Designation of Helix 1

[FelixCC2009]

Hello everybody. Happy new year.

I am still stuck in making the helix. Per the attached file shows, I cannot always make a helix I want in a right way. The problem occurs at the direction of it.

I understand the three steps of designating the direction of the helix as:
1. Decide the orientation. (I used the lower side srtaight line by clicking one end of it.)
2. Decide the start point of helix. (I chose the center of the small circle of draft.)
3. Specify the end of helix's centerline, on the basis of STEP 1. (I chose the center of the big circle, which is produced by a intersected curve.)

Then the confusion happened. I don't know why the start/end point of the helix I made is at that position. It seem not belong to any elements. (As my understanding, the start point of helix should be at the center of the small circle.)

Could somebody explain the right steps or understanding of orienting a helix? It will be really appreciated.

 

[JohnRBaker]

It's not clear what it is that you expected to get as a result. The the so-called 'start' and 'end point' of the Helix is defining the Axis of the Helix, not the start and end of the actual curve itself. Perhaps if you could provide an image of what it is that you're trying to create it might help.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[FelixCC2009]

The supplementary image is shown as the attached. I hope it would be more clear for my question.
Thank you.

 

[JohnRBaker]

If no orientation is given, a Helix curve is created relative to the current WCS. So in the attached example, I just defined the WCS in the proper orientation and aligned it with the desired 'start' point and then created the Green Helical Curve, which appears to meet your criteria.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[FelixCC2009]

Thank you so much.

But you see, you also said "if no orientation is given", just like what I intended to discribe in my original question.
So, could you please make a little more illustration for me to show how to make a correct orientation for a helix DURING CREATION, besides by adjusting the WCS?
Because I think there must be some methods allowing me to do that, according to the NX 6's 3-step dialog box of helix.

 

[JohnRBaker]

Trust me, the ONLY reliable approach that I have ever found is to define a WCS oriented with the Z-axis along the desired axis of the Helix, the X-axis aligned with the desired start of the Helix and the origin of the WCS at the desired origin of the Helix. Besides, since this approach is virtually foolproof, why would you ever want to use any other scheme?

It's important to note that if you're thinking that if you were to somehow use an existing snap point and an existing curve to define the origin and direction of a helix, that this would somehow create an associative relationship with the referenced objects, you would be wrong. Irrespective of how you define their origin and orientation, Helix curves are created fixed in space, period! Therefore, if you're looking for some sort of 'associative' helix, you will need to take a different approach, generally involving a Swept Feature using an Angular Law.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[FelixCC2009]

Yeah... I think I understand what you mean. I was just trying to find an approach which I am used to most. Sometimes, as a beginner, I think defining the feature of helix or something else with existing snaps would be more specific and intuitive. And now, after understanding your helpful instruction, I am thinking why the helix I created in the model starts at that point. It is neither the X-axis nor Z-axis. Just like what I said, "it looks not belonging to any elements."

Anyway, thank you very much!

 

[JohnRBaker]

The problem is that the Helix was developed during an era when very few curves could be created which where associated to the objects being referenced so it was not as important that you were always given a lot of options which allowed you to select other objects. However, you can be sure that if and when we get around to updating the Helix, that it will include many more interactive object-based options when it comes to locating and orienting the resulting 3D curve.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[ukhal]

Mr. Baker,
I use the helix function every day. I have to use work arounds to get what I require, including using Law Curves. To have a helix that can have variable pitch would make my models so much simpler.

I hope one day this will be incorporated in NX. It has been in Pro/Engineer (spit lol) since I first started usiing it in 1998.

Thanks for your excellent advice as always.

 

[eex23]

Check zip archive for some law based helixes. I hope it will help you.