Sheet Metal: Unfold from A-side For Woodworking

[ChrGBJ]

I'm trying to get Inventor to unfold from A-Side, i don't want it to use inner radius an unfold from that.

I do need to be able to offset A-Side radius a given amount, fx. 1 mm

This is the length i need.

This is what i gives.

Thanks for your help in advance.

[ChrGBJ]

I'm trying to get Inventor to unfold from A-Side, i don't want it to use inner radius an unfold from that.

I do need to be able to offset A-Side radius a given amount, fx. 1 mm

This is the length i need.

This is what i gives.

Thanks for your help in advance.

[kacper.suchomski]

Hi

This topic has come up at least a few times over the last year.
The expansion is calculated for the neutral surface, not for the edges.
The position of the neutral surface defines the K-factor, which you can change in the default sheet metal settings.

[kacper.suchomski]

Hi

This topic has come up at least a few times over the last year.
The expansion is calculated for the neutral surface, not for the edges.
The position of the neutral surface defines the K-factor, which you can change in the default sheet metal settings.

[pcrawley]

@kacper.suchomski is right - it's all about the k-factor and how Inventor makes the allowance for the way sheet metal stretches in a press.

1. Draw the neutral surface (the line between the A side and the "B" side - if that's what it's called?!) as shown in the image below.  (Use your existing sketch and offset it - don't try to calculate the dimensions)
   
2. Set the k-factor to 0.5 (halfway through the part)
3. Unfold it, you should get exactly what you are looking for:
   

 

[pcrawley]

@kacper.suchomski is right - it's all about the k-factor and how Inventor makes the allowance for the way sheet metal stretches in a press.

1. Draw the neutral surface (the line between the A side and the "B" side - if that's what it's called?!) as shown in the image below.  (Use your existing sketch and offset it - don't try to calculate the dimensions)
   
2. Set the k-factor to 0.5 (halfway through the part)
3. Unfold it, you should get exactly what you are looking for:
   

 

[ChrGBJ]

You are right in that i need it from the neutral surface, but it's not in the middle of the full thickness of the part.

This is for woodworking, so i need to make relief cuts allong the round corners.

I hope this clarifies my question.

[ChrGBJ]

You are right in that i need it from the neutral surface, but it's not in the middle of the full thickness of the part.

This is for woodworking, so i need to make relief cuts allong the round corners.

I hope this clarifies my question.

[johnsonshiue]

Hi! Then you set K factor to either 0 or 1. Setting it to '0' will obey inner faces length, while 1 is for outer faces length.

Many thanks!

[johnsonshiue]

Hi! Then you set K factor to either 0 or 1. Setting it to '0' will obey inner faces length, while 1 is for outer faces length.

Many thanks!

[pcrawley]

I'm not sure which curve is the one you want unfolded to a known length.  Is it the nearest edge, the black curve at 1mm or the yellow curve 2mm from the nearest face?

It's quite unusual to figure out k-factor this way - it is normally calculated as the ratio of the neutral axis to the material thickness and falls in the range 0 to 0.5.  It is usually calculated by bending a sample of material in a press because different materials, knives and V-blocks all produce different results - but in your case it's wood!!

So you really want to 'cheat' Inventor's sheet metal knowledge and just get it to unfold the part to a specific length - with no stretch allowances.  Work on the "ratio" part of the equation:  Take the distance to your 'true length line' from the A Side and divide it by the overall "thickness" parameter.  That's the "ratio" of thickness to neutral axis ('true length line' in your case) - and therefore your k-factor.  

Your part looks to be about 12mm thick - so if you want the black line at 1mm from A-side to be the true unfolded length, your k-factor will be 1 divided by 12 = 0.0833.  If it's the 2mm line offset from the A-side, then k-factor is 2/12 = 0.1667.

Sorry for the essay - I've never thought about k-factors that way.  It could be very useful in something I'm working on... thank you 😉

[pcrawley]

I'm not sure which curve is the one you want unfolded to a known length.  Is it the nearest edge, the black curve at 1mm or the yellow curve 2mm from the nearest face?

It's quite unusual to figure out k-factor this way - it is normally calculated as the ratio of the neutral axis to the material thickness and falls in the range 0 to 0.5.  It is usually calculated by bending a sample of material in a press because different materials, knives and V-blocks all produce different results - but in your case it's wood!!

So you really want to 'cheat' Inventor's sheet metal knowledge and just get it to unfold the part to a specific length - with no stretch allowances.  Work on the "ratio" part of the equation:  Take the distance to your 'true length line' from the A Side and divide it by the overall "thickness" parameter.  That's the "ratio" of thickness to neutral axis ('true length line' in your case) - and therefore your k-factor.  

Your part looks to be about 12mm thick - so if you want the black line at 1mm from A-side to be the true unfolded length, your k-factor will be 1 divided by 12 = 0.0833.  If it's the 2mm line offset from the A-side, then k-factor is 2/12 = 0.1667.

Sorry for the essay - I've never thought about k-factors that way.  It could be very useful in something I'm working on... thank you 😉

[ChrGBJ]

Thank you for taking your time to answer!

and it's the black line that i want to hit on both inner and outer radius from the same side at the same time. as johnsonshiu points out the K-factor moves in different directions for inner and outer, there must be a way to calculate it from the selected A-Side faces.

