Flat bed knitting machines capable of precise control of needle movement, individual knitted loops, and yarn delivery manufacture three dimensional tubular knit structures. Integration of electronic needle selection and mechatronic systems in modern flat bed knitting machines provides control for manufacturing three dimensional shell structures. The major impediment to manufacturing solid three dimensional knit structures using flat bed knitting machines is the need to accommodate yarn feeding to a reciprocating knitting system. Reciprocation of the yarn feeders leads to variation in yarn feed velocity, a problem that can be ameliorated by integrating a yarn accumulator device into the yarn carrier. UMIST is testing a prototype system to develop an efficient microprocessor feedback control system for the yarn accumulator.