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  1. #1
    I have a Bridgeport manual mill which i converted to CNC with servos, CSMIO control etc and ball-screws on the axes.

    I now have a really nice lower half of a CNC with good positioning accuracy and the large table i like plus lots of easy access and so on.

    The downside is the spindle/head - this is poor TBH and rattles (dog clutches gone) plus there is a vibration (maybe a bowed spindle spline but runs true at bottom.) The spindle is a QC/BT30 with drawbar.

    The knee is currently my B axis and is coded in Mach3 to take tool length compensation.

    My question is this - is it practical to rip the whole head off from the swivel ring on the base column upwards, bin it, and build a proper CNC Z axis to bolt on in its place?

    I am thinking maybe a steel plate weldment with HiWin rails, servo motor plus an ATC cartridge spindle - this would remove the wobbly/weak knuckle joint and give a decent Z travel which the BP lacks badly in, it will also remove the Quill, splines, clutch and so on from the drive.

    I currently have a large 3Hp AC motor on her, running 1:1 toothed belt under VFD/program control but that only gives me 4000rpm so would like some more. Maybe fit a 3kw (or more) AC servo drive.

    I can't fit a "proper" cnc in due to a low roof and low power(home shop business) so looking to mod the old girl if it was a viable proposition.

    Any tips much appreciated as always.

    Thanks

    Dave

  2. #2
    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.
    Most things are doable given enough time and money.

    My biggest concern with swapping that much cast with steel, would be resonance, however given the multiple tilts/swivels/nuts/bolts that already exist between the base and head, it will probably be an improvement.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  3. #3
    Yes, if needed it could be resin filled in the riser section maybe?.

    Its a crap-shoot i guess - was thinking 12mm plate, welded into box style weldments - big one for the swivel connector and riser section finishing in a vertical plate for the Z slide carriages. Then a box style extender starting with the Z rails and then motor/spindle cartridge.

    I guess it will need a medium/high pre-load rail set to ensure no slack in Z axes, good quality stuff and a decent screw to lift it all, maybe counterbalanced as well??

  4. #4
    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 would of thought a ribbed design would be better for the main section. That way you could get a reasonably nice L/Boomerang type shape going from the main body up to the vertical surface for the rails.

    I could be wrong, but I have something in my mind telling me U-shapes are just about as good as an enclosed box section, but it's not really something I know that much about.

    I think given the size and potential cost of the project, I'd be spending some time drawing things up in 3D software and running some FEA to see what works/doesn't work. A counter balance might be a reasonable idea, but a couple gas struts would probably be enough and reduce complexity. A quick google shows struts are available with up to 2500N (~250KG) force for not that much money (14mm rod with 500mm of stroke is available for 40+VAT from - https://gasstruts.metrol.com/fixed-f...ut-f-sd04.html )
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  6. #5
    Just to throw you a slight curve ball,

    I have a manual series 1 that I fully stripped and rebuilt a few years back, so I an very familiar with it.

    I recently purchased a series 1 interact.
    The head and 90 bend casting, bolt onto a std serues 1 column, with rhe usual 4 bolts ( and 2 dowls).

    If you can find one, it should go straight on. And they are usually QC 30 too��.

    They are a variation of the vari speed head, but most people (my self included at some point) pull out the vari pulleys and fit timming pulleys. ( usually 2:1 ratio unless you alsways want increased high speed. Possibly uprate bearings too) and speed control via VFD, controlled by CSMIO ( as you probabky already do.


    Also, fit the auto oiler too, id you go this kind of direction.

  7. #6
    Thanks, thats an interesting thought. Not sure it will get me where i want to be fully though as the head still uses a quill so has the usual splines etc and no option of an ATC IIRC?

  8. #7
    Ok 1 more thought....
    The 90 bend casting has a flat verticall face.
    This woumd make a good solid mount for anyrhing you could bolt to it. And if it's from a scrapper, it will be one if the few parts that could not be worn.
    A much more solid option than the ram and knuck joint affair.
    ( but then you loose the tilt option if course)

  9. #8
    That sounds good, i've been trying to find a picture of the part in question but not got one yet.

    I need the vertical face to be way back where the front of the round column/body is in order to get a decent linear rail system in as well as a motor and a spindle cartridge.

  10. #9
    The vertical face comes forward by 32cm from the top round part of the column.

  11. #10
    Ok, thanks.

    Its way too far out for my plan to work on that, good idea though.

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