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Blend Problems

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36 comments

  • Tim Heeney

    Hi CJ,

    Please post an image of your problem.

    There are a few tricks with the blend tool that's essential to know.

    Is the model 100% constructed within DSM?

    R

    Tim.

     

    ps - i agree, sometimes it's very frustrating - but, i have found that usually there's a certain 'procedure' to make the operation work...

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  • C J

    Hi Tim,

    Thank you very much. Yes, it's all within DSM.

    The attached JPG: If the surfaces are just scaled, then things are ok. Trying to be true to the Akula, the transistion between turret and hull can't be made in this way - spline roundings are needed. Even though all are drawed using mirror in sketch - and nothing seems dramatic, things fail. Either it won't blend or the result is an asymmetrical horror story. I have tried alot of things; guiding lines, surface "feets" (those helps somewhat), numbers/distances of surfaces... Things are even worse for the front part of the turret (it's steeper). In Blend it's like DSM can't recognize its "own" symmetrical creations - some kind of an internal tolerence mismatch? 

    BR

    Carsten

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  • Tim Heeney

    Hi CJ,

         'My task is easy: A 3D model of the russian Akula K-335 turret (submarine). This turret is smooth and for symmetrical, eqidistanted, uncomplicated surfaces the blend tool struggles enormously - and fails.'

    I will have a look at this for you... however, i personally do not have a high enough level of experience to know exactly how's it done.  In my view this is not a 'easy task'...

    DSM isn't and doesn't claim to be, a high end surface creation tool like 3D Rhino.

    DSM / Spaceclaim Blend Tool can do much, but it is only a simple tool. I have also struggled with it.

    I'll take a look though.

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  • Tim Heeney

    Hi CJ,

    Those ' Spline Roundings' seem a very tricky feature... sorry, i don't know how or even if it's possible within  DSM !

    My 'mate' on youtube ' 3D Exploration ' is very experienced and has published many videos using the Blend Tool. He's very good with Splines and manipulation, especially good with 'problems and work arounds'.

    I would not try to fillet or construct a fillet starting / ending in zero and perhaps a perfect tangent condition all along it's length isn't necessary either. Real world manufacturing ( for submarines ) wouldn't do that anyway - A CLOSE APPROXIMATION  is good enough i would think.

    At the front, i've ringed in red where the fillet / rounding apparently ( graphically) ends - perhaps it ends as a 'Ball / Spherical' segment there ( and at back as well ), again though, approx tangent only.

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  • C J

    Hi again

    Thank you. Yes, I know Rhino - it's very advanced. I am not expecting that DSM should match it.

    BR

    Carsten

     

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  • Jacant

    If you are prepared to share the file with just the 'stations' on, I will have a look for you.

    Just copy and paste them into a new file and attach here.

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  • C J

    Sorry, I just noticed your new answer. Thanks :-)

    The drawing you refer to is just something I use for guidence (I think it originates from Solidworks). I don't blend towards nulls or points. It does not work, I use small surfaces as end "points". The blend can fail at any point between surfaces, but typically where the deviations are largest. It is very sensitive/tricky, and as I mentioned, the Blend tool can easily produce asymmetrical solids from symmetrical surfaces. In the JPG, I just illustrate examples; I have tons of different surface setups in the bin.

    I recall a YouTube video illustrating the build of a model Spitfire wing. I think he used scaling and for this, the tool also works for me. 

    For my task, I'll try to combine two solids. An easy one (based on scaled surfaces) and a tricky one (the "roundings" between turret and hull). Hopefully simplifying things.

    BR

    Carsten

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  • C J

    Hi,

    Thank you. I have kept on deleting files along the way, collecting experince for new attempts. I'm not in the R&D engineer role at home = my recent files would be a complete mess to anyone else but me. Not at least  because the files are mixed up with all sorts of DSM experimenting (that's how I learn). When a new attempt fails, I'll clean it up and attach it.

    Thanks

    Carsten

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  • Jacant

    Have you got just the surfaces as shown in the image?

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  • C J

    Hi again

    For the rear turret/hull transition, I tried a different approach (some kind of half asleep thoughts). The photo should explain. To get a totally smooth transisition, I made the  surfaces start out parallel to the turret ground (using the 3 point arc option). Interestingly the Blend tool seems to work much better when surfaces shares axis. With this result, I expect to finalize the rear part of the turret without to much difficulty. The front part of the turret is no doubt more difficult, but ok.

