase converter. I've heard that you can vary the speed of a 3-phase electric motor with a VFD, so I stumbled across the Mitsubishi S500. Does that look like it will work?

    I've heard of the ability to "overdrive" motors if using a VFD like the S500. As I understand it, if I run the VFD at 120 Hz, the motor will be spinning twice as fast as it was designed to, right?

    Can a Bridgeport motor handle this? Does this damage the motor or any other part of a milling machine?

    I'm thinking about getting a less-expensive J head bridgeport, then and using a VFD to do most of my speed changing, leaving the belts in one of the higher gears. I mostly cut aluminum, so I believe this should work, and if I have the ability to overdrive the spindle, that would be great! If I'm correct, the maximum (standard) spindle speed for J heads is 2720 RPM. 5000+ RPM would definately be nicer for aluminum!

    Feel free to correct me if I'm wrong, offer me advise, or point me in the direction of good, inexpensive milling machines and VFDs.

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    Member HuFlungDung's Avatar
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    Hi NeoMoses

    Yes, you can run the frequency as high as you dare

    There are the usual mechanical hazards of running a motor at an rpm higher than it was balanced for, of course, and this includes the rest of the drive train on the mill head, too.

    Normally, there should not be too much trouble up to the 3600 rpm, since many motors are built for that speed. The quality of the motor's insulation has to be good, as frequency spikes can stress the insulation, and cause an eventual motor burnout.

    For single phase in, 3 phase out, you need to buy a Variable Frequency Drive that is approximately double the hp of what you would need if you had 3 phase input.

    I've retrofitted VFD's to various machines without problem. It is really nice to have the variable speed control available for your cnc to command.

    Have you checked Ebay for used mills? There are some real bargains there, if you have the means to do some retrofitting and repair.

    First you get good, then you get fast. Then grouchiness sets in.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Registered NeoMoses's Avatar
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    what about this machine? I've never heard of a "Santec" milling machine, but it's got a BPort head.

    It looks to have about the same travel as a standard Series I knee mill, but has a much higher table load. Anyone have any experience with these?

    My name is Electric Nachos. Sorry to impose, but I am the ocean.
    http://www.bryanpryor.com

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Member HuFlungDung's Avatar
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    Do you want cnc?

    There are some good deals to be had buying used, complete with ballscrews, etc, even if you have to put a new control on it.

    To buy a manual machine and convert it, is likely not the cheapest route.

    There was a Wells-Index cnc mill on ebay with an old Bandit controller, maybe it will get re-listed. I have one of these machines, and it is a decent machine, with a good quality Z "quill box", and precision ballscrews all over (as far as I know). Some of the retros have quite a chicken sh!t connection from the quill to the Z ballscrew. You don't see this until you get it home, though.

    First you get good, then you get fast. Then grouchiness sets in.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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BPort Series I and VFD questions

BPort Series I and VFD questions