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  1. #1
    Anyone here converted a manual Bridgeport mill to CNC?


    After building my plasma table and my mini-mill, both of which are working lovely, I WANT MORE CNC ;) ;)


    My old 9x48 Bridgeport is looking for some love but is it worth it?


    It would need a ball-screw conversion kit, these are available, plus I am guessing servo drives on X, Y and Z so I have encoder display, the knee doesn't seem to get driven on the few vids i have watched so far.


    On the plus side, it's already powered via a VFD :D and i could likely recoup some cash by selling the working power feeds, control box and new DRO i fitted last year.


    Worth a look or too expensive/not good enough...

  2. #2
    Yes, done it to something similar.

    https://www.youtube.com/watch?v=M_VAXZbv6hc

    has cost me around £3000 in total by now but only using steppers plus the cost of the machine. £1500 for the ballscrews as I went full hog with high preload and C3 accuracy. Also went with £300 worth of angular contact bearings to suit. Would have gone servo's if funds had allowed then.

    Do not sell the DRO, I find it invaluable as you want to be able to switch between cnc and manual and also helps calibrate steps per unit.

    From what I read the kit ballscrews are not as good as you are made to think, hence I went with my own ballscrews.
    https://emvioeng.com
    Machine tools and 3D printing supplies. Expanding constantly.

  3. #3
    Don't bother.
    Sell the manual and buy a dead CNC.

    You have a machine that's currently worth about £900 ? you throw close to 2K at it and have a machine worth £800
    Look for a BOSS 1 to 4 or an MDI machine. These were made as CNC, ballscrews, pressure oiling, a really nice quill where the ball screw is actually around the quill and not an add on that just wants to lever the quill sideways.

    Downside of these machine which is in your favour is the electrics were crap, sorry make that $hit. Result is the iron is very good as ost have stood the last 15 years acting a shelf somewhere.

    Beaver V5 here sold for £650

    http://www.ebay.co.uk/itm/Beaver-V5-...-/182111147591

    TOS CNC mill sold for £460 OK not working but that doesn't matter for a refit.

    http://www.ebay.co.uk/itm/Tos-CNC-Mi...-/252353975743

    You could have got 1/2 of that back reselling the controller.
    John S -

  4. #4
    I think you might be right there John, it's being in the right place at the right time to catch the machines when they pop up, plus getting some transport arranged.

    Will keep looking.

  5. #5
    Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?

  6. #6
    Quote Originally Posted by Davek0974 View Post
    Am I right in my belief that if i want real-time display of position in Mach3, I need to use servo's and encoders?
    No, you can use optical encoders too. There is a screen out there that allows you to have 2 DRO's. However, you cannot use these as positional feedback in Mach3
    https://emvioeng.com
    Machine tools and 3D printing supplies. Expanding constantly.

  7. #7
    Quote Originally Posted by komatias View Post
    Yes, done it to something similar.

    https://www.youtube.com/watch?v=M_VAXZbv6hc

    has cost me around £3000 in total by now but only using steppers plus the cost of the machine. £1500 for the ballscrews as I went full hog with high preload and C3 accuracy. Also went with £300 worth of angular contact bearings to suit. Would have gone servo's if funds had allowed then.

    Do not sell the DRO, I find it invaluable as you want to be able to switch between cnc and manual and also helps calibrate steps per unit.

    From what I read the kit ballscrews are not as good as you are made to think, hence I went with my own ballscrews.
    Hi, Where did you get the ballscrews from and did it include a larger yoke?
    Cheers!

  8. #8
    I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

    Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.

  9. #9
    Quote Originally Posted by Muzzer View Post
    I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

    Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.
    Thanks for the info I have already converted my Series 1 to CNC using the standard acme screws and also removed the handles 'cos I was getting fed up with getting the occasional thump. By the way I'm with you on appropriate accuracy for outlay I paid £130 for my Bridgeport as it literally had fallen off a lorry and the head casting was cracked. Another £150 in used spares got me going and I've spent another £700 on the CNC conversion. So value.

    One thing that puzzles me is the wall thickness on the standard Bridgeport yolk. I can see there is enough meat to machine out from 32mm to 40 mm but there does not appear to be enough wall thickness for the securing bolts without breaking through the wall. How did you manage?

    I guess I could buy a 2505 ballnut and dismantle the X axis to see better but I'm pushed for time as we are moving house in the spring so any info would be highly appreciated.

    Cheers
    David

  10. #10
    Not sure where you get the 32mm figure from. The yoke bores are designed to take bronze cylindrical leadscrew nuts, as opposed to being directly threaded. On my Series 1 BP clone, the original X&Y leadscrews were 1-1/4" ie ~32mm OD. The actual leadscrew nuts themselves were pretty much 39mm OD and the DFU2505 ballnuts are 40mm OD, so I only had to bore the yoke bores out about 1mm on their diameters.

    As for fixing, there's really no need to use all 6 holes. I only fitted two M6 screws and there was enough meat for me to drill and tap the holes. If you look at the tensile load that would cause an M6 bolt to fail, you'll see that this wouldn't be the first link in the chain to break.

    Here's a bit about the actual boring: https://mightyshiz.blogspot.com/2018...or-larger.html

    And fitting the thing back on the machine. Note that the Y axis ballnut may foul something (I forget - possibly the knee lift?), which required some angle grinder action on mine.
    https://mightyshiz.blogspot.com/2018...allscrews.html

    Murray

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