Move over machine tools here come robots
Charles Bates
02/17/2006
There is a classic failure to communicate in the machine shop. Robots run on brand-specific languages all their own, while conventional CNC machine tools read G-code generated through CAM software. But what if a robot's control was programmed to read G-code directly from a CAD/CAM program?
That robot could gain the functionalities of a CNC machine tool, including full 5-axis contour surface-machining capabilities, and it could be programmed in minutes to work on any 3- or 5-axis workpiece. Current technology typically requires hours, or even days of programming before a robot is ready to work. In addition, machining cells that included such robots could provide a low-cost alternative to machining centers and routers for secondary part operations and could eliminate the work-envelope constraints of those machines when dealing with large components.
Programming Plus Inc. (www.robotmachining.com) says its Robotic Machining Cell turns this "what if" scenario into a reality. The robotic machining cell hinges on software developed by the New Berlin, Wisc., company that smoothly translates CAM-generated G-code that is ready for a 5-axis machine tool into usable code for a 6-axis robot. No other company in the world has accomplished that, says Tim Brooks, robotic sales engineer at PPI. Programming Plus specializes in CAD/CAM, DNC and shop floor automation.
Programming Plus uses Delcam (www.delcam.com) Power-Mill software to generate G-code for Kuka Robotics (www.kukarobotics.com) robots in its robotic machining cells (RMCs). Since the cells function like machine tools, operators can turn the robot's spindle on and off, change rpms, and override speeds and feeds. Until now, such functions could not be done, says Brooks, because they were not within a robot's control.
Shops typically use conventional robots equipped with spindles for trimming, cutting and deburring around part profiles. But these shops must "teach" robots by moving them to multiple points around parts, and the more complex the part, the longer teaching takes. And teaching robots to go from one part to a different one requires even more teaching. Robots in a robotic machining cell move from one part to the next without having to be taught, and do so with less than 30 minutes of preparation time, no matter what the level of part complexity.
If an operator is unsatisfied with a robot's cutting path in a robotic machining cell, he can change the cutting path in the CAM system or he can manually teach the change and i-nsert it into the toolpath, resave the program, and run it. Also, since robotic machining cells use Delcam's PowerMill software, shops can conduct robot and part-machining simulations to check for possible collisions and obstructions, and do gouge checking prior to running a program. In addition, Brooks says his company's software soon will let shops monitor robots, via cameras, from remote locations over the Internet.
Programming Plus' software offers shops another benefit: resolving problems of singularity. Singularity occurs when all of a robot's axes approach being in line with zero. They increase their speed to keep up, they get to a point where they are moving too fast and, in a way, they lock up and stop. The condition is similar to constant surface footage on a lathe. The problem is that shops can not predict where singularity will happen.
Fortunately, as the robotic machining cell software transfers G-code to a robot, it evaluates the program for physical configurations that might cause singularity. If any are found, the software modifies the program to eliminate them.
Most shops do not associate 5-axis contour surface machining with robots primarily because it would take a great deal of time to teach a robot all the necessary data points. Instead, shops use CNC machine tools. I