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Author Topic: Bridgeport Knee Mill Conversion?  (Read 159089 times)

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Re: Bridgeport Knee Mill Conversion?
« Reply #10 on: May 12, 2016, 01:17:09 AM »
Gary, i dont understand your point.  i also peck drilled when i needed to, easy with 15" of cnc "z" travel.  one job comes to mind 5/8" drill thru 6" of 8620 steel with multiple length drill changes, did a lot of these parts.  
another job 1/8" drill thru 12" of cast iron (6" from ea end, and parts held so they extended below the table) also with multiple drill changes made easily possible by the free quill and snapchange holder.  no chip wrapping took place.

when i bought my mill, bed mills were also available, but 25% more than the knee mill i bought.  if i had the $$ id have bought the bed mill, but i didnt have it.  so, like Dave, theres a knee mill project waiting for me in my garage.  im lucky enough to have ballscrews and axis motors in place and more, but from reading this community and looking back on my 40 yrs in all kinds of machine shops, imho a simple stepper mach 3 add on would be a huge improvement to any hand cranked machine, even with old acme screws with high backlash.  one of the reasons i chose the machine i did was it had handwheels.  after about a year, i dont think i ever used them again.  i was 12 years self employed before the $$ crash in 2008 forced me to take a factory job, had i chosen high end manual machinery for my start up, id have failed in a year or so.  cnc is so important.  you cant make a circle on a hand bridgeport or a .5 radius in a corner with a 1/4 endmill.  or cut a 43 deg line.  its harder if the machine is not optimized but its still possible.  cant do that with your hands.
« Last Edit: May 12, 2016, 01:20:14 AM by metlcutr55 »

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #11 on: May 12, 2016, 06:12:11 AM »
Good points there, I have made many large holes - the only way i could do them was to buy a boring head or two and drill with the largest bit i had then slowly cut myself outwards to the finish dia - a fair while when you only have a 1" drill and need a 4-1/2" hole! That would have been a doddle with even basic CNC.

I have a small job i run little batches of - cutting squares on the end of 1/2" rod, currently use a collet block and rotate 4 times - basic CNC would be only one rotation step as it could cut opposing sides easily at one setting.

Looking back, there isn't really much I do that is hand positioned - its all DRO work from zeroes - basically manual CNC stuff, if i want to throw some holes in something I use the pillar drill :)

I think i will dig deeper into this and get some prices for a ballscrew kit.

Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #12 on: May 12, 2016, 06:35:19 AM »
Am i right in my belief that if i want real-time display of position in Mach3, I would need to use servo's and encoders?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #13 on: May 12, 2016, 07:02:14 AM »
Am i right in my belief that if i want real-time display of position in Mach3, I would need to use servo's and encoders?

Depends what you mean by "real-time display of position in Mach3"
If simply wanting a display in Mach of position then you could just hook up glass scales and input to Mach set up as Encoder inputs. If using the parallel port then there will be a limitation to the frequency and thus velocity, think 25KHz would be about Max if I recall correctly.

If wanting to have the axis position DROs constantly updated from encoder feedback then you would need a controller capable of doing that.
The CSMIO/IP-A does that but you would need analogue command servo drives (most Industrial AC/DC drives are ).
The Galil, DSPMC, Hicon I think can also update the DROs but not sure if they are "real time".

Hood

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #14 on: May 12, 2016, 07:44:31 AM »
I was thinking something like the Centroid Conversion where you can still twiddle the table axis handles and Mach3 shows the position change as a DRO.

I guess its not critical, maybe best just to pull the handles off completely and go CNC only, no need to worry about DRO stuff then.

Having seen the ridiculous torque available from the little screws on my mini mill, would steppers with maybe 2-1 or 3-1 reduction be a viable option for a Bridgeport?

Just thinking out loud and looking at pennies etc.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #15 on: May 12, 2016, 08:21:57 AM »
CSMIO/IP-A does that, disable drives and move axes by hand and they track.
Only need to home once each time you start Mach, disable the drives and you may see the DROs change, Z especially on my Chiron, it moves a small amount until the brake grabs. X and Y occasionally move as well, tension releasing on belt I suppose.
If you do not have such feedback then every time you disable a drive you really need to re-home, same with E-Stop etc that is true whether servos or steppers.

My BP conversion I had 916 ozin steppers with 2:1 reduction, worked well for many years. Would I personally go steppers? Not a chance Servos all the way for me :D

Hood

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #16 on: May 12, 2016, 08:30:22 AM »
Similar power on servos?

Just looking at stuff to price up  research etc.


Thanks
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Bridgeport Knee Mill Conversion?
« Reply #17 on: May 12, 2016, 08:57:30 AM »
You can't compare torques of steppers with Servos at all.
750w servo 2:1 would be fine I would think, 1 Kw definitely. Have heard people saying 400w but I am sceptical about that small.
They will be much more expensive than steppers but once you have had good servos on a machine you will probably not want steppers again :)
I put 1.3Kw Allen Bradley MPL servos on my Series 1 CNC after I took the steppers off and it was probably way more than needed but I had them sitting there anyway.

Hood

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #18 on: May 12, 2016, 09:07:41 AM »
something like this...
http://www.aliexpress.com/store/product/New-Servo-motor-and-driver-set-2-4N-M-0-75KW-3000RPM-90ST-AC-Servo-Motor/314742_760999511.html

No details on the drive though.

The hardest part is the Z axis on a BP, no perfect solution just lots of workable ideas it seems.

Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

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Re: Bridgeport Knee Mill Conversion?
« Reply #19 on: May 12, 2016, 10:30:50 AM »
Hmm, just had a thought  ;) ...

Instead of my recently 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 custom 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 that's 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......stupid or not.....?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives