Automatic dye dispensing improves right first time chiefly by
Answer: A
Manual weighing of small quantities is a real source of error, particularly for pale shades. The system also records exactly what went into each batch, which helps when a fault has to be traced back. Pale shades benefit most from the accuracy.
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State whether the following is true or false.
A batch that needs a shading addition still counts as a failure under right first time.
Answer: B
Correct answer: True
Right first time means the batch met the standard without intervention, so any shading addition counts as a failure however small it is. The definition is deliberately strict, because an addition costs a sample, a measurement, a decision and a second heating - and the machine is occupied throughout. Counting only full redyes as failures would conceal most of the loss.
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A redye costs roughly twice a first dyeing. If right first time rises from 80 to 90 per cent, by what fraction does the redye cost fall?
Answer: C
Correct answer: by half
Failures fall from 20 per cent of batches to 10 per cent, so the redye work halves and so does its cost - the doubled cost of a redye multiplies both figures equally and cancels. It is worth seeing the leverage: a ten point gain in right first time removes half the redyeing, because the redye burden depends on the failure rate rather than on the success rate.
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The most useful first step for a dyehouse with poor right first time is to
Answer: D
Correct answer: record and analyse why batches fail
Nothing can be improved until the causes are known, and they are rarely what the dyehouse assumes - unlevelness, wrong shade, poor laboratory to bulk correlation, water variation, substrate lot changes and weighing errors call for entirely different remedies. Recording the reason for every failure and sorting the record costs nothing and directs whatever is spent afterwards. Buying machines or changing supplier before that is a guess.
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Assertion (A): A dyehouse investigating shade failures records the reason for each one.
Reason (R): The distribution of causes shows where investment or attention will pay best.
Answer: A
Both are true and the reason gives the method: a small number of causes usually accounts for most of the failures, and the record is what separates the important ones from the occasional. A few causes usually dominate the list.
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Consider the following statements about the economics of right first time.
1. A redye roughly doubles the cost of processing that batch.
2. Improving from 80 to 90 per cent halves the number of failures.
3. The cost of a failure is limited to the extra dye used.
Answer: B
The first two are correct. The third badly understates the cost, since machine time, water, energy, effluent and the delay to every following batch all count and generally dwarf the dye. Delay to the following batches is easily forgotten.
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State whether the following is true or false.
Standardising the preparation of the substrate is part of achieving right first time.
Answer: C
Variation in scouring, bleaching or mercerising shows up directly as a shade difference at the dyeing stage. The dyehouse cannot correct for a substrate that changes from lot to lot. Preparation is where much of the variation begins.
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