Re: Bridgeport servo motors

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