Feature Script for a break off tab for bending.

bryan_lagrange

I come across this obstacle many times.

I have a part that I need to bend but the bend line is not parallel with edge to gauge from. Since we do not have a press brake with back gauges on different axis I have to do one of the following.

1) Etch the bend line then manually orient it between punch and die (not good for big run of parts) 
2) Create a fixture that will attach to the back gauge and is in the shape of the contour of the part or gets the edge parallel with the bend.
3) Create a break off tab by adding a tab to the end that will create an edge that will be parallel with the bend line. After bending, the tab is broken off and the edges are ground smooth.

Do you guys think this would be a good feature script to create option 3. If so anyone up for the challenge of creating this feature script?

Attached is a .pdf of what I described above along with images.

jon_sorrells

Added some manipulators for the width of the tab: https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/107cf4854dc70cbeed63cc98/e/b692addf96e4fd22a1078b04

brucebartlett

Yes please, Yes please. This is always a painful thing that has to be done on the end of the design. However really needs configurations so as to the get the finished part for assembly without the break-off tabs. If I had time and FS skills I give it a go but for me, if someone else can do it I will be a user and promoter. 

bryan_lagrange

I am thinking it could be added to the flat pattern of the model only and would not show up in the formed view of the 3D model. 

jon_sorrells

@byran_lagrange, how's this?
https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/4e888b5e5ed8eb49ddedb1fd/e/bcd29e4ce588a4a8309e55cb
The two edges you select need to be on the same face.  The hole/slit only works if the edge is straight.



Edit: updated link to V2 of the document, should be a little faster now.

bryan_lagrange

I like it

owen_sparks

Very nice, good work folks.

Owen S

jon_sorrells

It occurred to me that you probably want to line up with the center of the bend, not one end of it.
New version that does that: https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/bb290273762822d3864db4cd/e/b692addf96e4fd22a1078b04

Here's the before and after of what it is lining up with

bryan_lagrange

Nice work John

brucebartlett

Hi @jon_sorrells nice work witht this FS. Is it possible to add this to a curved face, I can think of examples where I have used break off tabs on curved edges as these are not easy to get a back stop for in a press.

jon_sorrells

@brucebartlett here you go
https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/0b12bb7ba33af1d7159428b2/e/b692addf96e4fd22a1078b04

bryan_lagrange

Just did a quick run through and this is a great feature. I will put it through a few more scenarios and will give you some feedback.

jon_sorrells

now at v5: https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/2b8f0f6ae67ddada28c0dceb/e/b692addf96e4fd22a1078b04
One of my coworkers suggested adding additional connections for the tab, so now there's an option for that.


Also, it can now handle more complex curves than it could before.

owen_sparks

Hi folks.  Forgive me sticking my nose in.

I wonder if it would be easier for the operator if the snap off parts were inboard a bit?

This way there is a definitive edge on either side to grind back too.

Cheers, Owen S.

owen_sparks

Also you'd probably want them to taper a bit to force the break to occur at the sacrificial end of the tab.  As it stands I think there is a 50/50 chance of taking a chunk out of the actual part.

OwS

bryan_lagrange

Here is a curve ball for you @jon_sorrells . There are instances when I have a part with multiple bends and none of the bends are parallel with the outer edge. In this case I have to make more than one break off tab on the edge so that there is at least one edge parallel with each bend line. 

@jon_sorrells can the feature script be adjusted to do this? (crossing fingers for a yes)

Here is a sample Onshape doc: https://cad.onshape.com/documents/971b4aa220787b5e7a9b3533/w/619f9a0b00182d01d30ccc32/e/44e8ab4cfd76821e05e2f175

Bryan

emagdalenaC2i

@bryan_lagrange Maybe it would be easier if you create a solid part and then convert to a sheet metal part or thicker the faces you want

Take a look at this sample

bryan_lagrange

@emagdalenaC2C The modeling of the part design is not an issue. As shown in the example I can design it.  The extra effort is needed when manufacturing this part. If you do not have a 6 axis press brake you need to create something to get an edge parallel with the bend line to make the bends. I normally create break off tabs to do this. The break off tabs are manually added to the flat pattern.The feature script shown here is an example of automating this function. The trick now is to get multiple bend tabs on the edge to be parallel to the bends.

brucebartlett

Neat idea, I have never done break-off tabs that reference across multiple folds but would work really nicely if done right. In these cases, I just cut small arrows/notches on the edge of the sheet on each end in the center of the fold and make the operator eyeball the arrows/notches to the center of the die. 

bryan_lagrange

We do parts for a local power sport company and I get parts with multiple bends at multiple angles with no edges parallel to the bend line. I use to etch the bend line or in some cases use notches like you. The only issue is if the operator loses focus and does not line everything up you get a bending error. The break off tab allows me to always have an edge so I can use the back gauge of the press brake and hit the bend line on a regular basis like any regular parallel edge bend. 

When I have to use the same edge of the part to place my bend tabs, for multiple bends, at different parallel orientations, I will have the tabs stick out at different height intervals with different widths. This is so I can note on the print which tab is for which bend and it also makes it easier for the operator to see and match the part to the print.

brucebartlett

bryan_lagrange said:

We do parts for a local power sport company and I get parts with multiple bends at multiple angles with no edges parallel to the bend line. I use to etch the bend line or in some cases use notches like you. The only issue is if the operator loses focus and does not line everything up you get a bending error. The break off tab allows me to always have an edge so I can use the back gauge of the press brake and hit the bend line on a regular basis like any regular parallel edge bend. 

When I have to use the same edge of the part to place my bend tabs, for multiple bends, at different parallel orientations, I will have the tabs stick out at different height intervals with different widths. This is so I can note on the print which tab is for which bend and it also makes it easier for the operator to see and match the part to the print.

Yes, I get it, nice way to manage these parts, next time I have a part with this scenario I'll use this method too. Now we just need the feature script to make the 3d modeling and drawings easier. 

Do you have and example with the drawings noting the different tabs for bends?

jon_sorrells

@bryan_lagrange, what would you want the tab(s) to look like for that?  Something like one of these?

And would you expect this to take one instance of the Break off tab feature or two?

bryan_lagrange

Nice work @jon_sorrells. I never though of using example l before with different profile edges on l tab. Something to try next time. 

Could you have it where we can specify the width of the break off tab.  I don't have to have them the full length of the edge for the break off tab.

Below is an example of how I would have made my manual changes in 2D.

@brucebartlett This is an example of how I create multiple bend tabs and label them to help the operator at the press brake. With a kerf width laser slit and a minimum tab to hold them you get a positive bend location using the back gauges of a press brake and minimum clean up after bending. 

Small parts I use 1 break off tab. When I get larger longer parts I use 2 so that the operator can use both back gauge fingers and it gives the operator more stability when bending the part.

jon_sorrells

Added some manipulators for the width of the tab: https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/107cf4854dc70cbeed63cc98/e/b692addf96e4fd22a1078b04

bryan_lagrange

@jon_sorrells your are awesome. This is a great feature script!

brucebartlett

Great work @jon_sorrells I'll look forward to using this. 

jon_sorrells

Now handles tabs for bends other than the one directly next to the tab.
https://cad.onshape.com/documents/eea009fcf35a0cd683265767/v/467c5a5872fdde831846abc9/e/b692addf96e4fd22a1078b04
If you update an old instance of the feature to use this version, you may need to toggle 'Opposite direction'.