# Help Please-Applications of Trajpar Variable

• posted

Hi All, I expect help regarding trajpar variable and its usage

1)Examples where it is used I saw its application only in Var Sec Swp 2)In relation where part dimensions are assigned to sketcher dimension the relation do not works. Can anybody provide little bit insight. Ex- sd3=d12-d15*trajpar

d12 and d15 are part dimension of curve created before using these in relation.

• posted

That's the main one, if not only one. (For future reference; there's also a trajpar_of_pnt function.)

What does "not works" mean?

For ...

... sd3 will be equal to [d12 - (d15 * 0)] at start of sweep, equal to [d12 - (d15 * 1)] at end of sweep.

Your best bet is to post a model somewhere so people can see WHAT IS and explain what you want to happen instead.

• posted

AFAIK, trajpar works only with VSS which is designed to allow the section to vary. I couldn't get trajpar to work, for example, on an ordinary sweep. Looking at your relation, I don't see anything which, in principle, should prevent it from working. I'm not 100% sure of how your relation will evaluate, but I'd try enclosing d15*trajpar in parentheses to make sure it doesn't evaluate to zero. Also, since trajpar (like t) varies from 0 to 1 when driving the sweep section dimension, make sure d12-d15 is never negative. Both zero and negative sketcher feature dimensions (zero length lines, zero diameter circles) are impossible and illegal. In short, get the evaluated max and min values that your relation generates and vary the section, manually, to these numbers to make sure it is capable of that variation.

BTW, there is some useful stuff in Help on trajpar under Part Mode.

David Janes

• posted

Hi , I will put the steps of creation as follows, 1)Datum curve of specific height and another of specific length

2)created trajectory for VSS 3)created section for VSS and then 4)entered relation for that sd3=d12-d15*trajpar

After this I observed no change > > wrote

• posted

I tried to duplicate your problem by following your steps and could not do so. Do I have to (in which case you should be using Inventor) explain why?

You use Google for email. Try their search functions. They are just so cool!!!

• posted

Patil, are you familiar with a sweep? It has two elements: a sketched section and a path (trajectory) that the section follows (sweeps). Generally, the path is created first and when the sweep is created and the trajectory selected, Pro/e sets up a sketch plane normal to the trajectory to sketch the section on. This is true also for the VSS. The first curve selected is the origin trajectory. As a side point, if it is composed of several curve segments, these may have to be combined into a single curve (composite, exact or approximate) with a copy/paste operation. If you don't know how to do this, you need to be asking about these detailed techniques. Additionally, the VSS provides the ability to select other trajectories that guide, not just the section direction (which is all the first trajectory does), but the shape of the section, the real VARIABLE section. With one or two additional trajectories, roughly following the first, the section, locked to those trajectories, will change shape as it follows the origin trajectory. How many trajectories can be used depends on section geometry. A circle, for example, can be varied in only one dimension ~ the radius, so two trajectories, at most, are needed. A conic arc could follow two or three trajectories. A box could follow at least two, depending on what was tied to the trajectory curves. A spline can follow any number of trajectories.

In your example or the steps presented, a couple things aren't clear. You have a curve of a "height" and a curve of a "length" but are these trajectories? How many trajectories? If a single trajectory, meaning they are joined so the VSS can follow them, the section needs to identify this single trajectory as the origin. Then, while in sketcher, make a sketcher relation that evaluates the feature dimensions and varies the sketcher dimension accordingly. Here my previous cautions apply regarding how this relation evaluates times 'trajpar' (mustn't evaluate to zero or negative for size dimensions). Following these simple rules, you should have no trouble using feature parameters in a sketcher relation. On the other hand, if you had a problem doing it this way, why not just use real numbers or ordinary parameters which can also be used in relations.

As to driving sections with a graph, this is also a particular function that can be used in a relation called EVALGRAPH. The graph is created first with 'Insert>Model Datum>Graph', then draw the dimensions and shapes that will guide the section dimension through its variation, e.g., starting dim, ending dim, distance, and the graphical equivalent of an algebraic equation. Or a starting dim, angle and distance or length. Or starting dim, starting angle and ending angle. There's stuff in the Help files on EVALGRAPH. The graph is evaluated in the same incremental way, over some limits, as if 't' or 'trajpar' were doing the incrementing.

David Janes

• posted

• posted

Neat, so what sketch parameter does the evaluation of these curves' length/height govern? And when it doesn't work as you'd expect, does the evaluation through the range of trajpar (0 to 1) make sense, is it physically possible? I'm sure you can change the curves in such a way, with certain values, to MAKE the section fail. I gave two circumstances where any size variable will fail if the product of trajpar evaluates to zero or a negative number. You didn't respond that this was NOT going on so I have to assume you didn't check or that your relation already checks for both conditions and prevents impossible values from being used. When the section fails to change, does the relation show errors? Are there any error messages at all? What version of Pro/e are you using? In WF3 there is now, under Options within the VSS definition, a check box for Constant section. If that's checked, it seems to override the relation. That's just a side point as your intermittent problem doesn't really sound like this situation, that is, unless this problem just started when you switched to WF3, then I'd check the VSS definition.

David Janes

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