Helical pattern

[mediumsliced]

Hi all,

I've been trying to get a trapezoidal protrusion patterned around a cylinder in a helical fashion. I tried creating a helical swept surface intersected with the cylinder surface for the trajectory reference curve, but Wildfire 3.0 doesn't allow me to pick the intersect curve as a curve pattern reference. Is there another way to create this geometry?



Thanks in advance!

 

[jeff4136]

Create a datum point on the curve. Pattern it.
Create necessary datum axes, planes and then
geometry features based on the original point
and the cylindrical surface. Group the subsequent
features and Reference Pattern it.


2007-03-26_064537_prt0001.prt.zip(WF2)
Edited by: jeff4136

 

[mediumsliced]

Thanks for your reply and example Jeff. I've tried it out. Got it to work, though it took some fumbling around. Thanks a million!

Attached is my finished part. Did it in WF3.0 though.


2007-03-27_021810_01_curve_pattern.prt.zip

 

[Dell_Boy]

A better, tidier way to do this this is to do BOTH the sketch plane AND orientation planes as datums-on-the-fly which enables you to pattern in both the angular and axial direction reliably without resorting to groups or ending up with datums for Africa.

Using this methodology, Jeffs short version can be done in 17 SIMPLE features instead of 197 and the long version in about 50 features instead of 259.



DB

 

[mediumsliced]

Thanks for the tip, DB. Your suggestion uses less features. Also interesting to note, with WF3.0, one can enter the sketcher without specifying an orientation reference, so we can leave out one more datun, so in short:

1) Create helical curve
2) Create and pattern points on the curve
3) Create an extrude feature with an internal datum axis referencing the first point and normal to the cylinder surface, subsequently create an internal datum plane referencing the point and axis
4) Reference pattern the resulting feature

 

[Dell_Boy]

Sorry but the link to my version of the model didn't upload correctly.

2007-04-03_054000_helical_pattern.prt.zip


You don't need either a helical curve or datum point. It can be done with simple protrusions.

It is not a case of using 1 less feature, it is using about 80-90% less features and going into sketcher without specifying orientation is actually a major contributing cause of your problems.



DB

Edited by: Dell_Boy

 

[mediumsliced]

I see what you mean. Your example helped greatly. Thanks for the tip!




2007-04-03_071312_helical_pattern.prt.zip

 

[trillicomm]

DELL_BOY,

You open my eyes on Patterning feature with 2 dimensions. Much appreciated!

t.

 

[mediumsliced]

Learn a new thing everyday. Keep lurking here and you'll reach guru status in good time.

 

[wsylvester]

Has the part become a assembly ? or is it still one part.


If it has become a assembly then you should create it there.


pattern a cylindrical cooridinate system and ref pat your blades


then you can assembly cutout your rotor..etc

 

[trillicomm]

I have a non-related question about welds:

If you weld the blades onto the cylinder, that makes them as one permanent unit. Do you still call that unit an assembly or a part?

 

[Dell_Boy]

The item was done as a part. If I was welding the blades on to a core I would have done it as an assembly.


DB

 

[trillicomm]

I agree with you and wsylvester, I would pattern the blades in assembly mode using coordinate reference.

 

[Dell_Boy]

A Clarification for the Noobs


With most cases there is hardly ever an absolute right or absolute wrong way to model something. Each method has its own distinct set of advantages and disadvantages and depending on how you are going to use it should result in different weightings of pros and cons.

In the above example there are at least 3 fundamental methods of modelling it.

1. A single part.
2. An assembly with the pattern defined in a "root" part and ref patterned in assembly mode.
3. An assembly with the patterning done entirely in the assembly.

There are also sub groups for both of the first two of ref patterning to some form of datum or direct patterning. I can't immediately think of an obvious way to direct pattern method 3 in a helical path. Also method 2 does not absolutely require a ref pattern to a datum. It could be ref patterned to some form of "weld prep" for want of a better description.

In general there are more patterning possibilities available in part mode that are difficult or impossible to achieve in assembly mode than the converse.


HOWEVER

If I was modelling an OEM part to drop into my assembly I would almost certainly use Method 1

If I needed to generate a B.o.M. or sub-component drawings I would almost certainly use Method 2 or 3

And there are probably a hundred cases in between these extremes.



This was done as a part because the original question was posed as a part.


DB

 

[dr_gallup]

I have a non-related question about welds:

If you weld the blades onto the cylinder, that makes them as one permanent unit. Do you still call that unit an assembly or a part?

I would probably merge the cylinder and the blades into a new part, particularly if I had to do significant machining on the resultant. Assembly cuts cause a great deal of extra overhead and I have had cases where an assembly with extensive cuts would regen and save fine one day then fail to retrieve the next.