Re: Digitizers, Renishaw

--- In CAD_CAM_EDM_DRO@egroups.com, Alan Marconett KM6VV <KM6VV@a...>
wrote:

> Hi Fred,
>
> Thanks for the comments. I can't afford one either, but did you

read

> the post from Peter? Not THAT sounds like something we could

make! If

> we scan like we are cutting cross sections, then I think we'd have
> contours to cut. We might be able to generate "scan contours" in
> vector, and then the output points would be arranged in contours...

My concern with the use of just a contact probe, is that controller
software must be open enough to modify it to detect the position at
contact. Not when the machine eventually stops, or even what the
target position is, but where exactly it is when the contact is
made. That's why I think the indicator is a better way to go. You
position to a known Z, stop, then independently read the indicator
value. There is no kinematic effects, no question about switch
bounce, no vibration, etc. The measurement is signaled by simple Aux
out & aux input kinds of signals, that nearly all teh progams can
support.

It doesn't take a metallic surface to detect the contact(like some
I've seen), and probably the biggest drawback from the Renishaw
system is that it takes some really complex software to detect the
position of contact. If you are probing a vertical slope at about 45
degrees, the contact is on the tangent to the ball. The smaller the
ball the better the accuracy, but you will always have some
uncertainty about the actual contact point, a it is possible to be
anywhere along the bottom 1/2 of the spherical tip. The picza gets
around this by using a tiny pin sized rod for contact sensing. I
expect that you could use a sharpened incicator tip and get nearly
the same quality of result. Indicator tips are cheap and readily
available in a variety of sizes. you can also easily make custom
sized ones so that you can probe with a 1/8 ball & then use the same
data points for a G-code file.

I confirmed today that Vector 9 will be able to handle unlimited
drawing size. You will be able to scan a series of points & input
them with the PLC commands as either discrete points, or as a poly
line type of construction. Vector will then either generate a spline
through them, make arc splines, or also be able to create either a
skin or a series of planar offset curves.

PS both StlTrans and Amapi can import point clouds directly. These
can both be saved as Stl files and Stlwork can machine these with
raster cutting strategies.

Best Regards,

Fred Smith
IMService