Re: Bridgeport Manual to CNC conversion...
Yeah seen those vids, its a nice tight job he did there. I modified my quill connector so that there is more meat below the screw - this takes the down thrust and eases the strain on the bolt a lot.
Tenths LOL, I love those discussions :) Having said that, i am really pleased how accurate my old girl is, plenty for my needs. Lately i had need to asses my probing accuracy, its only a basic probe with the three-point contact setup but i get repeatability of around +/-0.03mm which i think is pretty good for a conversion.
All good fun :)
Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
Davek0974
I was looking at those machines too ;) theres some good stuff on there at present.
The worst part with a BP conversion is the Z axis/quill drive - it has to be canted out in front of the quill and all the force must go through a single bolt into the quill - that bolt was never made to take anything more than a quill-stop :)
As the screw is driving the quill from one side there is a lot of axial twist moment on the screw which is not good, they work but i don't know how long for.
At the end of the day with a BP you take a machine worth maybe £3k, spend £8k on it and its worth maybe £3k - there is no return value here.
The return is you have an accurate machine which weighs 875Kg, has a small foot print, low current, spares are cheap second hand because so many were manufactured, many conversions have been done on Bridgeports and ballscrew drawings are available, if it breaks you can fix it.
Re: Bridgeport Manual to CNC conversion...
Of course, there is a value but you will never make money on a conversion.
Sadly the very flexibility of a Bridgeport is the downfall of a conversion - recently lost a fair bit of stock and time following a simple tool breakage, it was not working well, the homing position was off, just wrong, it took a while to discover that the small tool breakage had nodded and tilted the head by a few degrees in both axes!
It was only a small tool but must have bucked the head as it snapped, a fixed head machine with a table as big as the BP would be lovely but the height goes up due to having all the Z travel in the head not the knee and just won't fit :)
Lesson learnt - re-tram the head every time something happens!
Yes parts are plentiful, power is usable, rpm could do with being higher - currently running 1:1 3Hp motor at 4000rpm, I think she would take 5000 but the motor would not be happy so needs raising to maybe 1:1.5 ratio or so but then bottom end suffers and rigid tapping may not be possible, I was going to fit a servo drive up there but could not figure a suitable size unit that would give speed and torque needed.
Its a lovely machine though, helps even more as i spent so long using her in manual mode as well, get to know the sounds and feel of it so you can spot a CNC tool-path thats a bit over the top ;)
Re: Bridgeport Manual to CNC conversion...
Any reason not to go for this?
https://www.ebay.co.uk/itm/Bridgepor....c100005.m1851
Seller indicates its 2150mm to highest point. The newer interacts are too tall.
Thanks
Re: Bridgeport Manual to CNC conversion...
Looks reasonable, what can be seen of the ways looks good, will have ball screws, my only thought is the z travel but it can be worked with.
Re: Bridgeport Manual to CNC conversion...
The head on these cant be tilted over can they? Just realised, I can just about do 2150mm but the garage door is lower, fail.
Re: Bridgeport Manual to CNC conversion...
A smaller Harrison 600 has popped on another forum. Worth looking at, even for some manual milling (and perhaps CNC conversion)?
Re: Bridgeport Manual to CNC conversion...
Quote:
Originally Posted by
komatias
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!
Re: Bridgeport Manual to CNC conversion...
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.
Re: Bridgeport Manual to CNC conversion...
In the end, this is what I went for and is now for sale.
https://www.ebay.co.uk/itm/Bridgepor...torefresh=true