Waterjet Cutting Technology Review

Report 2: Process Improvements

New Technology which replaced Existing Technology: Water Jet Technology

With the Advancements in the control and equipment components, have pushed the Abrasive waterjet cutting technology into the mainstream. This technology has been recently used primarily in industrial areas and provides many benefits compared with conventional methods. In several cases in market these days, this technology is competitive with different cutting methods like plasma and laser cutting systems. Water jet cutters are wonderful tools that can cut huge variety of materials. The basic principle is that the use of fine jet of water at very high pressure to create a blade to cut materials.

At present, it is also used in the field of medicine. It is replacing the Oscillating saws, chisels which are standard instruments inevitable for bone cutting and socket generation for endoprostheses which have negative side effects such as distinctive heat and deformation impacts. It is the application of the water jet that offers eventuality of eliminating the negative mentioned features of technological process. There are also benefits and usage in different fields of medicine.

They were originally developed for the utilization within the mining of gravel and clay deposits to blast material from the quarry face. The first commercially usable water jet cutting system was installed in 1971. This resulted in the elimination of the use of commercial saws. It was designed for the contour cutting of furniture packing forms (Yadav, 2018).

Abrasive Jet Process Description:

In Industries, Abrasive and high speed coherent stream of water were utilised in Abrasive water cutter technology which can be used to majority materials. Water at very high pressures i.e., 40 to 55 thousand psi accelerates through a sapphire, ruby or diamond orifice. Vacuum was induced by the stream as it passes through a mixing region and sucks in abrasive. As it passes through the nozzle, water stream momentum accelerates and entrains abrasive. With a cutting diameter of 0.020” to 0.060” the stream exits the nozzle. Actual cutting is done by the high speed abrasive particles impact on the kerf face. The most commonly used abrasive in water jet cutting technology is Garnet (Talsco, 2013).

Waterjet cutter can cut most materials including stainless steel, mild steel, aluminium, plastics, glass, ceramics, stones and composites.

Figure 1: Abrasive Water Jet Cutter

For Medical use, Water jet cutting device consists of water reservoir, pump to create a working fluid pressure of cutting fluid, air compressor, the cutting head forming a fluid flow and a mixing chamber where the abrasive is added into the fluid. Sterile saline is used as fluid in the field of medicine (Hreha et al., 2010).

Figure 2: Scheme of Abrasive Water Jet Technology in field of Medicine (Hreha et al., 2010)

Water Jet in Field of Medicine:

In 1980, water jet cutter was first medical used for cutting bones and endoprosthesis. During the abrasive water jet cutting, it requires no heat which affects the cut material. Hence, this technology is suitable for applications where the structural change of material is not permitted. Compared to the industrial usage the critical temperature is much lower for medical applications. It is also used in dental surgery for cutting and grinding of dental materials. It is beneficial as there will be no generation of sound, pressure or hear and reduces anaesthesia needs. It gives healthy dental tissues and reduces the risk of jagged teeth and micro-cleavage (Hreha et al., 2010).

It is also used in the field of surgery at resection of soft tissues such as gall bladder, liver, brain, kidney, cleaning of traumatic wounds and prostate. Compared to the conventional methods using the water jet cutter as a scalpel resulted in more healthy tissue. It reduced the duration of myocardial ischemia and there was minimal bleeding (Hreha et al., 2010).

In the area of plastic surgery, it is a useful tool for degreasing of skin graft, removal of tattoos and liposuction. The results obtained were of greater accuracy, contour changes and without edema.

It is also used in dermatology to remove dead skin. The flow of water is dosed with drugs, such as anaesthetics to reduce pain, coagulation medications for better coagulation of blood, etc. (Hreha et al., 2010).

Figure 3: Overview of using water jet instead of conventional methods in the field of medicine (Hreha et al., 2010)

Benefits of Abrasive Jet Cutting:

Abrasive waterjet has many benefits compared other cutting techniques as it a cold cutting process and hence there will be no heat affected zones, has no warping and distortion, can cut any thickness and material, environmentally friendly, flexible, and low contact force of cutting stream (Talsco, 2013).

