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  • 12 Liter water container advice

    Discussion in 'The main mechanical design forum' started by alexbalague, Apr 3, 2017.

    1. alexbalague

      alexbalague New Member

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      Dear all, firstly thanks for taking the time out to read this. Also secondly I appreciate I am a new member so I would be very thankful for any help from readers here and hopefully once I have solved my problem I can give back some advice once I resolve my issue.

      I am hoping to get some advice on a project I am working on to construct a large 12 liter water container which will hold warm water upto a heat of 95c. I will need to have this ultimately constructed for a unit cost of a max USD15 (excluding factoring in the cost of the original mold). The container should meet the following requirements (in order of importance)

      - The container should be transparent
      - The container should be rectangular
      - The container should provide a ‘premium’ feel. I think the best way of providing this image is that the container should be very sturdy and so the container wall should not be thin.
      - A lid will also have to be manufactured separately
      - It should be able to hold warm water (upto a max temp of 95c) for a prolonged period of time (upto 3 days)
      - To help with insulation I would ideally like the container to be double walled with a vacuum seal. However another option which could be cheaper could be a silicone/fiberglass sleeve with a few holes in allowing users to see within the product.
      - It should be BPA free


      I have reached out to plastic manufacturers to get some advice on this but most are quoting a minimum of 6-10 hours consultation @ USD200-300 an hour. As I am new to this field I can not say for certainty these consultants will be the best use of my money to begin with. As a result I am hoping to gain some knowledge from you excellent people and how best to proceed with this project.


      - Who should I contact first? There appear to be some designers on guru.com who might be able to help
      - I am thinking about Tritan Copolyester as the plastic material. I understand its quite strong, has a premium feel and BPA free. Or is there something else?
      - How much per unit would it cost to manufacture? How much would the mold cost (I maybe wanting to make around 300-500 units of this a month)
      - Any other useful advice on proceeding?


      Apologies if I have missed providing any detail, I am new to this so would appreciate your patience, understanding and help.

      Many thanks
      Alex
       
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    3. Erich

      Erich Well-Known Member

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      The requirement to hold water at 95C for up to 3 days is the most demanding requirement. I assume you have no source of power to add heat during the 3 days.
      Based on experiences with SS vacuum coffee urns and old fashioned glass thermos containers, you will have great difficulty meeting this requirement with a transparent system. Before you spend money on consultants to choose a plastic, spend time and money on heat transfer analysis to show if you have a feasible product or not.

      Also your requirement will need some refining, like adding the lowest allowable temp the water can cool off to.
       
    4. alexbalague

      alexbalague New Member

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      Thanks for the reply. To be more specific the long term usage of a few days would only really be done at a max of around 60c. The 95c temp would really be only for a max of 30 mins.

      Not sure what you mean about the lowest temp it could cool off to. lowest temp this would go to would be room temperature

      thanks again for your help!
       
    5. Erich

      Erich Well-Known Member

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      You want to store hot water. At some temperature the warm water is no longer warm enough for your uses. That is the temp I meant as the lower value.

      If you were storing coffee 95 is nice and hot, 90 is still good, 86 is just drinkable and 85 is too cool and I would throw the coffee away.(This is a made up example with numbers I pulled out of thin air) So in this example I can tolerate a 9 degree drop in temperature. Now the question is how long does it take to cool off 9 degrees?
      30 minutes? 3 days? Huge difference in requirements (144x to be precise)
       
    6. alexbalague

      alexbalague New Member

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      Thanks for the reply again. There will be an external unit providing heat so the cooling off issue would not be a concern. In essence the insulation would help make the external unit more power efficient..

      However the main issue as per original question is how to investigate the manufacture of the unit is where I am struggling

      thanks again for your help!
       
    7. Dana

      Dana Well-Known Member

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      If you're talking injection molding, which is what you'd need for smooth precise surfaces and a "premium feel", that's going to be an expensive mold, likely well over $100,000, which would take a long time to amortize at 300-500 units per month. Blow molding tooling would be a lot less expensive, and the process would be more suitable for your projected quantities.

      Most plastic molders should be willing to work with you at little or no cost, provided you approach them with a feasible design mostly worked out. If you expect them to design it for you that's another matter, but $2-300 per hour seems excessive, more like a brushoff because they aren't taking you seriously.
       

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