Re: DC spindle motor

Shawn, are you sure you have the motor wired for 220V three phase
(Delta connection)? I use a VFD on my CNC BP with no problems and
plenty of low speed torque but had to convert connection from star
to delta. VFDs have quite a few set up parameters so these would be
worth a check.
Fred

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Shawncd" <shawncd@p...>
wrote:

>
> Hello,
> I recently picked up an older milltronics cnc mill. This was

someone else's

> half started project. One of the first things that I thought was

strange

> when I purchased this machine was the spindle motor setup. It

looks like it

> originally came with an adjustable sheave pulley system. This

original

> design is no longer there. It has been replaced with a 1:1 twin

pulley set

> up. The original AC motor that came with the mill is a 2.5hp. I

hooked up a

> vf drive to see how it worked and it doesn't work, at least not

very well.

> There is no low end torque what so ever. Has anyone ever done a

similar

> modification? I think a lot of the later model bridgeports are set

up with

> the same type of sheave system. What is the best way to get back

the low

> torque? Use a much larger AC motor and drive? Or maybe go with

a DC motor

> and drive setup? I can pick up a 3/4 horse 1750 DC motor with a

KB regen

> drive for a round $200 surplus. The base speed is the same as the

original

> motor, but I'm not sure how the torque will rate compared to an AC

motor. I

> Know horsepower is horsepower regardless of AC or DC, but the

torque

> acquired from an AC motor at low speeds is nothing compared to DC

motors. My

> goal is to use the features I have with my Ajax cnc control such

as rigid

> tapping and constant surface speed, ect. The spindle head does

have a two

> speed gear change. HI and LO. Even when I shift into low the low

end doesn't

> seem like its all there.
> Any ideas or past experiences would be appreciated
> Thanks
> Shawn
>
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