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Man Poo > Extrusion -> Shearing (F) > Flashcards

Extrusion -> Shearing (F) Flashcards

1
Q

What is EXTRUSION?

A

A manufacturing method that is used to produce long lengths of stock material. It is mainly performed on non-ferrous materials.

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2
Q

What material are the vast majority of EXTRUSIONS done on?

A

Aluminum alloys, which can be manipulated at relatively low temps and with only moderate force.

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3
Q

What are the parts of an EXTRUSION machine?

A

A rugged cylinder and hydraulic ram arrangement force the metal through the die opening.

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4
Q

What are the two ways EXTRUSION can be performed?

A

Directly and indirectly

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5
Q

What is DIRECT EXTRUSION?

A

A hydraulic ram pushes on the billet from the rear. Since the billet is constrained by an enclosing container (cylinder) its only exit is via a die at the front, which can be any shape.

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6
Q

What is INDIRECT EXTRUSION?

A

Indirect extrusion utilizes a container with a solid back end. The die is pushed back into the container by forces applied at the front.

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7
Q

What is an advantage and disadvantage of INDIRECT EXTRUSION?

A

This method provides support to the product as it emerges, but can interfere with the components of the ram and limit maximum product length.

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8
Q

What is a BILLET?

A

A solid circular bar stock of around 2 feet in length.

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9
Q

How are SOLID EXTRUSIONS of standard cross-sections usually created?

A

Direct extrusion through simple die openings.

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10
Q

What is the advantage of EXTRUSION?

A

It is possible to produce custom profiles with a shape not intended as standard bar stock, but rather created for a particular unique application.

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11
Q

What is a HOLLOW EXTRUSION?

A

A solid extrusion, but hollow; more complex

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12
Q

What is EXTRUDED TUBE STOCK?

A

A type hollow extrusion with a round or square cross-section.

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13
Q

What is a MANDREL?

A

A mandrel must be suspended in the die opening in order to extrude hollow parts. The shape and position of the mandrel will correspond to the hole running through the extruded part.

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14
Q

What approaches are used to support the MANDREL in the die opening?

A

SPIDER DIES and PORTHOLE DIES

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15
Q

What is a SPIDER DIE?

A

Thin “webs” bridge the gap between the die walls and the mandrel.

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16
Q

Do the SPIDERS interfere with the extruded product?

A

Although the spiders do shear through the metal during extrusion, the cut surfaces immediately fuse back together once the metal has flowed past the spiders.

17
Q

What is a PORTHOLE DIE?

A

They divide the main metal flow into separate streams through “porthole” openings in the die, before recombining them as they flow past the mandrel.

18
Q

In what ways are PORTHOLE DIES better than SPIDER DIES?

A

PORTHOLE DIES are more rugged and durable than the thin SPIDERS.

19
Q

What is another approach to HOLLOW EXTRUSION besides spiders or porthole dies?

A

Attaching the MANDREL to the RAM FACE as a cantilever.

20
Q

What are MULTI-CELLED EXTRUSIONS?

A

Extrusions made with multiple cells or holes.

21
Q

What is HOT EXTRUSION?

A

A process that allows the extrusion of steel at temperatures above the recrystallization point. These temps are needed to convert from cast to wrought structure.

22
Q

Why are high-temperature lubricants used in HOT EXTRUSION?

A

Because of the friction generated by the mill scale. One lubricant often used is glass.

23
Q

In HOT EXTRUSION, why do the die openings have a broad draft angle?

A

To cope with the lower plasticity of steel as compared to aluminum.

24
Q

What are other EXTRUSION PROCESSES used to create discrete components instead of long-length products?

A

COLD EXTRUSION and IMPACT EXTRUSION

25
Q

What is COLD EXTRUSION?

A

A die is used to extrude the metal up the outside of a descending punch. In COLD EXTRUSION, it always stays constrained within the die.

26
Q

What is IMPACT EXTRUSION?

A

A die is used to extrude the metal up the outside of a descending punch. In IMPACT EXTRUSION, the metal hugs the punch as it rises unrestrained above the confines of the die.

27
Q

What is WIRE DRAWING?

A

A process used to create very long lengths of product with a small diameter. The diameter of the wire rod is reduced through a series of dies.

28
Q

Describe the process of WIRE DRAWING.

A

The process starts with HOT EXTRUSION of WIRE ROD. This is similar to direct extrusion but includes additional pinch rollers that keep the product in tension as it emerges from the die. The WIRE ROD is coiled.

29
Q

What is SHEARING?

A

A process to cut large pieces of material into more manageable-sized pieces. Uses a fracturing approach where bending stresses are induced and raised to the point of metal failure.

30
Q

What is the key to SHEARING?

A

Leave a clearance between the upper and lower blades.

31
Q

What is the inevitable result of SHEARING?

A

A rough and uneven sheared edge.

32
Q

What is ROLLOVER or DROOP in terms of SHEARING?

A

Rollover/Droop occurs at the upper edge as a result of plastic (permanent) deformation.

33
Q

What is the BURNISH (or SHEARED ZONE) in terms of SHEARING?

A

The relatively shiny region where the blade penetrated the material in a true slicing action.

34
Q

What is the SLIP PLANE in terms of SHEARING?

A

The ugliest portion of the cut. It has a rough crystalline appearance and dominates the sheared face.

35
Q

What is a BURR in terms of SHEARING?

A

A BURR is present at the lower edge which represents a hazard during handling since it can be jagged and sharp.

36
Q

What is SHAVING?

A

A secondary process used to clean up the edge that has been sheared.

37
Q

What are the two approaches to SHAVING?

A
  1. Incorporating the SHAVING BLADE into the upper SHEARING BLADE as a single cutting tool.
  2. An additional sharp blade and reduced clearance as a separate step after SHEARING.
38
Q

What is PUNCHING?

A

A method of SHEARING that applies to cutting around an enclosed shape, such as a hole.

Man Poo (31 decks)

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