3D Cad (Lesson 101)

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by superjacent, Jun 19, 2009.

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  1. Dec 18, 2009 #21

    Dana

    Dana

    Dana

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    Not to be nitpicky, but the "CAD" acronym is usually taken as Computer Aided Design, which can be 2D or 3D (though why anybody would want to design in 2D escapes me), and "CAM" is Computer Aided Manufacturing (i.e. CNC).

    AutoCad ended on top for awhile due to agressive marketing and not enforcing software piracy laws, so that everybody had a pirate copy and thus knew how to use it. They tried to improve its usefulness for mechanical design with the "mechanical desktop" package, but ultimately they dropped the whole thing when they created their "Inventor" software (kind of an imitation of Solidworks).

    -Dana

    It did what? Well, it's not supposed to do that.
     
  2. Dec 18, 2009 #22

    shadow

    shadow

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    By chance did you mean 512mB ram?

    Regards,
    Serge.
     
  3. Dec 19, 2009 #23

    jumpinjan

    jumpinjan

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    Yes, 512 MB RAM on the video card; 1GB for computer RAM is minimum.
    Jan
     
  4. Dec 19, 2009 #24

    Woodenwings

    Woodenwings

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    Quite right CAD is computer aided drafting. or computer aided design.

    CADD is computer aided design and drafting. CAD/CAM is computer aided design and manufacturing.

    2D is a doddle!!

    I always teach it as CADD. just so people understand the distinction. Although Catia can skip the need for paper i have always had to print paper for certification and records. and for the guys to write on when they assemble.

    i would be bored and angry without a nice 3D design package at my disposal.
     
  5. Dec 29, 2009 #25

    Mac790

    Mac790

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    I can't agree with that, my specification Dell 9400 (I know it's old but I love it, this Laptop is unbreakable, has been working for last two years 24/7, day and night all the time, I had only one problem with fans), 3GB Ram memory, ATI 1400 256MB, XP SP.2, WUXGA, Solidworks 2009 student edition:), I never ever had any problems with different projects (attachments). I'm not exactly sure, how much parts are there in those assemblies (it was easier with Inventor, parts numbers were in the right bottom corner), for example there are over 350/400 parts only in the rotary engine. The good thing about Solidworks is, that you can hide unnecessary parts.
    btw those assemblies aren't finished yet.

    Note that for the Nieuport 17 I made the entire fuselage, engine, cockpit, etc but wings, landing gears and H/V stabs were made by school mates (there is a unnecessary cylinder in it at the moment:)). Other projects were made by me exclusively.
    The biggest assembly I made on my PC had 1021 parts, but I made it in Inventor. Of course I won't make 15/20.000 parts assembly on my PC but better graphic card won't help me in this either.

    Seb
     

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  6. Dec 29, 2009 #26

    jumpinjan

    jumpinjan

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    Your work on your Nieuport 17 is pretty nice.
    I have been creating a SolidWorks model of the Junkers D.I over the past 2-3 weeks (I been waiting to do this for about 6 years). Today I cut the fuselage stations.
    Jan
    [​IMG]
     
  7. Dec 30, 2009 #27

    Mac790

    Mac790

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    Jan,

    Nice, thanks for sharing with us, I have to confess that I've never heard about that plane before, I'm really surprised that in 1917, somebody (Junkers) built a metal monoplane without struts. Do you have blueprints? Are you going to make also internal structure?

    Seb
     
  8. Dec 30, 2009 #28

    jumpinjan

    jumpinjan

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    Its the "first" all metal production fighter. The Junkers J1 (a 1915 technology demonstrator) is the first all-metal airplane to fly (even though it was made from iron sheetmetal)!
    Yes, I will eventually create the metal inner structures, but for now I'm creating building plans for a 1/8 scale RC model.
    I have collected as much printed material out there without any factory drawings, I'm not sure if they exist, but there is one D.I survivor in the Paris museum to look at up close.
    Jan

    [​IMG]
     
  9. Dec 31, 2009 #29

    Othman

    Othman

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    Unless you're using a high end CAD package like Solidworks at your work (or you use own it for you private business), they are far too costly to be practical for the hobbyist or small business... unless of course you're into pirating software.


    Supejacent, if you want to have a 3D model that can be changed fairly quickly then you're looking for a package that has parametric modeling. This is a powerful feature that allows you to set dimensions based on calculations or by referencing other parts/features. This is not always easy to manage though, it takes some practice to learn how to set your models up right from the start. This will allow you to widen your fuse by 5" and watch all the frames automatically stretch and change shape accordingly.


    Big expensive packages can do this.


    I've used AutoCAD, Rhino3D, ProEngineer, Solid Edge and Alibre Design. They all have their pros and cons.


    AutoCAD - great for 2D, never really used the 3D too much.


