Sheetmetal Unbend Peculiarities

[NEALROSENBLUM]

Hey Everybody,

I just designed a series of curved glass panels for a high end staircase for one of my clients. The staircase angles upfrom the first floor to the second floor of the residence.

The customer had the ledge of the staircase laser scanned (just adjacent to the actual stairs), so I have well defined geometry to determine what the panels should look like. A channel will be attached to the ledge, and the glass panels will fit into the channel and then be fastened in place. I have gaps between each of the panels of .25 inches.

There are a total of 7 glass panels. Out of the 7 panels, only 4 of the panels are curved (cylindrical with R135.0 inches). The curvature is normal to the plane of the floor.

In order for the fabricator to cut the flat panels (prior to forming the glass), I used the Sheetmetal module to UNBEND the formed panels so that the fabricator would know how to cut the "blanks".

When IUNBEND the curved panels, I noticed a very slight curvature along the top and bottom edges of the curved panels. So in other words, each panel looks almost exactly like a parallelogram with the left and right edges vertical, and the top and bottom edges slightly angled to follow the pitch of the staircase. In my case, after unbending, the top and bottom edges have a very slight bow.

The panels are essentially cylindrical, and the top and bottom edges essentially take a helical path.

So I did an experiment. I created a vertical surface and I swept it along a helical trajectory (helical sweep). I have 2 options when I do this:

1. 
   
2. normal to trajectory – surface always tangent to trajectory
3. 
   
4. through axis – z axis always points in same direction as axis of revolution
5. 
   

I took a surface made using option 1 and then another using option 2. I then used the UNBEND functionality to flatten each of the panels and this is what I discovered.

When I create the surface I get that slight curvature along the top and bottom edges.

When I create the surface I get a perfectly straight lines along the top and bottom edges.

The UNBEND functionality does not give me an option to unbendthrough axis.

Any suggestions????

TIA.

Sincerely,
Neal Rosenblum
Geometrix Engineering, Inc.
201 N. 13th Avenue
Hollywood, FL 33019
Ph: 954-920-2049
Fax: 954-920-9574
Cell: 954-649-9399
neal@

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[bokm9606]

can you do a sanity check of the flat pattern from the SM package by:

1. copy the surface of interest as a quilt
2. using the flatten quilt function to flatten the quilt created in step 1
3. compare the flatten quilt geometry to the "flat pattern" geom created
in Sheet metal

?

Just a thought as for a sanity check..

I believe "flatten quilt" uses a different mathematical approximation than
the sheet metal module...

sounds like a fun project.....really cool

Pete

[NEALROSENBLUM]

Dear Pete,

When I started this project, I initially looked at the UNBEND in Sheetmetal versus the FLATTEN QUILT under the INSERT>ADVANCED menu item.

I ended up creating the surfaces and then THICKENing them to create the .500 thick glass panels. Then when I was all finished, I could treat the glass panels like sheetmetal and then UNBEND.

I think that my reasoning going this route was because I needed to provide the fabricator with both FLAT and FORMED panels (with dimensions, etc.). I think that I hadissues with the family table using the FLATTEN QUILT route.

Sincerely,
Neal Rosenblum
Geometrix Engineering, Inc.
201 N. 13th Avenue
Hollywood, FL 33019
Ph: 954-920-2049
Fax: 954-920-9574
Cell: 954-649-9399
neal@

[bokm9606]

A data management methodology for flatten quilt could be:

1. create part model in its formed, finished shape call "part-a".
2. at the end or near the end of the model tree, create these feature
copy the surf (surface copy)
add point to the model needed to flatten the quilt (datum point)
flatten the quilt
publish geom of the flattened quilt (publish geom)


3. layer off these newly created features in "part-a"
4. make a new model (part file) called "part-b"
5. copy geom of publish created into "part-a" into the the "part-b"
6. in "part-B", thicken the flattened quilt created via copied geom.

you now have 2 parts:
*formed state part
*flattened state part which is related to the formed state part

Create a single drawing or 2 drawing to control each mfg process step.

Extra credit if you can pass the "sheet-thickness" parameter from Part A to
Part B.....i think this is possible via parameters? Not sure if you can
"publish" a parameter value or not?

Food for thought.

Now I am hungry

Pete

[JamesKasson]

The curvature that you describe is normal. You may satisfy your curiosity by cutting a cardboard roll, such as a paper towel tube, on a bias by squashing it flat and shearing through it at about 45° with a pair of scissors. Then split it lengthwise up one side, open it up, and flatten.

The clip below is a flattened 180° r135 cylinder that exaggerates this effect.

[cid:image001.jpg@01CEE1CE.C8FB5470]

Regards,

James Kasson
Layout Manager
Steelhead Metal Corp.