How accurate and reliable is Inventor’s Flat Pattern?

[Breeze104]

How accurate and reliable is Inventor’s Flat Pattern?  We have clamping bands that we form in a press and then put a final sharp break in one end as a spacer once they are bolted together.  I am using the contoured flange tool to create the part.

The reason for the question is that I can’t make these numbers work together to produce a product that resembles this 2D dwg.  What ever you can tell me sure would be helpful.

See doc for pic of part

[jhollin1138]

I found this thread while looking for something else. I'm not sure if you still need the help or not, see attached.

I was able to get the exact Flat Pattern and a 3D model that looks very close to your 2D AutoCAD drawing. The AutoCAD drawing was missing allot of dimensions so I had to make a handful of assumptions.

[Breeze104]

Why did you not make the part the complete length to start out?  2ndly, why use the unfold and refold?

[mrattray]

That part could have been made with two features. One contour flange and one hole feature.

[mrattray]

Example:

[jhollin1138]

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@Anonymous wrote:

Why did you not make the part the complete length to start out?  2ndly, why use the unfold and refold?

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Why try and determine the complete length if you don't have to? Let Inventor do the hard work for you, isn't that what it is for? I just did enough in my sketch for my Contour Flange to establish a starting point.

The dimensional information you provided in the AutoCAD was very incomplete. For one thing, it doesn't provide the location of the holes after it is rolled/formed. The only way to locate the holes is to unfold the part, place the holes and refold the part.

[jhollin1138]

The way you generated the model, I agree that you could do just a Conour Flange and Hole. However, your model is no-where near the original information provided by the OT.

[mrattray]

I didn't even look at the AutoCAD print, I just looked at your model and then made up dimensions for mine to proove that it could be a two feature model.

This is a whole lot easier to work with (and was easier to draw)

Than this is:

[jhollin1138]

Again I agree your formed model easier the way you did it. However your model is not correct to the information that the OT provided. If you're not going to model a part correctly so you can do it 2 easy steps, is it really correct? Why not just model a cube and say "Look, I did it in 1 step?"

The location of the holes is only given by the OT in the Flat Layout (12-15/16" Center-to-Center) and not the formed part. You arbitrarily placed the holes in your formed model. Since the information on the hole spacing was only given in the flat, the only way to truly locate the holes would be in the flat. Starting with a Contour Flange, you would need to unfold/refold to locate the holes which is why I did it.

On a side note, using a patteren (added step) to place the 2nd hole is something I do since we use allot of bolted connections. Using a pattern to place holes alows me to place all the bolts in a pattern in 1 step. Although, in this case the OT is making an iPart and the functionality of placing bolts in a pattern is broken for iParts. Sometimes habits are hard to brake. 🙂

If there wasn't the 1/2" offset for the flanges (your model doesn't have this offset), I actually would have started with the Flat Layout per the OT's informatioon. I would have then used Bends to form the part. The 1/2" offset makes this method nearly impossible since you would need to accurately determine the angle of the 4" Radius bend, not fun to do.

[mrattray]

Then the original drawing is wrong. It is not correct to model to a flat. It is correct to model the holes in the folded part where they belong, to match whatever they bolt up to. Same with the bends, I don't care where the bend lines are in the flat. I only care about the finsihed part's fit and function. Where they end up in the flat doesn't matter, as long as they end up where they belong in the folded, finished part.

[jhollin1138]

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@mrattray wrote:

Then the original drawing is wrong. It is not correct to model to a flat. It is correct to model the holes in the folded part where they belong, to match whatever they bolt up to. Same with the bends, I don't care where the bend lines are in the flat. I only care about the finsihed part's fit and function. Where they end up in the flat doesn't matter, as long as they end up where they belong in the folded, finished part.

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I agree that the location of the holes in the formed model is more important but you don't have that information available to you. The only information you have in the drawing provided is the location in the flat, so that is what you have to use.

In my formed model, they ended up about 9-3/4" apart. I have no way of knowing if this location is correct or not. If I could verify this location based on my estimated location, I would go back and place the holes at that location in the formed model. But again I have no idea if this correct location since it wasn't given it and I don't have the part.

The ultimate problem is that the 2D AutoCAD drawing is very incomplete and is missing allot of important information in the finished part. The 1/2" offset isn't shown, the large radius for the formed flanges isn't given, the angle of the bent lip isn't given, the location and size of the holes. Even that Flat Layout is missing information. I don't remember seeing the width and thickness but that information might be elsewhere in a note or title block.

[JDMather]

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@jhollin1138 wrote:

The only way to locate the holes is to unfold the part, place the holes and refold the part.

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I didn't bother to look at the file, but I'm quite sure there are other ways to locate the holes (and I'm sure of this not even looking at the file).  I wouldn't begin to bother with flawed AutoCAD data though.

[jhollin1138]

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@Anonymous wrote:

I didn't bother to look at the file, but I'm quite sure there are other ways to locate the holes (and I'm sure of this not even looking at the file).  I wouldn't begin to bother with flawed AutoCAD data though.

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You are indeed correct. You can locate the "left hole" in the formed part based on the information provided on the flat layout (14-15/16"-12-15/16"-1-1/8"=7/8"). There is still no way to locate the "right hole" since you are not given that information in the finished part, just the flat layout (12-15/16"), you would have to assume something to place the second hole. Let's say the holes are centered over the center roll.

Since unfolding the part, placing the holes with the information provided and refolding seems to be treated as a crazy idea, I have generated another solution in 2 steps. However, the location has to be assumed in the solution. Also, the Flat Layout doesn't match up with the OT information.

[JDMather]

ahh, just went back through this thread from the beginning. Now I recall why I quit following it.  I just got curious why it was still continuing when all the relevant information was covered months ago.

1. AutoCAD data is probably wrong.  My $10 wager is save bet.

2. Model in finished form and then work on correct k-factor.

[mrattray]

Why would you use extrude for this? If I may borrow JD's famous line, you're still doing too much work.

Why are you using arc length dimensions? These are not manufacturable dimensions. I don't think they reflect the design intent, either.

[mrattray]

Here is the sketch I used to generate the same geometery (with made up dimensions):

[Breeze104]

Even though the drawing in my original word doc does locate the holes horz in the flat view (vert dim not given because it is centered) the end results of the hole position is somewhat irrelevant, because when we press these parts to form them the results varies drastically.  Due to the type of metal we use some bands will pop up out of the press (2 in) when the ram returns and others have to be pried out.  Because of this the finished hole distance varies a lot.  That is why I didn't give that dimension.

Also, the large radii vary as well depending on how soft or hard a band is.  Just as an FYI these variances are from band to band no matter if they come from the same sheet or not.

The flat pattern dimensions are most critical since that is what I am making the shop drawings from.  I have 9 different bands total I have to create.  The one in the word doc is the smallest of the 9.

The dimensions (whether measureable or not) in the word doc are the ones of most concern.  The other dimensions can be adjusted to make the parts fit on an 8" OD tube.

PS

The angle of the small break is about 70-75 deg.  That angle is determind by wether or not you can get a bolt thru it and whether or not when the bolt is tightened the lip slides off the flt end of the other band.  Hole dim is 13/32.

[jletcher]

Breez are you still messing with this one? LOL

[Breeze104]

Yes it has been on the back burner for a while but still bruning just the same...LOL

[Breeze104]

I gave this puzzle to the new boss who is and engineer and he is having a time with it and Inventor. He has gotten it close (to within a few tenths) but not getting the results he had hoped for.

[jletcher]

OK I will try to set you up this weekend if I get a chance...