When you work with water jet cutting it is easy to take certain aspects for granted. The water is mixed with abrasive garnet, this is what creates an unrivalled cutting force.
However, sometimes a question from someone outside our small circle of water jet enthusiast can get us thinking.
Why – we were asked – why is garnet used as the abrasive? What even is garnet? Might a different option not be even better?
Let’s answer that question.
Before explaining why garnet is used, it is first necessary to explain why an abrasive is required at all.
The abrasive is what gives the water jet its force. Without the abrasive, the high-pressure water stream can cut through some materials, but this would be card, paper and other relatively soft surfaces.
The abrasive transforms this, it turns the water jet into a force that blasts through objects, one that can cut through inches of thick steel, concrete and almost any other material.
The water jet is narrow and focussed, the abrasive is contained within this narrow beam. You get the accuracy of a thin cutting head – this through the water jet, but also the cutting power of something more akin to sand blasting, a cutting power well in excess of laser.
However, while the need for AN abrasive might not be in doubt, why garnet?
Garnet is the name used for a large group of rock-forming minerals. Most garnet is found near the earth’s surface when a sedimentary rock with a high aluminium content (such as shale) is exposed to heat and pressure.
The various forms of garnet range between 6 and 7.5 on the Mohs scale.
Garnet can also be made synthetically.
Why is garnet used over other options? Why is sand not used – after all, there is a near limitless supply of sand and, as shown in sandblasting, It can certainly be an effective cutting force.
The answer lies not in garnet being the only option, instead, it is the best option. Early water jet cutting machines did use sand and they were effective. However, nowhere near as effective as modern technology.
Garnet has advantages because:
It creates a powerful cutting force. Garnet breaks into tiny, sharp fragments that mix with the water to create a cutting jet that cut can through 25cm of almost any material.
The cutting force is highly accurate. The garnet mixes superbly with the water – this in the high-tech cutting machine, and so does not make the cutting jet wider or less accurate. The water jet remains suitable for cutting parts for electronics and other jobs where the highest degree of accuracy is essential.
The garnet does not damage the part being cut. A huge benefit of water jet cutting in general, and one that certainly exists when garnet is used as the abrasive, is that no damage is done to the edge of the part being cut.
With laser cutting, for example, heat is applied and this can scar the edge , cause micro-abrasions and even damage the structural integrity. Water jet cutting, despite the force applied through the garnet, is a process more akin to erosion – albeit very fast erosion.
The garnet comes in a range of different forms.
There is not a singular garnet, instead, it is a range of minerals with varying properties and degrees of hardness. It is, therefore, possible to use different grades depending on the part to be cut, thus the technology is cost-efficient. There is no need to use a higher grade of garnet to cut an object that could be cut by a version with a lower trying on the Mohs scale.
The garnet is affordable
Water jet cutting might be a wonderful technology, but it has to compete on price. Any business looking for parts to be cut will compare quotes and water jet cutting has to be able to at least match other options.
The ability to cut accurately, or even to a greater depth might count for little if the quote comes in far higher.
Garnet is the perfect mix of being a material that is readily available, easy to use and also affordable. It is not a hypothetical, synthetic, man-made abrasive designed to be the very best option. It is a naturally occurring substance that delivers the perfect results required.
The garnet is neutral
Whilst it might not be the prime concern of the client, post-cut there is the need to dispose of the waste from the cutting process.
Water jet cutting that uses garnet is a quick process to tidy, the garnet can be easily disposed of without damage to the environment. Water jet cutting is an option that is environmentally neutral, but also keeps costs down as the cleanup process is so straightforward.
Could a better option exist as the abrasive to go into water jet cutting? Theoretically, of course this is possible. A synthetic substance could be made that makes the cutting stream even more powerful yet without impacting accuracy.
However, this would be an extremely marginal gain that in reality was of no benefit to clients. As it is, water jet cutting can cut parts as required, in an accurate and affordable manner.
Recent water jet developments have been in the field of automation and the cutting of complex parts. Through XD cutting technology, water jets can now cut complex three-dimensional parts in one fluid motion.
There will be further developments in water jet cutting, but the use of garnet is likely here to stay.
At TMC, we are a water jet cutter who serve the whole of the UK and increasingly Europe too, with clients across the content trusting us to work on their projects.
Despite our success, we remain a company that focusses on every client and work on projects of all sizes.
If you think water jet cutting might be of use for your project, please do get in touch for an obligation-free chat.
Call us on 01625 610 441 or use our Contact Form.