A few technicians decide quality: a fix for plastics units

The senior setter rings in sick on a Tuesday night, voice croaky with fever. A front-loader lid mould is due on the big press. The junior fits it, heats the barrel and starts shooting. Short shots, then flow lines, then flash creeping along the parting line. By dawn a skid of grey scrap sits beside the press. On Thursday the senior returns and has saleable parts inside half an hour, after shifting the switchover point and warming the tool.

That gulf between two setters is the pattern. A tiny group sets the process, swaps the mould and rules on whether a blemish is acceptable. When one is missing, output sags and rejects climb. Shift attendance in a plastics factory is normally handled as a headcount sum. For setters it is a question of irreplaceable skill.

• Rejects swell on the days a particular setter is on leave, and shrink when he returns.
• First-off approval on a new run waits until one named person drives in.
• Mould changes are quietly nudged onto whichever shift the strongest setter is working.
• His mobile buzzes after midnight about sink marks or a jammed ejector plate.
• Nobody schedules his leave, so it either never happens or lands in the busiest week.
• Settings for the trickiest tools sit in a dog-eared notebook, or only in his head.

The visible cost is scrap and idle presses. The granulator spends the morning chewing rejected lids into regrind, and the regrind bin fills faster than the blend ratio can absorb it. A mould change that drags across a shift wastes the press and its operator together. Dispatches slip, and a buyer who spots warpage or weld lines in one consignment starts inspecting every consignment. Overtime piles onto the lone person able to rescue things.

The hidden cost is bigger. A setter summoned every night eventually accepts the offer from the larger moulder across the estate. When he goes, his settings leave in his notebook. New tools cannot be accepted with confidence, because nobody else can run a trial.

• Setting is absorbed by standing alongside. Back pressure, cushion, decompression and cooling time are nudged by instinct, and instinct is rarely put into words.
• Knowledge feels like security. A setter who alone can coax the two-cavity tool with its temperamental hot runner feels safe, so sharing feels like surrender.
• No time is carved out. Production pressure keeps the junior minding a press instead of learning to set one.
• Pay rewards doing, not teaching. The grade ladder has no rung for a setter who brings on a deputy.
• Setters are scarce. Seasoned people are hard to recruit, so owners cling to the one they have instead of growing another.

Machine group: toggle presses, big hydraulic presses, vertical insert presses, blow machines or the extrusion line.
Shift A, B and C: primary setter for this group on this shift.
Deputy who can bring up any mould in this group unaided, or the word NONE.
Who can approve a first-off and sign the limit sample.
Setting sheets on file for every mould in this group: yes, partly or no.
Planned leave for the primary setter in the next three months.
Date of the deputy's last unassisted mould change.

Complete it with the production manager in one sitting. Every NONE marks a machine group that grinds to a halt whenever one person is away. Most plants find several.

1. 1

   Appoint a deputy for each machine group

   Choose from operators who already pester the setter about why a value moved. Tell the deputy, the setter and the shift lead together.

2. 2

   Write setting sheets with the setter

   One page per mould: barrel zones, injection speed, holding pressure, cooling time, typical defects and the usual remedy. Photos of the clamped tool help. The setter dictates, someone else types.

3. 3

   Pair them on planned changes

   The second person does the mould change while the setter watches and corrects. Start with the simpler tools, then move to the tricky ones.

4. 4

   Put the defect standard at the press

   Limit samples and a photo board of acceptable and rejected parts, agreed by the setter and the inspector, so judging a sink mark is not one person's eye.

5. 5

   Reward teaching openly

   Add a grade or pay rung for setters who bring a deputy to sign-off, and praise it at the shift huddle.

6. 6

   Plan setter attendance and leave

   Spread primary setters across shifts and never approve leave for two in the same group together. Book their leave in the quiet weeks.

7. 7

   Review the map every month

   Count the NONE entries. The number should fall each quarter.

This is one of the patterns on our plastic manufacturing HR overview. Setter grading gets more depth on the injection moulding units page. Turning setter notes into training material is covered for blow moulders' skill-building. Much of what goes wrong when a setter is absent begins at the change of shift, the subject of shift handover in plastics units.