Build a new head for a BP series 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

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.

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??

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 )

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.

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?

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)

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.

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

Ok, thanks.

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