[ChrGBJ]

Thank you for taking your time to answer!

and it's the black line that i want to hit on both inner and outer radius from the same side at the same time. as johnsonshiu points out the K-factor moves in different directions for inner and outer, there must be a way to calculate it from the selected A-Side faces.

[pcrawley]

I put the workings in my previous post:

Your part looks to be about 12mm thick - so if you want the black line at 1mm from A-side to be the true unfolded length, your k-factor will be 1 divided by 12 = 0.0833.  If it's the 2mm line offset from the A-side, then k-factor is 2/12 = 0.1667

[pcrawley]

I put the workings in my previous post:

Your part looks to be about 12mm thick - so if you want the black line at 1mm from A-side to be the true unfolded length, your k-factor will be 1 divided by 12 = 0.0833.  If it's the 2mm line offset from the A-side, then k-factor is 2/12 = 0.1667

[ChrGBJ]

Sorry again, but the question wasn't how to calculate it, but how to hit 1mm in from the selected A-Side with both an inner and an outer radius at the same time.

Thank you for being patient with me

[ChrGBJ]

Sorry again, but the question wasn't how to calculate it, but how to hit 1mm in from the selected A-Side with both an inner and an outer radius at the same time.

Thank you for being patient with me

[kacper.suchomski]

K = offset from inner radius / thickness

[kacper.suchomski]

K = offset from inner radius / thickness

[ChrGBJ]

the sheet is 16 mm
i need it to be offset by 1 mm

so for (A) it would be 1/16 = 0,0625
and for (B) it would be 1-(K-factor of A) = 0,9375

but how do i define it in the rule, that it needs to use these?

the k factor can't always be 0,0625 because then it would not work for outer radius.
the k factor can't always be 0,9375 because then it would not work for inner radius.

sorry if i'm being dumb here.

[ChrGBJ]

the sheet is 16 mm
i need it to be offset by 1 mm

so for (A) it would be 1/16 = 0,0625
and for (B) it would be 1-(K-factor of A) = 0,9375

but how do i define it in the rule, that it needs to use these?

the k factor can't always be 0,0625 because then it would not work for outer radius.
the k factor can't always be 0,9375 because then it would not work for inner radius.

sorry if i'm being dumb here.

[kacper.suchomski]

Offset surface and use Unwrap tool.

[kacper.suchomski]

Offset surface and use Unwrap tool.

[ChrGBJ]

Sorry maybe i was a bit to fast on the trigger, will check it out, thanks

Original Message:
Unfortunatly that isn't a possibility, since i need hole and exstusions from the unfoldet part/s

[ChrGBJ]

Sorry maybe i was a bit to fast on the trigger, will check it out, thanks

Original Message:
Unfortunatly that isn't a possibility, since i need hole and exstusions from the unfoldet part/s

[kacper.suchomski]

You won't get it. Sheet metal module is optimized for the design of sheet metal, not wood.

Create a flat wood model using classic modeling tools, then bend it in the appropriate places (also using classic tools).

[kacper.suchomski]

You won't get it. Sheet metal module is optimized for the design of sheet metal, not wood.

Create a flat wood model using classic modeling tools, then bend it in the appropriate places (also using classic tools).

[ChrGBJ]

i'm aware of that, thanks for trying 🙂

[ChrGBJ]

i'm aware of that, thanks for trying 🙂

[Ivan_Sinicyn]

That's not quite correct. I experimentally matched the K-FACTOR to the CEIBA plywood. The flat pattern is pretty accurate.

[Ivan_Sinicyn]

That's not quite correct. I experimentally matched the K-FACTOR to the CEIBA plywood. The flat pattern is pretty accurate.

[kacper.suchomski]

Alternatively, create a sheet pan without cutouts and add the cutouts in a flat pattern.

Or check out the Unbend tool.

[kacper.suchomski]

Alternatively, create a sheet pan without cutouts and add the cutouts in a flat pattern.

Or check out the Unbend tool.

[ChrGBJ]

The unfold tool seems interresting, will check it out a little more

[ChrGBJ]

The unfold tool seems interresting, will check it out a little more

[pcrawley]

@ChrGBJ - I don't think you are going to get this to work the way you want.  I'd model it as two parts, each with the appropriate k-factor, then derive & combine them in a new part if you need a single part representation (just remember that it will not unfold correctly!). 

Although Inventor lets you work with multibodies in sheet metal, it isn't capable of unfolding each bend using a different k-factor.

[pcrawley]

@ChrGBJ - I don't think you are going to get this to work the way you want.  I'd model it as two parts, each with the appropriate k-factor, then derive & combine them in a new part if you need a single part representation (just remember that it will not unfold correctly!). 

Although Inventor lets you work with multibodies in sheet metal, it isn't capable of unfolding each bend using a different k-factor.

[YannickEnrico]

It is actually possible to unfold using multiple K-factors

You just have to draw the part correctly.

For each sheet metal function, you can define the unfold rule - And it doesn't have to follow the sheet metal rule.

I'll attach my model part for inspection

[YannickEnrico]

It is actually possible to unfold using multiple K-factors

You just have to draw the part correctly.

For each sheet metal function, you can define the unfold rule - And it doesn't have to follow the sheet metal rule.

I'll attach my model part for inspection