Sunday, January 6, 2008

Vision systems (Industrial Robotics)

Industrial Robotics













Robots have matured from their birth in specific industries with specific tasks to becoming versatile mechanisms that are ideal for straightforward pick-and-place applications, as well as challenging applications that can utilize the unique capabilities inherently built into robotics. After working with automation equipment for 20 years, I feel it's important to provide insights into my transition from hard tooling to robotics so that others can understand the significant differences between the two. The purpose of this article is to touch on several features that have made today's robot a vital tool for any application.

True Flexibility The term flexibility means a variety of things when discussing robots. Let me first discuss flexibility in movement. With six-axis robots available, movement is virtually unrestricted. The designer spends less time on how the parts are moved and more time on the tooling at the end of the robot that picks the parts. This flexibility allows the tooling to be designed with an eye toward multiple tasks. For example, picking boxes and pallets or assembling two different parts and then setting them on an exit conveyor.

The idea is having the robot do most of the work. In situations when the end-of-arm-tool cannot accommodate all of the different shapes or sizes of the parts, tool changers are added to allow the robot to pneumatically change end-of-arm tools. This type of flexibility in movement is very useful during the building of a robotic cell. Hard tooling does not lend itself to minor positional changes as well as robots do. These changes made "on the floor" often help with the overall productivity of the cell.

Flexibility in mounting. Floor, ceiling or rail-mount robots offer the designer an option with most applications that does not require additional mounting structures. This speeds up the engineering needed to develop mounts, as well as the outside fabrication requirements.

Flexibility in your long-term investment. Traditionally, the thought of reusing hard tooling would be unheard of, but robots can be re-deployed to accommodate changes in products or procedures. When reusing robots, only the tooling and programming need modifications. They eliminate the question of compatibility when attempting to blend a variety of hard tooling products from different component manufactures together in one assembly.

Because robots offer multiple axes and are self-contained, there is no need for a structural framework to mount the various components of hard tooling. They also greatly reduce the time needed for hard wiring of the system. For most applications, power is only required for the robot and air if needed for the end-of-arm-tool.

Another advantage of re-deploying robots to new applications is that it breeds continuity throughout the plant. When reusing robots there is no learning curve or additional spare part requirements, and only one point of contact for its electrical and mechanical components.

When I first started designing with robots, I had a tendency to limit their flexibility by thinking of only a single task, similar to hard tooling. I now look at the overall system and incorporate the robot to do as many tasks as possible. The key point is that robot flexibility allows the designer more options without having to deal with the compromises of hard tooling.
Industrial Robotics

Tuesday, January 1, 2008

Cartesian robot (Industrial Robotics)

Industrial Robotics
The machine at left can be called a Cartesian robot, though calling this machine a robot is really stretching the definition of a robot. It is Cartesian because it allows x-y-z positioning. Three linear joints provide the three axes of motion and define the x, y and z planes. This robot is suited for pick and place applications where either there are no orientation requirements or the parts can be pre-oriented before the robot picks them up (such as surface mounted circuit board assembly).
Industrial Robotics

Adept Technology (Industrial Robotics)

Industrial Robotics
The robot shown at right is made by an American company, Adept Technology. Adept is America's largest robot company and the world's leading producer of SCARA robots. This is actually the most common industrial robot. SCARA stands for Selective Compliance Articulated (though some folks use Assembly here) Robot Arm. The robot has three joints in the horizontal plane that give it x-y positioning and orientation parallel to the plane. There is one linear joint that supplies the z positioning. This is the typical "pick and place" robot. When combined with a vision system it can move product from conveyor belt to package at a very high rate of speed (think "Lucy and the candies" but way faster).

The robot's joint structure allows it to be compliant (or soft) to forces in the horizontal plane. This is important for "peg in hole" type applications where the robot will actually flex to make up for inaccuracies and allow very tight part fits.
Industrial Robotics

Fanuc (Industrial Robotics)

Industrial Robotics
This is pretty much the typical machine people think of when they think of industrial robots. Fanuc makes this particular robot. Fanuc is the largest maker of these type of robots in the world and they are almost always yellow. This robot has six independent joints, also called six degrees of freedom. The reason for this is that arbitrarily placing a solid body in space requires six parameters; three to specify the location (x, y, z for example) and three to specify the orientation (roll, yaw, pitch for example).

If you look closely you will see two cylindrical pistons on the side of the robot. These cylinders contain "anti-gravity" springs that are a big part of the reason robots like these can carry such heavy loads. These springs counter-balance against gravity similar to the way the springs on the garage door make it much easier for a person to lift.

You will see robots like these welding, painting and handling materials.

Industrial Robotics

Industrial Robots

Industrial Robotics
Modern industrial robots are true marvels of engineering. A robot the size of a person can easily carry a load over one hundred pounds and move it very quickly with a repeatability of +/-0.006 inches. Furthermore these robots can do that 24 hours a day for years on end with no failures whatsoever. Though they are reprogrammable, in many applications (particularly those in the auto industry) they are programmed once and then repeat that exact same task for years.

A six-axis robot like the yellow one below costs about $60,000. What I find interesting is that deploying the robot costs another $200,000. Thus, the cost of the robot itself is just a fraction of the cost of the total system. The tools the robot uses combined with the cost of programming the robot form the major percentage of the cost. That's why robots in the auto industry are rarely reprogrammed. If they are going to go to the expense of deploying a robot for another task, then they may as well use a new robot.

Below are some link or example of Industrial robotics:

Fanuc

Adept Technology

Cartesian robot

Industrial Robotics