I have a 3d sculpted cylinder and I would like to unrapt it into a flat object. Any hint on how I can do this ?
I hope this makes sense.
Gaston

Why do you want to unwrap it? It might give us better insight to the proper tools necessary to reach your goal.

Hi Phil,
I have a router equipped with a 4th axis but my cam program (Cut3D) does not produce toolpaths for a 4th axis so my workaround would be to create the 3d model in MOI3d, unwrap the object into a 3d flat object, generate the toolpath with the CAM software then feed the 4th axis with the unwrapped axis gcode. That should reconstruct the original object.

Gaston

Hi Gaston, only certain kinds of surfaces called "Developable surfaces" can be unwrapped into a flat pattern like that.

Basically the surface must have a completely straight edge in one direction as you move across it.

Anything that is curved in 2 directions at any spot on the surface cannot be unwrapped without distortion. Like for example if you try to flatten a sphere you can't make a proper flat version that you can reconstruct the sphere from by only bending the flat version back again (with no stretching).

If you do have a model that only has developable surfaces in it, then one possibility is to import your model into Rhino, which has an "unroll" command that can make the flattened version for you.

There is another tool available for making unwrapped patterns called Lamina design: http://laminadesign.com/ - but it takes polygon data and then calculates a flat pattern of the polygon data.

MoI does not by itself have any functions for that kind of unwrapping - it is somewhat of a specialized area so it may take some time before those functions can happen directly inside of MoI.


From your description, maybe instead of an automatic unwrap function you may instead need to kind of manually break your model up into some strategic pieces (for example if generally cylindrical maybe into octants) by cutting it with boolean operations, then arrange each of those pieces in a way that will be easier for you to cut, then reassemble the pieces afterwards.

- Michael

Hi Gaston,

This is rather like my need to flatten the ship model I am designing in MoI so that it can be constructed as a paper model.

Are you able to attach an image of your model (or perhaps the 3d file itself)? I would be curious to see how complex the sculpture is that you are trying to unfold.

I have found what appears to be a workable method by exporting to sketchup (requires MoI V2 beta) and unfolding using the free Google Sketchup and a free ruby script. I will track down the link to the script if you want it.

The Skoogle script can sometimes fracture the mesh in weird ways as it unfolds. As Michael has advised, I found it necessary to break my model up into some logical pieces. It is also necessary to play with the density of the mesh when you export. The simpler the mesh is the better your chances it will unfold.

Finally, even though I have broken up my model along segments that I want to enforce some unfolding order on, I still make sure the pieces are "joined" so that they export with vertices joined from piece to piece (where the pieces should be one part).

This link on the Papermodelers forum gives an idea of what can be achieved:

http://www.papermodelers.com/forum/design-threads/3049-hmas-sydney-ii.html

Mostly for what he is asking, that type of "unfolding" of a 3d model wouldnt work for his 4th axis machine.

His 3dCut has whats called "4-sided machining" so he could just generate toolpath for his actual solid model and then just index his stock with the 4th axis!

Another aproach for him could be, if he wants to "convert his Y axis to A" or something like that could be to utilize the "3d relief" type software and then wrap that on cylindrical stock (If thats the type of wrap he is after...Cylindrical stock.).

There is a free one called Zsurf that works good with MoI.

Here is a simple example (drawn with v2beta) where I loft some ellipses.
I then measured the distances from the axis to the edge of each ellipses at 45 deg interval then plotted a curve for each ellipse.
Then I lofted these curves to produce the unwrapped surface that could be used to reproduce the 3d object.
I have not tried it but think that would work.
Making the slices and plotting the length of the rotating vector is a tedious process when done by hand but would be an easy one by computer.

Gaston

Hi Gaston,

I believe you'll need to use Rhino4 for this kind of process.
The Command you're looking for is Flow.

As a Jeweller I've previously used a very similar process to what you're after with my Roland MDX-15 mill.
At the time I was using a "mechanical rotary unit" via a gear on the Mill's Y axis to drive the rotary.
The Y axis length is 101mm, so this meant that all rings had to be "stretched" out flat to fit the 101mm length.

One of the 3DWaxMill Forum Members named Ken Sanders wrote up a basic Tutorial on how to do this with Rhino4.
Hopefully this Tutorial will give you enough info to help achieve similar results for your model.

regards Colin

Hi Gaston - the more typical kind of unwrapping is to unwrap a surface to a completely flat shape, so that it can be cut out of some flat stock material like sheet metal, which can then be bent to reproduce the 3D shape.

But the example you show there, the "unwrapped" part is not flat, it is all bumpy.

I'm not sure how it would be possible to cut your unwrapped version there with some kind of material so that it could be bent back into the 3D shape?

I think if you want to cut that with only a 3 axis approach, you're going to have to split that thing up into many different pieces, or sections.