    Rhino 3D - very easy to use, great for surfacing and stylizing the airframe, but not good for making solid parts and editing.


    ProEngineer and Solid Edge - high end 3d parametric modeling. Great but Expensive! I personally prefer Solid Edge and the functionality of the 2D drafting module.


    Alibre Design - It was hard to go from high end packaged to this one, but once I changed my frame of mind I was able to work around the differences. Now it is the only package I use. The best part of about this package is that it is really affordable. The downside is that the dimensioning features of the 2D drafting isn't the greatest.


    For 2D drafting, the Solid Edge 2D drafting module is offered for free. Google it. By the way it has parametric drafting... quite useful.


    So in the end, I've combined the 3D modeling of Alibre Design with the 2D drafting of Solid Edge. I use Alibre to create the 2D views of my 3D models and then export them as DXF files, which I then open in Solid Edge to annotate them and make finished drawings. The downside is that I lose the link between my 3D model and 2D view. Oh well, small price to pay for a very affordable and powerful CAD system... and it's legitimate!


    Hope this helps.
     
  10. Aug 5, 2010 #30

    MountainLakeLabs

    MountainLakeLabs

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    All the best on your CAD adventure. A little tip that will save you much time, frustration, and money later:

    When you first start practicing with CAD, it's fine to make quick drawings. Connect the lines and all that. This, however, becomes a bad habit. Every time you connect one line to another or a line to a surface....make sure that is a "snapped to" connection. It's an issue that comes into play when maybe you design your own bracket or something and want a shop like mine to machine it. The CAM system is a stupid computer which requires only clean connected lines. It doesn't know what to do when you have lines that overhang or don't fully connect when zoomed in on. The bulk of the cleanup of CAD files prior to machining the parts is from lazy engineers and others who just never learned to connect the lines.

    If you can draw a cube of Aluminum or anything with connected lines, I can take that file and return to you a rock solid quote as to how much it costs and how long it will take to machine it. But, otherwise, we have to stick the CAD people on it for however long it takes to clean up. Where simple, that's cheap. Where complicated parts with hundreds and thousands of poorly connected lines, it's almost more work and time (=$$$) spent than if we had just redrawn the **** thing from hand drafting. Computers don't really make one any better or faster at engineering where done wrong. Pen and paper is often faster. "Oh my God! The Internet is down. We can't get our email." There is actually the old-fashioned telephone! Ever see these housewives and dweebs driving around all flustered when their GPS in the car goes out or Google doesn't map it? Too funny. It takes less time to pull out the old-fashioned street map and find your way there with no batteries required than it does waiting for Google and the printer to spit out directions; Takes more time to program or correct the GPS and put up with that computerized, eloquent-speaking, Englishman ***** voice yapping in your ears than just a good ol' AAA roadmap! :) Ever see these pampery-pooh kids nowadays? Afraid to ride their bicycles or go anywhere far from home if not electronically tethered to their mommies by cell phone. The more I use computers and electronics, the more I hate them. The more I can crank out parts for you lighting fast from a CAD file, the more I miss just talking to the old man machinist with magnifier glasses and getting his advice about better ways of doing things which the computer does not give.

    Anyhow, CAD is powerful, fun, and a great tool....but connect your lines well and you won't be throwing the computer out your window while cursing vulgarities at it. Snapped to lines save you oodles of time and money later when it comes to building the intricate things in automated fashion. But, where you don't have that or screwed up on the CAD files....go find the old man in his shop instead. He's not a slave to the computer system. :)
     
  11. Aug 5, 2010 #31

    Woodenwings

    Woodenwings

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  12. Aug 5, 2010 #32

    Tom Nalevanko

    Tom Nalevanko

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    This site is very suspicious. And AutoCAD is not made by SolidWorks which is not Dassault Systems.
     
  13. Aug 5, 2010 #33

    jumpinjan

    jumpinjan

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    Its only 2D.
     
  14. Aug 5, 2010 #34

    Woodenwings

    Woodenwings

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    Hey everyone, sorry the last post was kind of short. it may have sounded misleading.
    Yes this program is 2D.

    In 2003 Dassault Systems (yes the aerospace company) who markets SolidWorks and CATIA realised that it was difficult to crack the mid-range CADD market because Autodesk (AutoCAD)had such a strong foot hold. The Autodesk position was clear, they were the original. Autodesk was THE word in accessible 2D CADD for years. My first use of AutoCAD was in 1991.

    This is how Dassault Systems explained it to me (while I was working at Pratt &Whitney Canada, CATIA). AutoCAD was not patented, but trademarked. the actual commands and other things were able to be copied by anyone who dared. All of the iconography and a lot of the names for commands were trademarked.

    It seemed surprising but plausible that Autodesk could be shoved out of the low-end market by copying their program almost exactly! They had to rename some stuff, change the icons etc... and there you have it. I used to pay for it - it was called DXF Editor.

