Why does waste vary so much between crews on the same machine?

Picture a flexo printer-slotter running three shifts on one order book. The morning crew's scrap cage is half full at the end of the shift. The night crew's overflows. Both use the same board, the same inks and the same dies. So the owner starts to suspect the machine, or the night crew's attitude.

Usually it is neither. Waste that differs between crews on one machine is mostly a difference in practice. Crews vary in how carefully they set up, how they treat board and reels before feeding, and how quickly someone notices a fault and stops. Among the recurring patterns listed under packaging plant people issues, this one comes up constantly. Here is the longer answer, with the questions that follow it.

• Make-ready sheets. One crew mounts the plate, checks the die rubber and measures ink viscosity before the first sheet. Another adjusts as it runs, and every adjustment lands in the cage.
• Board and reel handling. Forklift tines crush flutes, reel edges get dented, and stacks parked near an open shutter pick up damp and warp. A crew that inspects at the feed table throws less away.
• Speed choice. Running hard on a warped stack causes misfeeds and jams. A good lead slows down for difficult board without being told.
• Time to spot a fault. Misregister, a smeared slot or a choked anilox can run for a long stretch before anyone pulls a sheet. Crews that sample at fixed intervals catch it early.
• Overruns and short counts. Some crews run extra to be safe, and the spares become scrap. Others stop short, and a rerun follows.
• The state of the handover. A die with torn rubber or an ink tray left half drained gives the incoming crew a bad start that is then booked against them.

The same list fits a slitter-rewinder, a pouch machine or a narrow web press, with other names for the losses. On a slitter it is edge trim, core waste, starred and telescoped rolls. On a pouch line it is weak side seals, wrinkled gussets, misaligned zippers and miscut pouches. On a cup former it is sidewall blanks crumpled at the turret.

Shift totals mislead. The night crew may get long, simple runs while days get short jobs with frequent plate changes, or the reverse. A crew doing six changeovers will make more start-up waste than one doing two, even if both work well.

Material varies by lot as well. Liner from one mill may curl more than another, and whichever crew meets that lot carries the blame. Dies wear, and one shift may always inherit the tired die because the fresh one went to the day job. None of this shows in a shift total.

1. 1

   Weigh waste against the job card

   Record kilos of rejects per job, not per shift. A platform scale beside the cage and one extra column on the job card are enough.

2. 2

   Split make-ready from running waste

   Use two bins or two entries: sheets lost before first-off approval and sheets lost after it. They have different causes and different fixes.

3. 3

   Note run length and changeovers

   A short job with two plate changes cannot be fairly compared with a long single-colour run. Write both on the card.

4. 4

   Record the board or reel lot

   Note the mill, the grade and any warp, crushed edges or loose cores seen at the feed. If one lot keeps turning up in bad jobs, the crew is not the cause.

5. 5

   Compare repeat jobs across crews

   After a month, pick repeat orders run by more than one crew. That is the fair comparison, and few plants have ever drawn it.

Plants rarely write down how their strongest crew works. The lead learnt it from someone senior, and it lives in habit. When crews are reshuffled to cover leave, those habits stay with the person, not the machine. Helpers rotate fastest, and a new helper at the feed table may not know what a crushed flute looks like.

Pay can push the wrong way. If the incentive counts sheets run rather than good boxes, a crew gains by racing through bad board. Blame does damage too. Where every reject starts a shouting match, crews hide waste under pallets or tip it into the baler before it is weighed. The worst shift can then post the best number.

Watch the best crew through three or four make-readies. Note what happens before the first sheet, not just during the run. Then write the routine with them, in their own words, on one page. People defend a method they helped write. They resent one written about them.

Train on live jobs. The strong lead stands beside the other lead for a few changeovers at shift overlap. Treat that coaching as part of the senior grade, so sharing earns credit rather than costing status. Then weigh again. If the gap stays, go back to the board lots and the die before you look at people. Plants with several converting lines will find crew grading for board and box work on the corrugated box makers page.

Job card number, machine, crew lead, date and shift.
Before the first sheet: plate mounted and checked? Die rubber and anvil cover inspected?
Ink viscosity measured? Anilox and doctor blade clean? Feed gate set to the board calliper?
Board checked at the feed for warp, crushed flutes and dented edges?
Sheets or kilos lost before first-off approval.
Who signed the first-off, and when?
Sample pulls during the run: how often, and by whom?
Overrun or short count at the end of the job.
Condition of die, ink tray and feed area at handover.

It can help if the design is careful. Reward good boxes delivered against the job, not raw speed. Adjust for run length, or crews on short jobs lose out for reasons they cannot control. A bonus that ignores job mix teaches crews to hide rejects.

Senior leads sometimes guard their routine because it protects their standing. Write teaching into the senior grade's duties, with money attached. Give credit on the floor when another crew's waste falls. A lead named as the source of a method has every reason to spread it.

Sometimes. If one crew's waste rises on this machine but not on another, or every crew struggles after a maintenance job, look at the machine. Worn feed rollers, a slipping drive or a loose slotter head will beat any crew. The per-job record shows this quickly, which is one more reason to keep it.

Put a scale beside the cage and add one column to the job card. Weigh per job for a month before reaching any view about a crew. Why stable crews keep their gains is argued in this piece on the crew as a unit. To turn waste per job into fair crew targets, see the performance process. For help rolling it out across several lines, use the requirements page.