Process Control and Right First Time Questions and Answers

Answer: A

Any addition, shading or redye counts as a failure however good the final result. The measure is a single number that captures most of what a dyehouse controls in its operation. Every correction counts against the figure.

Answer: B

Both are true and the reason gives the economics: a redye is the most expensive thing a dyehouse does, since it doubles the cost of a batch and delays every batch behind it in the queue. The definition is deliberately strict. Anything short of a clean pass is a failure. Machine time is the largest part of the cost.

Answer: C

Three hundred and forty of the four hundred passed without correction, which is eighty-five per cent. Well run houses achieve above ninety, and each point below that costs real money. Failures are what the arithmetic actually counts.

Answer: D

Each source must be controlled separately, and a dyehouse chasing shade problems without knowing which of the four is moving is working blind. Standardising each is what makes prediction possible. Four independent sources must all be held.

Answer: A

A commercial dye can vary by several per cent between deliveries, which shows directly in the shade. Standardising against a reference lot lets the same recipe be used from one delivery to the next. Pale shades reveal the difference first.

Answer: B

Both are true and the reason gives the necessity: a two per cent strength difference is easily visible in a pale shade, and the recipe cannot correct for what the dyehouse does not know about. The reference lot is kept for comparison.

Answer: C

Correct answer: a single number from a difference formula

A spectrophotometer measures both samples, the readings are converted to a uniform colour space, and a difference formula - CIELAB, CMC or CIEDE2000 - reduces the three-dimensional separation to one number. Compressing colour to a single figure is what makes an objective pass or fail decision possible, and it is why the formula used must be stated with the number.

Answer: D

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: several formulae are in current use, and a number means nothing without a tolerance against which to judge it. Statement 3 is wrong - the formulae weight lightness, chroma and hue differently, so the same pair of samples yields different values, which is exactly why the next item insists that the formula be named.

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the necessity. A tolerance of one unit means something quite different under CIELAB than under CMC, since the latter varies its weighting with the position of the colour. Specifying a limit without the formula therefore specifies nothing enforceable, which is why supply contracts state both, along with the illuminant and observer.

Answer: B

The Kubelka-Munk relation links reflectance to absorption and scattering, and the software solves for the concentrations that match the standard. A calibration database for each dye on each substrate is required first.