12/1/2008 | 4 MINUTE READ

Robotic Assembly: Simpler, Faster

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Here is a brief look at some of the tech that can facilitate your mechanical assembly operations.


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"2008 is a very challenging year in North America for the robotics industry and other capital equipment industries," said Åke Lindqvist, Group Vice President of ABB Robotics, and Chairman of RIA's Statistics Committee. "With the economy either in a recession or on the edge of one, manufacturing companies are being quite cautious when it comes to investing in automation. This is especially true in the automotive industry, the largest customer for robotics," Lindqvist explained.

RIA numbers show that orders from automotive manufacturers and their suppliers fell 43% in the first half of the year. However, non-automotive orders increased by 23% in units and 16% in dollars. Traditionally, orders from automotive related companies account for 60-70% of new robot orders. In the first half of the year, due to the decline in automotive purchases and the increase in non-automotive orders, orders between auto and non-auto were nearly equivalent.


Although this from the Robotics Industries Association (www.robotics.org; Ann Arbor) makes it clear that there is a fall-off of some note in OEM and supplier company orders for robotic automation, there are still plenty of applications where robots make good sense. Like in assembly operations. Whereas there has long been a use of robots for assembly in the context of things like spot welding panels in the body shop, the opportunities for mechanical assembly are growing, particularly as robots become more "intelligent" through the use of (1) sensors and (2) collaborative operations between robots. While these products and capabilities aren't necessarily new in and of themselves (e.g., there have long been vision systems), what's different today is that the functionality is being built in to the robots and it is now greatly simplified compared with when it was essentially a major project requiring all manner of engineering personnel (bordering on rocket scientists with degrees from MIT) in order to get the systems up and running. One of the characteristics of industrial robots is that they are, for the most part, industry indifferent: it doesn't matter if it is an automotive application or a consumer products task. Con rod pins and lipstick cases are essentially similar even though they're miles apart in use. So even if auto is falling off in application for the time being, there is considerable development going on among robot manufacturers in areas like assembly because they're finding greater use of automation in other industries, which can benefit auto.


A good example of the dexterity and productivity of a robotic arrangement for assembly was put together by FANUC Robotics America (www.fanucrobotics.com) for demo purposes. The system has handling of con rods and cranks so that crank pins and bushings can be fitted into the components. This system makes use of its F-100iA programmable positioning robot; an LR Mate 200iC/5L six-axis robot with a comparatively compact size (e.g., a 35-in. reach) that’s fitted with a FS-10iA force sensor that can detect as little as 40 g (it is rated at 10-kg); and another LR Mate 200iC, but this one equipped with iRVision 2D, a robotic vision package that requires just a camera and cable, and which, as the name implies, is a 2D vision system.



One of the things that people tend to be really good at and which robots have tended to be a bit dumb about is force sending. If you try to insert a crank pin into a hole, chances are you’re going to be adjusting the amount of force that you use as you locate and then fit the parts together. If you have a robot without a force sensor performing the tasks, then chances are there could be trouble. But by using a force sensor, as shown here, there is the ability to have settings for contact force, approach velocity, push force, etc. Robots certainly have dexterity; the force sensor helps add finesse.


As you can see from this section of the system, the robot on the right is dealing with the bushings and crank pins; it is the one that makes use of the vision system. The robot on the left is handling the components that are fitted into a fixture. A key here is how the robots can cooperate in order to perform the assembly task.



Light, Fast Assembly

When it comes to assembly applications for light payload applications, SCARA robots—not a brand, but an acronym: Selective Compliance Assembly Robot Arm—have long been the choice. After all, as the very name of the robot implies, it was developed with assembly in mind. While some companies tend to be more associated with the articulated arm robot that is familiar to people who don’t even know what industrial robots are (the robot with the large pedestal and the jointed arm) than they are with SCARA arms, the parallel joint configuration is sufficiently beneficial for these companies to offer SCARAs. Like Motoman (www.motoman.com). It has just released its YS-series of SCARA arms. The benefits of these robots is that they are generally fast and accurate. For example, the smallest of the four robots in the line, the YSZ450, has a payload capacity of 11 lb., a reach of 17.7 in. (or 450 mm, which is where its numeric designation comes from), and a Z-stroke of 6.7 in. It offers a cycle time of 0.409 seconds and a T-axis repeatability of 0.0006 in. Interestingly, the Motoman YS arms use the same controller and programming language as their six-axis mechanical brethren.



Unusual Arm

One of the most bizarre-looking robots to find industrial use is the Quattro from Adept Technology (www.adept.com). And it does have applicability in assembly. The s650 is a four-axis robot that makes use of four arms with a rotational platform. It is mounted in an inverted position, above the work area. The maximum payload capacity is 6 kg. Those arms have carbon-fiber construction. It offers a 1,300-mm work envelope; the Z-axis stroke is 250 mm. and it is fast, with a maximum speed of 10 m/sec.



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