Method for detecting residual amount of bottom threads

The invention discloses a method for detecting the residual amount of bottom threads. The method includes the following steps of a, setting the stitch length A of a needle, detecting signals through abottom thread detecting sensor, sending the bottom thread residual amount B during electronic control, and calculating the number (P=B/A) of threads capable of being sewn according to the residual amount B; b, recording the number C of threads sewn within a set region and the number E of sewing units D, and calculating the number (Q=C/E) of threads required by one sewing unit D; c, judging whether the sewing of one sewing unit D can be completed according to the residual amount B or not, if not, giving an alarm, and otherwise, giving no alarm. The residual bottom threads can be prejudged in advance, the reworking or stitch removing caused when workers are reminded of the lack of bottom threads in the middle of sewing is avoided, and the aim of bottom thread detecting original purpose is realized. 本发明请求保护的用于底线余量检测