Re: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION

Manel,
It depends on the linecount of the encoder you have on the motor. If you
have a 500 line encoder (very common) and drive it with a standard step/dir
drive you'll get 2000 steps per revolution due to the quarature nature of
the decoding.

Now, 20mm divided by 2000 steps equals 0.01mm. How about that. Now that's
resolution and not acuracy, acuracy is a whole other thing actually. But I
guess you really meant resolution.

However most people here would say that 0.01mm / step is bit much for a
metal cutting machine. So you may need som belt reduction for smoothness and
finnish. It depends on what uou want to do with the machine. A 2:1 reduction
gives you 0.005mm / step and a theoretical max speed (using Mach2 at 45kHz)
of 225mm / sec. Or your full travellength of 40" in ~4.5sec. Now that's
plenty fast IMO but you milage may vary.

Sounds like a very good setup you got there!! Whish I had it...... ;-)

/Henrik Olsson.

----- Original Message -----
From: "mfmiranda" <mfmiranda@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, January 24, 2005 6:04 PM
Subject: [CAD_CAM_EDM_DRO] BALLSCREWS QUESTION





I'm older to this list but this is my first question to the forum.
I'm looking at putting together my own CNC mill. I already have two
superb 40" german x/y linear assemblies and the servo motors (54V, 7A,
3000 RPM), everything saved from junk. I intend to use Gecko 340 and
Mach2.

The question I have regards to the TPIs of my ballscrews -they are
20mm - (0.8") - per revolution. This seems very large to my purpose.

I would like to know if some of you kind folk would take a moment to
figure the way I can use it with a minimum of acurracy, say 0,01mm,
using belt reduction, I guess.

Thanks very much,

Manel Miranda
Braga, Portugal