Re: [CAD_CAM_EDM_DRO] Re: Mill recommendations needed for new CNC Project

In this case ...
As Phil recommended, your boss WILL SAVE money if you buy the Tormach,
or something similar.
You may enjoy it more, if you do a retrofit (or not).

Regarding HP -
Fred is a knowledgeable long-time poster, but the HP stuff is not quite
right (no offense meant Fred !).
Spinning a cutting tool up to 5000 rpm takes way under 0.1 HP. You can
connect a dremel to a BP sindle with a 1/8" toolbit and it will spin it
to 5000 rpm in under 5 secs and keep it there forever. It wont cut
anything, however, but getting it there is not the issue.

Bridgeports had 3/4 HP motors for over 10 years (M-head and early
J-heads) ! and were by far the BEST TOOL available.
I have one.

My old BP motor is 3/4 HP, 3-phase, and has a mass of 18 kg.
It can DELIVER 3/4 HP at tool forever (rated continuous run), the 3/4 HP
is NOT the peak electrical input at the switchbox like in modern air
compressors for example, but rather 3/4 HP output at tooltip. Its almost
silent when running, like any good industrial motor. It still runs very
well even being about 50 years old.

Any INDUSTRIAL MOTOR of 3/4 HP or more will work.
In general, a VFD and a 3-phase motor are much better for many reasons -
they last essentially forever, provide faster and smoother acceleration,
deceleration and smoother running, and smoother cuts. 3-phase motors are
almost the same price as any small (industrial) motor. A small VFD is
only 100-200$. For the price, is doing a retrofit, the best may be about
1.5 HP motor and VFD (almost same cost as 3/4 hp). Surplus center in the
us is supposed to be very good and cheap. Many have been very happy.

CNCíng the knee is common and works well on BP size/type machines.
Just use a 3:1 belt reduction, and any 5 Nm and up motor. A Nema 34
6-9Nm (600-1000 oz-in) will work very very well.
Use at least HTD 5 mm pulleys (9 mm wide), better yet the 15 mm wide
ones. The smaller ones are not rated for the HP/torque at the low speeds
used (under 100 rpm).

The mass of the table keeps it backlash free-
this will not work on light/small machines under 400 pounds like the
tabletop mills. There you will need a ballscrew and zero-backlash solution.

mayfieldtm wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>, "Philip Burman"
> <philip.burman@...> wrote:
> >
> > Assuming the man hours to put it all together and make it work are
> > valued at commercial rates then a ready out of the box mill like a
> > Tormach at USD6,800 might make more sense.
>
> Thanks Phil. I've been trying to remember 'Tormach'.
>
> Actually, I'd rather go the ready made route, my boss wants to save
> some $$$. As to the reference to the 'man hours', I and my Machinists
> are getting paid regardless if we are working on this or other projects.
>
> By the way... thanks to Jon and others with your recommendations, I
> have a nice list now. I like the smaller table-tops like the Tang, I'm
> being pushed into something a little larger. I was looking at the
> Grizzly G3102 or it's equivalent, however, I've read on the web a
> couple of horror stories on issues with the G3102 and I'm wondering if
> these problems have been dealt with by Grizzly. I'll dig a little deeper.
>
> If I was to convert a Knee Mill. I'm thinking of controlling the Knee
> movement and leaving the spindle alone. On manual machines, I do most
> of any drilling operations using the Knee, except when I need to to a
> lot of pecking.
> Any thoughts on this?
> I'd like to see some examples of how others have handled a Knee
> conversion.
>
> Tom M
>
> .
>
>