Sweeping along a Helix

[robr78]

I am working in NX5 and I am trying to make a tap. The tip of the tap starts at a small diameter and finishes at a larger diameter. In creating the Helix I have chosen the "use law" option followed by the "linear increase". I get the helix that is desired but, when I sweep along it the cut twists and I end up with something other than what I am after.

How do you keep from having your section twist along an increasing diameter helix?

Paragon Medical

http://www.paragonmedical.com

 

[hudson888]

Firstly knowing what you're modelling might help as we've had cases like this where it turned out to be an oil groove where you could have used a tube/cable to create the same result.

When you sweep along a helix using a surface of orientation curve as a spine usually helps control the amount of twist. However even if you build your section as sketch on a plane that is positioned on on end of the helix you use for your guide curve then there is still a problem it either the pitch or diameter of the helix are variable. You can change the pitch when building helices from law curves and the curve function for a helix supports variable diameters. However when either if these changes are invoked the angle of incline relative to the base plane if the helix, or the section you are sweeping more importantly, will vary. This introduces a small error in the the calculation of the swept geometry. an axis as a spine curve provides some control but it may be imperfect.

I have encountered similar cases in the past and found it may be simpler to construct the section by other means often sweeping sections as a construction technique and thickening them to maintain the correct sectional volume.

Cheers

Hudson

 

[cowski]

If you pick 'vector direction' in the creation options and specify the axis of the helix, it should solve most of your problems.

 

[joycejo]

On the Swept dialog set the orientation method to "Forced Direction" and select a vector that is normal to the axis of the Helix. This will keep the section from twisting.

John Joyce
Tata Technologies iKS
1675 Larimer St.
Denver, CO

http://www.myigetit.com

 

[robr78]

Here is a picture of what I am trying to make.

http://files.engineering.com/getfile.aspx?folder=eaa3afd2-1c5a-4497-801a-55b65b5622f2&file=Tap.pdf

A client has submitted this to us in a pdf and I will have to remodel and make other design changes.

When I try to use the "swept" feature it just creates a solid. It will not allow me the option to cut away the material. I tried to use subtraction after making the solid but what I have left behind isn't correct.

Stated in my first post is the result I get when I "sweep along a guide".

I have not found where I can specify the axis to keep things from rotating about the guide as it sweeps.


Paragon Medical
www.paragonmedical.com

 

[Crocostimpy]

In Section Options, under Section Location try changing to whatever is not selected already; either Anywhere Along Guides or End Of Guides. Also, under Orientation Method, try Face Normals if it's not already selected.

I make threads on occasion. Picture threads on a plastic bottle. I've never made any on a conical type surface, but these settings have helped fix weird results, particularly Face Normals. Select the face that the threads are winding around. In your case it would likely be the conical face.

Mike

 

[crazydiamond]

Be sure to use ‘insert > sweep > swept’ not ‘insert > sweep > swept along a guide’. When asked to choose an orientation method, choose ‘vector direction’ and specify the centerline of the shaft.

Ron
Design Analyst

 

[hudson888]

Just be aware guys that if you do this with a variable helix the slope changes and a swept section oriented to the axis will not accurately observe that change. My technique for an earlier poster was to sweep a surface and thicken it etc to construct a simple section. If the section a something more complex like a rubber seal then constructing additional guide curves may be required if you are concerned to achieve a higher degree of accuracy.

Cheers

Hudson

 

[mmauldin]

Check out the attached file. It uses two helices to control the sweep and orientation of the section curves. I used law curves to create the helices, but two normal helix with a variable radius would work as well.