Abstract: Function demand aiming at roundness error detection of a large crankshaft connecting rod was described. Based on .NET platform and SQLite database, using three layers architecture and RS232 communication standard, the design of roundness instrument detection upper computer software was completed. The software realizes detection crankshaft roundness error and resolves large parts of the roundness error detection and calculation problems in the current manufacturing enterprises. In the practical application of the verification process, the detection achieves the purpose of realtime, high efficiency and accuracy, which effectively improves the machining quality of oversize crankshaft connecting rod,reduces assembly time, and solves economy, and safety problems caused by the work piece roundness error.

Key words: roundness measurement, upper computer, serial communication