Re: [CAD_CAM_EDM_DRO] Re: Cam making....

I am curious about your method for measuring your existing
cam. Using a dial indicator to measure the lobe shape will
not give accurate results unless the radius of the probe
tip is taken into account. Also, any slop in the indicator's
stem will contribute to errors.

Are these errors of concern? Perhaps such accuracy in an
antique engine is not necessary. Is the object just to get the
engine running and not to get the original horsepower?

Pete.

----- Original Message -----
From: "xj5373" <ian.c.haynes@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, March 24, 2007 6:03 PM
Subject: [CAD_CAM_EDM_DRO] Re: Cam making....


Well thanks everyone for the excellent advice, what a great group!
Summarising there is a technique for reverse engineering existing
cams;
Rotate in 5 degree intervals, measure with a dti and tabulate then
input to CAD as a series of lines
A technique for working from a hand drawn cam;
Import a scan of the drawing on top of a template made up of radial
lines at degree intervals using OSNAP intersection to find the points
To create the cam outline it is recommended to use arcs wherever
possible then use polylines to fill the gaps.
To smooth the polylines use the fit command.
The ideal method though is to draw the cam directly in CAD.

My next step is to get the first sample cam drawing from my colleague
and see what we are starting with, this is going to take a few days
though as he is away for a while. I will also investigate CV mode, I
assume this is CV mode in Mach 3. I have a bit of an issue with my
DXF conversions of JPEGs coming out as 3D polylines, I need to
explore converting them to 2D polylines before I can use the fit
command.

Just out of interest, the plan is to cast the cams in wax then
assemble them in the wax at the appropriate angles before committing
to casting. These are for JAP V twins where the inlet and exhaust
cams share the same shaft.

Dissappointed I didn't see the CNC cam grinder in Ebay, I would have
put in a bid!

I will give you an update when I get a real drawing to work with.

Thanks again

Ian