Bridgeport Manual to CNC conversion...

[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.

[John S]

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.

[Davek0974]

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.

[Davek0974]

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?

[komatias]

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

[Davek0974]

Hmm, just had a thought...

Instead of dropping around £2k on building a mini-mill/router, what I should have done is use that cash to convert the Bridgeport and fit an adaptor mount that enables me to hold the 24k water-cooled spindle - best of both worlds??

I could even mount a complete Z-axis on the rear of the ram where the slotting head should fit!

The BP has a lovely 48" bed, ok maybe it only has 9" of Y axis but thats still not too shabby I think, certainly I've done a hell of a lot of big jobs on the old girl.

So, what would the drawbacks be here?

The new spindle has the speed I need, I think a BP conversion can reach 4-5000 mm/min rapids which is where the mini-mill is set so thats no issue, ballscrews would provide the same accuracy as the mini-mill has presumably.

Hmmm......

[komatias]

You lose Z travel when you convert the bridgeport's quill and another bit more when you add the adapter to hold the high speed spindle. Apart from that, I cannot see any issues except the speed at which your motors are able to move the bed. Good lubrication is key here. 4-5000 is way to quick for stepper conversions but possible with good servos. I have restriced mine to 3000mm/min actually.

[V8kid]

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!

[Muzzer]

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.

[V8kid]

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