Process Intensification: Sonocrystallization (Ultra-sound enhanced crystallization):

Crystallisation is a technique for isolating molecules from a solution both from a purity and an isolation basis. It is one of the oldest unit operations and most of the pharmaceutical plants has a minimum of one crystallisation step in its synthesis and classically crystallisation has been a difficult process to manage or control. Sonocrystallisation allows the control of the crystallisation process without destructive techniques such that we can control size, particle size distribution, habit morphology and polymorphism. Also, to avoid dry milling, ultrasound was used for particle size reduction in the crystal slurry post-crystallization. Temperature cycling followed for particle size uniformity.

In 1927, Richards and Loomis, first reported Sonocrystallization which is a crystallization induced by ultrasound. In the former Soviet Union, it was actively studied from the 1950s to the 1970s. Since that point, sonocrystallization of different kinds of materials and the modification of diverse experimental parameters have been reported. During the 1980s due to advances in ultrasonic equipment, the industrial use of this technique increased, and, currently, it is common for generating crystals in the fine chemicals sectors and pharmaceutical. This technique involves the application of ultrasound energy to control the nucleation and crystal growth of a crystallization process or method (Kim & Suslick, 2018).

Figure 4: The schematic illustration showing the formation, growth, and collapse of a bubble induced by ultrasound waves

Ultrasound has a frequency higher than 20 kHz which is very high to be perceived by the human ear. These waves travel through liquids as longitudinal waves and has compressions and rare fractions. The peak about the line are compression or the area of high pressure and peak below the like are rare fractions or the area of low pressures as shown in the Figure 4 above (Syrris, 2018).

This results in predictable and highly repeatable crystallizations. It also offers several benefits such as increase in nucleation and crystal growth rate, good crystal size distribution, reduce the agglomeration and decreases induction time and metastable zone width (Syrris, 2018).

Nucleation is followed by the crystal growth phase occurs in crystallization. The nuclei which achieves the “critical cluster size” will begin to grow in size. Ultrasound radiation is controlled in sonocrystallization during the crystal growth phase. This is to determine the growth rate, shape, and size of the crystal structures (Syrris, 2018).

Sonocrystallization particle size can be controlled. When ultrasound is continuous, many nuclei are produced which results in small crystals as shown in Figure 5 below. When ultrasound is initially used, it produces only finite nuclei as shown in Figure 6. Nuclei can grow into large crystals as shown in Figure 7 and pulsed ultrasound radiation gives tailored crystal size distribution (Syrris, 2018).

Figure 9: The schematic of experimental apparatus for Ultrasonic crystallization Process

The system consist of ultrasound probe, jacketed crystallizer, ultrasound controller, magnetic stirrer and cooling or heating circulator. The sonication device consists of an ultrasound probe, generator, and controller installed in the jacket crystallizer. The maximum power and frequency of the sonication device were 400 W and 20 kHz respectively. The probe was placed in the centre of the jacket crystallizer in such a way that 1 cm of it is immersed in the solution and a magnetic stirrer to keep the solution well mixed. Circulator is temperature-programmed and is used to control the temperature of the solution. Salicylamide is used to reduce the particle size which was dissolved in methanol, and the mixture was poured into the jacket crystallizer. To ensure the complete dissolution of salicylamide, high temperature was maintained in the jacketed crystallizer. The reaction was controlled to be at temperature of 318 K. After the complete dissolution of salicylamide, the jacket crystallizer was cooled to −5 °C. Power ultrasound was introduced during cooling at a programmed sonication duration and intensity. Crystals which were produced were filtrated using a filter paper, and the wet cake obtained was dried in an oven at 50 °C (Kim & Suslick, 2018).

Benefits of sonocrystallization:

Sonocrystallization is beneficial compared to traditional crystallization methods such as sublimation, solvent evaporation etc. The induction time is reduced as the energy for primary nucleation was provided by ultrasound radiation. Sonocrystallization allows the crystallization to occur at lower super saturations and a high temperatures due to the narrowing of the metastable zone width. Nucleation rate increases which, enables the formation of many small crystals. Crystal growth rate is increased as there will be an increase in bulk-phase mass transfer of the solute to the crystal surface due to ultrasound radiation. Agglomeration will be reduced as cavitation shockwaves can shorten contact time between crystals. Sonocrystallization results in tailored crystal size distribution where large crystals are produced by burst insonation and small crystals by continuous insonation. Using ultrasound, crystallization is highly predictable and repeatable and has narrow particle size distribution. Also it avoids dry milling stage (Syrris, 2018).

