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(a) A continuous chip formed during parting-off is shown - Leaving Cert Engineering - Question 7 - 2018
Question 7
(a) A continuous chip formed during parting-off is shown. (i) Identify two materials which may produce a continuous chip formation when machined. (ii) Explain ... show full transcript
Worked Solution & Example Answer:(a) A continuous chip formed during parting-off is shown - Leaving Cert Engineering - Question 7 - 2018
Step 1
Identify two materials which may produce a continuous chip formation when machined.
Answer
The two materials that often yield continuous chip formation when machined are:
- Aluminum: Known for its ductility and low cutting resistance, aluminum tends to form long continuous chips during machining, creating a smooth surface finish.
- Copper: Similar to aluminum, copper also exhibits continuous chip formation due to its softness and malleability, resulting in an efficient cutting process.
Step 2
Explain the impact of continuous chip formation on: Surface finish
Answer
Continuous chip formation generally leads to a better surface finish on machined parts. Since the chip remains intact and is not fragmented, it helps in minimizing the potential for tool marks on the workpiece, resulting in a smoother and more uniform final product.
Step 3
Explain the impact of continuous chip formation on: Automated machinery
Answer
For automated machinery, continuous chip formation can be problematic as the chip can wrap around the tooling and interfere with the operation of the machine. This can lead to machine jams or misalignment, necessitating more frequent tool changes and maintenance.
Step 4
Explain the difference between a dovetail cutter and a slot drill in milling.
Answer
A dovetail cutter is designed to create angled grooves or joints, suitable for dovetailing. Its cutting edge is shaped to match the profile of the joint being formed. In contrast, a slot drill is a general-purpose milling cutter that can create straight slots or edges. It typically has a cylindrical shape, allowing it to plunge effectively into the workpiece.
Step 5
Outline one reason for balancing a grinding wheel.
Answer
One reason for balancing a grinding wheel is to reduce vibrations during operation. An unbalanced wheel can cause uneven wear, produce a poor surface finish on the workpiece, and lead to potential safety hazards, which can compromise both the quality of the grind and the operator's safety.
Step 6
Explain why a three-jaw chuck is not suitable for holding a square bar.
Answer
A three-jaw chuck has jaws that are positioned 120 degrees apart. When a square bar is placed in the chuck, it cannot effectively center the bar since it does not make uniform contact along all sides. This can lead to inaccuracies in machining and potentially compromise the integrity of the workpiece.
Step 7
Describe one method of holding a work piece securely when surface grinding.
Answer
One common method of holding a workpiece securely during surface grinding is using a magnetic chuck. This device consists of a flat surface that utilizes magnetic forces to hold ferrous materials securely in place, allowing for a consistent and stable grinding process without physical clamps that may obstruct the grinding path.
Step 8
Describe the use of a fixed steady when operating a lathe.
Answer
A fixed steady is used in lathe operations to ensure stability and prevent workpiece deflection during machining. It provides additional support, particularly when dealing with long or slender workpieces, by securing them at locations away from the tailstock, thus maintaining a straight and true work alignment throughout the turning process.
Step 9
Explain, with the aid of a diagram(s), the differences between loading and glazing of grinding wheels.
Answer
Loading occurs when fine particles and debris become trapped in the spaces between the abrasive grains on the grinding wheel, which can restrict its cutting ability and cause overheating. Glazing, on the other hand, happens when the grinding wheel's surface becomes shiny and smooth due to excessive wear, and the abrasive grains lose their sharp edges. This fault reduces the wheel's effectiveness in cutting.
Here, a diagram can illustrate the differences, showing a loaded wheel with trapped particles and a glazed wheel with a shiny surface.
Step 10
Describe a suitable wheel dressing process used to repair a grinding wheel.
Answer
A typical wheel dressing process involves using a diamond dresser to restore the profile and sharpness of the grinding wheel. The dresser, which consists of a diamond-tipped tool, is traversed across the wheel's surface to expose fresh abrasive grains and remove any clogging. This helps in regaining the cutting ability of the wheel and ensures consistent grinding performance.
Step 11
Explain two of the following terms in relation to CNC technology: Machine tool envelope
Answer
The machine tool envelope refers to the physical boundaries within which the machine operates, encompassing all axes of motion including the X, Y, and Z axes. It defines the maximum size of workpieces that can be machined and is critical for determining the machine's capability.
Step 12
Explain two of the following terms in relation to CNC technology: Software simulation
Answer
Software simulation in CNC technology allows operators to visualize the machining process without engaging the actual machine. It enables the identification of potential issues in the program, optimizing tool paths and ensuring that the setup is correct before actual machining begins, which ultimately saves time and reduces errors.
Step 13
Identify two safety features incorporated into modern CNC machines.
Answer
Two safety features commonly found in modern CNC machines include:
- Emergency stop buttons: These allow operators to quickly halt the machine in case of any unsafe conditions.
- Interlocking guards: These prevent access to moving parts of the machine while it is in operation, ensuring operator safety by minimizing risks of injury.