Abrasives make up one of the most important components in the waterjet cutting process. While a pure waterjet (without abrasives) can cut softer materials like foam and rubber, adding an abrasive substance enhances the jet’s cutting capability — to the point where you can cut glass, steel, and a variety of other components. As you might imagine, the type of abrasive used is extremely important in determining the machining outcome.
Professionals have tested various synthetic and natural materials for use in waterjet cutting, and the prominent choice for the industry is garnet. A garnet abrasive offers a reliable and rigid substance that forms sharp edges when fractured — providing superior cutting ability. Garnet offers the correct combination of durability, density, and particle shape to maximize the cutting capabilities of most common waterjets. On top of that, garnet is also mostly chemically inert — meaning it won’t react poorly with materials you’re cutting.
The Best Option for the Best Price
Although it’s possible to synthetically create garnet, for the purpose of waterjet cutting, the substance is found naturally in the earth; extracted from underground mines, and seashore locations. In its ideal form, the mineral looks similar to a ruby — although it’s much less costly. Processing the mineral for use in waterjet fabrication may include crushing it to a specific size, washing it, or simply screening it for a specific “mesh.”
On the MOHS scale — often used to determine the hardness and durability of minerals — diamond earns a level of 10 (the hardest substance known), while garnet usually falls around the 7.5 to 8.5 range. Though there are stronger minerals available, garnet generally offers the best level of hardness, for the most reasonable price.
As an abrasive substance, here’s what garnet has to offer:
- Significant hardness. Garnet can generally last a long time before needing to be replaced, making it a cost-effective abrasive.
- Options for recycling. In some cases, garnet can be recycled, depending on your chosen grit size.
- Environmentally friendly cutting and cleaning. Garnet is frequently used in blast cleaning next to bodies of water, thanks to its lack of chemical input.
Choosing the Correct Garnet
Not all garnet is equal when it comes to cutting. Some garnet solutions are far more productive than others — even though each mineral offers a similar chemical makeup.
On average, abrasive accounts for about 70% of the operating costs associated with waterjet machining. As such, the garnet you choose for any particular project will have a significant impact on the success, and economic impact, of your operations.
Garnet comes in a range of grit sizes, designed to provide different results; such as a smooth or rough finish, depending on the hardness of the machining material. In most circumstances, companies need to use finer grits for processes that demand higher edge quality, while larger grits are most effective in projects that require faster cutting.
Most of the time, when companies purchase garnet for waterjet machining, they receive the substance in a sand-type form, after it’s been run through a screen to obtain the exact sizing required. Garnets come in a range of “mesh” sizes, and companies generally choose a mesh size based on the material they’re cutting. Mesh sizes generally range from between 50 to 200, indicating the size of the garnet abrasive in “microns.”
Most fabricators that process a wide range of materials choose garnet mesh sizes that work on both thick and thin materials — typically 80 mesh. Specialist organizations that cut thicker materials (like granite or steel) might select a coarser 60 mesh, while companies that cut plastic or aluminum might stick to 120 mesh.
Using Garnet for Abrasive Waterjet Cutting
Standing fairly close to diamond on the hardness scale, and more affordable than similar minerals, garnet stands out as the top choice for most abrasive waterjet projects. Some garnet is better for cutting than others depending on its shape, hardness, sharpness, and purity; yet across the board, its durability, sharp edges, and low chemical input make it ideal for working with almost any material. Although other abrasives are available in certain circumstances, most organizations agree that garnet offers the best results, for the best price.
In the machining and fabricating industries, abrasive waterjet cutting is a process for accelerated erosion of hard materials like metal. A waterjet works by firing high-pressure water through an orifice, and into a mixing chamber, which uses a vacuum to introduce garnet sand into a water stream. While waterjets are versatile and powerful cutting tools, the heart of these machines are their jewel orifices – a tiny nozzle made of synthetic sapphire, ruby, or diamond – which the water is pushed through.
The jewel orifice is responsible for focusing the water stream, allowing for smoother, cleaner cuts. While diamond orifices last longer, they’re also by far the most expensive, which can make ruby or sapphire options more appealing for certain circumstances. Following, we’ll address the positives and negatives of each potential option.
Sapphire and Ruby Waterjet Orifices
Many people don’t realize that ruby and sapphire waterjet orifices are actually grown using the same base material: synthetic corundum. The only differences are in the chromium added to rubies to provide their red pigment, and the fact that manufactured geometries for each type can vary. Corundum is used extensively in various applications, due to its extreme hardness and easy reproduction. Five times more abrasive resistant than carbide, and ranking at a 9.0 on the Mohs hardness scale, corundum is high-temperature tolerant, resistant to chemicals, and reliable.
