Modeling a symmetrical part

[pkelecy]

I'm modeling a part that essentially looks like a three-leaf clover. Due to the symmetry, I've only sketched 1/6 of it, and should be able to form the rest through a combination of mirroring (to form one leaf) and patterning (to duplicate the other two).

My questions are:

1. Is it better to, (a) mirror and pattern the 1/6 *sketch* (to form a sketch of the whole part) and then extrude that into a 3D solid, or (b) extrude the 1/6 sketch into a 1/6 solid, then mirror and pattern it?

2. If I want to edit the sketch that a solid was extruded from, how do I get back into the sketch mode? I looked in PathFinder expecting to see some reference to it, but there wasn't any.

Thanks for the help. -Pat

 

[KENAT]

What version of SE are you in, ST?

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[pkelecy]

I'm using the latest version (SEwST) but operating in traditional mode. I'm doing a trial, and am now trying to model my own parts (which is showing how little I still know). SE seemed a lot easier when I was just doing the tutorials! ;^)

I did figure out (2) (RMB > Edit Profile), but still not sure about (1).

Thanks.

Pat

 

[KENAT]

That was the reason for my question, as I believe in SE the sketches are effectively dropped once the feature is created.

I've always been cautioned against mirror, but that doesn't mean I can justify why.

Try creating the 1/6 feature, then mirroring to get a complete leaf.

Then do a pattern (by default it tries to do quick pattern which probably wont work for this feature so you'll have to change to smart pattern) to create the other 2 leaves.

This may not be the best way but give it a go and see what happens.



KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[pkelecy]

Well, I haven't been able to figure out how to do this using the pattern command. The documentation describes it mainly in the context of an assembly (where there's a pattern on another part you're referencing).

So how do I simply duplicate a solid in a circular array about the z-axis? I'm guessing it's easy to do, but just poorly documented.

Pat

 

[KENAT]

Using the pattern command, which should be on your toolbar in part somewhere. You'll want to do a circular patter with 3 instances, I think.

I've not used 'V21' so can't be more definitive.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[donyoung]

Look under Help --> Index Keyword: Pattern
-- 'Pattern command (Feature)'

scroll a bit down and you should find some examples
of how to pattern a feature in a part

dy

 

[beachcomber]

Depends on what shape the 3 lobes are.
If they are circular I would probably just create the profile as 3 overlapping circles, trim and constrain, and extrude that as a single feature.
See attached pic.
To get back to the profile (I assume you didn't create a seperate sketch) RMB on the feature and then select 'Edit Profile'. You will also see 'Edit Feature' which will take you back to a position to edit any part of the feature creation, and 'Dynamic Edit' which will display the profile dimensions.
A double cick on the feature will also display the profile dimensions.
If you multi-select features and RMB > Dynamic Edit the dims will be displayed for all features selected.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

bc, - thanks for the example.

My profile is a little more complicated though. I'll post a picture of it so you can see. To do that though, I'd like to know how you generated your screen capture. Is that something built in to SE?

Also, I really like your light-blue background (looks better than the default gray one, imo). How do I change mine to look like yours? I looked in SE options, but didn't see anywhere there to do that.

Pat

 

[beachcomber]

Post the picture and I'll try and help - I've loads of time on my hands as I'm looking for a new contract.
Screen capture - I used File > Save As Image.
Click the Options button to set image properties.
Alternatively, if you want the whole screen use Print Screen on the keyboard, then paste into Paint or whatever.
The background is the default for V19 & V20 (I think).
It will depend on what you have set in the template.
To change it Tools > Options > Colours > Background.
You may then have to go to Format > View > Background > Type
and change it to Gradient.
As I said, I often change mine to SE Classic.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

Thanks bc. Got the background changed.

Attached is my profile. Any advice is appreciated.

Pat

 

[beachcomber]

I think I see what you are doing.
Are the 30deg lines the lines of symmetry?
If so I think you are on the right track - create this protrusion, then use mirror about the LH line.
Next do a radial pattern of the original & the mirror.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[beachcomber]

Pat - see attached
I mirrored abot the RH line, then created pattern.
By the way, its probably best to use jpg files rather than bmp's as they're smaller.


bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

Yes, those 30° lines are symmetry lines, and you captured the intent in your figure. Thanks for the example. The way you mirrored and patterned is what I had originally tried to do. I got stuck when trying to use the pattern command. It's not particularly intuitive (imo), and even though I got it to work, I'm still not clear on some of the steps(what the green dots are for and other stuff). I'm guessing those are used in more complicated cases.

Anyway, thanks for the feedback. I appreciate it.

