Stone is one of the most sensitive materials to shape with traditional cutting methods. Angle Grinders and Diamond blades were the conventional options for dealing with rocks, but both ways were inflexible and cost-intensive due to the frequent wear and tear of the blade and grinder. 

That all changed when waterjet cutters came on stage, and it has since become a staple for dealing with stones and other similar materials. Waterjet cutting stone is the most efficient method for handling minerals on an industrial scale. 

But different stones have different mineral compositions and require additional pressure and abrasive combinations. This guide will cover everything you need to know about cutting stones with waterjets.

Can A Waterjet Cut Stone?

The abrasive cutting power of a waterjet makes it the perfect tool for dealing with materials like stone. It prevents the cut from being jagged while providing outstanding efficiency. Waterjets are also highly precise, and you can use them to cut stone into shapes that would otherwise require manual chiselling.

Waterjet cutters don’t cut like a traditional industrial cutting tool like the diamond blade. It has no cutting edge, no blade or anything of that nature. What it does have, however, is high-pressure water flow. When filled with the right type and amount of abrasive, this pressurised water can grind away any material.

So, in essence, a waterjet does not “cut” the stone. It grinds it with extreme precision, leading to exquisitely fine separation. This process is entirely devoid of friction that traditional cutting tools exhibit. That avoids chipping the stone or compromising its structural integrity in any way.

How Does Waterjet Cutting Stone Work?

Waterjet cutting is a mechanical process that goes through multiple stages. The fundamental operating principle of a waterjet is like this– water goes to a pump, gets pressurised, travels to the cutting head through a hardline, and gets blasted out through a tiny opening with exponential force. That thin blast of water is what cuts the stone.

There are quite a few components of a waterjet cutter. You also need two external elements: water and abrasive material. Most people prefer using garnet as the abrasive element, as it is an industry-standard. Below is a detailed description of how things work:

Step 1: Filter

The process starts with clean, flowing water accumulating in the filter. You can do without the filtering process, but skipping it might pose a risk to the components if your water quality isn’t right.

Step 2: Intensifier Pump

The filtered water then travels to the intensifier pump, where the pressurising happens. An electric motor moves the pistons inside the hydraulic pump to steadily increase the water pressure.

The pressurised water then travels through a hardline and enters the accumulator. The accumulator holds the water with all its pressure.

Step 3: Hardline carrier

From the accumulator, the water then gets carried within a hard line. The hardline brings the water all the way to the whip stand, which is connected to the gantry. It helps hold the hard line in a flexible position so that it does get damaged when the gantry moves.

The gantry is the unit that moves the cutting head across the flat surface of the debris tank. It is run using a CNC system so that you can control it quite flexibly.

Step 4: Cutting head

The cutting head is mounted onto the gantry, and this is where a lot of the exciting things happen. The cutting head has a tiny circular orifice with a diamond at the centre. That’s where the water comes out after going through the hardline.

However, the orifice is separated from the nozzle by another hollow tube known as the mixing tube. The mixing tube is where you connect another pipeline that supplies tiny garnet grains. Once the water from the diamond orifice comes out, it flows into the mixing tube, which is much broader than the orifice itself. 

The extra space in the mixing tube creates a vacuum which pulls the garnet from its separate pipeline. The garnet and high-pressure water mixture then comes out of the nozzle and cuts the stone by grinding it down.

What Types Of Stone Can Be Cut With A Waterjet?

Waterjet can cut almost every kind of stone. It can cult every stone that’s commonly used in industrial projects. Some of them are as follows:

• Marble
• Limestone
• Precious stone
• Quartz
• Granite
• Basalt
• Obsidian

It is worth mentioning that a well-tuned waterjet cutter can cut any of those stones into any shape, regardless of their thickness. The only limitation is how much power your waterjet cutter can bring out. High-end waterjets can dish out up to 90,000 psi of raw pressure.

Applications Of Waterjet Cutting Stone

Waterjet cutting stone has numerous applications since stoneware is becoming an increasingly popular industrial commodity. A lot of significant industries use stone as base material, so a tool as precise as a waterjet is prevalent.

That said, here are some areas where waterjet cutters are used quite often:

1. Construction

Stone blocks are quite common in construction, and waterjet cutters can easily cut and shape them. Waterjet is also used in quarries for cutting large chunks of sandstone and limestone to make large stone blocks for various purposes. 

