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Author Topic: Help Getting Started  (Read 700 times)

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Offline AUTONUBTopic starter

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Help Getting Started
« on: December 30, 2011, 02:21:53 PM »
Hello folks,

I'm completely new to robotics but I'd like to take on a major project. I expect it'll be a learning experience but I'm confident I can eventually make it work. I know what I want to design and I can visualize its operation, but I'm having a little difficulty finding exactly what parts I'll need.  For example, I want my robot to move along a linear x-axis (back and forth according to my programming using an Arduino Uno microcontroller). However, I'm not sure what the best strategy would be to have the robotic arm mechanism move along the track. I'm using a solid steel support beam as a track. I can modify the beam (can weld it or add bolts or whatever). I also need the arm to move forward and back along the z-axis, but only by about 5 inches. The hand of my robot arm will be a simple drill bit the size of a 1" bolt (think of an electric drill with a bolt as its bit). The bolt will need to turn at a rate of between 7.5RPM and 25RPM, but I'll need fine control. In other words, momentum can't be allowed to continue to rotate the bolt after it reaches its intended rotations. The torque requirement of the bolt will be a minimum of 5 ft-lb. The weight of the item attached to the bolt will be about 18 lbs. This will obviously be a heavy duty robotic arm. I'm not certain of a servo can be used or not. I'm not too worried about the cost, as long as I'm not buying the wrong parts or throwing my money away for some other reason. It is primarily the method of moving the robotic arm which I'm requesting the most help with at the moment. It'll be heavy and I want to utilize the beam already available. I'll worry about sizing everything out later.

I don't expect anyone to design this for me, so I won't go into much more detail, but feel free to ask questions if I'm leaving out any information. And please be forgiving if I seem ignorant here. Everyone has to start somewhere. I'm just the sort who prefers to dive in head first. I'll be researching the tutorials and robotics websites in the meantime. Thanks for the help!


Offline Soeren

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Re: Help Getting Started
« Reply #1 on: December 30, 2011, 09:40:50 PM »
Hi,

It is primarily the method of moving the robotic arm which I'm requesting the most help with at the moment. It'll be heavy and I want to utilize the beam already available. I'll worry about sizing everything out later.
The most stable way to carry a substantial weight in a precise manner will be to make a "cart" with ball bearings as wheels.

Mill the beam to have like a "roof" with a 90° top angle like "^" and have 2 bearings riding at each side as if they were the wheels of a car with a 45° toe-in, to match the angle of the inverted V-shape, then (at least) one bearing at the middle of the beam, between the slanted bearings to keep it from tilting and a single bearing or two under the beam to secure it (at least these bearings need to be easy removeable, so it can be taken apart.
This will work as long as the Y-axis movement is not too large (which would require two parallel beams).

This principle have been used and proved their worth in large scale printers and plotters back in the days where each slide could easily be at least 5..10kg and the total weight got close to 80kg or more in some of them. Oil dampened schock absorbers was used to keep a Carriage Return char from sending the entire device through a wall or rip itself apart ;D

When you have a well running cart, you can move it by a timing belt loop (pulleys at each end of the beam, with one of the pulleys driven by a geared down motor).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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