Compensation without cables

Thermal compensation of a coordinate measuring machine’s principle structural components and the part being measured helps ensure measuring accuracy over an extended temperature range when the CMM is installed outside of a temperature-controlled area. Such a temperature-compensation system is comprised of temperature sensors and cabling running through the machine to its controller. The more sensors there are the more accurate the system, but these cables can cause mechanical issues and will eventually fray or break because of the constant CMM motion.

The COORD3 Universal vertical-bridge CMM with a Bluetooth wireless thermal-compensation system.

CMM builder COORD3 Industries Srl, Torino, Italy, has developed a Bluetooth wireless thermal compensation system for CMMs that reportedly allows the measuring system to automatically and dynamically compensate for thermal changes in the CMM and part without the cabling.

In addition to eliminating cable wear and maintenance, the wireless system is more efficient because it reduces the time and cost usually required to add a thermal-compensation system to a CMM, noted Elliott Mills, general manager for COORD3 Metrology LLC, the company’s North American subsidiary. The wireless system is an option for all of the company’s new vertical-bridge and gantry CMMs and can be retrofitted to an existing CMM from any builder.

The wireless system allows the CMM to perform with stated measuring accuracy from 16° to 26° C (60.8° to 78.8° F), according to the company. “The wireless temperature compensation system allows us to achieve the intended accuracy over the extended temperature range compared to the traditional window with a machine without thermal compensation, which is 20° C (68° F) ±2° C,” Mills stated.

“Our CMMs use gold-plated 0.1µm-resolution measuring scales that are free-floating in support tracks, thus eliminating any CMM structural changes from influencing measuring accuracy,” Mills said. “The scale free-floats are independent of the CMM structure as it expands and contracts. Traditionally, scales were rigidly fixed to the CMM and moved with the CMM structure, introducing measuring errors.”

Mills added that wireless thermal compensation also safeguards the part-measuring process even if the CMM is installed in a temperature-controlled room. “No room is perfect over a 24-hour period as temperatures ramp up and down,” he said. “Special gradients are also an issue for larger CMM installations.”

For more information, contact COORD3 Metrology LLC, Wixom, Mich., at (248) 397-5490 or www.coord3.com. cte