Let's Make Robots!

What thickness of acrylic to use?

(hopefully this is the right place to post this)

So, I'm in the planning stage of my first project, and I got everything pretty much narrowed down to what I want to use.

The only question that remains for now is:

I want to build my hexapod from acrylic plates, and now I am wondering what thickness to use.
It's pretty tough stuff but still light, I don't want it to be too thin so things will start bending, but I don't want to go overboard and use real thick stuff, so it will be a fat bot.

I can get 2mm plates from the DYI store around the corner, for a pretty good price, but I figure that will be a bit on the thin side?
I could, ofcourse, work with 2 layers of plates, but that will not be as pretty as I want it to be.

Any tips on this?

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I use 3mm and it's sturdy enough. 2mm was my plan first, but it seemed to wobbly. 3mm seems to be a good compromise between weight/stability.

2mm Acrylic is way too thin in my opinion and I wouldn't even waste my time. The Lexan may work but you have to consider your design first. How many support pillars are you going to have between plates? (With enough supports even thin materials will hold). If you can put bends in the material it will be more rigid and can further improve strength.How big is your bot? It's hard to say without these considerations. From my experience I would pay more for the Lexan, without a good chassis everything else is useless. Have you considered using metals? Sheet Aluminum is cheap, easy to find and just as strong as plastics. 

Thanks for your reply!

Yeah i thought it'd be too thin as well, I even doubt if 3mm Lexan is thick enough.

My preliminary design is a chassis of 50cm long and 25cm wide. It will have at least 3 supports on long edges (corner, half, corner) and 2 on the short edges (corners). Also the spot where the servo's will be placed will support the upper deck, so it will be supported on many spots along the long edges.
Then I will make more supports where needed.

I considered using aluminum but the problem is, it's harder to get in my neighborhood (the DIY stores don't have it, and if they do it's small pieces and profiles) and also harder to process.
Lexan and acrylic can be glued/bonded together, that's gonna be tough with aluminum. I could bend stuff, but I don't have any tools to help me do that, so that is why I wanted to go with a plastic.

Now, I kind of settled on acrylic, since I found some sheets online, which would suite my needs.

They shave sheets going from 1,5mm up to 100mm thick.
Most are 500mm*500mm, so that would be 1 plate for the chassis (both sides), and maybe 2 for the rest of the parts.(1 extra, just in case).

Would 5mm be thick enough to go with?

5mm should be enough. You may have to place some supports in the center but it's hard to tell until you have started working with the material. You can also bend plastics by modifying a hair dryer from a second hand store.

http://www.youtube.com/watch?v=WQGoKUVfe6g

I found they also have 3mm Lexan plates.

Polycarbonate(or Lexan) is tougher than Acrylic but a bit more expensive.

Maybe I'll just get a sheet of each and see what works better..

One thing you should remember is that lexan is "softer" which means it doesn't crack as easily, but it's not as "clear" as acrylic. From what I hear it's easier to work with though.

From my experience working with it Lexan is just a better material for this application. It will not bend as much as acrylic and it is tougher and sturdier. Acrylic is better when you need to make shapes that require lots of bends. Either way when you are drilling you need to use coolant or go in and out to stop the bit from melting plastic.

OK, that sounds good... I'll go check out the Lexan plates then.

I haven't seen them yet, and don't know what size they are, I only saw them online.
If they are big enough to build the chassis from, I think I'll go with that.

 

It might sound a bit disgusting but spit is quite a good coolant. That's what I use anyway :)

that's not disgusting, it's just highly convenient and cheap ;)