    Best Regards and thanks

    Carsten

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  • Tim Heeney

    Hi Carsten

    That's a good and interesting result.

    No 'Thanks' necessary - i did nothing...

    Please post up your final design - i ( very keen) and others ( hope!)  would be interested to see how this all  works out.

    Tim.

     

     

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  • Tim Heeney

    Hi Carsten

    I found the Edit as a ' Variable Radius Round' after pulling the edge...interesting that 0 value can be entered at a handle end and additional control positions can be added with local value applied.

     

    but increasing the tessellation visual quality is display responsiveness suicide!

     

    Good Luck with the sub.

     

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  • C J

    Hi Tim

    Great info, thank you very much :-)

    This describes very well what's going on around the rear end of the turret. I will try out this tecnique, super.

    I got some progress earlier today - and also had a look at the front of the submarine (I am all over the place; Gepard K-335 is after all only 113,3 m in length).

    Carsten

    ). Projecton and Pull are great tools.

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  • Jacant

    Sometimes you may get a better result if you 'Blend' the lines, then use the 'Combine' tool to join the resultant surfaces. Also use the 'Select Guides' option to control the bend.

     

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  • C J

    Hi Jacant.

    Interesting approach. Great knowledge.  Many thanks :-)

    Best regards

    Carsten 

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  • Tim Heeney

    Hi Carsten.

    I should have mentioned, i also made my turret section / segment solid / faces in a similar way to Jacant 's gif above - but i don't claim to be a DSM lofting expert ...

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  • C J

    Hi Tim,

    From what I have seen, I would claim you're both experts. 

    The main difference between your and Jacent's method - and the one I used, is that you are in control of the turret/hull intersection curve. I'll attach a description of the method I used here (simplified because I found that it works for a reduced number of surfaces). The resulting curve is defined by what's going on in the Blend algorithm. Therefore I would in general lean towards your technique.

    The reason I'm interested in smoothing techniques is related to how these submarines are constructed (here specific the Project 971) and I would like for a scale model to reflect this. Not being an expert, my guess is that these things have to do with reduction of turbulence/noise. Constructed previously to K-335 (Gepard) the Project 971 submarines had extreamly smooth turret designs - almost integrated with the hulls. There is a great photo displaying this; I'll attach it as well (Bratsk). I hope to draw and print Gepard (scale 1/72, electric model with static dive system) and then maybe Bratsk. Quite some tasks - with long timelines...getting a bit stressed thinking about it, haha. I'll try to set the process as the goal :-)

    Have a great saturday

    Carsten

     

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  • Jacant

    Here's one I did earlier. Only joking.

    The file can be found here.

    https://grabcad.com/library/akula-submarine-r-c-model-1 

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  • C J

    :-)

    Thank you very much. I haven't seen this before - it looks made for RC (like the Engel model). It must represent one of the subs from either Akula I Improved or Akula II (not one of the initial subs like K-184, and not the latest; Akula III = K-335 Gepard).

    I think the biggest challange for me is learning DSM ( :-) ) and getting the actual model lay-out fairly right. For the model it self - in this case K-335, there´s a russian internet forum debating it - this is also from where I've got various drawings (http://forums.airbase.ru/2018/01/t59938_7--apl-pr-971-shifr-schuka-b-gepard.html#p5863849 should drop you down in the middle of it, if interested).

    About drawing in 3D: I have alot to learn - and with regards to learning, something stands out to me; the difference between creating a model or duplicating a model.

    Thanks :-)

    Carsten  

     

     

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  • Jacant

    I tried to connect to that link, however I was blocked by Malwarebytes due to a Trojan. I would be careful in what you use from the site.

    As for learning 3D, it is always best to look at an existing model, dissect it to see how it was made. Even using some of the geometry to recreate it to help you understand how it was originally created. 

    The model in the link I gave is a 'Step' file so you will not be able to use it as it is. It has many geometry faults in it. You could however 'Split' the model up into 'stations' and use the geometry to create your own 'ribs' then using the 'blend' tool to create the hull. especially where the hull joins the turret. I would do it this way so you can create the natural flow from hull to turret. You can easily split it later.

