2. What is the Grinding Ratio? How does it affect the grinding process? What steps are necessary
to repurpose a grinding wheel that has become dull or loaded?
Grinding Ratio is defined as the ratio between the volume of metal removed from the workpiece
to the wear of grinding wheel. It represents the measure of the ability of a grinding wheel to
remove material. Dulled grains on a grinding wheel or chips are removed with a proper dressing
tool to make sharp cutting edges and make recesses for chips by properly extruding to grain
cutting edges.
3. Plasma Arc Welding (PAW) is a welding process that was not discussed at length in class. Explain
the process of PAW (the use of diagrams and figures is recommended). What are the
advantages of PAW over other fusion welding processes? What are the limitations of the
process?
A plasma is a gas which is heated to an extremely high temperature and ionized so that it
becomes electrically conductive. The plasma arc welding process uses this plasma to transfer an
electric arc to a workpiece. Within a copper nozzle in the plasma welding torch, a Tungsten
electrode is located and between this electrode and nozzle tip, a pilot arc is initiated. The high
concentration of heat to the small area is delivered by forcing the plasma gas and arc through a
constricted orifice. PAW is generally more precise than conventional Tig. It has more stable,
concentrated arc. It is stable at low amps, and short welding time is possible. Long electrode life
offers many more hours of welding than Tig before electrode contamination occurs.
However, it is very costly, produces ultraviolet and infrared radiation, and the torch is bulky and
hence manual welding may be difficult and requires training as mentioned.
4. What are burrs? What is deburring? What are the importance of deburring operations and why
have so many been developed? Provide examples of 3 deburring operations.
Burrs is a raised edge or small piece of material that remains attached to a workpiece after a
modification process. Deburring is a process of removing this unwanted burrs using a deburring
tool. Deburring process is important because for projects that require a lot of precision and
attention to detail, any displaced metal like burrs can cause critical and potentially hazardous
situations. Deburring is important to the safety of the workers and the consumers, and it also
helps to standardize the size, shape and perfection level of the parts when using deburring
machines. The examples of deburring operations include sanding, grinding, and polishing.