RE: [CAD_CAM_EDM_DRO] Re: CNC coil winder traverse

Hi Graham -

Neat stuff. I was looking at magnetic actuators for a portable
medical device...trying to find something cheaper than a pager
motor or solenoid. Any guess as to prices in high quantities
(1,000,000)? Off list, of course.

More on topic...You can have a super-resolution positioning
system, but how are you going to guide the wire from the spool to
the coil? Will you feed through a syringe or over a V-groove? It
seems you will have bigger accuracy issues at this end of things.
The wire may have a mind of its own getting from the guide to the
coil.

For a positioning system you could just take apart an old (or new
$49) CD-ROM drive and use the optical head positioner to move
around your wire guide - plenty of travel, high resolution, no
backlash, etc. Of course, you would need position feedback, but
for that you could mount a linear encoder strip to the moving head
(low mass) and mount the read head to the chassis. Some of the
older (and heavier) CD-ROM drives might be better, since they tend
to have sturdier components, stronger motors, and the parts are
bigger and easier to work with.

Regards,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Graham Stabler [mailto:eexgs@...]
Sent: Thursday, August 28, 2003 2:28 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: CNC coil winder traverse

OK, I will start with the application and then why I want to have
a
precision guide and then perhaps someone can tell me if a belt
driven
servo system with linear encoder will do the job well :)

The application is in the production of magnetic actuators for the
control of micro model aircraft. They typically weigh <1g and are
free standing air wound coils using an adhesive to stick the wire
together.

for more info see:

http://rcgroups.com/links/index.php?
sid=498277416&t=article&cat=232&id=4051

Raylex:

Why do I want perfect wound? Well it is for many reasons, if gives
a
coil with more turns for a given resistance and that provides more
torque. It also gives a coil with a repeatable outside dimension
and
that helps in using the coil in actuator assemblies. And finally
to
produce professional looking results.

I realise they are not forced to be perfect wound but it must be
very
repeatable and precise.

Sheldon:

I have seen the self correction thing before and it looks very
nice
but I suspect it maybe a little involved for what I am doing. I
work
with microscopes and CCD cameras every day and can think of a few
ways to build a system like that based on "machine vision" but I
don't think I would have the time or the drive to do it.

My coils are designed based on the drive circuit that will be
used.
Some are only rated at 25mA@5v (eg direct drive from pic) so are
around 200mA, to maximise turns they tend to use 0.05mm wire.
Dimensions are based around those of the magnet used.

John:

Thanks! My comments on ballscrew lead error were based on the
info I
got back from a couple of manufacturers I got quotes from.
Obviously
some are better than others.

I hadn't considered a std leadscrew with anti backlash nut because
for some reason I had got it into my head that ballscrews were the
king in terms of backlash, indeed as my "machining" forces will
be
next to nill it does make sense. Do you have a web link for BS&A?
I
will check them out. What are these screws like in terms of wear?
Can I depend on them after many many cycles? Can I also thank
Vajk
who emailed me with similar comments.

Group:

If I cannot find a leadscrew that suits my fancy then will my
servo
system of linear encoder, beltdrive and servo motor be suitable?

Thanks

Graham