Plastic Forming and Extrusion Questions and Answers

Answer: C

Correct answer: the auger folding the body over on itself

The auger drives the body forward in a helical path, and the successive turns meet as surfaces which do not always knit. Those interfaces are laminations: invisible in the wet column, and revealed as curved cracks when the drying or firing stresses find them.

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 mechanism. The helical flow leaves interfaces spiralling through the piece, and where the two surfaces have not fully bonded the piece is weak along them. Firing shrinkage then opens those surfaces, so the split follows a curved path that records the auger’s motion.

Answer: A

The shredded body passes through the vacuum before it is compacted, which is the only point at which air can readily escape. Once the mass has been consolidated any remaining air is trapped for good. The chamber therefore sits before rather than after the auger.

Answer: B

Correct answer: long products of constant cross section

The die imposes one section, and the material passes through it continuously, so extrusion suits pipes, tiles, bricks, rods and honeycombs. A one-off complex shape has no repeating section to extrude, and undercuts cannot be drawn through a die at all.

Answer: C

Correct answer: extrusion through a die with many fine channels

The honeycomb is a constant section repeated along its length, which is precisely what extrusion produces. The die is an intricate assembly of feed holes and slots, and its design is the whole difficulty - the body must arrive at every part of the section at the same rate or the block distorts.

Answer: D

Correct answer: False

The body does not simply take the shape of the opening: it flows faster where the section is thicker and where friction is lower, so a die cut to the product’s outline delivers a distorted product. The opening is shaped to compensate, and arriving at it usually takes trial and correction on the machine.

Answer: A

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

Both are true and the reason gives the mechanism. Uneven flow means the thick parts of the section run ahead and the thin parts lag, so the column bends or the section distorts. The die is therefore restricted where the flow would be fast and opened where it would be slow, which is why die design is empirical.

Answer: B

Correct answer: flatware and hollowware from plastic clay

A ball of plastic clay is placed on a rotating mould and a profiled tool shapes the other face - jiggering for flat shapes such as plates, jolleying for hollow ones such as cups. It is the traditional mechanised route for tableware, and roller-head forming is its modern development.

Answer: C

Correct answer: a heated rotating roller in place of a fixed profile

The roller turns as it descends and works the clay progressively rather than scraping it, so the body is compacted more evenly and the surface is better. Heating it prevents the clay sticking. The result is faster production and less waste than a fixed profile tool achieves.

Answer: D

They are considerably faster and give more consistent thickness, which is why they dominate modern tableware manufacture. The older method survives chiefly in studio and small-batch work. Hand jiggering remains useful where output is small.