68
Remanufacturing and Advanced Machining
• mesh #120–150 of sizes 90–105 μm
• mesh #180–220 of sizes 70–88 μm
• mesh #240 and higher of sizes below 60 μm (Llanto et al., 2021)
Moreover, it is possible to introduce a freezing agent into the water jet to produce ice
grains in the stream and thus to increase MRR (Korzhov, 2006). The author emphasizes additional benefits of this solution, such as minimized distortion of stream
characteristics, or increased wear resistance of nozzles due to the protective function
of the ice layer which appears on their working surface.
Depending on whether a workpiece is completely penetrated or an individual cut
into a defined depth is produced, waterjet machining can be subdivided into two
categories (Bergs et al., 2020):
1. Cutting through (CT)
2. Controlled depth machining (CDM)
CT is the standard industrial waterjet application. Here, the jet strikes a workpiece
surface and its erosive force removes the material, cutting a narrow groove into the
workpiece material. When the jet does not cut completely through a workpiece, then
CDM takes place. With an increased process complexity, CDM AWJ offers the possibility of shape machining with the potential to substitute conventional milling processes in some applications (Bergs et al., 2020).
The main influencing factors of the AWJ machining process are as follows
(Natarajan et al., 2020):
• Waterjet pressure is an important process parameter, since kinetic energy
of AWJ depends on the pressure level of water. When a certain threshold pressure is not reached, no material removal takes place. On the other
hand, pressure equal to the critical value represents a limitation to effective
cutting. In the working range, waterjet pressure is directly proportional to
penetration depth and material removal rate.
• Traverse rate indicated by mm 3 /min determines the quality of cut surfaces;
its major influence is determined by exposure time. A lower traverse rate
enhances surface quality as more abrasive particles are able to impinge on
the workpiece surface. It also affects the cutting rate of the process.
• Abrasives of various natural (garnet) and artificial (silicon carbide, aluminum oxide) types are used. Abrasive particle size, shape, and hardness
have a significant influence on AWJ cutting performance so that a greater
hardness of work material requires harder application of harder abrasives.
An increased size of abrasive particles increases particle disintegration. A
lower depth of penetration and material removal rate can be consequences
of a higher limit of abrasive particle size as impingement frequency on the
target material surface is reduced.
• Abrasive mass flow rate has an influence on AWJ material removal rate.
An optimum supply of abrasives yields a higher cutting performance with
Remanufacturing and Advanced Machining
• mesh #120–150 of sizes 90–105 μm
• mesh #180–220 of sizes 70–88 μm
• mesh #240 and higher of sizes below 60 μm (Llanto et al., 2021)
Moreover, it is possible to introduce a freezing agent into the water jet to produce ice
grains in the stream and thus to increase MRR (Korzhov, 2006). The author emphasizes additional benefits of this solution, such as minimized distortion of stream
characteristics, or increased wear resistance of nozzles due to the protective function
of the ice layer which appears on their working surface.
Depending on whether a workpiece is completely penetrated or an individual cut
into a defined depth is produced, waterjet machining can be subdivided into two
categories (Bergs et al., 2020):
1. Cutting through (CT)
2. Controlled depth machining (CDM)
CT is the standard industrial waterjet application. Here, the jet strikes a workpiece
surface and its erosive force removes the material, cutting a narrow groove into the
workpiece material. When the jet does not cut completely through a workpiece, then
CDM takes place. With an increased process complexity, CDM AWJ offers the possibility of shape machining with the potential to substitute conventional milling processes in some applications (Bergs et al., 2020).
The main influencing factors of the AWJ machining process are as follows
(Natarajan et al., 2020):
• Waterjet pressure is an important process parameter, since kinetic energy
of AWJ depends on the pressure level of water. When a certain threshold pressure is not reached, no material removal takes place. On the other
hand, pressure equal to the critical value represents a limitation to effective
cutting. In the working range, waterjet pressure is directly proportional to
penetration depth and material removal rate.
• Traverse rate indicated by mm 3 /min determines the quality of cut surfaces;
its major influence is determined by exposure time. A lower traverse rate
enhances surface quality as more abrasive particles are able to impinge on
the workpiece surface. It also affects the cutting rate of the process.
• Abrasives of various natural (garnet) and artificial (silicon carbide, aluminum oxide) types are used. Abrasive particle size, shape, and hardness
have a significant influence on AWJ cutting performance so that a greater
hardness of work material requires harder application of harder abrasives.
An increased size of abrasive particles increases particle disintegration. A
lower depth of penetration and material removal rate can be consequences
of a higher limit of abrasive particle size as impingement frequency on the
target material surface is reduced.
• Abrasive mass flow rate has an influence on AWJ material removal rate.
An optimum supply of abrasives yields a higher cutting performance with