Re: Linear bearing types?

Don Hughes wrote:

>
> From: Don Hughes <pencad@...>
>
> > For my applications, a vector-drawing machine was no good. I did
> > build a light-beam writing pen for my large Calcomp pen plotter, but
> > it really was a horror, and somewhat of a waste of time. I did use
> > it while some conceptual and laser light source problems were being
> > worked out, but the performance was pretty poor.
> >
> > My original plan, which is now fully operational and performing very
> > well, was a raster drawing plotter. I wrap the film around a drum,
> > which is conveniently machined to such a diameter that a multiple
> > of the shaft encoder's pulses comes to a nice unit measured on the
> > circumference of the drum. I used a drum such that the film's
> > sensitive layer is at a diameter of 6.519". 6.519" x Pi = 20.480"
> > If you had a shaft encoder with 20480 pulses per revolution, that
> > would give 1000 pulses per inch. So, I got a 1024 pulse encoder,
> > and attached a digital phase locked loop chip to multiply the encoder
> > pulses by 20. It works very well, although several 'experts' told
> > me it would be a cold day in hell before I ever got a PLL multiplier
> > to work on a mechanical system.
> >
> > I have an optical carriage that slides on 2 1/2" hardened and ground
> > shafts, on 3 Thompson linear bearings. The carriage is moved by
> > a 5 TPI Kerk leadscrew with plastic anti-backlash nut. It works
> > quite well, too. I had a cheap ballscrew without antibacklash on
> > it before, and the positioning was erratic, due to the backlash.
> > I use a 200 steps/rev stepper motor to move the carriage in
> > .001" increments.
> >
> >
> > Jon
>
> Jon:
>
> The reason I need the flatbed is to stationary mount the CO2 laser
> outside the flatbed and run the optics/mirrors to the cutting head. By
> doing this I can run it off HPGL files from inside AutoCAD's plot
> function by using the pen colors for the strength(depth of cut) of the
> laser and the pen up/down to turn on/off the laser. Your system does
> sound like it solved you're problems, but now that I have explained
> this, you can see why it would not be good for me cutting wood parts.
> So, the search continues for an old flatbed plotter of 'D' size or
> larger. If anyone knows of one about that they would like to part ways
> with, please give them my email addie. I am also open to any other ideas
> that our members may have if I can't find such a plotter. (maybe
> construct a flat surface and use a printer driver on rails or
> something...??)
>
> Regards,
>
> Don Hughes
> Vancouver, BC Canada.
> >
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>
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> Are you? If not, see our homepage for details.
> ------------------------------------------------------------------------
> welcome to CAD_CAM_EDM_DRO@..., an unmodulated list for the discussion of shop built systems in the above catagories.

Don;

Danplot will read a HPGL plot file, and output the steps to a controller
that takes step and direction inputs from the parallel port. Also you
can make the Z axis trip a relay or transister instead of driving a
motor. Talk to Dan Mauch at Camtronics and here.

What will you bu using the laser for? Is it for cutting wood? If so, how
much power
does that have to be and how much would a laser like that cost.

Bill