Sketch Driven Pattern inconsistencies

[arron.craig]

I have a sheet metal part derived from a heat exchanger with about 2000 tubes in it, the tubes are in a linear pattern with an x and y parameter.  

I have projected the tubes into a sketch on the sheet metal part and then created a second sketch for the centre marks of each tube. 

I then have a hole pattern of 6 holes to be placed over each of these centre marks using the "Sketch Driven Pattern" feature. 

This is a hole pattern built from 3x neighboring 6 sided polygons constrained to each other so is fully defined by centering on the tubes and coincident constraints for their corners without needing dimensions.

So other than the hole size, everything is driven by the x and y parameter from the tube pattern.

The problem I am having is that the sketch pattern is not actually being placed on these centre marks but anywhere from 0.001mm away.

This is causing issues with holes being counted 2-3 times in the drawing and is going to cause problems with machining. 

Any ideas what I could have done wrong? I am unable to share the files which I understand will makes things harder but is company policy so not much I can do. 

Projected Tubes:

Sketch for the 6x holes

Holes places, Sketch pattern points shown

Sketch driven pattern placed, pattern overlap not lining up.

[Xun.Zhang · Accepted solution]

Hello @arron.craig,

I don't have such problem, just simply add two lines from center to one of edge and set those two lines equally in your second image, please check out the sample below.

Then, It should works for you, hope it helps.

[arron.craig]

Thankyou Xun.Zhang, 

This solved the problem. Your method is much simpler but to me should net the same result, or am I missing something here?

[Xun.Zhang]

Hi @arron.craig,

I cannot tell where is the cause for your case without data.

Thanks!

[CCarreiras]

Your sketch is not fully constraian.

If the sketch is not fully constrained, you cant garantee if it is in the propper place, and if any problems arise, you cant be sure about the cause. In your case, maybe you just drag a little bit the skecth and it became out of the right place.

That's why we must have always the sketches fully constrain, this will avoid this kind of troubles.

[arron.craig]

Thanks Carlos but yes the sketch is 100% fully constrained, at least according to inventor in the bottom right. 

All derived sketches have also been checked and confirmed to be fully constrained. 

The green sketches in my images are misleading, the colors have been changed to be yellow for unconstrained. 

[CCarreiras]

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@arron.craig wrote:

Thanks Carlos but yes the sketch is 100% fully constrained,

The green sketches in my images are misleading, the colors have been changed to be yellow for unconstrained. 

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Green color is for  unconstrained geometry in the standard color scheme.

OK then, if you say ist's fully constrained, then the reason can be other thing.... but its solved anyway, so... 

[matthew.poylio]

Here I am, several years later seeing the same sort of issues.   Nothing has been solved.

Included is a screen shot of a part I'm working with.  Sketch is FULLY DEFINED.  There is only ONE point to define the location of the hole highlighted, yet here I am with two holes beside eachother.

Last time I had an issue and shared with Autodesk, the reply I got told me to create the multiple holes on the center marks in the hole feature.   Yes, I could do that, but then in the assembly I'd inserting the fasteners one by one and applying mates to each of them.

I'm using the tools Autodesk gave us to make an assembly model easier faster...  however, when it doesn't work, and Dasault had them beat at this years ago, what gives?

[johnsonshiue]

Hi Matthew,

You seem to be a happy SWX user. Unfortunately, Inventor does not work as well as it should for you. Just purely based on the image and the description, it does look like a bug to me. If possible, please share the file with me directly johnson.shiue@autodesk.com. I would like to understand the behavior better. It could be a corruption or a fixable bug or there was some sort of inconsistency that confuses Inventor.

Many thanks!

[peter.roman]

I think I'm having the same issue, a duplicate occurrence is being created on the sketch driven pattern base point.

I'm not sure what triggers it to be created, when I create the pattern feature it is correct, but then at some later point I'll notice I have overlapping parts in assembly patterns that select that sketch driven feature pattern.

When I go into the part and edit the pattern feature it fixes itself, but I've noticed it comes back sometimes.