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Sensors, Actuators, and Robotics » Good communities for mechanical projects?

April 17, 2009
by MacGyver
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I have a project in mind where I basically need to sort 9 objects, can reset the device manually in between uses.

Having no background in mechanical engineering, I realize there are hundreds of ways to accomplish this.

As an example to what I have in mind:

  • Could have objects in circular formation, stepper motor with servo's to grab the object, rotate it to receptacle, and then go grab next item.

  • Could have objects vertically arranged on 45 degree incline, held by a small pin. When pin releases, object falls(and just release in certain order). For this though, there is still the question of how to actuate the pin: Servo? Pulsing a small motor? Electric Muscle Wire to pull pin back? Some type of Solenoid? If using the PE of the objects on an incline, the actual force required to active is minor and I don't want to go overboard as this project could be expanded to have 50+ items, so would expect to need something cheap for each piece.

  • Could have objects in horizontal formation and usage of stepper to drive a timing belt or conveyor containing a servo or solenoid, which could either grab the object or just push it back causing it to fall backwards.

  • Also using gravity, could have each item held by little grabber arms, which are set to release in order. Then question of using servo for grabber? or a spring-closed grabber that a motor or muscle wire works against to temp. release it?

Then there is the entire issue of whether you can build something that is at its heart mechanical(ie a system of springs/weights that only needs a small electrical activation such as removal of a pin) vs. something that is entirely electrically based, ie a huge collection of servo's, steppers, motors and whatnot to do every motion

As you can tell, I seem to have many questions and have been overwhelmed by the different ways to go about constructing my projects.

So does anyone know of any good forums where experts at this type of thing give advice?

I realize that this is really an art, but without dropping much more money than I have actually buying many different devices and testing each of them, I'm really looking for some good advice from a community that already focuses on this sort of thing.

Thanks for reading!

May 06, 2009
by dcept905
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As you mentioned, there would be several ways to accomplish what you're trying to do. The only real way to figure out what would be the "best" solution would require a bit more information. For example, exactly what kind of parts are you sorting? Are they small and lightweight, large and heavy, metallic/non-metallic, what kind of sorting are you doing - by size, color, weight, etc? How far are you moving the objects? I'm not sure what kind of scale you're working with, but I've done a lot of industrial automation with PLCs and have done setups similar to this that have used conveyors and prox switches to detect each object passing or something like a small-scale palletizing robot may work? Basically any of the solutions you mentioned could work, the level of elegance and sophistication would depend largely on constraints presented by the objects themselves and your budget.


May 07, 2009
by MacGyver
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The objects would be around 2g-16g each, around 2-3 inches in size. Budget very small :)

I'm going for silence and speed, and thus I've gone for the 45 degree incline approach and I'm using multiple geared pager motors(solorbotics) with a pin attached directly to the arm to rotate the arm and thus letting the objects slide off the incline.

I'm seeing how this approach works out, but I'm still at a loss on how you could possibly account for all the variations that could occur to find the most elegant solution possible. Even just the placement of the motor with regards to the incline seem to bring on multitudes of options, without any clear winner among them.

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