Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> I see..
> all say: most important: KEEP IT SIMPLE.
> 
> 
> It just hapens i have some of this Molybdenum grease (in a spray 
can)
> here. So i will use it.
> 
> 
> The motors, again...
> 
> I wonder wich power the steppers should have.
> 200 steps is ok?
> Most motors are rated in volt / ampere....
> I know it would be better to compare them by N/m but the ones
> i have are not labeled in torqe...
> 
> 
> I have some, but they are too small i think...
> So please anybody having firsthand experience please tell me what 
is 
> needed.
> 
> 
> I also wonder if the main axis should be driven by one or two 
motors.
> If there is only one motor the screw is centered. or two screws are 
coupled
> by tooth belt...  isn't there the problem of carriage skew if the 
spindle
> is centered and the load applied on one side only?
> 
> 
> thanks
> st

The first answer is usually a question.  what is the size of the load 
you want to move ?

if all you are doing is a drilling platform, then your little motors 
are probably good enough.

Remember the loads to move a board are not much different than to 
move a printer head.

I am not a motor expert, but have figured out that there are mainly 
two versions of stepper motors.

the pressed can style.  these are the ones you find in small printers 
and such.

then there are the NEMA rated ones.  NEMA17 is 1.7 inches square on 
the mounting plate

NEMA23 are 2.3 inches square and NEMA34 are 3.4 inches square.

a NEMA23 is common in laser printers are other machines so you should 
be able to find them as surplus for not too much money.

Often 200 steps per rotation, with half stepping, you get a decent 
400 steps per rotation.

pleanty strong enough for light wood routing, very light aluminum 
milling and more than enough for a drilling machine.

Stepper motors are rated for voltage and amps.

You can run them at rated voltage for minimal power, or use a chopper 
style driver and use a MUCH higher voltage.  using 20 times the 
nameplate is very common.  in fact if you check a data sheet, your 5 
volt motor will show performance with a 48 V power supply.

Of drilling only considder a solenoid for the Z axis.  for routing, 
you can use a solenoid or leadscrew, but for milling, you need to use 
a very solid machine.  adds to the complexity and cost.  and that is 
one reason I am interested in a drill only version.

HTHs

and please post more questions.  we all need to review.

Dave