    Now they have made it better again and rebranded it free.

    Solidworks is a really great bit of design software. it is EASILY better than Autodesk inventor - because it is easier to use!

    I had to do some contract work where they used Inventor. they asked me "can you use Inventor" I said YES! how different could it be? My first 3d designing was with AutoCAD and inventor anyhow!

    After using, and getting used to CATIA and SolidWorks for several years I found Inventor to be a big horrible clickie nightmare. I later used SolidEdge - it is WAY better than inventor, but not as good as SW again. There is still lots of room for opinion and personal preference. This is just my opinion and preference. I feel qualified to give these as I have thousands of hours logged on SolidWorks and others.

    I urge you to try the software and tell us what you think!

    After leaving Engineering to become a teacher getting licences for software is a problem - you need approval!

    I have recently asked the School PC-LAN specialist to download the SW version of AutoCAD on 100 school computers for FREE! I'm looking forward to September when I can finally put AutoCAD-LT to rest. Why because LT is a piece of ****!

    AutoCAD continues to be a dominant force. there are several commands not present in the SW version like my favourite "Align"

    If any of you are having to simultaneously taper and add washout to a wing the ACAD Align command is for you! this is the only command that SW needs and doesn’t have to my knowledge.

    Try it on your rib sections!

    Cheers :ban:

    Shane
     
  15. Aug 12, 2010 #35

    sergiu tofanel

    sergiu tofanel

    sergiu tofanel

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    I have also been using AutoCad for years, and I prefer if for 3D modelling over any other package. This is just my sick preference, but if you know LISP (the language AutoCad routines are built upon), 3-D modelling becomes a snap.
     
  16. Aug 12, 2010 #36

    Dana

    Dana

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    Acad in 3D? <shudder> (Lost (In (Stupid (Parenthesis)))).... :)

    -Dana

    When only cops have guns, it's called a police state.
     
  17. Aug 13, 2010 #37

    sergiu tofanel

    sergiu tofanel

    sergiu tofanel

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    I know... you are not the only one rolling your eyes. But this is the only use I found for a class I took way way back in college: Structure and Interpretation of Computer Programming. The good people who taught that class thought it would be funny to teach us clueless freshmen scheme, which is a variant of LISP.
     
  18. Sep 4, 2010 #38

    ultralajt

    ultralajt

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    O.K., a question was placed on another thread, if there is a program that could make 3D model of fuselage if side and top views are available.

    There is no such porogram, but using some commands it can be done in Rhinoceros3D program.
    Of course, there is many ways to make 3D model using different approaches and sets of commands, but here is a presentation that starts with fuselage contours, following by cross sections and surface loft.

    I will show how it is possible to get 3D fuselage using just 4 to 6 lines...(4 enough for eliptic cross sections like sailplanes, more lines for more "boxy" cross sections)
    - upper fuselage contour
    - lower fuselage contour
    - side fuselage contour

    Of course, we are not able to have full controll over the cross sections as program do that by its best way, and that doesnt suits us well everytime.

    But this writting is only for presentation what commynds are used to go trough that steps. One can always use surface modifying tools to fine tune shape here and there later.


    So lets go drawing a fuselage!

    I will use a jpg drawing, a hand shetch of a vintage racer looking sport aeroplane, as an base for my 3d modelling.

    [​IMG]
    Now I will place this shetch into Rhino as an background image.
    View
    Background bitmap
    Place
    browse to and pick that image stored in my computer
    pick first corner and second corner, where you want this image to appear on your Rhino drawing space (I use Right view).

    Now you use bolean curve tool and draw a line that represent upper contour of the fuselage. Dont make any sharp cornerns! make smooth transitions! Look how I go with line over a canopy area!

    [​IMG]
    Note the curve avoiding coners at cockpit area!

    Now I draw also the bottom line (the belly curve of the fuselage)

    And we made also two aditional lines that will reopresent location of the widest fuselage line in top view.
    This will make our fuselage more beffier.

    [​IMG]
    Note all lines done. Of course, I draw them just roughly following the background shetch, but they can be made excatly as you want, up to your actual aeroplane measurements. As lines aee bolean cuves, we can still change or modify them to get closer to what we want. Just pick the "handle" point of a line and move to desired location. As you can see, I made lines at rear end of fuselage longer than needed.

    Now we move to the top layout of the fuselage to make line that will repesent side contour of the fuselage.

    As we did on side view, we just draw an bolean line over a side contour of the fuselage.

    [​IMG]
    Note the red line in top view. It is made to get a straight line for a fuselage centerline in top view.
    Note the green lines that are just a guidelines in order not to missalign sideview and top view lines.
    A yellow line is the side contour of our fuselage.

    What next?
    We must rotate side contour that we just make for 90 deg.

    [​IMG]
    Now we can see in perspective view that side curve is rotated and became also visible in top view.