Pat

 

[beachcomber]

The green crosses in the pattern profile show the position of each pattern instance, the dots are keypoints of the circle I think.
Basically the steps are:
1. Select features
2. Select plane for profile
3. Select linear or radial pattern (I will assume radial)
4. Select whether to pattern full circle (ie 360deg) or along an arc (less than 360)
5. Select whether Fit or Fill and enter number of instances - suggest looking in help and playing with these.
6. Position centre of pattern, and edge of circle.
7. Select Fast Pattern (default) or Smart pattern to complete.

Generally you will need Smart Pattern.
Fast was supposed to reduce data size, but only seems to work on very simple things.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

"The green crosses in the pattern profile show the position of each pattern instance, the dots are keypoints of the circle I think."

That's what I thought, but I noticed I could grab and move the dots around, changing their positions, without it effecting the positions or orientations of the parts in the final pattern. So I'm not so sure. Perhaps there another setting that need to be active. The only thing I did notice is that if I dragged the circle off center, then the patterned parts shifted accordingly.


Pat

 

[beachcomber]

"if I dragged the circle off center, then the patterned parts shifted accordingly".........
That's because the centre of the circle defines the rotation axis and should be constrained accordingly.
The circle diameter isn't really important but define it anyway.
I just had a play to see what the dots are as I never really took much notice of them before.
When you place the pattern circle a dotted line is shown from the centre to the cursor position.
When you click to place the circle edge, this will become the start point of the pattern, and is shown by one of the dots. I think the other is just a keypoint.
In some systems you need to define a rotation axis by selecting a cylindrical face or an edge or by creating an axis element.
SE doesn't work that way, you define the axis by the position of the pattern circle.
On the circle you should also see a direction arrow.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

"When you click to place the circle edge, this will become the start point of the pattern, and is shown by one of the dots"...

What I was expecting is that the starting point would also define the starting position as well. For example, if the starting point was in the 12 o'clock position, then the first object would be in the 12 o'clock position; if in the 8 o'clock position, then the first object would be in the 8 o'clock postion, and so forth. That would be useful. But from what I've seen, the starting point location is arbitrary and has no effect on how the final pattern looks. So why ask for it? For patterning an object in a 360° array, only two pieces of information are really needed - the centerpoint and the number of instances.

I've also noticed that after clicking a point for direction, the prompt says to "Click on elements, Click & Drag for rectangular fence, or Alt + Click to place the first vertex of a polygon fence". Do you know what that is about?

Given how well thought out the rest of the application seems to be (at least the parts I've tried), I'm surprised SE makes what should be a simple operation this confusing.

Pat

 

[beachcomber]

I agree the radial pattern command can be a bit confusing, but I've done a bit of experimenting and learned a bit about radial patterns that I didn't know before.
As you say, for 360° patterns the start point etc doesn't make any difference, but when you use the arc option they do.
Try this - I created a rectangular block to do it on.
Create a hole at the 12 o'clock position.
Select it start the pattern command.
Use the Arc and Fit options.
Click to place the arc centre.
Then click to place the start at the original hole centre, then define the sweep anti-clockwise.
Make the sweep 200°, and the count 5 (= 4 pitches of 50°)
You can dimension the arc angle using Smart Dim - note the options for radius, diameter, length and angle.
Click return.
You should now see 5 holes along the arc, starting from the original.
Now go back and edit the pattern profile.
Select the arc and the parameters should display on the ribbon bar.
Now click the reference point icon and select the cross marking the second instance (the first one AFTER the original hole).
Now click return.
You should now see that the pattern has shifted by one pitch, and the original hole is now the second hole in the pattern.
If you make the third cross the origin you will get a pattern symmetrical about the vertical axis.
I had NEVER realised this before !!!
I think the prompt you are seeing is just a prompt to tell you to pick something if you want to edit it - you will see it when you go back to edit the profile.
By the way, when doing patterns of holes I like to create the reference plane using the 'Features Plane' option, and then use the original hole as the feature.
Sounds like you are doing OK with SE.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

 

[pkelecy]

bc, - thanks for the mini tutorial. I tried it, and it worked (mostly) as you described. I think you must be using an earlier version of SE. In the current (SEwST) version, the "return" is now called "close sketch" (at least I think that's what you were referring to).

It would be more intuitive if the the dots in the pattern command actually matched the final feature positions (so when you change the reference point, for example, the dots shift accordingly and you see what the pattern is actually going to look like). This seems like an obvious way to do it though, so I wonder why UGS didn't?

Also, I noticed when using Smart Dimension to change the sweep angle of the arc, that sometimes it would move the endpoint (which I expected) but sometimes the *start point* (which I didn't expect). Do you know what is controlling this? It seems like not knowing which end will change would limit the usefulness of Smart Dimensioning this.

Well, I think I'm doing ok with SE, but the patterning threw me a little. It's the least intuitive part of SE I've encounter so far (or perhaps just not as well explained in the documentation and tutorials) but it's coming together, thanks to your good feedback. At least I'm more comfortable using it now.

Thanks again for your input. It's been very helpful.

Pat