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Origin Location w/ Sketches on Surfaces

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Message 1 of 13
divingdoug
1157 Views, 12 Replies

Origin Location w/ Sketches on Surfaces

When I am forced to use an existing part surface to start a sketch, the origin of the sketch invariably has no correlation to the part origin (UCS Origin). It seems it ties to some feature or point on the surface instead.

 

Is there any setting or method to force the sketch origin to be aligned with the part origin.  Obviously it will only be aligned in two axis' but for the sketch, there is no need for a 'Z' axis (3d sketches aside).

 

I end up going to Edit Coordinate System to move the sketch origin to align with the part origin (UCS origin). That way I can always reference from a point that is consistent throughout the various sketches in the part.

 

Along the same lines, it seems that when a new sketch is created, IV orients the x-y plane based on random chance.  Sometimes it its the plane in the same orientation as the UCS sometimes it turns it on its side and sometimes it flips it upside down.  

 

This is using the three basic planes, not constructed ones.  It just isn't consistent.  So I often fins myself editing the coordinate system to reorient the sketch as well.

 

So, anything I can do to affect these two conditions from their default behavior would be appreciated.

12 REPLIES 12
Message 2 of 13
ampster402
in reply to: divingdoug

In Application options, Sketch tab, do you have the option "Autoproject part origin on sketch create" enabled?

 

Enabling that will always provide a point in your new sketch that is based off the part origin at 0,0,0

 

I don't know if this will solve your situation or not since you said you relocate the sketch origin.

Message 3 of 13
divingdoug
in reply to: ampster402

That option is enabled.  Many sketch origins still do not align with the part origin.

Message 4 of 13
JDMather
in reply to: divingdoug


@divingdoug wrote:

That option is enabled.  Many sketch origins still do not align with the part origin.


What difference does it make? 

In 12 years of using Inventor I have never had a problem or concern with this.

Just curious.


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Message 5 of 13
divingdoug
in reply to: JDMather


@Anonymous wrote:

What difference does it make? 

In 12 years of using Inventor I have never had a problem or concern with this.

Just curious.


The difference is when you want to intentionally reference dependent sketches to the part origin. (which I do often)  This way when you come back and make changes to your upper level sketches, it doesn't affect the dependent sketch entities, positions, loss of origin reference, etc.

Change a sketch enough and you lose the entire origin of a dependent sketch if the origin was based on a feature the first sketch generated.

 

Think in terms of real parts.  When you measure parts, the proper way to do it is to measure relative to a datum. A common position. Yes sometimes there are multiple datum's on some parts and you may need multiple reference points or 'origins' in the construct of your part.  But a part with dozens of sketches should not have a different arbitrary origin for every sketch.

 

Example:

If I place several points (to become tapped holes say) on a surface, how their position is references can have a big impact when I come back and edit the sketch that creates the surface they are sketched on.  If the origin for the points sketch is aligned with the part origin, I can modify the upper level sketch all day long an not affect the positions of the points.

If the origin for the points sketch is referenced by some corner of the surface they are sketched on, then modifying the sketch that drives that surface will have a high likelihood of upsetting the position of the points and a decent chance of losing the reference to the origin all together.

 

Don't take this personal but this is something that bugs me about this forum.  I ask questions to try and figure out why certain behaviors occur and how I can change them. A lot of times instead of getting a straight answer, I get a "Why do you need to know" or "You shouldn't have to do that" or "Don't try to do what you want to do, here is the 'right' way"

 

If it's something that is just part of the application that can't be changed, then just say that and I'll continue my work around as I do with so many IV idiosyncrasies. If there is a way to change the behavior with a setting or some technique, then that's all I am asking for.

 

In 12 years of using Solidworks, I never had an issue with multiple origins and sketches in bizarre orientations. But I try not to preach the superiority of SW (any more) when I am looking for information about Inventor.

Message 6 of 13
ampster402
in reply to: divingdoug

Can you provide some simple example files showing your difficulties?

 

When you first start a sketch on a surface, depending on if you have the option set, it will auto project the surface you are placing the sketch on.  If that is causing you grief, why not turn off that option?

 

And no matter what you do, if you project the origin, either automatically or manually, that is 0,0,0 in any sketch, no matter where you place it.  That's your datum per say.

 

Sorry I'm not understanding the issue you are trying to convey, providing simple example files might help.

 

Message 7 of 13
divingdoug
in reply to: ampster402

Here is a series of pics that shows both conditions I am having to work around.

 

Pic 1 - View being in an iso position, I highlight the right plane (YZ if you have not changed the names in the template as I have, I like my planes to match my views in name)

 

Origin-1.png

 

Pic 2 - I actually select the right plane (Yes, a bit redundant in the steps)

 

Origin-2.png

 

Pic 3 - I choose create 2D sketch on right plane.  Notice that the view has rotated the right plane sideways. (see view cube)

 

Origin-3.png

 

Pic 4 - In sketch after I have edited the sketch coordinate system. Notice again the view cube.  In the real world, when you first look at the right side of something, you generally do not turn it on it's side. You just rotate it 90 degrees to the left.

