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  1. #1
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 1 Week Ago Has been a member for 9-10 years. Has a total post count of 1,600. Received thanks 110 times, giving thanks to others 69 times.
    Bought a lovely machine from Norman12, thank you once again.

    Time to start the conversion. Ill get some pics up later of what I have. I dont expect too much to happen whilst its cold as my garage is not heated.

    Starting questions, I will likely go Centroid Acorn, gives me the ability to have a stable platform driving the 3 (and 4th axis later) as required.

    Electrics - original SEM DC motors, have been converted to better encoders. I'd love to use these however I need to find suitable drives, hope that works and be left with possible future maintenance issues. The SEM motor (not sure if they are all the same), grabbed the first one I saw uses a MT 30H-44, stall torque of 2.1 NM which is very low. Anything modern should be much better? MAX RPM is 3100, 140 V and 'Pulse Amps' of 26.

    I also plan to use a VFD on the spindle, Norman12 has done some conversion already but would like to mount the spindle motor low if possible to save roof height.

    I'm aware there are a set of motors / drives for sale on this forum which might suit, the seller is slow to respond and its late December anyways, so can wait.

    Has anyone been able to put a set of wheels under a Bridgeport for moving it around a workshop? Ive got massive wheels under Thor but my worry is that it as a lot more height.

    Thanks

  2. #2
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 1 Week Ago Has been a member for 9-10 years. Has a total post count of 1,600. Received thanks 110 times, giving thanks to others 69 times.
    The motor specs are 0.65KW, 3100 RPM, 2.9 NM stall. I reckon a 0.75 or 1.5 KW servo would be a good replacement. Thoughts?

  3. #3
    Hi Chaz,

    Not sure if this helps you any.....

    I chose these in the end. ( the Std SEM motors on mine were 3.2 NM. They worked pretty well too)

    £176.12 50%OFF | 90ST-M04025 220V 1000W AC Servo motor 4N.M. 2500RPM 1KW servomotor Single-Phase ac drive permanent magnet Matched Driver
    https://s.click.aliexpress.com/e/b1hpQbat

    Physically much smaller than the SEM originals.

    Shafts are same OD ad SEM, but a bit shorter, so I will probably have to make some custom timing pulleys with long spigot ( at least for Z axis anyway).

    In hindsight, the 1.8KW version has a longer shaft and is still smaller than the SEM motors. ( but I am also mindful of electrical max demand of machine)

    Regards

    Mark
    Last edited by swarf-boy; 20-12-2018 at 11:12 PM.

  4. #4
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 1 Week Ago Has been a member for 9-10 years. Has a total post count of 1,600. Received thanks 110 times, giving thanks to others 69 times.
    Quote Originally Posted by swarf-boy View Post
    Hi Chaz,

    Not sure if this helps you any.....

    I chose these in the end. ( the Std SEM motors on mine were 3.2 NM. They worked pretty well too)

    £176.12 50%OFF | 90ST-M04025 220V 1000W AC Servo motor 4N.M. 2500RPM 1KW servomotor Single-Phase ac drive permanent magnet Matched Driver
    https://s.click.aliexpress.com/e/b1hpQbat

    Physically much smaller than the SEM originals.

    Shafts are same OD ad SEM, but a bit shorter, so I will probably have to make some custom timing pulleys with long spigot ( at least for Z axis anyway).

    In hindsight, the 1.8KW version has a longer shaft and is still smaller than the SEM motors.

    Regards

    Mark
    Thanks Mark.

    They look identical to these and similar to what JazzCNC has reviewed.

    https://www.aliexpress.com/store/pro...33e437083PnCNp

    Have you tried yours yet? I dont mind a bit of bracket modification, can do alu on my other mill but dont want to put major changes in if not needed.

    Would you get the 1.8KW instead?

  5. #5
    Hi Again,

    All I was getting at, was that by being mindful of max amps and trying to stick to a similar power motor, I have ended up with a little more mechanical work to do ( not the end of the world really, I have a Colchester lathe and a manual series 1 and dividing head).

    But if max amps were not an issue, I would have gone to motors with a shaft that better matched, that way, I could just slip on the original pulleys.
    Part of the issue for me, is that my pulleys are like new. Also Bridgeport use imperial pitch pulleys, so they can be pricey to buy. ( I could not just swap out the Z axis screw pulley for a metric version either, without pulling the head apart.)


    Yes I have the motors. 7 day delivery ( don't use Fedex, as they bang extra charges on and DHL is cheaper, anyway if purchasing multiples).
    The people at Master Jiang Store converse very well in good English too, so that helped. ( most helpful people)

    Motors also have nice long leads too (3M. Longer available also). Encoder covers are alloy. Cable plug and sockets are metal too.
    Drives have been hand sealed on PCBs too, which I liked.

    I have powered them up, but not had them moving yet, as my 24V PSU has not arrived yet.

    Regards

    Mark

  6. #6
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 2 Days Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,908. Received thanks 360 times, giving thanks to others 8 times.
    I'd aim for servo's similar power wise to what was fitted, as too big has the potential to do a lot of damage if things go wrong. I got told from a very reliable source that those interacts will handle the original servos running the axis into the end stop without doing any damage, if something does go wrong.

    Plus you want inertia to match somewhat, as too big an imbalance can cause tuning problems. I was advised 110 would be better for my Shizouka which is a couple hundred kilos heavier than a Bridgeport.

    One thing to be aware of with the cheap Chinese servos, is they use mains voltage for control power, so if mains power gets cut i.e. due to an e-stop, you've lost position. It's not the end of the world, but one of the things I like about my lathe is the position never gets lost during an e-stop, as the encoders are permanently live.
    If you want a copy of the BST servo manual, drop me a message, and I'll email it over.



    Oh, and is this a potential replacement for Thor, or are you just wanting to burn a few more KW to help keep the workshop warm? :-)
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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