When I started in the shop, machine tools were dumber than fence rails. Load the paper tape, adjust the rheostats for feedrate and spindle speed, click, click, click the offset thumbwheels, push cycle start and pray. Programs were keyed into a Teletype machine; when changes were needed, the printout was redlined and sent back to the programming office for laborious corrections. CAD/CAM systems and the mainframes to run them cost more than a new house. Probes were something they sent into space, and the only thing high speed was the steel we used to cut parts.
What a difference a few decades make. Today, the combination of complex software, inline probing systems, and increasingly intelligent machine controls give machine tools uncanny decision-making abilities, anything from stopping the machine a split second before one of us error-prone humans crashes it, to automatically adjusting cutting tools and part programs based on the in-process inspection information.
Perhaps the best known of these technologies is in-machine probing, although Dafydd Williams, general manager of Renishaw (Canada) Ltd., Mississauga, ON, hesitates to call it adaptive. “In process measurement using a touch probe or inline CMM is more along the lines of process control,” Williams says. “It’s about checking tool wear and managing temperature fluctuations that may affect part size. Adaptive machining is when the actual part program is automatically modified based on in-process measurement.”
In Renishaw’s definition of adaptive machining, a touch probe is used to validate part location and condition, and the resultant information is sent to some “really deep and very clever software.” This software analyzes part features to determine whether the NC program must be adjusted or “morphed” in to bring part dimensions into spec, or to compensate for certain material conditions. “Let’s say that a customer has an expensive casting, and they need to discover what state the workpiece is in before machining,” Williams explains. “For example, is there too much material, or is the casting warped or oriented incorrectly?. Those arequite complicated problems to deal with on a machine tool.”
hat’s where NC-PerfectPart comes in. Metrology Software Products Ltd. (MSP), an associate company of Renishaw located in Northumberland, England, has developed a software program that assesses current part conditions based on data collected via a probing system, and then rotates or shifts the machine coordinate system to suit.