Slip Casting Questions and Answers

Answer: C

Correct answer: about 11 per cent

Shrinkages compound rather than add: \[ 1 - (0.97 \times 0.92) = 1 - 0.892 = 0.108, \] about 10.8 per cent. Simply adding the two gives 11 per cent as well, which is why the approximation is usually acceptable - but the compounding form is the correct one, and the difference grows with the size of the individual shrinkages.

Answer: D

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

Both are true and the reason gives the necessity. The piece leaves the mould at the mould’s size and then loses about a tenth of every linear dimension between there and the finished ware, so the mould - and the model it was made from - must be oversized by exactly that allowance. Getting the figure wrong is not correctable afterwards, since a fired ceramic cannot be stretched.

Answer: A

Correct answer: need an added binder to give green strength

Clay particles are plate-like and develop real strength as they consolidate, so a clay cast can be handled straight from the mould. Alumina and similar oxide powders are equiaxed and give a green body with almost no strength at all, so an organic binder is added to hold the piece together until firing - and is then burnt out in the schedule.

Answer: B

The first two are correct. The third is wrong, since equiaxed oxide particles give almost no green strength on their own and a binder has to be added. Plate-like clay particles are what give traditional bodies their green strength.

Answer: C

Correct answer: True

Slip flows into shapes a punch cannot reach: hollow ware, complex curves, undercuts released by a multi-part mould, and thin walls in one piece. Pressing needs a die that opens along a straight line and a punch that can travel, so it is limited to relatively simple forms. That freedom of shape is what keeps slip casting in use despite its slowness.

Answer: D

Building a wall by capillary suction takes minutes to hours, whereas a press cycle takes seconds. Casting is chosen where the shape demands it rather than where output is the governing consideration. Output per mould is low, so many moulds are run in parallel.