A Story: Single-Piece Flow in a Job Shop
A cool thing about manufacturing leadership is that you can lead a wide variety of operations. I was working in consumer products manufacturing, and I switched employers after a company buy-out. With my new employer, I took responsibility for an operation that produced microwave cables for the defense, aerospace and satellite markets.
Microwave cables are specialized transmission lines used to carry high-frequency signals with minimal loss and distortion. In radar systems, they connect transmitters, receivers, and antennas, enabling accurate signal timing and target detection. In military jets, microwave cables support electronic warfare, navigation, and communication systems, where performance, shielding, and resistance to vibration, temperature extremes, and electromagnetic interference are critical. These cables are lightweight and phase-stable to maintain signal integrity during high-speed maneuvers. In satellites, microwave cables route signals between onboard radios, antennas, and payload instruments. They must withstand radiation, vacuum conditions, and wide temperature swings while maintaining precise electrical characteristics to ensure reliable communication and data transmission over vast distances.
In summary, these are high tech products built to mission critical specifications.
In this plant, we produced the cable itself, we machined and assembled the connectors, and we assembled these custom components into cable assemblies through cable prep, soldering and electrical testing.
When I first took over the plant, it was hard to ignore the complete chaos that existed in the cable assembly room. Stacks and stacks of product bins everywhere, a high rate of product failures, disgruntled employees and a stressed-out supervisor constantly fire fighting issues. It was nuts!
What was the root cause of all this chaos? BATCHING!
For decades this operation did batch work at every step in the process. Bins with job packets held production orders of various quantities ranging from about 10 pcs up to about 70 pcs per order. These are pricey cable assemblies, so needless to say, there was a lot of cost and revenue associated with each job.
This is how the process went.
- Cable prep was batched by job, returned to the bin and staged in stacks with all the other prepped orders.
- Solder operators would then look for the supervisor and ask what job they should solder next. Then they would look for the assigned order and solder the appropriate connectors on to each end of the prepped cables and return the assembled cables to the bin and stack the bin in a random staging area.
- Then a test technician would find the supervisor and ask for their next priority. Once informed they would find the job and start testing the cables on a Vector Network Analyzer (VNA). Each job had very specific test requirements and specifications. Jobs that failed were stacked to the side for engineering review, that is, whenever an engineer could get to it. Jobs that passed were moved to QA for a final physical inspection. Again, staged and stacked and prioritized via a verbal conversation with the supervisor.
- A QA inspector would review the product for physical defects and out of spec conditions. Jobs that passed were moved to shipping and jobs that failed were moved to a hold status for Material Review Board (MRB) disposition.
I said, “Stop the Madness!”
I assigned a Process Engineer who had Lean and Six-Sigma experience to the room. His nickname was JC. I tasked him with creating assembly cells and implementing single-piece flow into the assembly room.
After decades of batching, changing the culture was difficult. It took a lot of hand holding. JC was essentially camped-out in the pilot cell. But JC did an incredible job.
Starting with cable prep area, he studied the process and realized there was a changeover required on the prep equipment. There was a cable prep machine that had to be set up for various prep styles and dimensions. One job could have various prep requirements, and each end of the cable could be different from the other end. This was tricky to force into a single-piece flow model. But JC did some math and found that small batches of 5 pieces would keep up with our takt time and significantly reduce our defect exposure.
Next came the soldering operation. Previously, Solder Operators worked in isolation on complete jobs. But JC changed that model. He placed them in-line, in a cell with a Cable Prep Operator. So, after the improvement it looked like this; there was one Cable Prep Operator prepping 5 cable at a time and one Solder Operator soldering a connector on to one side of the cable, then another Solder Operator soldering on the other connector. JC also assigned some quality inspection responsibility to the Solder Operators. Like why wait until the end of the process to inspect for defects? JC fixed this.
Perhaps the biggest challenge we faced was with the Test Technicians. Previous to single-piece flow they worked together side-by-side in their own space. Now JC was going to break up the band. He moved a Test Technician to anchor this pilot assembly cell. This move was met with much resistance, but I helped JC navigate through this culture problem.
Single-Piece Flow Success!
Once the tech was moved in-line in the cell, the improvements were dramatic. Immediately, product velocity sped up. What once took weeks to get product through the room, now took hours. What once surmounted into catastrophic quality problems, now was identified and corrected in minutes. What once stored bins and bins of products and tied up cashflow, was now just a few orders, representing low inventory and high cashflow. What was once steady overtime requirements, became 40 hours of smooth workflow and stellar OTD performance.
We put a Bow on It!
Our final steps included:
- Expanding our pilot cell into seven other cells in the room.
- Adjusting router flow to mirror the new process flow.
- Having the Production Planner prioritize and stage the jobs for each cell, pre-shift.
- Planting an Engineer in the room to support quick troubleshooting.
- Implementing visual controls.
Fast forward 3 months, the once stressed-out, firefighting Production Supervisor was now very chill. They no had time to lead people instead of just reacting to issues. The culture has shifted and employee morale in this room was the best in the entire plant. Employees had a twinkle in their eyes and a bounce in their steps and smiles and laughter abound.
Single-piece flow can work in your job shop too!
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