How to get a flat pattern for the top deck of a curved surfboard model

brad_phelan

I have the following surfboard model


The top deck is a developable surface. ie: it is bent in only one direction. 


I want to be able to generate a drawing of the top deck, but flattened so I can send it to a CNC router or laser cutter to cut out the wood for the top deck.I will then bend the top deck over a frame to generate the correct shape.

However I can't for the life of me figure out how to flatten the top surface out as required.

daniel_splawski

I've run into this exact same issue on a different project that I was working on.  If anyone has any input, I'd love to hear it as well. 

konstantin_shiriazdanov

there is Exact Flat app in appstore, but i never used it myself
https://appstore.onshape.com/apps/Manufacturing/3RPIJMNQJ2SXMC7IZEUELB23XF3VEXVAAKM4UUA=/description

emagdalenaC2i

Hi, could you share the document?

I will try to test it with a simple one and share it, but maybe it did'nt work with your model

emagdalenaC2i

Ok, my first attempt is to measure and create the flat part

It will work if that's a simple part

https://cad.onshape.com/documents/01ac924b58a0d766cfa18c83/w/04fa0c16babb09f0f71328b4/e/6dd406e7b2abc3d9b6cfd752

brad_phelan

@emagdalenaC2C  That looks like a promising strategy except instead of doing it by hand it looks like a job for a feature script or a more complex use of a feature driven pattern. Basically we need a plane that intersects the surface which can be measured and then used to generate the flat curve.

This is my progress so far. It should work but I can't seem to keep the sketch points in the correct relative position.

https://cad.onshape.com/documents/43aea59b2094e097bd3dd16b/w/fd03fb5272eb38e34b225c66/e/f1ca948d5adda964ca317112


 

konstantin_shiriazdanov

this is actually a crazy solution, but if soft allows - why not https://cad.onshape.com/documents/eca0fa6398213f46bfaba7c6/w/a7ca4e3b1356df7302e9a35c/e/133eec1dd3ac473255c7fb9b

emagdalenaC2i

What do you mean "keep the sketch points in the correct relative position"?

brad_phelan

@konstantin_shiriazdanov Nice  I can't quite tell what you did different to my solution to get it to work correctly?

@emagdalenaC2C I mean the difference between @konstantin_shiriazdanov's solution and mine. He got the points to stay in the correct position whilst mine drifted around. I can't see what he did different to get this to work.

konstantin_shiriazdanov

feature pattren deletes external references from sketch, even references to the origin, so you need to add a fix constrain to some base point

i have actually a Sketch Wrapper FS - it wraps sketch edges to the cylindrical and cone surfaces, if you are intrested in automation of this process this FS can be modified to perform inverse transform

emagdalenaC2i

ok, got it

brucebartlett

@konstantin_shiriazdanov I love to see FS to unwrap a surface to a sketch if it's not too hard to program. 

brad_phelan

@konstantin_shiriazdanov  I see now. Thanks

brad_phelan

@konstantin_shiriazdanov If you could do the inverse wrapping operation without the crazy feature patterning that that would be great. After looking around I see a lot of people miss this feature. Sheet metal only works with flat faces where it should be working for cylinders and cones as well. I guess OS will eventually upgrade sheetmetal to do this.
 

konstantin_shiriazdanov

ok, then i'll modify that FS to unwrap regions of cylindrical and conical surfaces

emagdalenaC2i

@brucebartlett that FS is not too easy

We can create a simple one, but working just in a few and easy cases

konstantin_shiriazdanov

ok, now V7 version of Sketch Wrapper FS can unwrap faces on cylinder and cone surfaces
https://cad.onshape.com/documents/eca0fa6398213f46bfaba7c6/w/a7ca4e3b1356df7302e9a35c/e/133eec1dd3ac473255c7fb9b

brad_phelan

Awsome

brad_phelan

How do I import this script. I can't find it under "custom features" by searching for "sketch wrapper"

brad_phelan

Don't worry. I found it.

