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ViaCad / Shark > 2d/3d how-to carve piston groove
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  1. #1
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    Jan 2006
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    2d/3d how-to carve piston groove

    hi all,
    i am fairly new to CAD, but i can absorb the tutorials rather easily.

    i have the 2d/3d v8 Trial, which i believe is the Pro version ??

    anyways, what method for creating a square groove into a solid cylinder, like making a ring groove in a piston? i can stack cylinders of differnt size and then join them, but there is of course the easier way that i dont know.

    1) since i know the toolset somewhat, what about adding two lines on the dia of the cyl (piston, solid round block, etc) making a segmented surface and then pushing that surface inward? would this work (it should), but how to create that surface to push on?
    2) create a 2D shape in 3D editing (like a lathe tool) and position it in correct location, create a 3D solid by rotating around cyl axis (making a ring) then subtract ring from cyl? would this work? if so how to create that ring solid?

  2. #2
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    35538
    Similar to #2. Draw 1/2 the profile of your finished piston with the groove, and revolve it into the piston. Don't use Viacad, but any 3D CAD program can do this.
    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
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    Quote Originally Posted by ger21 View Post
    Similar to #2. Draw 1/2 the profile of your finished piston with the groove, and revolve it into the piston. Don't use Viacad, but any 3D CAD program can do this.
    do you mean you dont use ViaCAD, or are you saying i should not use ViaCAD ?

  4. #4
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    viaCAD just went haywire, lots of blinking screen. new file, playing around, i had a few concentric circles in Top view in 3D edit, i tried to drag up a surface between two circles and then everything went haywire. has to kill it via task manager while screen was blinking.

    my PC is HP all-in-one with Radeon HD 4200 series (256MB) running latest driver. this HP is x64 Win7 w/ AMD Athlon II X2 260u & 8GB RAM

    maybe a conflict with my specific system.... dunno, but if so means i will need to build another system for viaCAD.

  5. #5
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    so i do this demo, after lathe'ing i added 0.1 linear rounds to the edges, then i tried to pull the inner surface along radius to try and make it fatter, and ViaCAD becomes non responsive, held CPU at 50%.

    i am as newbie as they come, not sure why this software either cant handle my newbie'ness, or just doenst handle bad user requests properly. a simply "hey, i cant do that" message would be better than a freezing program, etc.


  6. #6
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    Sep 2012
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    Quote Originally Posted by CNC_Kid View Post
    viaCAD just went haywire, lots of blinking screen. new file, playing around, i had a few concentric circles in Top view in 3D edit, i tried to drag up a surface between two circles and then everything went haywire. has to kill it via task manager while screen was blinking.

    my PC is HP all-in-one with Radeon HD 4200 series (256MB) running latest driver. this HP is x64 Win7 w/ AMD Athlon II X2 260u & 8GB RAM

    maybe a conflict with my specific system.... dunno, but if so means i will need to build another system for viaCAD.
    Pretty much any 3d CAD system is going to have trouble without a dedicated video card with closer to 1gb of ram. Some handle it better than others, but for the most part an all-in-one type computer is going to make sophisticated modeling difficult. In ViaCAD, I recommend avoiding the push pull feature in most cases. It works well if you have good hardware, but I do find it to be otherwise a bit flakey on laptops, or other systems with built in graphics. Also, even if you have a good system, push/pull in ViaCAD somewhat negates a lot of the parametric functions, so it's just more kosher to create geometry without the aide of push pull. The equivalent is to just draw a line perpendicular to the plane that your geometry is on, select your closed contour of lines/arcs, choose the sweep one rail tool and then select the perpendicular line. This will extrude the geometry into a solid to the length of the line. I you want to adjust it, you can select the line and change it's length. That's what parametrics are for.

    Push pull modeling is more a direct modification to the part, not a parametric modification. I find that UNDO after using push pull has about a 50/50 chance of crashing Viacad, which is just another reason to avoid using push pull unless you have no other option. It's often not even the fastest way to create a geometry anyways. If you want to do a lot of push pull modeling, that's where Bonzai 3d excels IMHO.

