If anyone can bear to help a newbie, I™d sure appreciate a couple of pointers...

I™ve got ViaCAD 2D v7 (Build 968). I™m creating a 2D drawing for laser cutting the components for a model bridge.

I have drawn a complex curved truss structure, with the lines coloured appropriately to provide the sequence of laser cutting. OK so far.

I now copy this drawing for the many such trusses, and have to scale each one (slightly), to allow for the different sizes of the trusses, by stretching them horizontally. When I do this scaling, I get problems with some of the lines.

It seems that some (perhaps all?) of the Arcs are changed to be a Control Point Spline (and change the colour to Punch Blue). I can't see why this should occur - geometrically, the Arc should be able to be scaled into another Arc? And the Control Pont Spline shows up as a crudely segmented line, which is only an approximation of the required Arc.

What am I doing wrong? How else can I accomplish this in ViaCAD?

Many thanks
Rob

When you scale arcs differentially, you've created elliptical arcs or Beziers, which are subsets of spline polynomials. The segmentation is how the computer's graphics represent it. If you choose the line tool and run the cursor against the arc, you'll see that the Logicursor's detection of 'on' proximity isn't 'on' the segmentation between vertices, it follows the true arc more closely. *edit* [COLOR="Red"]it strikes me that that's perhaps what you're nervous about, because a line will snap to the true arc and looks disconnected from the segmented approximation[/COLOR]? You've got a choice of resolutions in the Inspector that'll refine the onscreen display and output. VC does represent curves with polylines as 2D output, and there are some other ways to change the resolution of those polylines, depending on what output format you're intending to use.

Aha - it sounds like this is what I'm seeing. The scaling does have to convert a circular arc to an elliptical arc - and I assumed that ViaCAD was clever enough to do this seemlessly. I'm now guessing that, because it changes the type of the line, it's not smart enough to reuse the colour, and so it assigns it to Punch Blue. And the laser cutting firm wants colours, not layers, for the cutting instructions. So I need to separate the colours in the Master into multiple layers, scale them in each copy, and then recolour the layers appropriately - bummer!

And, yes, I'm nervous that this "Control Point Spline" appears as a segmented line - and it appears this way if (for example) I export the file as a .bmp. So what will the laser cutter do? I guess that I'll have to check with the laser cutters?

If anyone's still interested, here is a simplified file - the After is the same as Before, but scaled horizontally by 5%.

Thanks, guys
Rob

Memphisjed, thanks for the flashback. after reading your comment I had a very vivid memory of assigning pen colors in autocad 12 or 14. It is amazing how long old ways live on in CAM software. I know, these things just work that way. It would be nice to gracefully bolt on feature recognition into these old CAD/CAM Apps, but tht will probably never happen. Its a good reminder of the constraints of building parts defined by old machines and their old software.