Bridgeport Manual to CNC conversion...

[Davek0974]

Hi all,

been a while since this thread

For those who don't know, my Bridgeport was rebuilt with servos and larger motor, plus i added an auxiliary high speed spindle for aluminium work. The job in hand is shown in the pictures below, 5mm Aluminium, lots of holes and intricate features. I use 2mm single-flute and 5mm single-flute carbide tools for these.

Previously, I had already built a custom mini-mill to make these (and learn CNC) and still have this (its currently up for sale but no takers yet).

My reason for adding the aux spindle to the Bridgeport was two-fold - one, to save space and two, to make more use of the very expensive Bridgeport conversion which would otherwise only see intermittent use.

Now, when doing these on the Bridgeport, I am seeing bad vibration or chatter on the tool, it appears to be vertical oscillation but tonight also suffered bad enough radial oscillation to break a 5mm tool ! When it goes into oscillation it makes you jump as its very noisy and you instantly know it will end badly either in poor finish or broken tooling. Tonight I was testing tool sent from my supplier as a "Better" option this was a two-flute carbide, probably the reason for the breakage as two-flute tools need a more rigid setup.

So, something is not happy - my reservation is the spindle mount (shown below) - its canted out over to one side and although it's clamped to the quill and into an R8 collet in the main spindle, it must be allowing deflection from the cutting forces.

Ok, so I have a bad situation, is there a way forward here?

Obviously I can take the dust-sheets off the mini-mill and carry on but I just don't have the space long-term and wanted to make more use of the Bridgeport as mentioned. I really want a one-size fits all solution here.

If I run the small tooling on the BP main spindle at 3000rpm (top whack) the run time per part-set will go from about 30minutes to several hours probably - feed rates go from 900mm/min to 25mm/min so i don't think thats an option - it needs more RPM's.

What can be done here guys???

Spindle-speeders?? I have seen these but they have mixed reviews and i doubt they would like a 5mm tool much as mostly used for engraving etc.

One idea I quite like is to spin the ram on the BP around and build a custom Z-axis completely, and mount it where the BP slotting head normally sits. This could be built as heavily as desired with linear guides and a servo or stepper etc.