Could i have assistance on how to obtain material for my robot please?

[Bciaren]

Hello everyone!  I'm new to the site and have been using The society of robots site heavily to try and learn how to build a robotic arm for my senior project.  My group decided on a challenging project and we have an idea on how we're going to build it, but material is a big problem we've run into.  I can't determine how much torque is needed per joint if I don't know the actual weight.  In order to account for weight I have to add up the weight of the servos, wires, material, etc.  Weight of the material is something I can't figure out, especially when I have no idea on how to obtain.  Could I get guidance on this issue?  The material we want to use is aluminum, but shaping it is also confusing..

[MrWizard]

First you make a scope for the project what does it need to do, what does it need to be capable of....
Then you go measure and calculate the forces, which is directly related to the materials and solutions.
Select the right materials, size and shape. Sensors etc etc...Check for electronics that is supported by libraries under Arduino or C.
Then you need to seek some knowledge of manufacturing, some you can do yourself, some by more experienced hands.
Check, soldere the electronics, wire and connect, double check and measure with a multimeter if all is decently connected.
Then you going to program or code (this is the fun stuff), fix the mistakes and troubleshoot until quirks and bugs are gone.

Take pictures of the process and make a nice report, blog some here...

Happy roboteering.....nobody said it would be easy :-)

[MrWizard]

You can use Lego, like I did or Meccano. Old radio's, tv's , old toy cars with RF transmitters, basically old electronic stuff or buy new....
Search Ebay where I found some great stuff, some send for free, very low prices.
If it is for a school project may be you can get some sponsers, write to Mouser, Farnell, Digikey, Element14, RS-Electronics, Sparkfun etc...
Hobbyking is a good place for servo's.

There are some basic controllers you can use like an Arduino Series, Axon (much better ofcourse).

[Azraels]

For my first arm I used clipboards. Just remove the clip and you have a nice board, not sure if they are mdf or hdf, but they worked good are light weight, cut easily. Just make sure after you get all the holes cut that you give them a coat of good quality spray paint because if you get any moisture on the boards they can warp.
 I also used some of those aluminum pieces you can get at hardware stores.
Also just learn to look at the way things around you can be used to make things other than there intended purpose.
Aluminum can be shaped cheaply with jigsaw, hacksaw, dremel with a metal cutting router bit, and a file. You just have have patience.

[waltr]

The weight per unit volume of almost any material is readily available using Google.

A reasonable source of small quantities of structural materials is available from McMaster-Carr (Google them).

You are probably going to need to 'prototype' the structural members of your robot to determine what will be strong enough but also light enough (this will be where you make trade-offs in the design).

Does your team have any access to a metal working shop?
What tools are available would determine which materials should be considered.

[Bciaren]

Thank you so much for the responses!  We just want to make a robotic arm on wheels that could lift up light weight objects.  I'll post our design shortly..

[Bciaren]

First you make a scope for the project what does it need to do, what does it need to be capable of....
Then you go measure and calculate the forces, which is directly related to the materials and solutions.
Select the right materials, size and shape. Sensors etc etc...Check for electronics that is supported by libraries under Arduino or C.
Then you need to seek some knowledge of manufacturing, some you can do yourself, some by more experienced hands.
Check, soldere the electronics, wire and connect, double check and measure with a multimeter if all is decently connected.
Then you going to program or code (this is the fun stuff), fix the mistakes and troubleshoot until quirks and bugs are gone.

Take pictures of the process and make a nice report, blog some here...

Happy roboteering.....nobody said it would be easy :-)

We intend to use arduino, no sensors (as far as I know).  The purpose of the project is to have the motion of the arm mimic the motion of a human arm.  We can safely say that we finished researching the gadget that will control the arm, now it's all about researching how to construct the arm!

[MrWizard]

Aluminium will I think do the job

Use boxed or triangle constructions

http://www.crustcrawler.com/products/AX-18F%20Smart%20Robotic%20Arm/images/Side_View1.jpg

View this perhaps an idea..

[Bciaren]

Hey everyone!  This is an isometric view of our proposed design!  The gripper is a placeholder until we can agree on a design for the end effector (this was properly explained and cited on our proposal).  This is our first hypothetical design and as you can see, it's not original, but I'd love your comments, critiques and suggestions.  We plan on using 5 DOF's for the arm and one or two on the end effector depending on it's complexity.  We want to get it to lift at least a tennis ball.  Based on those dimensions, I was able to calculate the torque needed at each joint (assuming the tennis ball was in hand), however my biggest concern was how to construct the base.  You see, I want the arm to rotate up to 135 degrees and so I drew rotating plates (pink) attached to a shaft (blue) which would be spun by a gear on the servo (red), but I'm not sure how that's really constructed or if it's feasible.  Any suggestions on how to research this?  Or do I have this all wrong and should re-do this drawing ASAP? 

Note*  This is my first time doing a 3D CAD drawing, I've always done 2D ><



Base


Front view of base


What you're seeing is an old revision.  The only changes that were made was the bottom plate.  It was expanded to fit inside the proposed chassis.

[Bciaren]

I should apologize for taking forever to post this (exams and homework >< ) and also thanking everyone for their helpful responses!

After thinking about it, I don't think I need those yellow plates.  The shaft will be holding all the weight.  I guess my only question is how do I attach a shaft to something it needs to rotate.  A circular plate with hole size equal to the diameter of the shaft, how does it stay in place and rotate.

[idee17]

You could use a large circular bearing, or if this is being done on the cheap, a lazy Susan table thing works well.