Because rubies use a robust inlet edge radius of around .001″ (depending on the diameter of the orifice), they can sometimes withstand greater abuse than sapphires before failing; however, they also create a shorter coherent jet stream. Ruby can also produce a stronger vacuum than sapphire. On the other hand, sapphires use “sharp-edge technology” to produce a longer, smooth, coherent stream for cutting.
When to Use Ruby and Sapphire Orifices
Unlike many orifice materials tested in the past, ruby and sapphire can stand up to harsh environments without significant corrosion. Unfortunately, both ruby and sapphire can be vulnerable to minor impacts from debris in the high pressure system, which may destroy their integrity.
Although ruby and sapphire orifices often cost far less than a diamond orifice, they only last for anywhere from 0-40 cutting hours, compared to the hundreds of hours you’ll get out of a diamond. If a manufacturer needs to change orifice combinations frequently, sapphire or ruby could present a less risky choice; frequently changing the nozzle not only increases the likelihood that debris will enter and damage the orifice, but it also heightens the chance that the orifice might be lost, leading to a wasted investment. While a lost ruby or sapphire worth $20 may be frustrating, it’s not nearly as catastrophic as a lost diamond, worth hundreds of dollars.
Diamond Waterjet Orifices
Diamond waterjet orifices combine the robust inlet edge radius of rubies with the sharp edge technology of sapphire, to offer a maximized jet stream, benefitting from smooth cutting and robust material integrity. Rated at 10.0 on the Mohs hardness scale, diamonds are the strongest available orifice for waterjet machining. Four times harder than sapphire or ruby, diamond orifices are becoming the industry standard for most jewel orifices, capable of offering versatility for effective use in many cutting applications.
Because diamond orifices improve stream quality, the resulting cut is often smoother – making diamond an ideal choice when cutting expensive, or incredibly detailed components.
When to Use Diamond Orifices
Some machining components may require time-intensive, detailed cuts; and replacing a jewel orifice midway may ruin the results. Using a diamond orifice that can last longer – usually a minimum of 600 cutting hours – can prevent wasted materials, and reduce uneven wear in the cutting head.
Though they are more expensive than rubies and sapphire, the longer lifespan of the diamond makes it particularly beneficial for large-scale tasks. Diamond orifices are often preferable in machining organizations that use multiple cutting heads, as operators can switch out orifices reliably and routinely, either once or twice a year. With ruby or sapphire heads, orifices can wear out at different speeds, leading to constant changing.
Choosing the Right Orifice
While most industry experts commend diamond as the best option for waterjet cutting orifices, there are equally valid reasons to choose ruby or sapphire, especially if your specific manufacturing process requires frequent changing of orifice combinations. The right choice for your business will depend on your personal circumstances, including your budget, the specs of your cutting jobs, and your short-term and long-term machining goals.
If you’ve had experience with ruby, sapphire, and diamond orifices in the past, how did you rate each one in terms of performance? Let us know in the comments below!
Efficient and innovative machining companies use waterjet technology to shape and cut various materials with a high-pressure water stream. The thin, versatile stream allows waterjets to be fast, accurate, and flexible – leading to clean, detailed cuts in a range of materials without a change to the material properties or the development of a Heat Affected Zone. For companies that thrive on efficiency, waterjets include a quick set-up time, speedy cutting, and highly-controlled cutting accuracy.
Today, we’ll be looking into the technology behind waterjets, and how they work to deliver a precise result — no matter the task. From the parts within the waterjet system, to how those components work throughout each step of the process, this article will provide a comprehensive look at one of the most popular cutting techniques on the market.
Step 1: Setting Up the System
Waterjets manufacture components to exact specifications, which requires the use of a computerized system responsible for following a design. Technicians place a client’s material on a bench top unit beneath the waterjet nozzle, and during the cutting procedure, that material will either move to facilitate a fixed head, or the nozzle itself will move to follow a pattern. Most moving waterjet heads use a Computer Aided Design program for enhanced accuracy.
When used properly, waterjets can cut through:
- Stainless Steel
Step 2: Creating the Stream
Waterjets use water forced through a tiny hole, known as the “jewel” or “orifice”, to concentrate extreme pressure over a small space. The speed at which the water moves through the orifice creates a high-velocity jet. Creating this stream involves two primary steps:
- The intensifier or pressure-pump pressurizes water at levels of up to 60,000 PSI. The water moves into the system through a filter and booster pump. The filtering process is crucial, as water must be clean before it reaches ultra-high cutting pressure to protect components from damage. A water-treatment system removes harmful minerals from the water.