    But now we must place that top side contour to match both lines on the side view that were previously drawn between upper and lower contour as a line where fuselage side line will be placed.

    It is an simple mater!

    Let mirror side contour first, to get two! (we need two of them..we can also use copy comand)

    [​IMG]
    See mirrored line over a red centerline. See top view and perspective view.

    Now we will use simple Rhino command to "married" two lines and get one at the place we want!
    We will use "intersecting curve projections".
    Just pick one of the side curves and one of the lines at side view and click this button:
    [​IMG]

    and new line is created!

    [​IMG]

    Lets do that with another pair of lines!

    [​IMG]

    Of course you will notice that lines (yellow) are somehow odd... one on left side, and another on right side.
    We just pick both and mirror them around fuselage ceterline on the top view window.

    Lets mirror them and hide or erase all other unwanted lines!

    [​IMG]
    I make lines in color, so you can see on different views where each line is placed.
    I remove all other lines that helps me het up to here.

    Now we need just thoese 6 lines.

    What next?

    We will use another interesting Rhino command to get fuselage cross sections that will goest exactly between the lines that we already prepared.

    [​IMG]

    Now we must pick contour lines in proper order. I pick as follows:
    bottom contour, bottom left, upper left, upper contour, right upper, right lower.

    [​IMG]

    If we mix order, the fuselage cross section will be crooked...like 8 number or worse!

    Now we pick the locations of cross sections. Do wherewer suits you.

    [​IMG]
    Showing the cross section locations.

    And finished:
    [​IMG]
    Note the different desnity of cross section locations. More dense where we dont want porogram to go his own way. See more dense at cockpit area.

    And let see these cross sections that were just automatically created in all views:
    [​IMG]
    Note: yellow cross sections! That wee need!

    Now erase or hide all lines except these cros sections!

    [​IMG]

    WE will now use these cross sections to create a surface over them!

    We will show all sections and choose command Loft. (menu Surface, command: Loft)

    [​IMG]

    If we want surface, that goes excatly over our cross sections, we will choose option "Tight", we can also use option "Straight sections" (maybe when we shape metal plane), or left Rhino to smooth surface ("Loose") avoiiding sudden bumps and voids..

    I choose "Tight" in this case.

    [​IMG]

    As we confirm our choice a surface is created:

    [​IMG]

    Now we go to the details!

    We will cut oppening in the cockpit area.

    We just make a plilyne that will goes trough a opening line in a side view:

    [​IMG]

    Now we use split command and split fuselage surface at line we just made.
    We can erase surface part that we dont need or use it as a canopy glass if the shape is O.K.
    Here is not the case, so I will erase that part.

    [​IMG]

    Now I will make a windshield.
    I will draw a windshield rear frame and after that create a surface between frame and front cockpit edge.

    [​IMG]

    We need two rails and two coss sections to make a canopy surface.

    Rails are upper canopy contour, left canopy openning edgem, and cross sections are rear cockpit edge (turtledeck edge) and forward canopy opening edge.

    We will use command Surface, Sweep 2 rails. And surface is created.

    [​IMG]

    This is only one half of surface we need. We can mirror it now ar later.

    Now wee draw a line that will represent rear frame of the windshield. Then we will split surface at that line.
    Then we will erase unnecessarry part of surface..tre rear part as wee need just windshield in my case.

    [​IMG]

    Now look what we have!

    [​IMG]

    Now only minor work is needed to complete that fuselage. For instance trimming front end for a spinner, closing rear end, making surface offset toward inside (if we want to presentate fuselage sandwich thickness), make some bulkheads and fuselage formers, arange cockpit internals as seat and instrumental panel, headrest, cockpit edges leather padding, wing root attachments, vertical and horizontal tail, landing gear and of course the wing.

    If you are interested in hot to do that simple way, tell me, and I will continue this presentation as I came today up to this stage:
    [​IMG]
    [​IMG]

    Regards!

    Mitja
     
    Last edited: Sep 4, 2010
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  19. Sep 4, 2010 #39

    bradyaero

    bradyaero

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    A fantastic tutorial Mitja, please continue as you are one of the few to explain some of these techniques for airplane design. Especially the use of 'Curve from 2 views' where most of the magic happens!

    One quick point, most of the time there is only need to work on 1/2 of the fuselage, so when you are finished you can simply mirror your fuselage to get the completed result.
     
  20. Sep 4, 2010 #40

    orion

    orion

    orion

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    I agree, well done. One point though, given that we're working in NURBS here, it's not always a good idea to work only on one half since when you mirror you'll often find that the surface at the centerline is not exactly level, which means that when you mirror you'll end up with a crease in the middle.

    Also, with Rhino it is usually best to use as few cross sections as possible but use the profile lines (upper and lower keel lines and the butt lines) to control the loft.
     
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