    Otherwise, here's 3 ways to create a cylinder with grooves. I'm sure there are probably half a dozen more ways as well, these are just the 3 most obvious to me. Personally, I would use the first option I show, which is the option Gerry suggests as well. The more time you spend at the 2d level, the faster the model will come together overall. Adding/subtracting entities can become time consuming where you could have just drawn what you meant in the first place and revolved it (as in the first example). Everyone has their own workflow, you just have to figure yours out as you get familiar with the tools. Video is uploading, should be available soon:

    Viacad 2d 3d V8 Sample Piston - YouTube

  7. #7
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    Quote Originally Posted by CNC_Kid View Post
    so i do this demo, after lathe'ing i added 0.1 linear rounds to the edges, then i tried to pull the inner surface along radius to try and make it fatter, and ViaCAD becomes non responsive, held CPU at 50%.

    i am as newbie as they come, not sure why this software either cant handle my newbie'ness, or just doenst handle bad user requests properly. a simply "hey, i cant do that" message would be better than a freezing program, etc.
    I think it's more like you're trying to run before you have learned to walk with ViaCAD. It's not that picky generally, and it will do things that most other software would consider in error (like complex filleting). In some cases, it's a matter of figuring out where to select something or what order to do things it. For what you're trying to do here, I think that you really need to learn the parametric side of ViaCAD before you proceed. I'm going to lunch for now, but when I return I'll do a quick video showing how you can use the parametric features of ViaCAD to make these kinds of adjustments to the part.

  8. #8
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    i can do the piston model w/ grooves using 2D lines in 3D edit mode and doing a lathe around axis line. that example was awesome, thanks.

    the push/pull works in most cases for me. pulling/pushing surfaces is a nice feature, and i dont think i have gone past beginner mode on anything i was doing. the tutorial video i posted has to be beginner-101 in terms of creating a solid from a sketch. pulling/pushing a cylinder surface inward on radius (which is all it allows i believe) should work.


    i can push/pull any of the numbered surfaces here. not sure why the tutorial one balked on me. surface #2 was not there until i pulled #5 inward (that section out from under the radius'd top edge, etc). i can push/pul #'s 1,2 & 3. how would i pull #3 up the Z axis using parametric way?
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  9. #9
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    Quote Originally Posted by CNC_Kid View Post
    i can do the piston model w/ grooves using 2D lines in 3D edit mode and doing a lathe around axis line. that example was awesome, thanks.

    the push/pull works in most cases for me. pulling/pushing surfaces is a nice feature, and i dont think i have gone past beginner mode on anything i was doing. the tutorial video i posted has to be beginner-101 in terms of creating a solid from a sketch. pulling/pushing a cylinder surface inward on radius (which is all it allows i believe) should work.


    i can push/pull any of the numbered surfaces here. not sure why the tutorial one balked on me. surface #2 was not there until i pulled #5 inward (that section out from under the radius'd top edge, etc). i can push/pul #'s 1,2 & 3. how would i pull #3 up the Z axis using parametric way?
    Click image for larger version. 

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    To adjust the surface height of number 3 in your diagram, you would go back to the 2d geometry that created the 3d part, and then adjust the position of the 2d geometry. This is where I think you should go back and learn the basics first. If you know how to efficiently adjust the 2d geometry, you'll be just as efficient as adjusting the 3d geometry. Once the 2d geometry is reconfigured, the 3d geometry is automatically updated to reflect the changes to the 2d geometry that created it. If you start push pulling surfaces, the 3d geometry is no longer a representation of the 2d geometry that generated it, so it gets much trickier to use the parametric features.

  10. #10
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    Quote Originally Posted by mmoe View Post
    To adjust the surface height of number 3 in your diagram, you would go back to the 2d geometry that created the 3d part, and then adjust the position of the 2d geometry. This is where I think you should go back and learn the basics first. If you know how to efficiently adjust the 2d geometry, you'll be just as efficient as adjusting the 3d geometry. Once the 2d geometry is reconfigured, the 3d geometry is automatically updated to reflect the changes to the 2d geometry that created it. If you start push pulling surfaces, the 3d geometry is no longer a representation of the 2d geometry that generated it, so it gets much trickier to use the parametric features.
    so in essence, a push/pull will not update the 2d geometry. and yes, once i changed it 3d and went back to 2d to say change dia of a circle that was used to create the cylinder, i got an error message. the push/pull tool uses offset #. is there any way to see the XYZ #'s of that surface while doing push/pull.

    i didnt use 2d for that green wheel. i made block, then another block to subtract out the hole, then another block (edited the one used for the hole) to create a step in the hole, then i just used push/pull.

  11. #11
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    Quote Originally Posted by CNC_Kid View Post
    so in essence, a push/pull will not update the 2d geometry. and yes, once i changed it 3d and went back to 2d to say change dia of a circle that was used to create the cylinder, i got an error message. the push/pull tool uses offset #. is there any way to see the XYZ #'s of that surface while doing push/pull.

    i didnt use 2d for that green wheel. i made block, then another block to subtract out the hole, then another block (edited the one used for the hole) to create a step in the hole, then i just used push/pull.
    As you may have gathered, I'm not a huge fan of the push pull feature in Viacad. I'm not that against the concept, I just think that it's in it's infancy where Viacad is concerned. Other software such as Bonzai 3d or Creo have got that function dialed in to another level, so if you have seen it work well, then the shortcomings of the feature in Viacad make it appear more of an eyecandy feature than a useful one. Every now and then it comes in handy, but I don't consider it a staple of Viacad, just a peripheral.

