Hello Guest it is September 17, 2019, 11:44:32 AM

Author Topic: Bridgeport Knee Mill Conversion?  (Read 159015 times)

0 Members and 1 Guest are viewing this topic.

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #30 on: May 13, 2016, 03:36:11 AM »
thanks,

I think height is going to be the killer, they are just too tall to fit in :(

Its looking like my only option is to retrofit the standard machine, the two main stumbling blocks on that appear to be the cost of the screw kit and the way the quill is driven.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Bridgeport Knee Mill Conversion?
« Reply #31 on: May 13, 2016, 03:53:34 AM »
Heres a few pics of the way I did the Z on mine, it left access to the tilt bolts which I probably never even used after I CNC'd :D
Hood

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Bridgeport Knee Mill Conversion?
« Reply #32 on: May 13, 2016, 03:54:33 AM »
Some more.

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #33 on: May 13, 2016, 03:59:13 AM »
Thanks, that seems to make sense, what sort of screw dia on that ?

I gather a smallish motor is only needed on the Z?

Still not sure as to stepper or servo, read good things about both, servo's do seem better but at cost.

Also still have to find a screw conversion kit.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #34 on: May 13, 2016, 05:01:45 AM »
Thanks Hood, looks good.

I know there is one in there, but the top thrust bearing seems to be hidden??
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Bridgeport Knee Mill Conversion?
« Reply #35 on: May 13, 2016, 05:20:46 AM »
Stepper on Z was 400 ozin or so if I recall.

Steppers work fine if you don't mind max rapids of about 2500mm/min and accel of maybe 150mm/s/s max, or at least that is the most I could get.

Thinking of servos then look on eBay at Samsung Servos, guys in Korea usually selling them at a reasonable price second hand. I had a 400W one on the wee lathe and they are decent drive/motors, made by Samsung/Allen Bradley in Korea.

The top bearing was just a standard bearing sunk into top plate, two angular contacts in the bottom bit.

Recess in the back of the upright plate was to align to the head as the section of the head that is milled away is seeming the bit that is done first and quill is bored to that.

Hood

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #36 on: May 13, 2016, 05:30:26 AM »
Sounds good, yes this two registers on the front of the quill are for position references.

As for speeds, does it really matter on a mill? Most of my cuts are way lower than that as the motor speed is pretty low anyway.

Does acceleration make a difference?

Will check out the servos and thanks again for helping so much, its looking interesting now.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #37 on: May 13, 2016, 06:27:23 AM »
Just had a lengthy chat with my supplier of bits and they seem to favour heavily 8NM stepper-servo's for this task. The specs read well, basically a closed loop stepper and DSP drive with variable current etc. Price was about £250 per axis for motor and drive/cable.

Being stepper also means i can use my existing knowledge of BOB's and USB motion controller etc.


More options to throw in the pot.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline RICH

*
  • *
  •  7,358 7,358
    • View Profile
Re: Bridgeport Knee Mill Conversion?
« Reply #38 on: May 13, 2016, 07:19:34 AM »
Davek0974,

Link below just for thoughts....it's for the Z on an Atlas mill.

http://www.machsupport.com/forum/index.php/topic,7396.msg127816.html#msg127816

One pic shows the Z driven by using a small stepper ( 80 in oz) using the Z fine feed.
That was no good / don't do as you end up with backlash. Similar to what Hood posted is a 500 inoz 23 stepper mounted to a plate which is attached to the mill head. There is a preload bearing in the mounting block and have no backlash.

Acceleration can become important...ie; For 3d milling you can a have a lot of small
moves in combination moves.

Size wise, the experience from reliable users for stepppers / motors  which provide satisfactory service for "what you want to do" for a "very" similar sized machine is good advice.

If one were to "design" what they want, they would define desired  preformance,calc's would be done, consider experience of others, etc. That will provide confidence in what will be done. It gets rid of the subjectivity in doing the conversion.
Today there are manny programs to assist in doing design as compared to years past
where all was done manualy.

Just some thoughts....

RICH

Offline Davek0974

*
  •  2,577 2,577
    • View Profile
    • DD Metal Products Ltd
Re: Bridgeport Knee Mill Conversion?
« Reply #39 on: May 13, 2016, 07:47:22 AM »
Nice job there, thanks.

The Z always seems to be the weak link on conversions from what i have been reading.

I am liking the idea of closed-loop steppers, the drivers can ramp the current up/down depending on the load so if there is a tight spot which you get on worn machines it will ramp up to overcome it, if it still can't then it faults out, normal steppers would just stall.

2:1 or 3:1 reduction on X&Y ?

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