Bridgeport CNC (Factory, non retrofit?) Knee Mill Qs
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  1. #1
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    Default Bridgeport CNC (Factory, non retrofit?) Knee Mill Qs

    Hello All,

    I am going to see a few items for sale today that are needed in my shop (mainly some steadies that fit my long bed CNC) and the owner of the shop, who is quite old and retiring/downsizing sent me some pictures of this knee mill he is trying to sell. His son is actually handling these sales. I was not planning on getting a CNC knee mill - just a standard Bridgeport, or similar, but now I am somewhat interested as I am comfortable with CNC controls for the most part, and this machine looks great in pictures. Of course, pictures are often misleading regarding condition of machines... but I'm wondering if anyone of you can confirm if this is a Bridgeport OEM CNC or a retrofit. If Bridgeport OEM controls, does anyone have anything good to say about this machine and its controls. I have NOT heard good things in my internet readings regarding Bridgeport control systems IN GENERAL, but I don't want to dismiss this machine because I have read a few threads in the past. Does anyone know the model? I am hoping there is a better nameplate in person - I will find out this evening.

    Asking $4500 for the machine - and because I know nothing about the controls the price does not mean much to me yet.

    Thanks for any thoughts or advice.

    EDIT:****sorry about the pictures, trying to figure that one out here.
    img_7896.jpgimg_7895.jpgimg_7894.jpgimg_7893.jpg
    Last edited by rollerman13; 06-30-2020 at 08:22 AM. Reason: noticed pictures are sideways!

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    I don't know anything about that control but I do have experience with old cnc knee mills.

    When buying a machine like that I always assume it will need a control retrofit. I then base the price off of the rest of the machine's components.

    From then on, everyday that the old control powers up and continues to run is considered a bonus.

    25-30 year old electronics just don't have a predictable lifespan. Leaky electrolytic capacitors, poor solder joints, broken traces, ect. Something will eventually take the system down and replacement parts are stupid expensive.

    For what it's worth, the machine does look like it was taken care of pretty well. It also doesn't appear to have ever run coolant which is a good thing.

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    Thanks for that bit of info. I will heed your advice - I don't think I am willing to go through a control replacement as there are plenty of other projects going on around here. I can imagine the cost of the control system replacement could surpass the cost of the entire machine (although perhaps not as these knee mills seem pretty straight forward).

    Garrett

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    I think that is an original OEM Bridgeport arrangement, the control is some pc-based "VXT" or something like that (had read up on those years ago). However, it is not like the Heidenhain Interacts, as it has the pivoting head, standard table, and different servo mounting etc--it's sort of a pseudo-CNC-kneemill conversion. Bridgeport had so many versions of hardware and software on knee-mills, and fixed-head CNC's it's mind boggling. I will say that I've had a one of the fixed-head Series 1 Interacts for about 7 years (circa 1995, Heidenhain TNC 2500 control), and that is built like a tank (for a CNC Knee-mill), and has been very reliable. I have extra drive boards, and the other electroncis (CPU, relay boards etc), don't have a single electrolytic cap on them that I can find. Last I heard, you could put an upgraded Heidenhain control on these (whether worth the cost is another questions). There seem to be quite a few of the TNC's/Interacts still alive, but don't see many of those PC-based conversions or pseudo-conversions. The mechanical parts on the fixed-head bridgeports are good, and they used that base mechanical design for lots of different controllers and versions over the years--the old Boss machiness with steppers all the way to the servo Heidenhain TNC's till about 2000 or so.

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    That looks like a Bridgeport DX32 control.
    PC based, using servo motion board.
    My friend has some Bridgeport VMCs using that same control (486 CPU, Siemens drives).
    Old control, but versatile and at least PC parts are available. Easy to change to an LCD, swap old hard drive out for an IDE SSD (DOM), ...

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    Looks like a V2xt with a Boss control. Generally speaking the control is so unreliable that the iron is in great shape. There is only one place in the states that will work on the axis drive motors $$$ EMI supports the control. All you have to do to get them to help you troubleshoot it over the phone is give them your credit card number. I finally got tired of spending 1000.00/month keeping mine running and retrofitted it with a Centroid control. I can't say enough good about the Centroid, super easy to program it is great. Expensive, yes but worth it.

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    Quote Originally Posted by moonlight machine View Post
    Looks like a V2xt with a Boss control. Generally speaking the control is so unreliable that the iron is in great shape. There is only one place in the states that will work on the axis drive motors $$$ EMI supports the control. All you have to do to get them to help you troubleshoot it over the phone is give them your credit card number. I finally got tired of spending 1000.00/month keeping mine running and retrofitted it with a Centroid control. I can't say enough good about the Centroid, super easy to program it is great. Expensive, yes but worth it.
    What was failing most/most often?


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by rpseguin View Post
    What was failing most/most often?


    Sent from my iPhone using Tapatalk
    I had lots of trouble with the axis drive motors, they had an encoder built in for which no parts were available to John Q Public. The only place that would work on them was in Chicago. They would decide whos motor to fix first by how you shipped it to them! So if you next day aired your 50 lb motor you would get reasonable turn around and if you mailed it you could get it back in a month or so. I ended up buying spare motors. Everything in that giant cabinet was a failure waiting for a time to die. I replaced all the axis drive boards one at a time.
    I replaced the motherboard once as well. The last straw was when it once in a while would do an uncontrolled X+15.0" move. EMI said it was a bad x axis motor cable, 900.00 please! I said no chance, bought my Centroid kit, did a deal with EMI to sell them all the electronics and axis motors for 4000.00 OK great except when it was time to cut the check they would only pay 2000.00. I don't even want to know how much I spent on all those parts I sold back to them.

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    Default Bridgeport CNC (Factory, non retrofit?) Knee Mill Qs

    Quote Originally Posted by moonlight machine View Post
    I had lots of trouble with the axis drive motors, they had an encoder built in for which no parts were available to John Q Public. The only place that would work on them was in Chicago. They would decide whos motor to fix first by how you shipped it to them! So if you next day aired your 50 lb motor you would get reasonable turn around and if you mailed it you could get it back in a month or so. I ended up buying spare motors. Everything in that giant cabinet was a failure waiting for a time to die. I replaced all the axis drive boards one at a time.
    I replaced the motherboard once as well. The last straw was when it once in a while would do an uncontrolled X+15.0" move. EMI said it was a bad x axis motor cable, 900.00 please! I said no chance, bought my Centroid kit, did a deal with EMI to sell them all the electronics and axis motors for 4000.00 OK great except when it was time to cut the check they would only pay 2000.00. I don't even want to know how much I spent on all those parts I sold back to them.
    Thanks for sharing!
    Sounds frustrating!
    My friend has a pair of Bridgeport VMC 760/22 with DX32 controls and Siemens drives.
    They have been pretty solid, but they aren’t used as production machines.

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    Quote Originally Posted by moonlight machine View Post
    Everything in that giant cabinet was a failure waiting for a time to die.
    A perfect description. It sounds like we both learned this one the hard way and came to the same solution.

    Mine was my first mill - an Anilam Crusader M control plagued with issues. I spent well over 40 hours in just reading and watching youtube videos learning how to repair 30 year old electronics. I spent more time working on that control then I did running the machine!

    After the 3rd time something in the cabinet "let the magic smoke out", I refused to even find out what happened. I parted out the Anilam, sold my spare parts stash and bought a Centroid allinone DC board.

    I have $4650 in my retrofit. I did get some of that back from selling my Anilam parts but the time lost will never be recouped.

    This is a short summary of the events that lead me to develop the standard from my previous post when buying any old cnc equipment.

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    IMO, I'd find a fixed head BP to retrofit; the hardware is solid on those, and they used it for many years in lots of variations and controls. It's probably about as good as it gets for knee-mill CNC hardware with moving quill, and was designed specifically as a CNC machine, not a hybrid or 'conversion'.

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    Quote Originally Posted by car2 View Post
    IMO, I'd find a fixed head BP to retrofit; the hardware is solid on those, and they used it for many years in lots of variations and controls. It's probably about as good as it gets for knee-mill CNC hardware with moving quill, and was designed specifically as a CNC machine, not a hybrid or 'conversion'.
    What I want is a 3 axis CNC/manual bedmill like a Trak DPM RX3 or something similar, so sprung handles on X and Y and a quill handle, but also a CNC controllable moving column for Z instead of cranking a knee.

    But, I’m nowhere near being able to afford one of those and my truck is misfiring, so I’ll just keep biding my time and saving my pennies and keep my eyes peeled for an affordable one or a retrofit candidate.

    How much is/was a 3 axis Centroid system?
    What if I already had servos and drives? AC servos?
    Do they support manual mode?

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    Call or email them: CNC Controller for Bridgeport V2XT DX-32 CNC retrofit controls for Knee mills.

    $.02 worth - it does look pretty much like a V2-XT, which I used for years in a university setting. No problems with electronics during that time, although it was bought new.

    If the machine you looked at is fully functional at the moment (the screen looks surprisingly good), and the price comes down to reflect the issues with repair cost risks, I'd grab it for around $3.5K or so. Yes, you'd have to gamble a bit, but if it demos well and can be moved safely, you can do some pretty good work on them.

    The Faraday Cup detectors on WIND (image upper right: The WIND-SWE Instruments Page - MIT Space Plasma Group) were made by me from Mg (gold plated afterwards), and are extremely lightweighted despite being made mostly of magnesium. Lots of undercuts, tapered sections, and very close tolerances for keeping the various tungsten mesh detection elements properly tensioned and oriented.

    A rough schematic of the cup is shown further down the page, but it doesn't give a hint of the complexity of the actual parts.

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    Quote Originally Posted by rpseguin View Post
    What I want is a 3 axis CNC/manual bedmill like a Trak DPM RX3 or something similar, so sprung handles on X and Y and a quill handle, but also a CNC controllable moving column for Z instead of cranking a knee.

    But, I’m nowhere near being able to afford one of those and my truck is misfiring, so I’ll just keep biding my time and saving my pennies and keep my eyes peeled for an affordable one or a retrofit candidate.

    How much is/was a 3 axis Centroid system?
    What if I already had servos and drives? AC servos?
    Do they support manual mode?
    No Idea what the current price for a Centroid control is. When I did mine I bought the best one they had with all the bells and whistles and most of the options as well. I had lots of work for it and no time so
    I bought the plug and play control. If you are handy with computers and such I hear you can do the whole deal on the cheap.

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