3D CNC routing of plywood sheets

Discussion in 'Software' started by Mike Inman, Nov 17, 2018.

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  1. Mike Inman
    Joined: Oct 2018
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    Mike Inman Junior Member

    Has anybody worked through the whole process of hull/bulkhead/stringer design in plywood on to 3D CNC routing of the plywood pieces?

    If so, what software / process did you use? Any challenges with the CNC mill shops understanding the CAD output?
     
  2. wet feet
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    wet feet Senior Member

    I haven't done it for a hull,but I have produced the framing for several plugs using Rhino.No problem with the CNC shop because I used the dedicated RhinoCam to generate the cutting files and just had the operators load the files and run them on the CNC on our premises.I did provide a stack of small prints to aid in labelling the parts and to specify the sheet thickness and tool diameter.
     
  3. Mike Inman
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    Mike Inman Junior Member

  4. TANSL
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    TANSL Senior Member

    I have experience in the development of construction drawings (CAM) metal boats. Definition of pieces and extrusions, nested parts, files for cutting by numerical control, sketches for the preparation of profiles, lists of parts, used material and waste, calculation of weights and centers of gravity, etc.... a whole "system" to generate all the necessary information to build a metallic structure. I use AutoCAD together with my own software. In My Gallery, in this forum, you can see some example of my work in this field. I have partricipated in the structure of more than 30 metallic boats. I think the system that I use can easily be adapted to the construction with plywood / wood. If you think I can help you, please send me a personal message.
     
  5. wet feet
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    wet feet Senior Member

    The basic level.To avoid lots of gouges in the spoilboard on the machine I cut the bevels as a series of contours at intervals and left the final cleanup until the framing was assembled.It is entirely possible to cut all the bevels that aren't undercut.I found it very helpful to be able to use the same piece of software for the whole process rather than having to export iges/step files and then open in a CAM program that might not cleanly deal with them.
     
  6. JamesG123
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    JamesG123 Senior Member

    CAD/CAM pretty common in nearly every industry these days except for old school craftsmen. Often its easiest, even a "shortcut", to model the whole object as part of the design process and when its finalized, you "pick out" the parts of it that will be machined and export them their own files and orient / prep them to be CAM files.

    Most 3D software suites will have plugins for generating G-code, but it has to be tailored to the machine its actually going to be run on. That is why CNC shops are going to want your model file (.STL etc.), because they are going to run it thru their own interpreter and g-code generator tuned for their machines.
     
  7. TANSL
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    TANSL Senior Member

    Without wishing to argue and fully respecting any contrary opinion, I believe that any CAM program is capable of exporting / importing files.igs, or similar, without any type of problems. What happens, in my opinion, is that Rhino is not really a CAD/CAM program (please, nobody be offended by my statement) and, from what I have experienced, it may have problems with the import / export of files not generated by it. And, of course, I agree that working with a single software is preferable to exchanging information between several different programs. But that is possible to do with any software that is really CAD/CAM.
     
  8. John Perry
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    John Perry Senior Member

    Since you say you are working with plywood I wondered why are you are considering 3D routing? If the panels of a chined hull are cut with 2D router there will be small Vee notches where the panels join but epoxy loves to fill those notches. The more chines the smaller the notches become.

    Yes, I have been though the whole process building a small boat, only 15 foot LOA, but the process would be the same for a larger boat. I used Solidworks for the design and for generating a .dxf file for each panel then used a program called 'mynesting' to layout all the pieces (nearly 200 pieces even for just this small boat) on standard size plywood sheets. The output from 'mynesting' was a .dxf file for each plywood sheet and this was acceptable to the company that did the cutting for me. The cutting was actually done with a CNC waterjet cutter, I got a comparative quote for CNC routing but that was more expensive. The accuracy and finish from the waterjet machine seems fine for boatbuilding work, I dont think routing could have been any better. Mind you, dirty water in the waterjet machine did stain the wood - but not a problem unless you want a clear varnish finish. I made a few silly mistakes at the design stage, not thinking through the sequence of assembly properly and thus putting a few of the tabs and slots in the wrong places, but apart from that the whole process worked out fine.