    To answer your question, yes and no. The push/pull feature allows you to enter a specific amount of push/pull, but it's relative to the starting position of the face that you are changing, not the absolute length/height of the object. You can see the extents of the object and get the size or position, but it will not show that information at the entry boxes. If you have a part that you made to a specific size/shape to start with and then require design change that can be quickly done with push/pull, you can make that change to a specific value. If you don't know how big the object is and are trying to hit a target size, the only way I can think of that will allow you to do so is to create a construction line of the correct length starting at the end of the object where you are not adjusting it, and ending out in space in front or behind where you want to push/pull a face to. This will give you a snap that can position the face exactly where you intended.

    I get the impression that you're trying to get precision models by winging it in 3d, but that really isn't how to best approach a final design. That approach works well for a quick study model where the actual dimensions are not as critical. For those parts where you want a very specific result, you will find that it's just best to start in 2d and work you way to 3d when the supporting 2d dimensional geometry is complete. Here's a quick example made by my 12 year old (6th grade) for a school project of how simple working from 2d to 3d is, but how complex the shapes can be. He generated his top and front/side views of his glasses to create the front section and one ear piece, extruded each view and used the intersect tool, then changed the earpiece to surfaces and rebuilt them using the "Thicken" tool so that the thickness follows the surface normals, then radius'd various edges. While some of his geometry could use a little cleaning up, I think it's an excellent example of how complex of an object you can create with such a minimal amount of drawing effort. He drew this in about 3 hours, and has about 20 hours of CAD experience in total, so not too bad. If even the most experienced CAD user tried to create this using 3d tools, it would probably take a full day or longer. The same level of CAD user could generate it this way in 30 minutes. Anytime I work with people on how to generate 3d models, I can't stress enough how much better it is to stick to 2d for as long as possible and for as much detail as possible. It's just faster and more specific, while affording the opportunity to modify the 3d model very quickly by adjusting the generating 2d geometry. In this drawing, any change to the front or top profile of the geometry will update the front frame of the glasses. Because of the use of the "Thicken" tool, which required breaking the solid into surfaces, the ear pieces have lost that capability, but they can be very quickly regenerated from a modified profile anyways, so you always want to save that 2d geometry just in case.

    Designed and 100% modeled by my 12 year old in Viacad 2d/3d V8:

  12. #12
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    i dont think i know enough about Via CAD to build precision or complex models. i think i learned enough in last two days to build some simple parts for a project i am working on. i am working on a tube baffle for a rifle. my design calls for minimal need for CNC'd parts to keep costs down. many parts in my design can be punched and/or punched-&-formed. i need to have a couple of parts CNC'd because these have special features that cant be had any other way, etc.

  13. #13
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    Push Pull was just introduced in V8. (Was it already in the pro version?) Not surprised it has some issues. I have not used it yet, but it sounds like it doesn't do exactly what I was hoping for which is a sort of stretch/morph of complex 3D obejcts.
    Bob La Londe
    http://www.YumaBassMan.com

  14. #14
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    Quote Originally Posted by Bob La Londe View Post
    Push Pull was just introduced in V8. (Was it already in the pro version?) Not surprised it has some issues. I have not used it yet, but it sounds like it doesn't do exactly what I was hoping for which is a sort of stretch/morph of complex 3D obejcts.
    What you are talking about is called "direct modeling". It's OK in Viacad, but I'd say it's an emerging part of Viacad's technology and not really it's specialty. If you want to try a system designed for direct modeling from the ground up, Creo Elements/Direct Modeling Express (not very catchy) is a free product based on the technology that Creo uses on their full versions, which are probably more expensive than Solidworks. It's not easy to learn and there is very limited tutorials, etc., so you really have to battle through to learn it, but it is very powerful. The other downside is that it only saves to an STL, but again it's free so hard to complain.

    Bonzai 3d, which I've recommended elsewhere as well, is also a very good direct modeling system that can save to just about any file format you'd want. It's downside is mostly in the cost ($500), but if direct modeling is something you are interested in, there just aren't that many direct modeling systems out there that are mature. Bonzai 3d is very stable and at a mature level in it's development, which I think puts it in a class by itself among direct modeling software in that price range.

    PTC - Creo Elements/Direct Modeling Express 4.0

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