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  • Some design questions from a newbie

    Discussion in '3D rendering gallery' started by COSenna, Jan 30, 2015.

    1. COSenna

      COSenna Member

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      Hello,

      I have a project in the works that I need some advice on. I am not a 3D designer, I just came up with the concept and had a guy model it for me. Being that I found this guy on fiverr, I cannot tell if he has any professional design experience, and therefore I do not know if the threads he designed will work. Obviously I would like to hire a professional to do this right, but I can't afford that. So, any help I can get will be very much appreciated!

      Just for clarification, all three pieces when assembled, will be about 1"x1"x1" and will be made of anodized aluminum. I am planning on having this assembly machined and what I need to know is about the threads. As seen in the pictures, the two bottom pieces are going to be threaded into each other with a 1/16" piece of plastic in-between them. The current model you are looking at still needs a few changes so bare with me as I explain the details.

      The center (red) piece has two male threads on it. On the bottom thread, underneath the lip, Is going to be a 1/16th" solid area. This is where the piece will snug inside the plastic. Because of this, I need the threads to be able to be tighten very tight so they do not come loose. What kind of thread design should I use for this? The top piece is meant to be taken on and off when needed. It still needs to be tight but not as tight as the two bottom pieces.

      As far as manufacturing goes, I need a cheap but quality machinery that does good anodized aluminum work. I will need at least one prototype, but I am sure you all already know that. Any ballpark figure on how much you think a prototype of this type/size will cost me would be awesome too! I have contacted a few CNC machinists in the US and China but have not received any feedback yet.

      Thanks for the help in advance!
      [​IMG]
      [​IMG]
       
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    3. CK T.

      CK T. New Member

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      Hi COSenna,

      1. If you want the black pieces in aluminium, the manufacturing process shouldn't be CNC machined but die casted. It is gonna be costly even if it can be machined out.

      2. For the thread to join tightly, it depends on what is your objective. You can glue it if you want a permanent joint, or include additional O-ring if you want it to be water tight.

      Cheers
      CK
       
    4. K.I.S.S.

      K.I.S.S. Well-Known Member

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      Hi COSenna,
      Did the person that 'designed' this for you not specify what thread type and pitch they incorporated into the model?
      There is basically no material wall thickness in either the green or the red component, as the thread depth occupies all the space.
      At a glance, this doesn't appear to be any recognized commercial thread, but rather something that was randomly drawn and revolved on a 3D CAD program.
      As you have thin walls, consider something such as a UNF/UNRF (controlled root radius) thread.
      Also, you'll find that this will be a very expensive thing to machine - it will also not be cheap to die cast owing to the requirement for collapsible sliding cores in the mold and the unsuitability of the separate components to integrate into a 'family' mould.
      Two stage injection moulding (unblown and blown) would be the most cost efficient production process, but for a prototype, depending on your requirements, why not just grow one on a 3D printer if you only want to assess generic aspects of your design?
      And if the bottom section is not required to ever separate from the mid section then do away with that thread entirely and use straight walls with an adhesive or ultrasonic welding. (Or combine the two components into a single component - sometimes, less is more...)
      If it is required to sometimes separate. then use the same thread but bonded with something like Loctite 243 thread glue.

      K.I.S.S.
       
    5. zaccutt

      zaccutt Member

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      K.I.S.S said everything I wanted to say.

      Why are the walls so thin? If you want to machine it consider a redesign but like he said 3D printing is very cost effective. You could basically buy your own cheap 3D printer for the cost to machine that.

      If it needs to be so thin you may consider doing away with the thread and making it more like a kinder egg - pressure fit.
       
    6. COSenna

      COSenna Member

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      First of all, thanks for the replies!

      After reading what you all said, I decided to do a redesign and I am looking now for someone with actual experience to model it for me. Is there anyone or anywhere I can look on this forum for someone who could help me out with this and not cost me an arm and a leg? I can do very specific drawings to make it as easy as possible.

      Also, I am deciding to do away with the entire middle piece and replace it with a "washer-like" piece that has a female thread on the inside. Anyone know where I can find one of these? Maybe a site that sells parts like this? After I get the dimensions of the piece, I can start the rest of the design. This is to keep production costs down as much as possible. As for the use of a 3D printer, I need these pieces to be anodized aluminum so that is out of the question. Maybe for a prototype tho!

      I do see what you are saying about the walls, I didn't even notice before. The guy obviously had no idea what he was doing... all these pieces do need to be as light as possible tho!

      Thanks again for all the help!

      COSenna
       
      Last edited: Feb 11, 2015
    7. jagengrg

      jagengrg New Member

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      Call around to the High Schools and Jr. Colleges or vocational schools. Many have 3D systems. They love to get real world examples to work on. I don't know how complicated your device is but these things always look simpler than they are. Some mechanical engineering schools use real world projects as sr. projects or if too simple a class project. You may need to provide a few bucks for materials but usually there is no cost for the rest if part of a class.
       
    8. ChrisW

      ChrisW Well-Known Member

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      Don't rule out "3d printing". It's not as new as you might believe and aluminium can be laser sintered and anodized. Instead of "3d printing" search for "Rapid Prototyping". The process you need is SLS, selective laser sintering.
      All the earlier advice is accurate, you would be better die casting if you get to volume but take advice from the die-caster before completing your design as some are easier than others.

      A small part like this can be quite cheaply made, a UK business who specialises in short run die-casting is PMS Die casting, www.pmsdiecasting.co.uk. I have commissioned quite small runs from them in the past.
       
    9. andreme

      andreme New Member

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      Hi COSenna, I would start off by telling it is likely you will not find a machine shop willing to make this part at all. The thin walls make it impossible to hold and the shape does not lend itself to machining.

      If you want to keep that cross-section then I recommend you reconsider your material selection. If it has to be aluminum then it needs to be designed in a machine-able way, including thicker walls and with standard threads, custom threads are possible but it will be difficult to find someone to make them. I have been through that before.

      Typically when making aluminum prototypes the goal is to test functionality not appearance. Once proven the concept works then the way it looks can be designed. Unless there is a very good reason the part has to be like this, make a simple representation of what you need, test it, then proceed to refine it into a more appealing look.

      Post some sketches of you revised design and if its something I can do quickly I will give it a try. Make sure that the dimensions are clear and include a cross-section
       
    10. Lochnagar

      Lochnagar Well-Known Member

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      Hi Cosenna,

      Just an "off the wall thought" - but you might be as well explaining what the purpose/function these parts are supposed to serve - so that the engineers on this forum can pass comment on whether they feel the "design" that you currently have is the optimum for the job - since there is no point in going into mass production with something - that perhaps could be better conceived.
      Hope this helps.
       
    11. mgpedersen

      mgpedersen New Member

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      Screw machine

      Looking at your original design, that would be an easy part to make on a screw machine or lathe (it doesn't have to be CNC). Thickening up the walls is probably necessary, especially to accomodate a real thread and there might need to adjust for the thread cutting operation in the design. Even for production a screw machine would be a good way to get an inexpensive part without a lot of capital investment. If you could consolidate the red and blue parts together (run that blue tapered section up to the inside of the red dome wall) that would further save you money.

      It's hard for us to know what you mean about buying an off the shelf part, if you could post a sketch it would be helpful.
       

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