    The 'mynesting' program is one you download then pay a fee each time you use it, I have heard that there is now at least one program that does the same job free of charge but I dont know any more than that.

    I have a bit about the project here: Hostellers Sailing Club - Design and Construction of a 15' rowing boat http://www.hostellerssailingclub.org.uk/index.php/articles/design-and-construction-of-a-15-rowing-boat
     
  9. DCockey
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    DCockey Senior Member

    Rhino by itself does not do CAM but there are plug-ins which do.
    What file formats did you have problems importing or exporting?
     
  10. TANSL
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    TANSL Senior Member

    Mainly, but not only, exporting native Rhino files.
    Believe me, I would not say it if I had not had, on several occasions, that uncomfortable experience.
     
  11. wet feet
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    wet feet Senior Member

    I have had other problems in the past when using Mastercam with imported .igs files.Very often there would be surfaces that didn't appear to be joined after two stages of conversion into the system and the first step was always to look for and repair any discontinuities in order to avoid a 3D surfacing cut reaching the edge of an entity and then diving through the adjacent and apparently un-connected surface.By activating the check for gouging function for all surfaces this could be discovered before finalising the program but this absorbed quite a lot of time and at the time Pentium 3 chips were doing the toolpath calcuations.There would also occasionally be a phantom surface that had to be deleted or moved to an inactive layer.

    I found that when using Rhino and it's associated CAM module that I never had any gouging problem and never needed to amend any of the polysurfaces.I had occasion to send a few 3D objects to a fellow that was running Alphacam and he found all sorts of un-joined surface edges.I suspect he had set the tolerances to a very low figure on his system in the belief that it might improve his accuracy.My experience was that for wooden components a general tolerance of 0.1mm was as fine as was necessary in practice and using anything with a couple of extra zeros inserted might look impressive but added to processing time and unless you had a temperature and humidity controlled workshop didn't necessarily result in much of an advantage.After my first contact with him I resorted to checking for naked edges and joining all surfaces.With that much extra work we overcame the problem.I seem to remember that he was paying an annual licence fee that we were not subjected to with Rhino.All in all I found Rhino capable and good value.I will be watching this thread with interest to see what the participants have found to be better as I am always open to new ideas.
     
  12. TANSL
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    TANSL Senior Member

    In my opinion Rhino is a great program but even it with his plug-ins can study many problems that some types of boats pose to a naval technical office. That on the one hand. On the other hand, there is a lot of documentation that accompanies a project, drawings, tables, lists, sketches, etc. and that Rhino can not perform.
    However, there are programs that do all that, but in which the generation of 3D models is too laborious. Therefore, it is quite normal to use Rhino to create the 3D model and export it to other real CAD/CAM naval softwares. That's where compatibility problems arise.
     
  13. DCockey
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    DCockey Senior Member

    I've heard of problems when importing 3D models from Rhino into at least one naval architecture program if trimmed surfaces are used in the Rhino model. Apparently some software does not allow trimmed surfaces.
     
  14. wet feet
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    wet feet Senior Member

    Could you fellows tell me which CAM program you have found that doesn't have a problem with importing other file types please?I may have to do some Christmas shopping.I have heard good things about Hypermill,but haven't actually used it.It would also be nice to know what post processors are included in the package.Thanks in advance.
     

  15. TANSL
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    TANSL Senior Member

    The best, of course, is not having to import / export files between the various software. and for the user it is also very desirable not to have to deal with several programs but to do everything with a single platform. Good CAD / CAM programs do not need to change platforms to perform different jobs. but they are very expensive, although, depending on the number of projects / year you plan to do, they can be cheap.
    Having said all this, what you should do is a detailed description of the jobs you want to do, consult with the different dealers, and test yourself with the different test versions that all the programs have. Another very important thing to take into account is the learning curve / time of each software and, also, for totally subjective reasons, you will be more comfortable with some programs than with others, and that is also very important.

    A good drawing program will allow you to easily define the pieces, perform the nests and bring the cutting clichés directly to the machine. Most current numerical control cutting machines are capable of dealing with files in iges, sat, dxf, dwg, ... format, that is, you do not need a post processor that generates G-code.
     
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