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Nov 14, 2008
10:30 PM

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Nov 14, 2008
10:30 PM

style features

I am attempting to create a curvature continuous style curve that closely follows and references two arcs. Essentially, the new style curve will run through the arcs and provide a transition between them. I'm having trouble with the final result as it has unwanted inflections. Both arcs are convex and I essentially want a curvature continuous radius between them. Any suggestions?

6 REPLIES 6

Nov 15, 2008
01:03 AM

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Nov 15, 2008
01:03 AM

David, The best way to eleimnate inflection would be to add more points or change the start and end locations of the curve(If the inflection is at the ends of the curve) Adding points should resolve the inflection point issue but would add complexity to the curve.So my advice would be to add the least number of points that resolve the inflection issue. You can also try and create a curvature continous curve by a datum curve through points and have curvature constraints.Then use tweak option to get the desired curve. Hope this helps, Rameet

Nov 15, 2008
12:39 PM

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Nov 15, 2008
12:39 PM

David, Rameet is pointing you in the right direction. Let me make a couple more suggestions for doing this simply. 1. Create a **Datum Point** on the original 2-arc **Curve** using **Ratio**. Now pattern the Point. If you set the Ratio to 0.2, for example, set the number of instances to 4. Now create a new Datum Curve with a Spline through the end points of the original curve and the new patterned Datum Points. 2. If you want even better fit, create construction arcs continuing the original curve ends(equal radius at both ends), and make the Spline tangent to the construction arcs. 3. You can do something similar by laying arcs on top of the original arcs,terminating just short of the junction point, then creating a tangent 3-point Spline joining the arc end points, passing through the original junction point, and tangent to the new arcs. David

Nov 15, 2008
02:06 PM

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Nov 15, 2008
02:06 PM

Thank you all for the quick response. I thought I might be trying to over control the style curve with too many points so I've eliminated about as many as I can while still approximating the original controlling datum curves. However, I'm still struggling to avoid the inflections. I'd like to get some further clarification and some additional ideas for the following if I can...all related to the same issue. 1. I've heard about dynamic curvature plots. Does this mean it is possible to display the curvature of a style curve as I manipulate it so I can see the effect of moving the various points in real time? If so, how do I do it? 2. Is there a way to tell PROE that a curve should only have positive curve (i.e. only be convex as opposed to concave). It seems this might be a way to avoid the inflections. 3. Finally, is there a way in Style feature to relate a curve to controlling datum curves (i.e. arcs, lines, etc. created with standard PROE geometry) so the free points will update/move with the controlling geometry? Thank you all for your help!

Nov 15, 2008
02:59 PM

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Nov 15, 2008
02:59 PM

David, Response to your questions: 1. Sketch a spline, while its still highlighted in red pick **Modify**, then pick the funny looking **Curvature analysis tool** icon in the dashboard to give a graphic display of curvature. Move the points and the display will change dynamically. 2. I don't think there's a way to flip a convexity toggle switch to control a spline. 3. Haven't yet discussed the "approximation" option available in Sketcher. Create separate sketches for the arcs and lines you are connecting. Start a new sketch and copy all the separate pieces directly ("Use Edge"). While still in Sketcher, pick all the copied pieces (Ctrl key), then go to **Edit>Convert to>Spline**. Finish the sketch. Now if you change dimensions controlling the original "pieces" you should get the update you are looking for. David

Nov 15, 2008
04:23 PM

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Nov 15, 2008
04:23 PM

Thank you. I'll give all of this a try. David

Nov 17, 2008
02:43 AM

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Nov 17, 2008
02:43 AM

David, Below are the answers for your queries.. 1. I've heard about dynamic curvature plots: You can get dynamic curvature plots by #Analysis >> Curvature >> pick the curve and set the radio button to saved. 2. Is there a way to tell Pro/E that a curve should only have positive curve: Yes. You will need to have BMX license for this. The steps are: a) Create datum points through which the spline/curve must pass. The datum points should be parametric. i.e should have dimensions driving it. b) Now make the Style or â€˜Curve through datum pointsâ€™ through the points. c) Now create an Analysis feature for curvature for the curve by #Analysis >> Curvature >> pick the curve and set the radio button to â€˜Featureâ€™. This will make parameters that will give you the min and max curvatures for the curve. Hit the green check mark for finishing the feature.Make sure that in the â€œFeatureâ€� tab the MIN_CURV and MAX_CURV parameters are set to â€œYESâ€�. This step needs to be done in standard Pro/E and not in Style mode. d) Now we will use feasibility/optimization studies to make sure that the curve has +ve curvature. #Analysis >> Feasibility/optimization >> Set the goal as â€˜Maximizeâ€™ the â€˜MIN_CURV/( Analysis name in step (c ) ). This name will be available in the drop down menu. e) We also need to specify the Design Variables i.e the things Pro/E can change by hitting the â€˜Add Dimensionsâ€™ tab. For this case we will give the point dimensions created in step (a). Also give the variation for each dimension by giving the max and min values. f) Click â€˜Computeâ€™. g) You will see Pro/E displaying the graph of the study. It will give the message whether it was successful to achieve the result or not in the message window. If unsuccessful you need to change the min/max values of dimensions or the constraint value. Also if you want to specify the exact min value of the curvature you can do that too by specifying the value in â€˜Design Constraintsâ€™ and giving the â€˜MIN_CURV/( Analysis name in step (c ) ) to a value. I have given the procedure for the minimum curvature for the whole curve only. But the same can be done for points lying on the curve too, to have better local control. In that case you will need to create an Analysis feature by #Analysis >> Geometry >> Points. Create a feature for this too. Then follow the steps from (d) to (g) to have a specified curvature at the point. 3) Finally, is there a way in Style feature to relate a curve to controlling datum curves: Yes. You can select the datum curves and points in Style that have been created in standard Pro/E. You just need to have the Style curve points by selecting the SHIFT key and selecting the existing curve/point. Now this curve will be referencing the datums created earlier and update when you change the datums in Pro/E. Also you can import standard curves in Style by #Insert >>Curve from Datum and pick the datum curve. This will create a spline curve matching the existing datum curve. Hope this helps.. Rameet