conWIP stands for constant Work in Process and is one of Hopp and Spearman’s most favorite strategies in their groundbreaking book “Factory Physics”. Other than Kanban, which requires inventory at every reporting point, conWIP spans multiple levels and sends a signal from the demand source across multiple stations to a point where orders are being ‘pushed’ through the system. The signal ‘pulls’ from the source but the pull doesn’t go from source to source to source – having to find inventory at every point – but rather goes to the first (of many) sources and releases a set of orders, with the spec from the demand, which it pushes in a sequence to fulfill the demand and fill the container back to ‘full’.
The way configured this into SAP was by way of the special procurement type ‘direct production’ (in standard 52), which creates and schedules a collective order. Make sure your lot sizes are set to EX with no min or max, so that the conWIP cycle has a consistent batch quantity