I have machined parts that are made of aluminum and anodized black. The reason that I chose aluminum is because:

  1. It can easily be machined and is low cost and is common, so easy to buy
  2. It is light weight compared to steel
  3. It can take heat
  4. It is easy to finish with oxidation

The parts are used on a CNC machine so being lightweight is important so that the machine can move faster.

But, I need my part to be significantly lighter weight, so would like to switch materials, but not pay a lot to get a prototype made.

  • Is there another metal that is a good substitute?
  • Can a plastic laminate be used? For example, plastic parts that I can get machined then add a high temperature tape to reflect heat?
  • 2
    $\begingroup$ This is a valid question, but we could provide you with better answers if you could define the problem a little better. What is the part doing (what kind of forces does it experience?) If it's just a coolant nozzle, for example, plastic can certainly handle that, but if it's a rotating component with a radial load, that's less likely. What temperatures do you expect your machine to experience? Does it have to be the same size and shape to do it's job, or could it be smaller with a stronger material (ie. are you concerned with density or strength-to-weight ratio?) $\endgroup$ – Ethan48 Jun 20 '15 at 15:46
  • $\begingroup$ For completeness of other answers a la part (A), the only reasonably priced, machinable, corrosion resistant alloy that has lower density than common aluminum alloys is the magnesium alloy AZ31B, which is about 1.77 g/cm^3. However, finding it may be difficult as the alloy is dangerous to produce, so there are very few producers. Prices range around 5 USD/kg, but not clear how much you have to buy and in what form. But depending on the requirements of your part, you may be able to go another route entirely, which will likely work better. $\endgroup$ – wwarriner Jun 21 '15 at 17:21
  • $\begingroup$ The AZ31B looks like an option, after watching several videos on youtube describing it and showing machining of the metals. I also found online sources at taobao.com that sell very small quantities, so purchasing should be fine. I will work with the engineer to determine how the drawings should be changed to the new metal. For the machine shop, I will do my best to educate the boss on the risks, I think a video showing risks would be better so will try to find one. $\endgroup$ – Allen Jun 21 '15 at 23:53

I'm not sure how your part looks, but I can tell you about temperature and plastics.

I've blasted phenolic composites with 600 °F (310 °C) and haven't had a problem. There are high temperature epoxies and vinyl esters that get to lower temperatures - and those are a lot more commonly available. I wouldn't touch them with anything over 300 °F (150 °C) though.

All composites range from 0.05 - 0.07 pci (1.38 g/cc - 1.97 g/cc), depending on if you use more reinforcement, or more resin. The phenolic can be as strong as an epoxy laminate, in testing. For glass reinforcement, you can guarantee breaking strengths of 25 ksi (200 MPa). If you designed your parts with a professional, orienting the fibers, you can get above 500 MPa. Wikipedia cites breaking strengths going into the GPa range, but there is no guarantee your part will have that - those are lab sample strengths, not actual usable part strengths. Bear in mind fiberglass is fatigue resistant (better than your aluminum!), but only if the part is designed with a factor of safety of 5.

Hope that helps you understand the world of high temperature composite substitutes.

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  • $\begingroup$ This is helpful. I have seen phenolic rods and sheets available at the local market and can purchase them to test. $\endgroup$ – Allen Jun 21 '15 at 23:58

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