Re: Cam making....

> Hi Ian,
>
> as a second thought i would forget the manual method of drafting and scanning
> and draw the cam in Autocad. Many years ago i used autocad to produce cams for
> Swiss Auto lathes.You should be aware that the min rad on the cam must be
> greater than the cam follower, My approach would be to calculate the rise's and
> falls and the angle then draw these on autocad from x0,y0 ie Line, 0,0 to
> @length<angle. then join all the end points wit a polyline using the Fit option
> be careful this may cause true position of the thro of the can to be outside the
> true path. (only Pedit the parts of the line that require it if you have true
> dia's in the path leave these alone)make the path up of several polylines if
> need be.
>
> Neville

Neville.
I also do cams for old vintage racing bikes and what i do is place the pattern cam on a stepper driven dividing head and move round in 5 degree increments and make a chart up.
From this chart I can then do a CAD drawing with spoked lines directly entered from the chart just as you have stated.

About the only way our methods differ in in the collection of the initial data.
This method also works for face cams where the new cam is duplicated by using the side of the to and the blank is ran in a 4th axis.


John S

>
> NEVILLE WEBSTER <nevillewebster@...> wrote:
> hi ian,
>
> you could try PEDIT pick the line then use FIT as the option this will smooth
> the polyline but keep all the critical highs and lows
>
> Good luck
>
> Neville
>
> xj5373 <ian.c.haynes@...> wrote:
> Firstly, many thanks for all the help with the ELCB problem.
>
> My miller spends a lot of its time making patterns for lost wax
> casting parts for obsolete engines mainly associated with Morgan
> Three Wheelers and now and then the odd exotic motorbike.
> Latest idea is to make cams. A colleague is planning to draw the cams
> 5 times life size on paper (probably a bit of magic goes into this
> step....) so step one is to scan the drawing into the PC and get a
> JPG. I then want to convert to a CAD file so have come across IMG2CAD
> which allows me to convert the scan to a DXF file. This then is
> loaded into my copy of Autocad LT. The cam shape is a 3D polyline and
> if you zoom in it is pretty bumpy. The plan then was to scale the
> drawing back to normal size then feed the DXF file into Mach3 to
> generate the G code. A dry run indicates that all this works but I
> would like to smooth the polyline in Autocad LT before sending it to
> Mach3.
> My knowledge of Autocad is limited at best and I have had a poke
> about looking for a command that will allow me to smooth the polyline
> but so far no luck.
> Does anyone have any advice on smoothing my scanned polyline cam
> profile in LT or even a better idea on how to go about this?
> Thanks
>
> Ian
>
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