What Is Transfer Delay in Lot Streaming?

Transfer delay is the flat handling lag, in hours, that applies after a transfer batch is ready before the downstream step can start. It captures the physical time to move parts between stations: loading a tray onto a forklift, driving it across the plant, setting it down. Transfer delay sits on top of the lot-streaming overlap rather than replacing it, and it is the same flat amount for every batch on the step. EDGEBIC by User Solutions uses transfer delay so an overlapped routing accounts for the real move time instead of assuming parts teleport.

How it works

Lot streaming overlaps two sequential steps so the downstream one begins before the upstream one finishes. The overlap is triggered by a transfer batch, a count of finished pieces that, once ready, signals the next step can start on them. But being ready is not the same as being there. The parts still have to travel, and transfer delay is the time that travel takes.

Transfer delay is flat: it is a fixed number of hours added after each transfer batch becomes available, not a value that scales with quantity or run time. Thirty minutes of forklift time is thirty minutes whether the tray holds 25 parts or 250. It layers on top of whichever lot-streaming model the step uses, so the downstream step becomes eligible a set time after the batch is ready rather than the instant it is ready.

It is worth separating transfer delay from two neighbors. Transfer batch size decides how many pieces trigger the handoff. Queue time is a shift-aware buffer for staging or inspection that sits after a step by design. Transfer delay is narrower than both: just the physical move of a ready batch.

A concrete example

Picture a machining station handing parts to a deburring station across a plant. The machining step finishes a tray of 25 parts, and the transfer batch of 25 says the tray is ready to move. But an operator still has to load that tray onto a cart and push it 200 feet to deburring, which takes half an hour. That half hour is the transfer delay.

Without it, the plan would assume deburring starts the instant the 25th part is machined, which is not physically possible. With a thirty-minute transfer delay, deburring becomes eligible half an hour after each tray is ready. The overlap from lot streaming is preserved; the plan simply stops pretending the move is free.

In the plant, "thirty minutes to load the tray onto the forklift and drive it to the next station" is exactly a transfer delay: flat, per batch, on top of the streaming overlap.

How EDGEBIC uses it

Transfer delay is a value on the routing step, entered alongside the transfer batch size that drives the overlap. Setting the batch that triggers streaming is covered in how to set a transfer batch size in EDGEBIC, and the whole overlap mechanism, including where the delay layers in, is in EDGEBIC lot streaming.

Because transfer delay only adds a lag, it never changes which pieces trigger the handoff or how many machines run the step. It works with the transfer batch, the companion glossary term, rather than instead of it. If a transfer batch is being ignored entirely, the cause is usually the continuous-process model rather than the delay, as explained in my transfer batch size was ignored.

Modeled correctly, transfer delay keeps an overlapped routing honest: the streaming still shortens the run, but the move time between stations is finally on the plan. For the wider vocabulary, see the manufacturing glossary, and to see lot streaming inside a live plan, explore EDGEBIC.