Pro Sheet Metal Design Intent Problem

[Kamdmai]

I have a design intent problem, I have sheet metal formed as a ocotogon each octogon will have a tab bent inward but it will only be in the middile, say one wall in the octogon is 10 across we'll i want a wall say 4 inches in the middle bent inward which is fine if your goin to use a wall with a relief. here is my problem the tabs bent inward will not be flush with the top of the octogon, they will protrude up and over. yes i can use the the add wall flat and then add a bend to it but this defeats my design intent to control the length of the tab. lets say i make it 2 inches, i want to control this, using the wall and bending it is great except if someone changes the radius the won't realize they threw the length of my tab off. what i did was used an extruded wall and created a datum point at the corner of three surfaces picking the green side of the wall, a datum goin thru the center of the octogon(datum right) and the top datum. i then sketched my wall with a arc and a straight line and dimesioned per my design intent from the created datum point to the end of the line and then created the thickness of the surface( the dotted white lines that represesnt the white side of the part) and dimensioned the dotted line to control the inside radius. it is my understanding i should control the sheet metal part with the inside radius dimensions. i then made the feature both sides 2 inches i now have a wall with my design intent (the length of the tab is contolled) rather the flat wall then bend technique. my questioin is this correct? i got excatly what i want but i have my doubts by driving the radius this way. all other sheet meatal feature seem to have an internal radius option driving the radius(you know ...with bend# thickness or 2x thickness and the cool round corners if you sketch with all straight lines) rather than creating the inside radius and dimentioning it yourself. it works but am i right or wrong? any suggestion are appreciated

 

[im4cad]

I still have some "clouds" about what you were saying, but I'm pretty sure I understood your case.
First of all, it doesn’t really matter if you use the internal, or external radius option while creating your wall. You can pick whichever you want depending of your case, and keeping in mind the wall thickness.
Second, I think you can use an edge instead of creating a datum point to create your wall.
Third, if I imagine your wall created in sketch mode from an arc and a straight line, trying to control the length of the wall from your reference point, and thinking about your concerns if someone is going to modify the radius I can tell you that no matter if you’re trying to control the length with either an horizontal, or vertical dimension, the length of the wall will change when changing the radius.
To check this out create a copy of your part, create flat patterns for the original part and the copy, create an assembly using coordinate systems, change the color to one of them, change the radius of one of them and regenerate, and you’ll see that those two walls are not exactly the same.
I think you can control the length of the wall to be constant using a relation (even if you change the radius), but probably you have to give up one of the vertical, or horizontal dimension that controls the wall.
Anyway, there’s a chance that I didn’t understand 100% percent your problem.
im4cad
Pro Design Services, Inc.

http://www.cadproe.com/pds/home.asp

 

[Kamdmai]

------------ ---|----------|
/ | | \ | | |
/ |____| \ | | |
/ \ | |
/ \ |----------|

(half of octogon)top view rightside view

ok i tried to sketch part of what i am asking. sketching a octogon and extruding it is easy but adding the tabs in the center is what dosent seem to work for me. i dont want the tab to go the full length of the wall, and i dont want it to be flush with a relief either, if i use create wall with radius and pick the edge it wants to go the full length of the wall, i dont see a way to control the length and have it in the center with that command. i want a partial wall so i used #extrude wall no radius (i'm sketching the radius) pick the edge and then use by point and pick my created datum point then sketch what i want:


radius here> ---* <(datum point)
|
2&quot; tab> |

i can redefine the extruded wall both sides and give it my depth. this way my 2&quot; is always 2&quot; i dont care if the flat pattern gets bigger or smaller. this way if i change the bend radius my design intent to always have a 2&quot; tab will be intact no matter what i make the radius. it's hard to convey an idea with dash lines but i hope this helps clear up my gibberish if there is a way to create this with out all my extra steps please advise. thanks for replying any feed back is appreciated.

 

[im4cad]

Sketches are good enough to explain your case, and it’s exactly what I thought, but I was thinking you are concerned about having a constant length, not width for your tab.
Speaking about your 2” width, this will never change, no matter how big the radius is, and there’s no need to talk about intend design for a constant length in this case, that will always be 2” being an extruded wall with a fixed depth related to a fixed datum plane.
im4cad
Pro Design Services, Inc.

http://www.cadproe.com/pds/home.asp

 

[Kamdmai]

ok, thanks for the quick answer, i'm only on day 4 of learning pro sheet metal on my own. it's not goin to bad i have some more questions but i think ill start a new topic when i get home later. i work a second shift and what i work on is classified and i can't get outside internet access from work so i'm asking questions from home. it would be nice to have it in front of me when i'm typing so i can write all the menu picks i'm makingbut oh we'll i guess i could write it on a sheet of paper. thanks again.