Cycle Time Reduction on a Legacy Production Line

Note: specific figures, part numbers, and company details have been generalized or removed due to confidentiality.

Background

The line in question had been running for close to a decade: a high-volume machining and assembly operation feeding a major automotive transmission program, running close to around the clock, six days a week. Multiple engineers had already worked it over the years. The obvious wins were gone by the time this project started.

Role: Project Engineer, leading a cross-functional team of about 10 Duration: 6 months Stakeholders: Plant Operating Committee, Quality, Maintenance, Automation, Production, Accounting

The problem

Cycle time across the line had plateaued, with every station running at roughly the same pace and no single clear bottleneck to chase. With no single bottleneck operation, this wasn’t a “fix one machine” project. Shaving time off one machine alone wouldn’t move the line’s overall output. The whole system needed to move together.

Approach

• Time study and constraint mapping. Walked every station on the line to build an accurate as-is cycle time baseline, rather than relying on nameplate or historical spec sheets, which drift from reality over years of operation.
• PFMEA on proposed changes. Any modification to machine parameters or tooling went through a Process Failure Mode and Effects Analysis first, since a scrap increase would have wiped out the value of any cycle time gain.
• Lean / Six Sigma problem-solving structure. Used a DMAIC-style approach to keep the project disciplined: define the target state, measure current performance station by station, analyze where time could be recovered without touching quality-critical parameters, implement changes in a controlled sequence, and control with updated SPC limits after each change.
• The washer station risk. The trickiest part of the line was the final high-pressure parts wash, which had a known history of debris occasionally escaping visual inspection. Speeding up that station without changing the failure mode’s detectability required rethinking the process, not just the timer settings.
• Contingency planning. Every proposed adjustment had a rollback plan documented before it went live on the floor, given the line’s near-continuous run schedule left almost no room to “try it and see.”

Tools used

MS Project, Excel

Outcome

The line came down to sub-target cycle time with no increase in scrap rate, verified over multiple production weeks after implementation.

What could have been done better

OEE on this line was consistently below target, and the initial focus was on reducing downtime and fixing machines through preventive measures. That took a lot of trial and error, since machine failures had many contributing variables. Tackling cycle time first would have increased parts made and OEE sooner, building a parts bank that could have freed up time to troubleshoot machines down to root cause instead of working through failures under pressure.