Time Shifting is an important concept when it comes to tracing of materials or products through a manufacturing process. While traditional OT use cases tend to focus on individual machines, i.e. the "Where", material tracing adds a "When" component.
As digital information is accumulated on a "Material Ledger" time goes by: process variables measured on different machines or station points in a manufacturing process for the exact same piece of product or lump of material comes with different time stamps for each of these station points.
The Time_Shift() Function
This function shifts a value stream laterally along the time axis, i.e. into the future, or into the past. In the example below, we shift hourly cycle counts by 1 hour into the future, to be able to show count at the end of an hour together with count at the start of an hour.
Example: time_shift($.cycle_shift_hourly, '1 hour'::interval)
The Get_Material_Flow_Time(speed_attr_ref, density, length_attr_ref) Function
This function calculates how long it takes, at any point in time, to travel a length at a speed. Both length and speed can be attribute references. We provide an interval to control the density of values returned, for instance every 30 seconds.
Example: get_material_flow_time($.relative_speed, '30 second'::interval, $.relative_length)