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  1. #1
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,375. Received thanks 102 times, giving thanks to others 67 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: 17 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,375. Received thanks 102 times, giving thanks to others 67 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 10:12 PM.

  4. #4
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,375. Received thanks 102 times, giving thanks to others 67 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: 15 Hours 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 2,282. Received thanks 262 times, giving thanks to others 6 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.

  7. #7
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,375. Received thanks 102 times, giving thanks to others 67 times.
    Quote Originally Posted by m_c View Post
    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? :-)
    Hi, thanks for the info. I'm in two minds about the sizing. One part of me wants to get the machine running quickly and without too much fuss, so near bolt on replacements is nice. In terms of limits, assuming they work, is there still a concern?

    For E - Stop, depends how you wire it. If you use normal E Stop circuitry via the Acorn, you will likely just disable the drives (like what happens on Thor and CS Labs). You do not switch off anything else.

    Not a replacement for Thor, I dont think. The table is not as big as I had hoped for but it will do. The idea was to have something that can deal with big flat steel / hard metal plates for things. With Thor, it was designed for high speed alu type machining. I might make new brakes for Thor (motor mounts) on the Bridgeport. It was too good a deal to pass on and I've always wanted one.

    I could buy the replacement drives and run with the DC motors but Ive had DC motor issues before (Spindle on Triac) and not keen on that. I just want something that works reliably.

    A lot of the drives being shown are all the same manufacturer, so perhaps just find the best priced ones?

  8. #8
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 15 Hours 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 2,282. Received thanks 262 times, giving thanks to others 6 times.
    Quote Originally Posted by Chaz View Post
    Hi, thanks for the info. I'm in two minds about the sizing. One part of me wants to get the machine running quickly and without too much fuss, so near bolt on replacements is nice. In terms of limits, assuming they work, is there still a concern?

    For E - Stop, depends how you wire it. If you use normal E Stop circuitry via the Acorn, you will likely just disable the drives (like what happens on Thor and CS Labs). You do not switch off anything else.

    Not a replacement for Thor, I dont think. The table is not as big as I had hoped for but it will do. The idea was to have something that can deal with big flat steel / hard metal plates for things. With Thor, it was designed for high speed alu type machining. I might make new brakes for Thor (motor mounts) on the Bridgeport. It was too good a deal to pass on and I've always wanted one.

    I could buy the replacement drives and run with the DC motors but Ive had DC motor issues before (Spindle on Triac) and not keen on that. I just want something that works reliably.

    A lot of the drives being shown are all the same manufacturer, so perhaps just find the best priced ones?
    When was the last time you checked all the limits were working on your machines?
    With modern AC servos, limits aren't as high priority as they used to be, as if an encoder fails, the drive should realise it's outputting the AC to get the motor to move, but it's not seeing the encoder move, and fault out.
    With DC servos, the drives have to rely on the controller realising there is an encoder problem, but often by that point they'll of run into a limit switch, as the drive will of been outputting an ever increasing voltage in the hope the encoder moves, not knowing the motor was still moving at an ever increasing speed.

    My concern of using more powerful servos than what was originally fitted, would be potential damage should you do something stupid while using the machine. I know you could always lower peak current, but I'd personally put in the extra effort to mount smaller servos, than cripple bigger servos.

    E-stop is always a bit contentious. Personally for CNC machines, I prefer that all drive power is ultimately cut in e-stop. It might not cut immediately (I'd guess the BST drives have a switch mode supply running from the mains, and not the main DC capacitor bank, so would need power to remain on to control a fast stop), but I'd want it to cut as soon as practical. The chances of a drive failing in use are pretty slim, but it's more for during setup, where a wrong setting could cause a runaway. Plus in future, you never know what/who may be changing things they shouldn't.


    DC servos do work well, but you need to weigh up the benefits/costs of drives for them. They do need maintenance (clean out, and new brushes occasionally).
    If you still had the original servo amps, then it would make economic sense to go with a suitable +/-10V controller, especially as they've already got quadrature encoders fitted, then swap them out for new AC servos as and when needed. However the cost of suitable drives, is likely to be not much less (possibly even more...) than new cheap AC servos and drives, so the economics don't really make much sense for spending money on drives for motors that might not be working correctly.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  9. #9
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,375. Received thanks 102 times, giving thanks to others 67 times.
    Acorn control board and MPG ordered yesterday, so getting ready to start retrofitting.

    I managed to get a quote from DMM. Great company, quick response.

    They have a Nema 42 replacement motor (fairly new, released a few weeks ago). My motors (According to them) are Nema 42.

    The ones they are proposing are same shaft size which is very helpful (5/8th inch) as I am struggling to find direct replacement pulleys with 12 and 13 teeth respectively (14 is minimum generally).

    The issue is the motors are not a perfect fit (mounting holes are a bit different - 75 PCD vs 82 PCD, probably minimal effort to sort this but they are fairly pricy and potential import tax from Canada. These are 1.3 KW servos, running off 220V (so high volt feed). Including 3 meter encoder and motor cables plus the Acorn DB 25 cable and programming lead, these work out at around £500 ish per axes.

    I know the stuff from BST Automation and other sources listed are cheaper. Id like to have as little mechanical fuss / changes to make this all work (most seem to have 19mm pulleys), so modifications will be necessary but it looks like exact like for like change, so mods will have to be done anyways.

    Thoughts?

  10. #10
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 15 Hours 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 2,282. Received thanks 262 times, giving thanks to others 6 times.
    DMM sales are always very quick to respond.
    Their tech support, not so quick. There have a been a couple guys using KFlops that have had issues. One just couldn't get a drive to tune in analogue mode until he fitted their suggested mains filter, yet all the other drives were fine without the filter, and the issue moved with the drive, not the wiring.
    Somebody else blew a drive up within seconds of turning it on, which was apparently due to being over-voltage, and due to them not fitting the recommended mains filter they wouldn't warranty it, yet the other drives never failed.
    Plus they use capacitive encoders.

    Their big advantage as you've discovered is they've specced the motors so they're far more likely to be a drop in replacement for old stepper motor systems.


    Personally if cost was the main concern, I'd opt for cheap Chinese.
    What tooth profile are the pulleys?
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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