Nexus between Automated Process Control and Human Operators and the Challenges:

Automation control system provides us with consistent performance, efficient, Uniform, reliable, fatigue-resistant, and has no attention span limits but it lacks judgement, cannot be programmed for all eventualities, lacks sentient knowledge and subject to wear and tear. Also, it is constrained by human limitations in installations, design and use and adapted responses must be programmed by human programmers. Conversely, humans provide adaptability, judgement, can use experience and logic, can learn and adapt, has sentient knowledge and interactive but the human component is inconsistent and their attention span, vision, reach, strength and hearing are limited. They subject to fatigue, emotion, alternative motivations, bias and distractions and they are forgetful (Haight, 2007).

Every year due to the contributing factor, human error many incidents occur in the industries such as spills, injuries, unplanned equipment downtime and fires. Usually, supervisor or operators would stop their truck and check upon unusual noises or unfamiliar vibrations and request the maintenance to the repair of a leak, a bad order bearing or some other problems. To accomplish work objectives experienced operators can rely on sentient knowledge which they gained by working in the field for long time. Experience enables them to tell how the process is running by smell, sound and sight. But as industries rely more on computer-controlled automation, it is less likely to obtain this sentient knowledge (Haight, 2007).

Process engineers have the ability to examine the producing or assembly processes and give suggestions that may improve product output which is a major area of concern for many industries, as increasing the product output with increasing costs increases profitability in the company. Process engineers are experts at bottlenecking operations and also, they can address the problem underlying help minimising or resolving defects in the product. Also, they can enhance the overall product quality by analysing production systems, raw materials, equipment and component parts. They are able to assist with targeted improvements by making suggestions about areas which need to be improved to maximize results and returns. By analysing the operations and by coming up with ways to work efficiently, they can reduce labour costs which is in general a major expenditure in many industries. They can reduce energy usage by pointing both big and small in many cases and help better utilizing resources. They can design systems and give invaluable inputs in regards to new systems. They can improve consistency by spotting the areas and by offering process control solutions. Most of these roles which process engineers do can enable the smooth operation of the process (Polaris, 2014).

In general when an error occurs in the system it could be because of system itself or operator as they have connection which is a source of failure (Mishev, 2006).

Appendices:

• Haight, J. M. (2007). Automated Control Systems Do They Reduce Human Error And Incidents? Safety Engineering.
• Hreha, P., Hloch, S., Magurova, D., Valicek, J., Kozak, D., Harnicarova, M., & Rakin, M. (2010). WATER JET TECHNOLOGY USED IN MEDICINE. 17(2), 237-240.
• Kim, H. N., & Suslick, K. S. (2018). The Effects of Ultrasound on Crystals: Sonocrystallization and Sonofragmentation. Crystals 2018, 8(7), 280. doi:10.3390/cryst8070280
• Mishev, G. (2006). Analysis of the Automation and the Human Worker, Connection between the Levels of Automation and Different Automation Concepts Sweden: Jönköping School of Engineering. Retrieved from https://www.diva-portal.org/smash/get/diva2:228706/FULLTEXT01.pdf
• Polaris. (2014). Engineering.  Retrieved from http://www.polarisengr.com/engineering/12-things-didnt-know-process-engineer/
• Syrris. (2018). Sonocrystallization. Retrieved from https://syrris.com/applications/what-is-crystallization-and-what-are-the-methods-of-crystallization/what-is-sonocrystallization/
• Talsco. (2013). Abrasive Waterjet Cutting – Application and Capability.  Retrieved from http://www.talsco.com/abrasive-waterjet-cutting-application-capability/
• Yadav, V. (2018). Water Jet Machine/Machining Project Report. NIET. Retrieved from https://www.slideshare.net/VivekYadav209/water-jet-machine-project-report