 

Origin-4.png

 

Pic 5 - Created a sketch.  The circle (to be hole) in the sketch is on the origin and everything pretty much is dim's from there.

 

Origin-5.png

 

Pic 6 - The extruded part. Though it may not be clear, for this I did a mid-plane extrude so that my part origin was centered between left and right.

 

Origin-6.png

 

Pic 7 - I select the top surface for my next sketch.

 

Origin-7.png

 

Pic 8 - I start teh sketch and notice where the sketch origin is.  On a corner of two edges. Looking at the part, there would be a high liklihood that I would edit my angles of the original sketch or a length or something.  This would totaly screw with this sketch were I to use this origin for nay basis of positioning.

 

Yes, the part origin is projected onto the sketch. The problem I have with this is that this point canb too easaily be deleted. Yes you can re-project it but what a pain.  If I reposition thus sketch origin to align with the part origin, I will always have a fixed reference point to the part no matter what I do to the originial sketch.

 

Origin-8.png

 

I would edit the coordinate system of this sketch to position the origin to align with the part origin.  To me, this should just be standard behavior.

 

Hope this explains.  Meeting now.....

Message 8 of 13
JDMather
in reply to: divingdoug


@divingdoug wrote:

 

Yes, the part origin is projected onto the sketch. The problem I have with this is that this point canb too easaily be deleted.



I never delete projected origin.  I never show or worry about local origin as in your images.

Before doing CAD work I worked out on the shop floor as a machinist for 8 years.

On any particular machine setup there is only one origin, that is my datum.

That is the same way I work in Inventor (and SolidWorks and Creo).

I guess I still mimic the way I would set up a machine on the shop floor.  Old habits are hard to break.


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Message 9 of 13
ampster402
in reply to: divingdoug

I don't recall where the option is, but there is one to prevent it from rotating when starting a sketch.  I do remember that disabling that option didn't work for everybody, for some all they had to do was twist their view slightly then start the sketch.

 

About your concerns with pic 8 and where the "part origin" ends up, I have never had an issue with, nor have I ever paid any attention to where the little ucs-type, three legged triad thing ends up.

 

I have always used where the default "Center Point" origin is, and in your pic 8, it's that little dot near the center of the area you selected to sketch on. 

 

That is 0,0,0

 

Perhaps you're doing too much work by constantly relocating that ucs triad - ugh - correct terminoligy escapes me now and not sure what that triad thing is called.

 

I agree that the little dot is easy to delete, I've learned over time to be very careful what I'm selecting to delete if I'm close to that little Center Point dot.  Chances are if I deleted it by accident then I deleted something that was tied to it.  If so, re-project the Center Point and re-add what ever was attached to it - or just be careful what you select to delete in the first place!

 

HTH

 

 

Message 10 of 13
ampster402
in reply to: divingdoug

Also, there are times when you want to draw a circle to use an extrude-cut on to create a hole, no doubt about that.

 

But for most holes, I'd use a sketch/hole point to denote where a hole is going to be, finish the sketch then come back and add a hole using the hole command.

 

This will at least add some intelligence to the hole so you can pull that info easy into the drawing.

Message 11 of 13
JDMather
in reply to: divingdoug

Another thing I do is (almost) always have the Origin Center Point visible. At least when working on other peoples' parts, the first thing I do is turn on the visibility of the origin.


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Message 12 of 13
divingdoug
in reply to: JDMather


@Anonymous wrote:
I never delete projected origin.  I nevershow or worry about local origin as in your images.

Before doing CAD work I worked out on the shop floor as a machinist for 8 years.

On any particular machine setup there is only one origin, that is my datum.

That is the same way I work in Inventor (and SolidWorks and Creo).

I guess I still mimic the way I would set up a machine on the shop floor.  Old habits are hard to break.



I have spend my fair share of time on the shop floor as well, layout work, machining, etc.  This is why I relate things to the 'real world'.

 

I don't intentionally delete the project origin. It just is too easy to delete it when you make a large selection.  It should be a fixed, unalterable entity. My whole gripe on this is that if the sketch origin was placed where the projected origin is, there would not even be an issue to deal with.

 

At this point, I consider this a closed issue as my original question, "Is there any setting or method to force the sketch origin to be aligned with the part origin" has been answered by essentially no answer, I take the answer to be a resounding NO.

 

 

 

FYI,  the hole in the displayed sketch was for illustrative purposes.  It could have been any feature that I wanted to tie to the part origin.

 

 

Second FYI, displaying the part origin has limited usefulness since it does not show up when you are in a shaded view and part of the solid is in front of it.  If it is not visible on the screen it cannot be selected for any command.

Message 13 of 13
JDMather
in reply to: divingdoug

This topic has come up here several times in the past.

 

In particular there is one long-time user of Inventor well known to this forum who had described the same frustration with the behavior that you describe.

 

I have just never paid any attention to it, the issue has never had any bearing on my work in any way, shape or form.

(Except when someone else brings me a "broken" ipt where they have fooled with the coordinate system (usually when dealing with sketch text)).

But I have been curious to see examples as sometimes I realize that I have gotten so set in a way of doing something that I miss a good technique or new function.


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