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Material Choice: Durability, Cost, Weight

  1. Feb 25, 2006 #1
    I was wondering if you could guide me in my choice of material in one of my projects.

    I must design a robot capable of being very cost efficient, light, and durable. What material is best suited for this? It's difficult to research this sort of information on the internet, due to such a high amount of material classifications. In one of my books, Plywood, Steel, and Aluminum are said to be very Strong, and Steel is said to be the most cost effective. However, there is no information regarding weight. Also, is "Strength" necessarily equal to "Durability" ?
  2. jcsd
  3. Feb 25, 2006 #2


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    It's not just the materials you select. You can make something very light AND strong if you properly design the components. Think of how roof trusses can be made of light assemblages of framing lumber, yet still hold very large snow loads. Apart from trussing, the shapes of your components contributes greatly to their stiffness and strength. I have a loading ramp made out of arched aluminum box girders connected by extruded aluminum rods welded across them, which form the deck of the ramp. The ramp can't weigh more than about 30# or so, but has a load capacity of 1500#, so I can load my Harley or John Deere tractor into the back of my truck. The trick for you is to find off-the shelf stuff that has the structural properties you need, to keep the costs down. You might want to take a trip through a harware mega-store and look at all kinds of materials. Don't overlook the plumbing and electrical sections (PVC pipe and aluminum conduit come to mind...). PVC can make pretty good bearing material, too for parts that need to slide or rotate. Good luck.
  4. Feb 25, 2006 #3
    You could always use http://www.harvel.com/piping-clear-pvc.asp":bugeye:
    Last edited by a moderator: Apr 22, 2017
  5. Feb 25, 2006 #4

    If you don't mind:

    How would aluminum conduit, steel, and PVC pipe compare in price, durability (strength), and weight? I know that aluminum conduit and PVC pipe are much lighter than steel, and probably cheaper.
  6. Feb 25, 2006 #5


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    Normally, one goes to a parts/materials catalog or calls a supplier for a quote. Most places on-line require registration in order to get information.

    One could go to a hardware store and get a cost for basic aluminum conduit and plastic (usually PVC) tubing.

    Steel tubing is not very common outside of finished products, as part of the frame or structure of some product like a chair, tent, etc.

    Some steel tubing suppliers -


    http://www.metalcraft.com/contact.asp - for quote

    Al has a specific gravity of 2.7 and steel is about 7.85-8 depending on alloying elements.

    Another useful reference - http://www.mcelwee.net/html/densities_of_various_materials.html [Broken]
    Last edited by a moderator: May 2, 2017
  7. Feb 26, 2006 #6
    I would aluminum alloy is your best bet if you're making a robot. Normally its pneumatic operations and small motors that power it would want less burden on the weight. But it depends.

    If you want strength per volume, steel.

    Simply put, if you have to handle cyclic loads on small parts that may flex, it is probably best to use pvc or steel because they respond better to fatigue than aluminum.
  8. Feb 26, 2006 #7


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    Once again, another person falls into the trap. You can't base material selection criteria on such loose wording as "cheap", "light", "durable", etc...You have to put real numbers to those descriptions and then you can go from there. The design that you have in mind will also play a great part in what you can choose. There's nothing saying that the entire robot has to be out of the same material.
  9. Feb 26, 2006 #8


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    Question Zero : What do you want your robot to do ?
  10. Feb 27, 2006 #9
    I had a followup question on 02/18/06 , i did not recieve an answer.I know no one is obligated to answer any question , but you did reply to my topic.
    if you dont know the answer , at least say so.

  11. Feb 28, 2006 #10


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    You might find it helpful to make comparisons in terms of cost-specific density, cost-specific stiffness, and cost-specific strength.

    As Fred says, if you can quantify your parameters then you'll be able to arrive at an optimum solution, - you'll never get a real compromise between cost and anything without putting numbers in there.
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