Re: Low range gears on Bridgeport Series 1

--- In CAD_CAM_EDM_DRO@y..., ptengin@a... wrote:

> Group,
>
> I just completed installing a VFD on my Bridgeport series 1 J

head. It

> runs like a charm. I only have single phase power here so the VFD

is the

> converter, variable speed and dynamic brake all rolled into one.

Well, now

> that the new motor runs so nice and quite, I notice a lot of

bearing noise in

> the backgear assembly. I could go in there and refurbish affected

parts but

> before I do that, I figured I would ask all how often they use low

range now

> that the VFD can give superb low RPM performance.
>
> I used a 3 HP TEFC motor and a Yaskawa 3 HP VFD. Since the

original motor

> on the machine was a 3/4hp, I opted for the 3 HP motor/vfd package

to give

> good torque at low Rpm's. I don't think the machine itself could

handle the

> full 3 HP endmilling etc. Removing the backgear parts and storing

them in a

> box sounds like a reasonable thing to do if the motor can handle

low RPM

> applications. What have you folks found?
>
> Thanks
>

Peter
I use a lot of Yaskawa invertors, in fact I'm an agent so I can get
good discounts.
From experiance do not drop below 15 Hz. Below this you loose torque
and motor cooling. In fact on some of our machines above 2 Hp we fit
a 120m square mains fan on top of the motor cowling and feed it with
the invertor input supply.
Also you may want to adjust the carrier frequency selection. On our
UK invertors it's option 46. By altering this you can smooth the
motor out and maybe get rid of the bearing noise.
I personally would keep the back gear. It's harder to refit it for
the odd time you may need it.

John Stevenson.