2D Helical Sketch

[atw257]

Is there a way to make a 2d helical sketch. I need to draw a baffle for a base plate that has a total of 3.00 Rev. - 11.44 pitch. I understand how to do a helical sweep on a say a cylinder to create a spring, but I can not figure out how to make a helical sketch on a 2D surface. I can easily accomplish this task in AutoCAD, but you can not import splines from AutoCAD to CREO 2.0.

Any help would be appreciated.

Thank you

 

[solidworm]

2D Helical Sketch? that's spiral, right? you can draw any curve using its equation. for spiral in polar coordinates thats r(THETA)=a+b*THETA. if that's what you want, i can guide you further.
maybe you want a projection of a helix on a 2d plane?

 

[atw257]

Yes I want to draw a spiral that has 3.00 rev.- 11.44 pitch. I've never used an equation to draw anything in CREO 2.0, so I have no idea how to go about doing that .

 

[solidworm]

ok, here's a screenshot i took :
first you should add a "curve from equation" feature. just type equation in the search field on top right corner (magnifying glass icon),it'll show you where it is on the ribbon. then fill the parameters as shown, the equation is r=a+b(theta), a is the start radius, so you can change it if needed, b defines the pitch, which is 11.44" for every revolution(11.44"/360 degs), Z=0 defines the plane on which the spiral is (xy plane)

 

[atw257]

That is exactly what I was looking for. Thank you very much! I am having trouble getting the curve to be on the xz plane. I tried specifying Y=0 but this did not work. Also how would I flip the curve if i wanted too?

 

[solidworm]

that equation uses the cylindrical coordinate system, in cylindrical coordinates each point is designated with with a unique r,theta,z so unfortunately you can't use y=0 for xz plane. what you can do is to add a datum coordinate system, with its Z axis pointing in part's Y direction. then reference that new coordinate system when creating the curve. the equation wont change then.

 

[solidworm]

another way is to just rotate the curve you already have. select the curve, copy it (ctrl+c) then "paste special", and select apply move..., then select to rotate instead of linear movement, select the proper axis from the default coordinate system, and the degree of rotation (90)

 

[atw257]

Is it not possible to sweep a section across the curve I have made ?

 

[solidworm]

it is possible, but if you need the spiral to start at r=0, then you should be careful with the diameter of the pipe you're sweeping over the helix, if its too large it'll be self intersecting at r=0. not possible in real world, and creo sometimes cant make the shape either. did you have trouble using sweep? what profile and sizes did you use for the sweep? if it self intersects, then you have to either reduce your profile size at the center(r=0) and gradually expand the profile over the trajectory to its full size or reduce your profile dimensions for the entire trajectory.

 

[solidworm]

actually with those dimension for the helix and assuming that it starts from r=0 (center),and the center of profile pierces through the helix, any profile with a width exceeding 0.9104"*2 will be self intersecting (overlapping).

 

[atw257]

I have r=3.5 as my starting position. When I try sweeping across the curve CREO could not generate the sweep. I ended up using the curve as a reference and drawing a spline on top of the curve to create my sweep. I didn't think it should be this hard though. I would assume there would be a way to just sweep along the curve.

 

[solidworm]

of course you can use sweep with that curve, upload your part, i'll have a look at it.

 

[atw257]

Well after restarting CREO and my computer I am now able to sweep along that curve. Not sure why I wasn't able to before. Thank you again for all your help.

 

[sdesaulles]

Hi, I found this very helpful, but was completely unable to make the spiral lie in any other plane.
you say here " Z=0 defines the plane on which the spiral is (xy plane)" If I leave it out of the equation, or put in Y=0 or X=0 it still lies in the same plane. I note a later post suggesting you have to put in a separate coordinate sytem to control the orientation - which is correct?

By the way, anyone wanting the spiral to run in the opposite direction, putting R=(a+b*Theta)*-1 seems to do the trick, (I was being advised to copy and paste special by my PTC support but is seems that would double the data)

Does everyone find that this generated a very large file size? I put in a couple of spirals and it was up to over 25Mb.

Thanks

Stephen

 

[dr_gallup]

Yes, you need to add a new Csys or redefine the original so that Z points in the direction you want.