Re: INDEXER-2

"Arne Chr.Jorgensen" wrote:

> > The other thing is more completely described as an indexing
> head.
> > As used with a general, 3-axis CNC machine, it looks kind of
> like
> > a dividing head (which has a crank on the side, and each
> revolution
> > of the crank turns a lathe chuck so many degrees (often 9
> degrees)).
> > Instead of the crank, there is a button which can be pressed by
> a
> > tool in the spindle of the CNC, and it advances the lathe chuck
> by
> > a predetermined angle.
>
> What is this used for ?

Well, let's say you have a straight 3-axis CNC mill, and you need to
drill 3 holes 120 degrees apart around the outside of a round part.
You set the indexing head for 3 stops / revolution, and tell the cad/cam
programmer where the center of the rotary axis is, and where the
advance button is on the indexing head. In operation, when the
program needs to advance the indexer to the next position, it
stops the spindle and drives the tool down on the advance
button, then performs the next maching step. These units are
generally completely mechanical - force on the button works
pawls and indexing pins to turn and lock the chuck.

>
> Back to the electonics :
>
> Jon again:
> > One is a device, usually connected to a stepper driver, that
> makes the stepper
> > step through so many steps when given one pulse. Modern ones do
>
> > accel/decel on those steps, as well. This is an
> electronics-only box.
>
> I am not sure if I follow this: Let say you have a 200 step pr.
> rev. motor. Let us say this "one" indexer puls do execute 10
> steps.
> Then you will have the motor go 20 step pr. rev. ? Is this right
> ? Sounds like you downgrade the whole thing ?

Well, the whole idea here is that one switch closure will make some
mechanism advance by a precise amount, like move a conveyor
belt by 6 feet, or make an arm swing by so many degrees.
These are often used where there is no CNC control, or where
the CNC control is not configured to drive any more axes.
You would often set the indexer to go several thousand steps.
Many of them have 5, 6 or more digits that can be programmed
for the length of the move.

Jon