Subject: Re: Home Brew CNC

From: [email-masked] (Ian Kirby)
Date: Mon, 21 Nov 1994 08:26:21 +1100

In article <[email-masked]>, [email-masked]
(Ron Ginger) wrote:

> I am starting to build a home brew CNC milling machine. 
> 
> I'm going to use a Sherline mill as the base. I bought  a 3 axis translator 
> board from American Scientific Instrument Co, in New York- 516/361-9499.
> 
> I bought the DANCAD complete package and have just looked at the video tape 
> supplied with  it. Lots of nice examples on it.
> 
> I was planning to connect the step motors via tooth belt drive, but I see 
> several examples of direct coupling of motor to shaft.
> 
> Has anyone else experimented with this? is direct coupling or belt drive 
> better? The series in HOME SHOP MACHINIST a couple years back showed all belt 
> drive.
> 
> ron ginger
A lot of work has been done in this field by Dan Mauch of Washington state
([email-masked]), and I believe he has a series starting in
October Nuts & Volts magazine.  Dan has contributed to this group in the
past, and may post an update of his work if he reads this.  I believe he
also uses the DANCAD/DANCAM packages.
Regards, Ian. (Hi Tim)
-- 
Ian Kirby.                          Ph: +61 42 213353
Dept of Mechanical Engineering,     Fax:+61 42 213101
University of Wollongong.           Email: [email-masked]
Northfields Avenue,
Wollongong. 2522.
NSW Australia

---

From: [email-masked] (Dan Mauch)
Date: 22 Nov 1994 06:38:43 -0800

:Yes a sherline mill can be run on stepper motors. It depends on how you 
want to run it if you use timing belts or direct drive. Here is what you 
need to consider. 
	What is the maximum speed that you want the table to travel? Let 
say for giggles that you want it to run at 17 inches per minute, If you 
have a 10 thread per inch lead screw then your motor at direct drive 
would have to turn 200 step X 10TPI X .1= 2000 steps per inch X 17 =34000 
steps. Most Nema 23 motors run well at about 110RPM or 200X110 or 22000 
steps per minute with direct drive. So you can see that 17 inches per 
minute will not be likely. You could go to a chopper drive that would run 
the motors up. Stepper motors lose most of their torque when you run them 
at high speed so you would have to gear it down to get the torque you need.
I think the pragmatic approach would be to buy the largest motor that you 
can and direct drive them.