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In the 3D printer shown opposite, a leadscrew mechanism is used to move the printing head vertically - Leaving Cert Engineering - Question 8 - 2019
Question 8
In the 3D printer shown opposite, a leadscrew mechanism is used to move the printing head vertically. (i) Describe, with the aid of a diagram, how the leadscrew mec... show full transcript
Worked Solution & Example Answer:In the 3D printer shown opposite, a leadscrew mechanism is used to move the printing head vertically - Leaving Cert Engineering - Question 8 - 2019
Step 1
Describe, with the aid of a diagram, how the leadscrew mechanism raises and lowers the height of the printing head when in use.
Answer
The leadscrew mechanism consists of a threaded screw and a nut which moves along the screw when rotated. As the stepper motor turns the leadscrew, it translates rotational motion into linear motion. The pitch of the screw determines how far the printing head moves vertically with each complete revolution.
A diagram of the setup would show:
- Stepper motor connected to the leadscrew.
- Leadscrew with a nut attached to the printing head.
- An indication of the upward and downward movement as the screw rotates.
Step 2
Describe, with the aid of a diagram, an alternative mechanism which will allow the table of the printer to move forwards and backwards.
Answer
An alternative mechanism for moving the printer table is a toothed belt system controlled by a stepper motor.
In this mechanism, a toothed belt runs across pulleys, where one of the pulleys is driven by a stepper motor. As the motor turns, it moves the belt, which in turn moves the table.
A diagram should illustrate:
- The stepper motor attached to a pulley.
- The toothed belt wrapped around the pulleys.
- The connection of the belt to the table which facilitates the forward and backward motion.
Step 3
Explain how a worm and worm gear transmits motion through 90°.
Answer
The worm and worm gear system converts rotational motion from the worm into rotational motion at a right angle (90°) in the gear. The worm, which is a screw-like component, engages with the gear, which has teeth that mesh with the worm. When the worm is turned, it rotates the gear, allowing for efficient motion transfer and torque multiplication due to the gear ratio. This type of configuration is commonly used in applications requiring significant reduction in speed.
Step 4
Outline one energy conversion which occurs in a car battery.
Answer
In a car battery, chemical energy is converted into electrical energy. When the battery is connected in a circuit, a chemical reaction occurs between the electrolyte and the lead plates, producing a flow of electrical current. This current is used to power the vehicle’s electrical systems and start the engine.
Step 5
State one advantage of a toothed belt drive over a chain drive.
Answer
One advantage of a toothed belt drive is that it operates more quietly than a chain drive. The toothed belt can absorb shock and vibrations, resulting in smoother operation, reduced noise, and less wear on the components compared to the continuous metal chain, which can rattle and generate noise.
Step 6
Describe, with the aid of a diagram, the operation of an idler gear.
Answer
An idler gear is used to change the direction of rotation in a gear train without affecting the gear ratio. When a driver gear rotates, the idler gear transfers the motion to the driven gear, allowing them to turn in the desired direction while keeping the same rotational speed.
A diagram would depict:
- The driver gear, idler gear, and driven gear.
- Arrows indicating the rotation directions.
Step 7
Explain how a lifting mechanism may operate using a ratchet and pawl mechanism.
Answer
A ratchet and pawl mechanism allows movement in one direction while preventing it from slipping back. The ratchet rotates in one direction, and the pawl engages with the teeth of the ratchet to lock it in position. When the ratchet is turned, the pawl moves over the teeth, allowing for upward movement. This mechanism is often used in lifting equipment like hand winches, where the load needs to be held securely after being lifted.
Step 8
Describe, with the aid of a diagram, a suitable retractable mechanism for the spraying arms.
Answer
A suitable retractable mechanism for the spraying arms can consist of linkages that fold the arms back into a storage position. A pair of linkages connected to the ends of the arms can function similarly to a scissor mechanism. This design can be powered by hydraulic cylinders or manually operated.
A diagram would illustrate:
- The expanded spray arms.
- Their retracted position, showing how the linkages fold together.
Step 9
Describe one advantage and one disadvantage of retractable boom spraying arms.
Answer
One advantage of retractable boom spraying arms is that they provide a wide spraying area, increasing efficiency in application. They can also be stored compactly when not in use, reducing space requirements.
A disadvantage is that the linkages and mechanisms can be prone to wear and failure over time, potentially leading to more maintenance and repairs than fixed arms.