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The control knob shown is to be machined on a centre lathe or on a CNC lathe - Leaving Cert Engineering - Question 6 - 2012
Question 6
The control knob shown is to be machined on a centre lathe or on a CNC lathe. Describe any three of the operations used to produce the control knob. (b) Describe an... show full transcript
Worked Solution & Example Answer:The control knob shown is to be machined on a centre lathe or on a CNC lathe - Leaving Cert Engineering - Question 6 - 2012
Step 1
Describe any three of the operations used to produce the control knob
Answer
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Knurling: This operation involves creating a textured pattern on the surface of the control knob to enhance grip. It is performed by a knurling tool pressed against the workpiece as it rotates.
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Taper Turning: This is achieved by offsetting the tailstock or using a taper turning attachment. It modifies the profile of the knob to a conical shape.
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Drilling: For the purpose of making holes in the knob, drilling is employed using a drill bit held in the tailstock. The bit is fed into the rotating knob to create specified diameter holes.
Step 2
Describe any three of the following in relation to machining
Answer
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Cutting Speed: This is the speed at which the cutting tool engages with the workpiece, generally measured in meters per minute. The formula used is:
where D is the diameter of the workpiece and n is the spindle speed in revolutions per minute.
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Depth of Cut: This refers to how deep the cutting tool enters the material, measured perpendicular to the cut surface. It affects the amount of material removed and the finish of the surface.
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Feed: This is the distance the cutting tool advances during each revolution of the workpiece, typically expressed in mm/rev. Adjusting the feed rate impacts the surface finish and machining time.
Step 3
Step 4
Name two other methods of work-holding on the lathe
Answer
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Three Jaw Chuck: This type of chuck automatically centers the workpiece by employing three adjustable jaws.
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Four Jaw Independent Chuck: In this method, each jaw can be adjusted independently, allowing for precise centering of irregularly shaped workpieces.
Step 5
State one safety precaution to be observed when turning long shafts on the centre lathe
Answer
One safety precaution is to ensure that all components, such as the driving plate and live/dead centres, are secured and tightened correctly. Additionally, it is vital to stay clear of all rotating parts during operation to prevent accidents.
Step 6
Explain any three of the following Computer Numerical Control (CNC) machining terms
Answer
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CAD/CAM: This stands for Computer Aided Design and Computer Aided Manufacture. CAD software is used to create designs, while CAM translates these designs into instructions that the CNC machine can follow.
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Z Axis: In a CNC lathe, the Z axis denotes the movement along the length of the workpiece, parallel to the center line. It assists in determining the depth and position for operations.
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G Codes: These are command codes used in CNC programming that control the movement and operation of the machine. For instance, G00 represents rapid movement to a specified location.