A customer reorders a capping machine first built four years ago. One change: a taller bottle. The engineer who drew the original left last spring. His successor opens the model and finds a cam with an odd dwell and a bracket with a slotted hole nobody can explain. He can copy both or redesign both. Either way, he is guessing.
Among the strains listed for machine and equipment builders, this one makes the least noise. A drawing states what a part is. It seldom states why. The why lives with whoever made the call, and it walks out with them.
Signs in the office and on the floor
- Shop queries about one model sit for days, because only one engineer can answer them.
- A repeat order is handled like a fresh design, since nobody trusts the old drawings.
- Revision letters climb on a drawing while the change notes say 'modified' and little else.
- Field engineers still ring a designer who moved to another product line long ago.
- Spares for older machines need someone to measure a worn part, because the detail drawing is missing or wrong.
- A fault cured once at a customer site reappears on the next machine of that model.
The bill for keeping it in one head
The cost spreads thin, so it rarely gets counted. Retrofits on old machines are quoted high, because the estimator adds a cushion for guesswork. Changes drag, since every odd feature must be worked out again from scratch. The trial run catches problems the original designer had already solved once.
Pay feels it too. An engineer who alone understands a best-selling model knows his worth. That is fair while he stays. It hurts when he takes leave during a rush, and it becomes a crisis when he resigns.
Why the gap keeps reopening
- Release deadlines crowd out reasons. The drawing reaches the shop the night before cutting starts, and nobody writes down the thinking.
- Title blocks have no box for intent. They hold material, finish and tolerance. Nothing says this slot lets the fitter absorb casting variation.
- One engineer per model. Small design offices give each product to a single person, so nobody else ever questions the choices.
- Calculations live on one laptop. Shaft sizing, bearing life and motor selection sit in a personal folder.
- Trial fixes skip the office. A fitter elongates a slot at trial, the machine runs, and the drawing never hears about it.
- Designers are judged on sheets released. Writing notes looks like slowness, so it loses to the next deadline.
Checks before changing anything
- Take the last three machines released. Ask a second engineer to explain five features that are not obvious, and note how many need the original designer.
- Count the live models that only one engineer has ever touched.
- Read the reason field on recent change notes, and count how many are blank or say only 'revised'.
- Ask the assembly foreman how long a drawing query usually waits.
- Find where sizing sheets, vendor datasheets and trial findings are saved, and who can open them.
Fixing it in order
- 1
Name a second engineer for every live model
The second engineer reviews each release and answers shop queries when the owner of the model is away. Rotate pairs yearly so the knowledge spreads past two people.
- 2
Attach a decision note to each release
Half a page with the drawing set. It lists the features a newcomer would question, and the reason behind each. Write it at release, never at resignation.
- 3
Hold a short release review
The designer, the second engineer and the senior fitter walk through the model before parts are ordered. The fitter's questions expose the choices nobody wrote down.
- 4
Keep calculations beside the model
Sizing sheets, gearbox and motor selections and vendor datasheets go into the shared folder for that model, named by revision.
- 5
Pull trial and field fixes back into the drawing
Every change made at trial or on site gets a change note with its reason, raised within the week. Add a box for drawing affected on the service report.
- 6
Count notes in the designer's review
Decision notes and answered queries sit beside sheets released when a designer is assessed. Whatever gets counted gets done.
- 7
Use any notice period model by model
If a designer resigns, schedule recorded walk-throughs of each model he owns, steered by the second engineer's questions.
Model and revision covered by this note.
The customer need behind the design, in one or two sentences.
Features a newcomer would question, each with its reason.
Calculations and datasheets used, and the folder that holds them.
Known weak points, and what was tried at trial.
Second engineer who reviewed this release.
Date written, and date checked by the reviewer.Holding the habit through a rush
The habit breaks first in a busy quarter. Protect the release review even with dispatch close, because it costs far less than a repeat failure. Put any model without a second engineer on the owner's monthly risk list. Succession planning gives each key designer named cover, so the risk has an owner.
Special purpose builders feel this hardest, because every machine is new; the profile of one-off machine builders explains why. Owners wanting the quick version can turn to our question-and-answer post on this risk. Where the gap runs between sales, design and service rather than inside the office, read how knowledge moves between departments.
