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Remanufacturing and Advanced Machining
1.12.2 main comPonenTs of a waTerjeT machining sysTem
A waterjet machining system essentially consists of a high-pressure pump, cutting
head, cutting table with a coordinate motion system, abrasive hooper, and flow control system (in the case of AWJ), and a computer-based controller (Korzhov, 2006).
In addition, the system may be equipped with collision prediction and resolution systems, a system of several cutting heads, a mechanical system of initial pre-machining
drilling, or a system that disseminates energy of abrasive water jet after machining
the workpiece and collects the used abrasive, etc. AWJ systems may be automated to
various degrees, including robotic waterjet machining systems.
A high-pressure pump is the core element of a waterjet cutting system that drives
pressurized water in the nozzle. As a rule, it employs a special double-acting or
single-acting multiplier, but its particular design depends on machining conditions,
such as pressure drop or a required fluid flow (Korzhov, 2006). This way, expected
efficiency and quality performance can be achieved.
The cutting head plays a role in forming a final high-pressure jet with characteristics appropriate for cutting. Essentially, the cutting head consists of an orifice, a
mixing chamber, and a focusing tube, as depicted in Figure 1.17.
Abrasive particles are fed by air into the mixing chamber, whereby the resulting abrasive jet travels through the focusing tube and momentum is transferred
to the particles. When the accelerated abrasive jet exits the focusing tube, it
impinges on a workpiece causing the removal of its material. It is common practice to maintain the standoff distance, i.e., the distance between the tip of the
focusing tube and the workpiece, between 1 and 2 mm, which is widely accepted
as the optimal value for most scenarios (Copertaro et al., 2020). Improper alignment of the orifice in the cutting head can cause additional wear in the mixing
tube walls shortening its life and reduce the efficiency of AWJ. A well-aligned
and coherent AWJ stream ensures the most efficient cutting, enhances the cutting
force, and reduces the kerf taper in the cut profile. Moreover, a greater orifice
diameter reduces cutting efficiency due to a higher flow rate of water that lowers
the concentration of abrasive particles (Natajaran et al., 2020). As far as nozzle
inner surface is concerned, it was demonstrated that maximum efficiency can
be reached using a catenoid profile, while a conoid profile is better than conical
(Gusev et al., 2012).
FIGURE 1.17 Example of a waterjet cutting head: 1 – Orifice, 2 – Abrasive inlet, 3 – Mixing
chamber, 4 – Focusing tube.
Remanufacturing and Advanced Machining
1.12.2 main comPonenTs of a waTerjeT machining sysTem
A waterjet machining system essentially consists of a high-pressure pump, cutting
head, cutting table with a coordinate motion system, abrasive hooper, and flow control system (in the case of AWJ), and a computer-based controller (Korzhov, 2006).
In addition, the system may be equipped with collision prediction and resolution systems, a system of several cutting heads, a mechanical system of initial pre-machining
drilling, or a system that disseminates energy of abrasive water jet after machining
the workpiece and collects the used abrasive, etc. AWJ systems may be automated to
various degrees, including robotic waterjet machining systems.
A high-pressure pump is the core element of a waterjet cutting system that drives
pressurized water in the nozzle. As a rule, it employs a special double-acting or
single-acting multiplier, but its particular design depends on machining conditions,
such as pressure drop or a required fluid flow (Korzhov, 2006). This way, expected
efficiency and quality performance can be achieved.
The cutting head plays a role in forming a final high-pressure jet with characteristics appropriate for cutting. Essentially, the cutting head consists of an orifice, a
mixing chamber, and a focusing tube, as depicted in Figure 1.17.
Abrasive particles are fed by air into the mixing chamber, whereby the resulting abrasive jet travels through the focusing tube and momentum is transferred
to the particles. When the accelerated abrasive jet exits the focusing tube, it
impinges on a workpiece causing the removal of its material. It is common practice to maintain the standoff distance, i.e., the distance between the tip of the
focusing tube and the workpiece, between 1 and 2 mm, which is widely accepted
as the optimal value for most scenarios (Copertaro et al., 2020). Improper alignment of the orifice in the cutting head can cause additional wear in the mixing
tube walls shortening its life and reduce the efficiency of AWJ. A well-aligned
and coherent AWJ stream ensures the most efficient cutting, enhances the cutting
force, and reduces the kerf taper in the cut profile. Moreover, a greater orifice
diameter reduces cutting efficiency due to a higher flow rate of water that lowers
the concentration of abrasive particles (Natajaran et al., 2020). As far as nozzle
inner surface is concerned, it was demonstrated that maximum efficiency can
be reached using a catenoid profile, while a conoid profile is better than conical
(Gusev et al., 2012).
FIGURE 1.17 Example of a waterjet cutting head: 1 – Orifice, 2 – Abrasive inlet, 3 – Mixing
chamber, 4 – Focusing tube.