CNC basics
To better understand the problems involved to successfully use your Rhino data for a CNC-controlled machining or cutting type operation, you need to understand the CNC process and how it works. Hopefully, this little primer will help.
First, a couple of definitions
CNC – Computer Numerical Control – Taking digitized data, a computer and CAM program is used to control, automate, and monitor the movements of a machine. The machine can be a milling machine, lathe, router, welder, grinder, laser or waterjet cutter, sheet metal stamping machine, robot, or many other types of machines. For larger industrial machines, the computer is generally an on-board dedicated controller. But for more hobbyist types of machines, or with some retrofits, the computer can be an external PC. The CNC controller works together with a series of motors and drive components to move and control the machine axes, executing the programmed motions. On the industrial machines there is usually a sophisticated feedback system that constantly monitors and adjusts the cutter's speed and position.
Desktop CNC – There are many smaller modelmaker-hobbyist style desktop CNC machines. In general these are lighter weight, less rigid, less precise, slower, and less expensive than their industrial counterparts, but can do well for machining objects out of softer materials such as plastics, foam, and wax. Some desktop machines may run a lot like a printer. Others have their own closed command system and perhaps even dedicated CAM software. A few will also accept standard G-code as input. Some industrial standard desktop machines do exist with dedicated controllers for doing precise small work.
CAM – Computer Aided Machining or Manufacturing– Refers to the use of various software packages to create toolpaths and NC code to run a CNC controlled machine, based on 3D computer model (CAD) data. When the two are used together, this is generally referred to as CAD/CAM.
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Note: CAM does not actually run the CNC machine, but just creates code for it to follow. It is also not an automatic operation that imports your CAD model and spits out the correct NC code. CAM programming, like 3D modeling, requires knowledge and experience in running the program, developing machining strategies, and knowing what tools and operations to use in each situation to get the best results. While there are simple programs that for the inexperienced user to get started without too much difficulty, more sophisticated models will take an investment in time and money to become proficient.
NC code – A special relatively simple computer language that a CNC machine can understand and execute. These languages were originally developed to program parts directly at the machine keyboard without the aid of a CAM program. They tell the machine what moves to execute, one by one, as well as controlling other machine functions such as spindle and feed speeds, coolant. The most common language is G-code or ISO code, a simple alphanumeric programming language developed for the earliest CNC machines in the 70s.
