Converting a simple turbocad file

[martim@ozemail.com.au]

I'm a raw beginner when it comes to CAD. I have drawn a curved shape (using a spline curve) in TurboCAD, and tried to convert to a ShopBot file. It all sort of works, but the ShopBot file consists of only three or four steps. There are no instructions for drawing the curve.

Any hints?

Cheers

Michael Johnson

[bill.young]

Michael,

The short answer is... To get a curve into a ShopBot-usable format you'll need to "explode" the curve and turn it into a polyline; a series of short line segments. Just select the curve, then go to the "Format" menu item and click on "Explode". There's also a button on the toolbar; it's the one with the two dark-colored overlapping squares with a little square at each of their corners.

Now a little more detail. A curve in TurboCAD (and lots of other CAD programs) is saved as a series of control points or nodes that define the shape. These are the places that you clicked to draw the curve. If you select the curve before it's exploded and then Right-click, you can see these points by clicking "Node edit"; they're the blue squares.

TurboCAD has two different types of curves. In a TurboCAD "Spline" type of curve, the curve goes through these points, but a "Bezier" curve's points are away from the curve and just "influence" the shape as if they were pulling on it. A "Bezier" curve is usually smoother, but harder to work with if you need a precise curve. A "Spline" type curve is usually easier to control, but can more easily get kinks and funny spots.

Before you explode the curve you can change some of it's properties by selecting the curve, Right-clicking, and selecting "Properties". If you select the "Curve" tab you can change it from a "Spline" to "Bezier" and see the difference in the shape of the two types of curves.

A more useful trick is the ability to change the number of line segments that the curve is broken into when it's exploded; the more segments there are, the closer the polyline will be to your original curve. In version 4 the default is 20 segments, but you can increase it to 200 in the "segments" box. Remember to make any changes to the curve BEFORE you explode it; once it's exploded it's too late.

Hope this helps,

Bill