The transportation of individual units between operations may be impractical and
uneconomical. Therefore, in practice, sub-batches rather than units are forwarded between operations. Then, if Q units are manufactured in b sub-batches of equal size (where 1 - b < Q), each sub-batch can be treated as a unit and the operation time of each sub-batch expressed as (Q/b)tj. Converting (1) to accommodate this condition, a general expression can be found for the technological cycle time of both the sequential and combined movements as a function of the lot size: