Re: Bridgeport servo motors

I have the motors but have not yet converted the mill. It is
a 1969 variable speed and I am in the process of rebuilding the
entire mill. Probably be back together and running (without
conversion), in about a month. Like I said before, someone on
the list used these same motors on a Rong Fu direct drive and they
said they worked OK, but were at their limit. I figured I would
gear them down 3:1 and give the extra torque to make them work
good on the Bridgeport. I don't think 80 in/min will bother me.
It is still a Shi* load better than turning the cranks by hand!

Scott




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "braidmeister"
<braidmeister@y...> wrote:

>
> Scott,
> What are you using, Ameteks? Have them running yet? Anyone else using
> these on a BOSS & getting decent performance out of them?
>
> -Brady
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
> <polaraligned@o...> wrote:
> >
> > These motors were custom made for HP. They are brand new. They
> > even came in the brand new packaging. I guess in your situation
> > you are looking for a set up that will "bolt in" for your Boss.
> > I know I can't run these 1:1, but I am just trying to figure out
> > what ratio I need. I'd like to do the conversion right the first
> > time. I am very interested to see how your motors work out.
> > I did check them out a couple of weeks ago.
> >
> > Good luck,
> > Scott
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "braidmeister"
> > <braidmeister@y...> wrote:
> > >
> > > Scott,
> > > The Ametek's look very appealing initially, but I don't like them
> for
> > > a Bridgeport for several reasons:
> > >
> > > 1. Many of the Ametek ones don't have a 2" or longer shaft on
> them.
> > > You need 2" or better if you want to bolt right up to a BOSS
> factory
> > > belt drive.
> > >
> > > 2. I don't think that they have enough power to run 1:1, and the
> > > highest RPM I have seen them rated to is about 2000 RPM or so. So
> if
> > > you did gear them down to 2:1, you might see a max rapid rate of
> 150
> > > if they can pull the load.
> > >
> > > 3. They are used...not sure the condition of them, but they were
> > > designed for a reel to reel tape drive...
> > >
> > > I don't have any direct experience with these motors and
> initially
> > > was looking at them. Surplus center sells a few variations of
> them.
> > > The 36v model has a 5/8" X 2" shaft that will bolt right up to
> the
> > > BPs drive belts.
> > >
> > > I just bought 3 of these puppies:
> > > http://www.surpluscenter.com/item.asp?
> UID=2005020410354708&item=10-
> > > 1802&catname=electric
> > >
> > > I chose them because they will definately have enough power for
> the
> > > retrofit running 1:1. I don't plan on running them full voltage,
> so
> > > my rapids will be a little slower...but still capable of over 400
> IPM
> > > in theory. I'm going to shoot for the 150-200 IPM range and be
> happy
> > > with that.
> > >
> > > The reasons I chose them are they are cheap @ $80 ea, they have 2
> > > 5/8" shafts that are 2.5" long, and they are 9.125" long at the
> body
> > > so they will fit between the Y axis and the knee. I will have to
> > > shorten the shaft on the Y...but it sure beats trying to EXTEND a
> > > shaft, which is the case with the treadmill motors. So, aside
> from
> > > shortening the rear shaft and making some type of mounting/face
> > > plate, these are a bolt-in deal. I really didn't want to fool
> around
> > > with extending shafts, drilling shafts for encoders or coming up
> with
> > > some type of external belt-drive because the motor was too long
> etc.
> > > Belt drives are not cheap...
> > >
> > > I haven't decided on a servo drive yet. I am leaning towards the
> > > Rutex though because it has more features that the
> Gecko...although
> > > wiring is a bit more complicated.
> > >
> > > Hope that helps,
> > > -Brady
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
> > > <polaraligned@o...> wrote:
> > > >
> > > >
> > > > There has to be a difference between a new servo motor at $800+
> and
> > > a
> > > > brand (not surplus) treadmill motor at $100+.
> > > > I have servo motors that I paid, what some would say "dearly"
> for,
> > > > from a dealer on e-bay. He has sold hundreds of these surplus
> > > motors
> > > > and has excellent feedback. He states that as many as half
> have
> > > been
> > > > used sucessfully on Bridgeport retrofits. Of course, he has an
> > > > interest in selling motors so....
> > > >
> > > > Here are the motor specs:
> > > >
> > > > Torque constant: 44oz-in/amp
> > > > Voltage constant: 32.5v/1000 rmp
> > > > Peak torque: 600 oz-in, or 37.5 in-lb
> > > > Nominal voltage: 40vdc
> > > > Maximum voltage: 60vdc
> > > > Demagnitization current: >20amps
> > > > Terminal resistance 2.60 ohm
> > > > Max rpm at 50vdc is about 1200 rpm
> > > > No-load current <.51 amp
> > > > armature inertia .09oz-in-sec^2
> > > > 4 bolt holes in face for easy mounting.
> > > >
> > > > They came with 1000 CPR Renco encoders pre-mounted. I may move
> > > > the encoder to the leadscrew though. The seller states that
> > > > these are the largest servo's that a Gecko will drive. The
> motor
> > > > also has a heavy duty front ball bearing. At $150 per motor
> with
> > > > encoder installed, I find them to be quite reasonably priced
> > > > considering they are "real" servo motors.
> > > >
> > > > The big question, If I decide to use these motors, is what my
> > > > reduction ration will be. I need to trade off between torque
> and
> > > > speed, and the BIG unknown is what torque is REALLY needed to
> > > > drive my Bridgeport. I would rather err with a higher reduction
> > > > ratio than find myself without enough torque.
> > > > If I go with a 3:1 ratio and triple my torque I will get 80
> inch per
> > > > minute rapids. More than an inch per second SEEMS plenty for
> me.
> > > Why
> > > > do people need such fast rapids on a mill? What do you think
> about
> > > > even a 4:1 reduction? Will I regret it later? Do I ask too
> many
> > > > questions? I mostly mill small parts, say 6" on each side or
> less.
> > > >
> > > > A fellow CNC'er here used these same motors on a Rong Fu mill in
> > > > direct drive and said they worked, but were at their limit. My
> 3:1
> > > > reduction will triple the torque, and after all, the only forces
> > > > different between my Bridgeport and the Rong Fu is the dead load
> > > > of the larger table. (The Rong Fu leadscrew is also finer
> at .1" per
> > > > revolution). The cutting forces should be identical.
> > > > The BIG question is will I produce enough power with these
> motors
> > > > to drive my Bridgeport. What do you think?
> > > >
> > > > Scott