An Anchored Job Did Not Hit Its Target Date

A bottleneck-anchored job that misses its target date has one of three causes: the bottleneck work center has no capacity in the target window, the target start date is in the past, or the feeder steps before the anchor cannot finish in time to hand off. Each surfaces as an anchor configuration error. Checking the bottleneck's capacity, the target date, and the feeder chain in that order finds it quickly.

EDGEBIC by User Solutions anchors a job by fixing its constraint operation to a target, scheduling the steps before it backward from that anchor and the steps after it forward, with buffers protecting the constraint. This is the Theory of Constraints approach. This post, part of the EDGEBIC troubleshooting guide, walks the three reasons an anchor fails to hold. For how anchoring works, see TOC anchor scheduling explained.

What Anchoring Promises and What It Needs

Anchoring pins the bottleneck operation to a target time so the constraint sets the pace and everything else works around it. The steps that feed the bottleneck schedule backward to arrive just in time; the steps after it schedule forward. Buffers absorb variation so the constraint is protected.

That promise holds only under conditions: the bottleneck must have real capacity at the target, the target must be a reachable future time, and the feeder work must be able to finish before the anchor starts. When one of those fails, the anchor path reports a configuration error and the target is missed. This is a more specific failure than a job that simply finished later than its due date; the anchor path has its own preconditions.

Cause 1: The Bottleneck Has No Capacity at the Target

The anchor needs the constraint machine to have a real, open window at the target. A bottleneck with no shift hours, zero instances, or a target window blanketed by holidays or downtime gives the anchor nothing to land on, and the path fails.

How to tell: the bottleneck work center's configuration is thin in the target window: no shifts, no instances, or the window is covered by calendar blocks.

Fix: confirm the bottleneck is properly set up with shifts and at least one instance, and that its target window is not erased by holidays or downtime. See how to flag a work center as a bottleneck and the zero-capacity checklist for the capacity factors. Then re-run scheduling.

Cause 2: The Target Start Date Is in the Past

Backward scheduling from the anchor needs the target to be in the future. If the target start date sits in the past, there is nowhere to schedule backward into, and the anchor path fails outright.

How to tell: the job's target start date is earlier than now, or so soon that the feeders cannot precede it.

Fix: set the target start date to a realistic future date that leaves room for the feeder steps, then re-run scheduling. See how to anchor a job to a target start date for where the target lives.

Cause 3: The Feeder Steps Cannot Finish in Time

Even with the bottleneck placed correctly, the steps before it have to complete before it starts. If those feeder machines are loaded or their operations are long, they cannot hand off to the constraint at the target, so the anchor cannot begin when planned and the tail runs late.

How to tell: the bottleneck itself is placed on time, but the pre-anchor steps run right up to or past the anchor's start, leaving no handoff room.

Fix: free capacity on the feeder machines by rescheduling lower-priority work, shorten the feeder operations if possible, or move the target later so the feeders have room to finish. The anchor is only as good as the work that reaches it.

The Order to Check

1. Target date. Confirm it is a reachable future time. A past target fails the anchor immediately.
2. Bottleneck capacity. Confirm the constraint machine has shifts, instances, and an open target window.
3. Feeder chain. Confirm the pre-anchor steps can finish before the anchor starts.

Fix the first failing item, re-run scheduling, and re-check.

Prevention

• Flag only the true constraint. The engine anchors on the first bottleneck it finds in step order, so flag exactly one work center as the bottleneck. Multiple flags make the anchor ambiguous and can pin the job to the wrong machine. A flag with no target date on the order looks inert instead, because the job simply schedules forward: a bottleneck flag that did nothing without a target date covers that case.
• Set targets in the future with room. A target date needs enough lead time for the feeder steps to precede it. Leave slack rather than pinning the anchor to the earliest possible moment.
• Keep the bottleneck's calendar clean. Because the constraint sets the pace, a holiday or downtime block in its target window is more disruptive than elsewhere. Review the bottleneck's calendar before anchoring.
• Understand the difference from plain backward scheduling. Anchoring is more than working back from a due date; it protects a constraint. If you only need to hit a finish date, plain backward scheduling may be the simpler fit.