From Freeship to CNC

These forums are amazing. You all make it that way. Thank You.

So, I now have a complete boat design file saved in Free Ship 2.6 . I want to take this file and make it workable in a CNC format, so I can have a Plug made. This is a Model that is 1 meter in length. I am hoping to keep things simple. There may be more than one way of going about this. I would really like to hear them all. I know there are a lot of details that will have to be worked out between the CNC company and myself regarding the plug and what I want to use it for. I am mainly interested in just getting a file that they can plug into their systems. Thank You, in advance.

I may only have an hour left on the forums tonight so please don't take offense if I don't respond right away.

 

It's simple, just export the 3D model in format, for example, igs.
In any case it is best that you talk to the owner of the CNC router to find out which file format supports his machine.
Cheers

 

Freeship can export the linesplan into several formats. Here are your options:



I think the best option is to export into 2D DXF, which is readable by nearly every CAD software. The CNC workshop will then be able to transform it into whatever other format they need, or into a set of coordinates.

Cheers

 

Be careful with IGES.

Freeship/Delftship does not use NURBS to represent the surfaces, hence it has to divide them into several pieces when converting to IGES (which is a NURBS format). You might end up with an unfair surface with gaps between the surface pieces or even have trouble with arbitrarily and faulty set surface normals (which define what is "inside" and "outside").

Bitter experience here, folks...

In general I find data exchange with Freeship/Delftship and other CAD/CAM software a huge problem, which is a pity since apart from that I like Freeship/Delftship a lot.

 

Olav, can you tell us a bit more about your bad experience? I have used the export options in the past and have not encountered anything really relevant or which cannot be easily fixed.

 

Sure, Slavi.

Especially in areas of great distortion like forefoots, bulbous bows or afterbodies of merchant ships (i.e. with gondolas) the single surface from Delftship is divided into up to hundreds of little pieces which form an unfair, non-continuous hull surface.

As an example here is a small 450 TEU container vessel designed in Delftship and then exported to Rhino as an IGES. The screenshots are from Rhino.

At first you see the large number of individual surfaces (177 in this case - the original Delftship model is made of 4 surfaces/layers - hull, transom, forecastle and poop) and even a large hole in the forebody.



Eventually this hole disappeared after several new attempts to export the model, since Delftship calculates the IGES export (and consequently the division of the NURBS surfaces) in a slightly different manner each time.

Another screenshot shows the afterbody of the vessel in Rhino's wireframe mode with the direction of the surface normals visible.



Note that most arrows point inwards but some point outwards. This has to be flipped if you want to do some hydrostatic calcs with a Rhino plugin such as RhinoMarine or Orca3D or you'll get faulty results. I also assume that this may cause some serious trouble with a CNC machine or a 3D printer. Admittedly not a very big problem to fix, but quite a tedious work to do.

One might be better off with a Delftship model that is made like an IGES surface, i.e. with four points for every face and all internal points connected to four faces. However, this would dispense with the beauty of Delftship's way to model a hull where you can put your control points wherever an in whatever number you like.

See also this discussion on the Delftship forum.

 

Good info, thanks. The hulls I have created so fare are of much simpler form (small power and sailboats up to 12 m), which might explain why I didn't encounter big problems. I am also very penny-wise when it comes to the usage of control points in Freeship. I always try to use the minimum number of control points required by the hull form, and always try to keep them in regular rectangular arrays. But I realize that you are working with much more complex shapes, so sometimes it is not possible to work them out in that way.
Regarding the normals to the surfaces, did you try to first flip them in a correct way in Delftship, and only then export them to Rhino? That might be a much simpler way, imo.
Cheers

 

Yes, simpler shapes will cause much less trouble, although even areas like the forefoot even on simple hard-chine planing hulls can be a mess.

Same with me, although I try to overcome my "traditional thinking" in sections, buttocks and waterlines a bit, since this is not how surface modellers work.

Not always, but it can occur occasionally like in this example - and I make a living with a lot simpler shapes (but that's a different story). By now I like to model hard chine hulls directly in Rhino, but complex merchant ship or superyacht hulls can be designed so easily in Delftship that I'd prefer to stick to it.

No, I didn't do anything with the model in Delftship. The original Delftship hull has no problems with normals pointing in the wrong direction; this occurs only during the export as an IGES. But I'll try it out tonight, though.

 

Good Day Gentlemen,
Once again, good heads bring good results. Its a good day when I learn something with the morning coffee.

Thanks a lot for your input.

 

OK, I had a look at my container vessel hull in Delftship yesterday evening.

You can change the direction of the surface normals in Delftship, but In my opinion it's much more tedious to do there than in Rhino. However, the major problem is the unfair and sometimes even not closed* hull surface after the conversion to IGES format...


*Hydrostatic software or plugins will abort the calculation once the "leak" gets immersed.

 

Have you tried the GHS export? Rhino can import that. Not tried it myself but I have had a file from Prolines (Iges V4.x) that was 1.5mm unsymmetrical on a 4m dinghy hull at the sheerline!. Rhino has the tools to get the Normals right and also good tools for surface rebuilding within very small tolerances to get fair shapes. A couple of tenths of a millimetre is irrelevant on a 4m dinghy hull as there is at least that in the CNC foam cutting.

Might also be worth playing with the import IGES in Rhino, you can set custom parameters. If you look at the various 'flavours' say for ProE and SolidWorks they are not the same. I always start with an incredibly tight tolerance in my base Rhino file to try and eliminate problems later. Not sure all the other systems are quite as 'tight'. Sometimes that area can generate problems.

 

Since RumnCoke model is not very complicated, maybe the solution is to re-build the model with a program that does not have so many problems when exporting iges format files.