brad_phelan

Damn.. It doesn't work for my example obviously. I have a "developable surface" It is not a cone or cylinder but it bends only in one direction. I'm sure script could be generalized. I'll try and take some time to understand the script and make some changes

konstantin_shiriazdanov

it uses analitical formulas for map, don't think it can help in the case of arbitary developable surface, sorry. possibly feature pattern of section planes can be the best way

jake_pill

Moving this one back up! I have run into a very similar issue. I've tried exactflat but its wants to distort the parts. Has anyone come up with a solution here?

lana

@brad_phelan
If you surface is extruded ( lines in one direction) Onshape sheet meal handles that.
https://cad.onshape.com/documents/22a9d060420e06525bd4cd3a/w/49cbbe98f6408015d2774185/e/ae75efeb21f138ca7ad2f23c

7Cs

Is there any solution to flatten a boat hull?

S1mon

terence_orcy said:

Is there any solution to flatten a boat hull?

It really depends on how complex your boat hull is. In general, if it is developable, there may be a way to do it with Onshape, although it may not be easy without turning it into a ton of triangular facets. If it needs to have some stretch (i.e. compound curvature), Onshape doesn't handle that natively.

There are other tools like Exactflat or Rhino which can do this kind of thing much more easily.

7Cs

S1mon said:

terence_orcy said:

Is there any solution to flatten a boat hull?

It really depends on how complex your boat hull is. In general, if it is developable, there may be a way to do it with Onshape, although it may not be easy without turning it into a ton of triangular facets. If it needs to have some stretch (i.e. compound curvature), Onshape doesn't handle that natively.

There are other tools like Exactflat or Rhino which can do this kind of thing much more easily.

Thanks for repling. ExactFlat could do for sure, but wont open on my OnS, don't know why. It says it is free.. but when i open the app inside the OnS, shows "efonshape.exactflat.com refused the connection". 

Rhino, is the best tool so far, but it isn't cheap, ... i could just use a cracked version (which is ilegal and could harm my computer).

OnS is the ONE program that could do all i need in regard of hobbiest 3D plans except this part. Flattening a hull. ( the Yellow part is the a example of what i want to flat and cutoff from a plywood sheet.)

EvanReese

I'd love for Onshape to work out a native sheet metal loft feature. In the meantime, you can polygonalize it into triangles and flatten that. Here's a workflow you can use to do that somewhat parametrically (but it's definitely not perfect).
https://cad.onshape.com/documents/5719159de3d4e239df49c1fc/w/38e3e6374da47aac6c49f0eb/e/4201ded7e51a21f96f220b20

7Cs

Evan_Reese said:

I'd love for Onshape to work out a native sheet metal loft feature. In the meantime, you can polygonalize it into triangles and flatten that. Here's a workflow you can use to do that somewhat parametrically (but it's definitely not perfect).
https://cad.onshape.com/documents/5719159de3d4e239df49c1fc/w/38e3e6374da47aac6c49f0eb/e/4201ded7e51a21f96f220b20

S1mon said:

terence_orcy said:

Is there any solution to flatten a boat hull?

It really depends on how complex your boat hull is. In general, if it is developable, there may be a way to do it with Onshape, although it may not be easy without turning it into a ton of triangular facets. If it needs to have some stretch (i.e. compound curvature), Onshape doesn't handle that natively.

There are other tools like Exactflat or Rhino which can do this kind of thing much more easily.

Thanks for helping out. I got the ideia what you explained and as a hobbiest, this is very close to perfection. I really need to understand more about Onshape first, ..for exemple, the steps that have: (x) on it , is the first time I see it. But you showed that is possible. I will read more about what you did there and try to duplicate the process. Thanks again for it! 

SethF

@terence_orcyThat's a variable feature, and it is super flexible and useful. https://cad.onshape.com/help/Content/variable.htm

EvanReese

I'd consider this method to be "advanced modeling". Not that it can't be learned by anyone, but that it's not very obvious that it's possible or how it works when you're learning. No promises to do so in any useful amount of time, I may use this as a case study to make a quick Youtube video showing the workflow and put it on our channel.