Glossary · System coordination, integration and orchestration
Upstream blocking
Also known as: Blocking, Blocked state
German: Blockierung durch vorgelagerte Station
In production lines, upstream blocking is the condition in which a machine or station cannot pass its finished output on because the downstream station or buffer is full or not ready, so it must stop, and the blockage propagates to the machines upstream of it.
- System integration
In one sentence
Upstream blocking occurs when a machine cannot pass on its output because downstream is full, so it stops and the blockage spreads upstream.
Example
When the palletizer stops, the accumulation conveyor fills up, the case packer becomes blocked and, a minute later, the filler upstream is blocked as well.
How it applies
- Engineering: Buffers between machines decouple them and delay blocking. Line designs often run the bottleneck machine continuously and size buffers so that short stops elsewhere do not block it.
- Operation: Report blocked as a separate state from faulted or starved. PackML, for example, distinguishes blocked and starved conditions for loss analysis. A blocked machine is not the cause of the loss; the cause lies downstream.
- Analysis: Blocking and starvation data show where the true bottleneck of a line is.
- Documentation: Explain the state indications on the HMI so operators look downstream when a machine is blocked, and describe how buffers and line speeds interact in the line documentation.
Upstream blocking vs. starvation
Blocking propagates upstream from a full or stopped downstream point. A Starvation state propagates downstream from a stopped upstream point.