- Secondly, the filtered water flows through the small orifice to create the cutting stream. Direct drive or intensifier pumps can create the high-pressure required for cutting. Some machines use hydraulic oil pressurized at 211kg per square centimeter to power a piston.
The cutting stream can move at a velocity of Mach 3 – three times the speed of sound – depending on the water pressure. This process is applicable to both pure, and abrasive jets.
Step 3: Adding Abrasive Material
While pure waterjets use the stream of water exiting the orifice to cut through materials like foam, fiberglass, or soft rubber, they’re not effective for cutting harder materials. An abrasive jet works much like a pure waterjet, but as the stream of water leaves the orifice, an abrasive material such as garnet, mixes into the stream. The water beam accelerates those abrasive particles to speeds fast enough that they can cut through much harder materials. The resulting jet moves through a “mixing” or “focusing” tube to create a far stronger cutting mechanism.
Waterjets can use various abrasive materials, including diamond, corundum, garnet, and olivine – so long as the particle size is between 0.2 and 0.5 mm. Usually, the machine stores the abrasive substance in the pressurized hopper before it travels into a metering assembly which controls the level of particles fed to the nozzle.
Step 4: Making the Cut
Once the component design is integrated into the waterjet cutting machine through the use of CAD software, the device can program tool paths that map out the cutting process. Following the cut, the residual energy from the cutting stream dissipates into a catcher tank, which stores spent abrasive and kerf material.
In some circumstances, professionals fill catcher tanks with materials like ceramic – designed to slow the jet and reduce the chance of damage to floors and underlying fixtures.
Using a Waterjet
Waterjets are effective and environmentally friendly processes for machining that create precise, clean results, without giving off hazardous waste or vapors. As you can see above, the process for setting up and using a waterjet is simple enough for a professional to follow, assuming he or she has the right training and equipment.
If you’ve used waterjet cutting before, how did you find it compared to other machining practices? Do you have experience using a waterjet machine yourself? Let us know in the comments below.
For any business or industry, it’s crucial to have access to the latest, and most valuable tools on the market. While there are many different manufacturing processes that can complete complex projects and produce parts, waterjet cutting is a solution that is rapidly growing in popularity, thanks to its various unique capabilities and benefits.
Waterjet cutting is capable of shaping a wide range of different materials, by working similarly to the environmental process of water erosion. The process focuses a thin stream of water, accompanied by an abrasive material such as diamond, on a particular area of a piece of material, cutting it into the shape desired. The numerous benefits and impressive abilities have allowed waterjet cutting to find applications in a diverse number of industries, from aerospace, to mining, architecture, and more.
Following, we will cover just some of the unique capabilities of waterjet cutting — and it may be able to offer for your upcoming projects.
Feature 1: Capable of Cutting Virtually Any Material
Abrasive waterjet machines are incredibly versatile cutting solutions that are capable of cutting almost many materials. These machines are ideal for constructing complex and highly detailed shapes quickly and precisely. Often, waterjet machines offer an ideal alternative for materials inappropriate for thermal or laser cutting, and are exceptional for projects which require little to no thermal stress.
The versatility of the waterjet makes it appealing to almost all industries – as there are very few materials that it cannot work with, including tempered glass, and some forms of advanced ceramic.
Feature 2: Efficient and Fast
The process of using a waterjet machine is fast and efficient, completing complicated and extensive tasks within as little time as possible. Waterjet machines can be set up quick due to the use of advanced and easy-to-learn technology. From there, the cutting head can move carefully across the material according to the shapes and results required.
Because most material cut with a waterjet will require the same head and the same process, there are no changes needed in between material alterations. What’s more, the movements of the machine can use computer programming, which means that workers simply have to stand back and watch as stunning parts form.
Feature 3: Little to No Heat Generation
Unlike many other forms of cutting, the waterjet cutting process is “cold”, meaning that there is no thermal pressure generated in the zones surrounding the cut. The use of a cold cutting process means that metals and other materials can be shaped to standard without accidentally changing the intrinsic properties of those materials through warping or distortion. Unlike plasma, laser, and flame cutting, waterjet and abrasive jet procedures place no heat or mechanical pressures on the material used, meaning that companies can achieve the ideal results, without risk.