    You said above  ...I hope to draw and print Gepard (scale 1/72, electric model with static dive system)... 

    You must have a big 3D printer at that scale.

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  • C J

    Hi Jacant.

    I haven't had any (virus-malware) problems with the site. I have even become a member.

    Big printer? You know, in Germany they print out houses ;-) 

    My plan is to split the model - in say max 200 mm pr. section. A 1/72 Gepard would be approx 1574 mm in length, 189 mm in max hull diameter. With a separate turret (or is it called sail?) a Creality Ender 3 could do the job (I haven't bought a printer yet). Due to the need of nuts and bolts to ensure a waterproof yet accesible design, I’ll probably go for a inner pressure hull. 

    For Akula models, I will say this: It is very difficult to get the lay-out right. Note the high numbers of deviating models/plans of the same submarine seen on the internet (typically being either Leopard, Vepr or Cheetah (Gepard)). This mostly relating to russian navy secrecy and public availability of info/photos at a given time since the launch of K-284 in 1984. The over all best model I’ve seen is no doubt by Некоторый пират (from the russian forum (alias name)). With good availability of photos etc. he made this in 2018-2020. 

    The model you refer to has a rounding between the turret and hull that does not reflect any of the Project 971 subs. In DSM it would no doubt be the fastest way to get things done (pull plus rounding with fixed radius) but I chose not to. In trying to get closer to the target I also learn more about DSM – refering to what you and Tim previously showed me in this thread. In addition my own attempts. 

    Like most, I'll not get the design perfect for a model of K-335. I do however want to be able to realise/replicate what I see - or what I think I see. 

    BR

    Carsten

     

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  • C J

    - for making sections, using DSM Shell something like this can be done (I haven't decided yet)

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  • C J

    A problem I have come across - and this is something all scale modellers could be interested in. How to make "construction lines" on the surface of a model. In 2D one could use Offset Curve and Pull, but for surface lines on say spherical bodies.....?

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  • Tim Heeney

    Hi CJ.

    For construction lines on 3D surfaces - imprint a face and pull. Here i used 2 stars and the surface inbetween was pulled...

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  • Jacant

    There are a number of ways to do this. one as you have shown, by using the 'Project' tool.

    You could just draw on the curved surface using the 'Face Curve' tool then select the line and create a cut with the 'Cylinder' tool. Or draw a 'Square' at the end of the line and 'Pull/Cut' by using the 'Sweep' option.

    I have repaired most of the anomalies on the Akula that I downloaded. Here is a link to the file if you are interested. The model is about 785 mm long.

    https://we.tl/t-rRyX0rXnGy 

     

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  • C J

    Hi Tim and Jacant.

    Thank so much for your time on the matter!!!

    Also thanks for the link, Jacant. About repairing anomalies: In DSM there is a "Geometry Check" was that the tool you used?

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  • Jacant

    You're welcome.

    Yes I used that along with the 'Body Interference' tool. (Display tab - Show Display - Body Interference).

    Then as you know, create a sphere or cylinder around the suspect part, delete it then 'Fill'. I have a few other little secrets on how to repair.

    There are a number of parts that are duplicated in the same place. I have not deleted these.

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  • C J

    Hi Jacent,

    His model  is very well made - one of the best I have seen. He is way better than me with DSM, so I can only comment on his lay-out. These submarines a very tricky to get right - or nearly right (lack of info and so on). With leaning turret sides and large rear dome he is not going for K-335 but one of the earlier subs in the class.

    If you know him, or he wants to tweek his model then some photos of the real deal might be helpful

     

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  • Jacant

    I am a member of this site, I do not know him personally.

    If you join Grabcad, you could answer yourself on his work.

    https://grabcad.com/chen.kang-2/models 

    Here's a few of my models, done years ago when I was learning Designspark.

    https://grabcad.com/jacant-1/models 

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  • C J

    Hi Jacant,
    Thank you - yes, I'll try to join.
    For your drawings; you are on a level others are dreaming of. I note your extended use of roundings - something seen in prof mechanical enginering (...lack the english words here; in danish it's "kileproblematik" - to avoid sharp edges in critical places). My skills in DSM are, as you know, very limited. I started out trying to draw left/right caster blocks for Traxxas Bandit (RC car). Before attempting printing I plan to go with roundings (still haven't decided which printer to buy)

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