curve equation

[BertilRogmark]

Is there a way to write the spiral curve equation in a cylindrical coordinate system in  such a way that the pitch is zero in the beginning and the end so that the curve starts and ends tangent to the start and endplanes that are normal to the trajectory center axis?

[kdirth]

Modified sketch and extended sweep:

[KenFarley]

The curve is doing exactly what you told it to. Perhaps you're not understanding how the evalgraph function works.

You're telling it to use the curve you defined with the name "ANG".

The "t" value is used to specify the "X" value in the graph "ANG" that will be used to determine the "Y" value. The resultant "Y" for the specified "X" is what is returned.

So, to get the coils to be tangent or have dz/dt = 0, you need a horizontal line. So your graph should have:

horizontal line -> radius -> sloped line -> radius -> horizontal line.

The vertical line at the end is saying "keep the theta constant" which results in a curve segment parallel to the spiral central axis.

[KenFarley]

If you redefine the curve as I suggested, you then use it to define the Z, via the following cylindrical curve equations:

r=75
theta=numcoils*360*t
z=numcoils*coilpitch*evalGraph("ANG",t)

[BertilRogmark]

Many thanks to all, mainly to KenFarley who's suggestion I have followed.

Therre are a number of parameters that control three different curves with tangential connections and I can within reason manupulate all aspects of the part through those. So far so good.

The resulting part is attached and it shows what I wanted but for one important issue.

When I try a variable section sweep I can do it for any one of the three curves, however, I cannot sweep along the total of the three curves in one "fell sweep"(joke) but have to do it curve by curve.

Is my intention not doable?

[Chris3]

I don't know if its possible in Wildfire 3, but certainly in later versions you can make a copy feature and then combine curves into one in the copy feature.

[tbraxton]

I am pretty sure you can copy multiple curves into a single curve in WF3. You will need to deal with the problem of the trajpar variable used on this copied composite curve. The composite curve of the copy feature used as a trajectory will affect how the graph gets mapped. This means that you will need to map the x axis of your graph features to correspond to the curve length of the composite curve.  This may require writing some relations to get things to work as intended.

[KenFarley]

The sweep works fine for me, using Creo 9.0. What you have to do is define the curves in "Details" tab.

I pick the first curve in the chain I want, then <Ctrl>-select the remaining curves, in order. The sweep is shown, and I can switch it from a solid to surfaces, etc.

The sweep user interface is not very straightforward about what it needs.

[kdirth]

You should be abe to use One By One or Tangent Chain to collect all three curves during sweep trajectory selection.

From wildfire youtube video:

[BertilRogmark]

I dont know if I am too old or my software is too old but I am stuck.

The part I submitted in my last reply has all the properties that I want but for the fact that I cannot make a composite curve from the 3 existing curves whatever advise I follow.

Wildfire 3.4 should be able to do this, but I am not.

I guess I have to stick to doing 3 individual sweeps, one for each curve which is what I have done in the atteched version.

Using these curves gives me at least exactly the desired result; there are no kinks or discontinuities where the curves meet each other.

[kdirth]

Take a look at this video starting at 1:10:  Variable Section Sweep Demystified in Pro/ENGINEER Wildfire (youtube.com)

Here is a video on the sweep for WF 4.0 (WF 3.0 is very similar):  How to use sweep tool in proe (youtube.com)

[BertilRogmark]

Thanks for the video tip but it did not help me.

In the second part of the video where a "sausage" is modelled, the trajectory is built from picking the separate parts of what is seen in the model tree as one curve holding down what I hear as the shift key.

When I hold down the shift key the software will not let me pick any curve at all.

If I hold down the Ctrl key I can pick the individual curves but the appear in the reference menu as origin, curve1, curve2 which is no good.

I still hope to be able to make a composite curve from the three curves and then hope that the software will not say: Not usable as trajectory.

[kdirth]

Have you tried combining them with a copy?  Select one curve and press Ctrl+C, Ctrl+V, then hold shift to add tangent entities.

Composite Curves in Wildfire - PTC: Creo Parametric (Pro/ENGINEER) - Eng-Tips

[BertilRogmark]

As I have stated before: PTC like other powers moves in mysterious ways!

I have tried you advise back and forth but only arrived with 3 new separate copies of the 3 existing ones.

I then found that if I changed to ”Legacy” in the Applications drop-down menu and then chose Insert-Model Datum-Curve I finally found the alternative ”Composite” – ”Exact”- selected the 3 curves on screen – selected Done – and voila!!

Problem solved!!!