Re: [CAD_CAM_EDM_DRO] Servo/Stepper on a Surface Grinder

On April 27, 2006 08:03 am, Marcus wrote:

> Hi Alan:
> I have a couple of comments and questions:
> First, if you intend to retain the rack drive on the long axis (X??) it
> should be simple to isolate the motor completely from the machine, by
> adding a toothed belt sprocket to the handwheel shaft and a splined
> sprocket to the driving side with a fork to slide the driving sprocket in Y
> so it remains aligned with the driven sprocket.

Rather like driving the spindle in a mill head or drill press ? .. yes, I'm
starting to think hard about that as an option.

But as for removing jerks, I'm not so this will help. I've found timing belts
to be extremely "stiff", with no give whatsoever, and so the jerks of the
motor are perfectly passed through to the pulley at the other end.

Only if there was some sort of spring-loaded tensioner would the jerks get
taken out.

However, this scheme _does_ allow for a 3 phase (and hence very smooth) motor
of nearly any size ...

> You will only suffer from motor mass if you attach it to the grinder table
> and use it to drive a screw.

I can't imagine ever doing this.

What I may do is to replace the rack/gear with a toothed belt and pulleys.


(The gear/rack doesn't fit that well anyway. I remember you being concerned
that after the grinding of the ways, we might also have to grind the rack to
get the clearance back. Turns out I have to SHIM the rack.

It just occurred to me now that it can't be the original gear, but one with
fewer teeth than stock .. the only explanation for the added clearance. The
fact that the gear says "Boston Gear" while every other piece appears to have
been made in house kinda reinforces this opinion.)


So, timing pulley replaces the current gear on the left side.
Belt firmly attached to the table somewhere in the middle
Motor with pulley on a bracket on the right side of the saddle .. or mounted
to the bench and driven via the splined arrangement.

The beginning of a plan ...

> All the electronic bafflegab I can't help with at all!!!

Thankfully, for me that's the easy part. <G>


I may be obsessing about all of this a wee bit, but it's such a nice little
machine, I want to think the whole thing through completely.


Thanks for the time !


Alan

--
Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada


The Spartans do not ask the number of the enemy, only where they are.

Agix of Sparta