One thing that I have heard of people doing before is to take numerous planar sections through the model, for example here I have set up some lines to the side:



Then use Construct / Curve / Project to project those lines on to your solid - this forms a set of contour lines:



Then you actually throw away your main model and focus on these contours, just cutting one at a time so that you have a series of slabs that you then glue together.




Maybe something like that would work for you?

But maybe things would be a lot easier on you if you could make use of some more flexible axis cutting though...

- Michael

Hi Michael,

Not totally off subject, is there a way of determining arc length or perimeter length of an ellipses or any other irregular shaped curve, within MoI.
A script maybe ?

-

Hi Danny,

> is there a way of determining arc length or perimeter length
> of an ellipses or any other irregular shaped curve, within MoI.
> A script maybe ?

There isn't anything set up for it currently, but I can add something in for the next beta that can be accessed by a script.

- Michael

Michael,
The unwrapping that he is after would be if he had "Cylindrical stock" loaded into a machine that would rotate (or 4th axis) with th "Y" moves. So if you think of his flat surface as that, then he is on the right track but I dont think his theory allows for the extra length in the cylindrical unwrap.

Danny is asking the appropriate question which is something you answered for me and provided the functions to produce the conversion from the input values. I'll find the thread and post it for Danny. This was the "Draw arc by length" instead of degrees thing you answered for me.

Danny,
This kindof talks about it and methods for getting this value.


http://moi3d.com/forum/index.php?webtag=MOI&msg=2558.1

SO think of his CNC as having a table that moves in x,y,z.

X moves left and right. Y moves forward and back. And Z moves up and down. With a lessor software, it wants you to draw things flat, then it takes the Y value and makes that value "ROTATE" the workpiece. essentially making the surface of a cylinder "Flat".

Its different than the unfolding stuff for paper or sheetmetal. It's more a toolpath thing. And you cant "Unfold" a 3d model in this manner.

I hadnt tested his theory though. But if it worked that way, and it could be done on the cad side, it would be a much sought after tool! :O

The software he has now does this "Slab Slicing" also. Just as you explain here.

Hi Burr - I guess I kind of see.... But really I'd expect for that kind of process that is specialized to how a particular rotating machine works to be handled by a CAM program that knows a lot of details about how that particular machine operates and can analyze things appropriately for it.

MoI is focused much more on just creating the model data and not really directly on the machine interfacing part of the process.

I wish I could make MoI focused on doing every possible thing! :) But there is just not enough time available for me to make it do every possible function, especially ones where there are much more comprehensive programs available to focus on that area.


Maybe I still don't quite understand what the main purpose is - it kind of sounded to me like Gaston wanted to get a 4-axis type cut with CAM software that is only currently set up to do 3 axis stuff...

- Michael

>>>>>Maybe I still don't quite understand what the main purpose is - it kind of sounded to me like Gaston wanted to get a 4-axis type cut with CAM software that is only currently set up to do 3 axis stuff...
>>>>

Thats basically it, I believe too. Most software under $10,000.00 doesnt do "true 4th axis". It does whats called "indexing" (just rotating the rotary by a provided value at some given point) or "wrapping", where they take one of the x or y values and convert it to an "a" (rotary) value. conversion axis*(360/(2*pi))/radius. The software does this conversion but in "2d". So drawing a circle that needs to be wrapped on a round bar is actually an ellipse.

to cut a 3d model, he needs to read his surface in 2d. I was kindof trying to answer him also with the previous post. The method he used to unwrap the model was cool but didnt take into account the "stretch" that happens with the conversion.

Anyway, thanks.

>>>>Hi Danny,
> is there a way of determining arc length or perimeter length
> of an ellipses or any other irregular shaped curve, within MoI.
> A script maybe ?
There isn't anything set up for it currently, but I can add something in for the next beta that can be accessed by a script.
>>>>>>>>>

I could use this also!

Thank you Michael and all. You guys are amazing :o)
I knew it could be done :)
Using Construct / Curve / Project allowed me to generate profiles easily. This is a big step

In the file attached you can follow the creation of the surface I'm looking for by lighting up objects in order.

Now I *only (:o) * need to find an automated way to move, rotate and position the sector profiles along the linear path line.
Is this possible? Any suggestions?

Gaston

Hi Gaston,

> Now I *only (:o) * need to find an automated way to move,
> rotate and position the sector profiles along the linear path line.
> Is this possible? Any suggestions?

Sorry, no there isn't any automated way to take a radial arrangement of curves and move them along a straight line path.

It's still not very clear to me exactly what you are trying to do. Could you possibly give some more details on your equipment and your overall plan of how you want to produce your finished design?

Note that the surface that you are generating with the "straight line" arrangement is not identical to the original 3D surface - the distances between different peaks and valleys in your shapes is different in the "straight" one versus the 3D one, that produces different shaping when you loft a surface through the straight one for example.

So there is a kind of distortion happening with the method that you are using here, it is not actually a directly "unwrapped" version of the other surface.

- Michael