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### Can I draw accurate french curves

Posted: Tue Aug 11, 2020 3:25 pm
I am trying to draw a cross section of an airplane wing, which involves a bunch of coordinate points in a 2D plane, and a curved line passing over those points without any consistent radius. Is there any way to do that in DataCad? I have perused the curves menu to no avail. Bezier and B-spline neither work for this because you have no control over the curved line, just the points.

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 3:46 pm
Looks like a job for 3D Contour:
3D Contour

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 3:57 pm
Okay, I'm so ignorant of a program I've been using for literally 20 years... I ventured into the 3D menus, clicked on 3D Entity, clicked on "contours", and then drew about 5 or 6 line segments , but all I got were straight lines. Is there a tutorial somewhere? I can see how this would absolutely work if I could decide how to input the co-ordinates (relative cartesian, etc) and then smooth the lines. This is for a real aerospace design project by the way... not some decoration for a house design.

ETA: no they were not straight... After doing it again, I see that it does curve the lines. I'm guessing the "stiffness" button controls the smoothness?

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 4:14 pm
Could these polylines that I just drew using contour be given to a CNC machine or a 3D printer to be cut out of aluminum sheet?

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 4:19 pm
Creating contours is similar to creating Bezier or B-spline curves. You place a number of control points that define the curve. DataCAD accepts up to 256 control points. Unlike Bezier or B-spline curves, the contour curve that DataCAD generates passes through the points that you draw.

➔ To draw a contour:
1. Choose Contours from the 3D Entity menu. The Contours menu appears.
2. Choose the type of contour you want to draw: Natural, Cyclic, or Tangent.
Natural creates a contour that begins at the first control point you select and ends at the last point.
Cyclic creates a contour that connects the first and last control points with a smooth curve, making a closed shape.
Tangent creates a contour that connects two additional points to the control points, making a tangency at the end of the contour.
3. Use the Stiffness option to determine the curvature as the contour passes through each control point. A high stiffness forces the contour to remain flat as it passes through each point. To set a stiffness for the contour, choose Stiffness from the Contours menu and choose or type a stiffness value and press [Enter].
4. Choose Divisions and enter a value to indicate the number of line segments you want to use in between each control point. The further apart your control points, the more divisions you need. If you set too many divisions, your display regeneration time slows.
5. Choose the elevation at which you want to draw this contour. Z-Base, Z-User 1, Z-User 2, and Z-Height are the four standard elevations at which you can enter a contour control point. You can use Add Index or Sub. Index to alter these values. To set the Z elevations, Z-User 1 and Z-User 2, choose one of these elevation options from the Contours menu, choose or type an elevation value, and press [Enter].
6. Determine if you are working with tangent contours. Only with tangent contours, select a first tangent point, the point before the curve. This point determines the direction of the curve as it enters the first control point.
7. Select the control points. You can choose up to 256 control points for any one contour. You may select Add Index or Sub. Index to enter the next control point at a new elevation. Choose Add Index to add the value of the Index setting to the current Z elevation value. Choose Sub. Index to subtract the value of the Index setting from the current Z elevation value.
• If you are working with tangent contours, specify the ending tangent point. This is the point after the curve. It determines the direction that the curve heads as it enters the last control point.

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 4:25 pm
George W. Burns CPBD wrote:Could these polylines that I just drew using contour be given to a CNC machine or a 3D printer to be cut out of aluminum sheet?

The short answer is yes: You can export your DataCAD drawing to either DXF or DWG format. From there, the drawing can be imported into CAM/CNC software, where it will be transformed into G-code, the programming language that controls and directs the CNC milling machine.

### Re: Can I draw accurate french curves

Posted: Tue Aug 11, 2020 4:50 pm
Thank you Mark!