Manufacturing Processes Multiple Choice Questions on “Abrasive Jet Micromachining – 6”.
1. Powder flowability is affected by particle size and surface texture.
a) True
b) False
Answer: a
Clarification: Powder flowability and compatibility are greatly influenced by particle size, size distribution, moisture content, and surface texture.
2. Adhesion between particles can be increased by moisture.
a) True
b) False
Answer: a
Clarification: Inter particle adhesion is further enhanced by moisture that adsorbs readily onto these hygroscopic (having a tendency to absorb moisture) surfaces.
3. Relative humidity can affect adhesive forces.
a) True
b) False
Answer: a
Clarification: The relative humidity of stored air can have a major influence on the adhesive forces at the interface of particles. But one of the major difficulties with the AJMM process is the handling of very fine abrasive particles.
4. Movement of powder leads to stratification.
a) True
b) False
Answer: a
Clarification: It is well known that the movement of powder leads quickly to stratification and the creation of gradient of particle size and/ or shape. Such problems result in alteration of the powder mass flow rate during the course of AJMM experiments.
5. Powder feed control of micro-blasting systems is divided into _____
a) 2
b) 3
c) 4
d) 5
Answer: a
Clarification: The powder feed control of two micro-blasting systems is considered into two types.
• Pressurized powder feed system
• Fluidized bed powder spray system.
6. Vibratory or screw feeding systems are another approach to control the powder mass flow rate.
a) True
b) False
Answer: a
Clarification: Other approaches to the control of powder mass flow rate include vibratory and screw or auger feeding in which the powder is fed to the conveying air through an auger (similar to the tool used for boring earth).
7. In powder feeding systems, powder bridging, compaction, and agglomeration are desirable.
a) True
b) False
Answer: b
Clarification: Introducing a vibrator to a screw system improve the steadiness of the powder feed But the improvement diminishes with fine, more cohesive materials such as zeolites and cement powders due to phenomena such as powder bridging, compaction, and agglomeration.
8. In AJMM, the powder is fed _____
a) through air stream
b) through a water pipe
c) along with a gel, which improves the adhesion between particles
d) in the form of batches
Answer: a
Clarification: The powder is fed through the air stream from a pressurized reservoir through an orifice and mixing chamber. The system utilizes an oscillating valve that splits the operation cycle into two halves.
9. The operation cycle is activated when the entire system is pressurized.
a) True
b) False
Answer: a
Clarification: The operation cycle is activated by a switch only after the entire system, including reservoir, has initially been pressurized by closing the nozzle end and opening the oscillating valve to the main air supply.
10. During powder feeding, the oscillating valve is open for the first half of the operation cycle.
a) True
b) False
Answer: a
Clarification: During the first half of the operation cycle, the oscillating valve is open, allowing air to flow from the pressure regulator to the mixing chamber while some enters the powder reservoir and the rest flows out through the opened nozzle.