Feature 4: No Fixturing Required
Because the waterjet process utilizes a very precise stream of water to erode and shape materials, the need for fixturing is often reduced. In other words, with waterjet cutting, companies will not have to worry about weighting the materials in place or clamping them to avoid mistakes.
Feature 5: Safe, and Environmentally Friendly
During the cutting process, a waterjet machine eliminates smoke, fumes, and airborne dust particles, ensuring that contaminate cannot be released into the atmosphere and lead to operator exposure risks. This can make the process of cutting materials like fiberglass and asbestos much safer and easier.
What’s more, waterjets produce no hazardous waste, meaning that companies can minimize disposal costs, and maximize upon the use of reusable scrap material often lost to traditional cutting methods. Similarly, parts can nest closely together to maximize the value of materials, and the water used during the process can be recycled through a closed-loop system.
Feature 6: Incredible Precision
Finally, waterjet cutting is extremely precise, with typical tolerances of around +/-0.1mm for many materials. Waterjets give manufacturing companies the ability to routinely cut parts with precision, through the use of computer software. What’s more, they are capable of tight tolerances, even when the requirements of the projects force them to stray from straight-line geometrics.
Waterjet cutting systems are some of the most versatile and beneficial tools on the market. The process provides companies with a wide range of unique capabilities and advantages, making it an ideal solution for tackling problems that other technologies simply cannot address.
Fiberglass is a complex and often messy composite to work with, primarily because it contains tiny fibers made of glass and other materials. Because the reinforcement fibers used within fiberglass are abrasive, they often clash with other abrasive tools, shortening the lifespan of the machinery in question, and potentially damaging the material in the process. Many cutting methods also heighten the risk of overheating during the cutting process, leading to further damage.
There are numerous factors to consider when selecting the right method to handle fiberglass, from the discomfort and danger that can result from irritating dust fibers that come into contact with workers’ skin, to the possibility of delaminated composites ruined by burrs, edge chipping and poorly trimmed edges. With that in mind, companies who want to achieve the perfect finished product must take care in selecting the perfect tool.
Waterjets Could Be the Best Method for Cutting Fiberglass
Cutting methods that rely extensively on the use of “heat” generate a great deal of friction, which typically heighten their chances of damaging composite materials. On the other hand, waterjet cutting is a controlled-erosion, low-temperature alternative that doesn’t introduce heat-related stress to the materials involved.
Waterjet technology works by using a thin stream of water directed towards a material at a high speed, under significant pressure. By eroding the material alongside an abrasive material intended to make the tool more effective at shaping harder materials, waterjet cutting offers smooth edges, and precise results. Waterjet systems are capable of penetrating a wide range of different materials, from steel and armor plating, to fiberglass and ceramic tile.
Waterjet cutters can actively eliminate airborne fumes, contaminates, smoke and dust particles from the materials it is working on. In other words, waterjets improve the working environment, and reduce the risks associated with operator exposure.
The Advantages of Using Waterjets to Cut Fiberglass
Waterjet technology is capable of cutting virtually any material, without superheating the area adjacent to the cut in order to keep material integrity intact — an important factor in many cutting projects wherein excessive heat could damage remaining material. Not only is waterjet technology a “green” option, but it can also minimize costs for companies by cutting off large pieces of reusable scrap material that traditional cutting methods may ruin.
Waterjet cutting also expends minimal force on the fiberglass, reducing fixturing and ensuring that the material remains in place throughout the cutting procedure, producing the same results time and time again with expert precision. Following are just some of the benefits of using waterjet methods to cut fiberglass materials:
- Environmental concerns related to cutting hazardous materials are reduced as airborne contaminants are eliminated or reduced
- The erosive process of waterjet cutting reduces rough edges and burring, meaning that additional finishing operations are not required
- There is no risk of thermal distortion of parts with waterjet technology, or thermal stressing to the material
- Waterjets are capable of achieving a significant degree of accuracy, and cutting profiles are not confined to straight-lines, meaning that part complexity can be as high as required
Handling Fiberglass Projects with Safety and Precision
The versatility of waterjet cutting allows it to be a useful application in almost any industry. Not only are there a wide range of materials that waterjet machines can cut, but the evidence suggests that the results of cutting materials like fiberglass can be highly improved with waterjet technology.
Through waterjet precision, companies cutting fiberglass parts can reduce the environmental hazards of fiberglass dust and contamination, while achieving a finished piece free of distortion, burring, or the harsh, damaged edges caused by other cutting methods.