Marble tiles and stone tiles are also cut using waterjet cutters. Using waterjet cutters instead of traditional diamond blades is usually more energy and cost-efficient. Stones used in pavements also benefit from waterjet cutting for similar reasons.

2. Decorations

The interior decoration industry also uses waterjet cutters in various sectors. Granite table tops, workstations, decorative tiles, and many others fall into this category. The genuinely innovative segments are still the custom-designed goods that various companies are starting to dabble in.

The 5-axis waterjet has a very flexible and precise cutting angle that is above and beyond any traditional cutting method. You can use these to mass-produce decorative pieces that would otherwise take sculptors months of chiselling work. A Gentry 5-axis full scale waterjet cutter can do almost every kind of precise stone crafting.

Advantages Of Waterjet Cutting Stone

There are several advantages of using waterjet to cut stones and minerals. For one, it is significantly cheaper than similar industrial cutters like laser and plasma. It also boasts cheaper operational costs compared to those. 

Waterjet cutters also have unique practical advantages that make them a better choice for cutting stones. Here are some examples:

1. Perfect for Heat Sensitive Material

Waterjet cutters are a cold-cutting process that generates no friction or heat. That makes it the perfect tool for cutting heat-sensitive items. Rocks usually aren’t very heat sensitive, but it’s best not to expose them to too much temperature.

However, large slabs of rocks can have water pockets in them, which could cause dangerous explosions when cutting with a laser or plasma cutter. That is why a waterjet cutter is still the best option for cutting larger stones.

The cold-cutting process also puts far less stress on the material. That helps prevent discolouration or any other heat-related reactions.

2. Stronger Cutting Force

Waterjet cutters are brutally effective at cutting thicker objects compared to laser or plasma cutters. The pressurized water cuts through rocks effortlessly as long as you keep feeding it garnet. The abrasion cuts through the stone, leaving a smooth surface.

Due to its strength, Waterjet is the preferred method of cutting larger objects these days. It also cuts without leaving any cracks on the stone, so that’s another reason to consider it.

3. Dustless

One of the most significant health hazards while dealing with stones is dust. Long-term exposure to stone dust can easily lead to respiratory issues. However, waterjet cutters are completely dust-free because the water pushes all the debris into the gantry tank below.

While you will need to clean up the tank eventually, it comes with zero health risks to you or your workers.

4. Precision

Waterjet cutters are deceptive and precise and keep improving with newer technology. The current most advanced versions can utilise 5-axis cutting heads to move the nozzle to a 60° slant. That allows the waterjet to curve delicate designs on the stone.

On that note, you can also etch different designs on a stone’s surface by carefully adjusting the output of the waterjet. For aesthetic reasons, such is often done on marble, granite, and obsidian.

5. Environmentally-safe

Waterjet cutters use recyclable materials for their operation. The water can be purified and used again, and you can also recycle the garnet at special facilities. In the long run, none of the material goes to waste. The machines don’t even use too much water during the operation. 

Since it is a heat-free cutting method, and there’s no friction generated in the process, there isn’t any harmful gas emission either.

Tips And Precautions For Waterjet Cutting Stone

All-in-all, waterjet cutters are very simple and easy to use. You can even do the technical maintenance yourself after a few training sessions. Still, there are some risks of using waterjet cutters if you overlook some safety regulations. 

Here are some tips and precautions that may make your experience with the waterjets more enjoyable:

1. Don’t Keep The Waterjet Stationary For Too Long

We weren’t joking when we said waterjets could cut through anything, including your floor. That’s why keeping the waterjet at full power and blasting at the same spot for an unnaturally long time is never a good idea.

The gantry will have a lot of water, dampening the cutting force once the water jet goes below the cutting surface. But that’s not enough to entirely stop its erosion. Some people like putting AR plates or abrasion-resistant plates below the gantry to safeguard against such situations.

However, it’s usually not necessary to go that far. Just using it with caution is enough to avoid such unfortunate outcomes.

2. Place Wood Sheet Below

When cutting small shapes or outlines into a slab of stone, you would want to place cardboard or something on the support ribs. The support ribs are quite a bit far apart, and your small cutouts would fall into the quagmire of the gantry if you don’t have anything to catch them from falling.

You could always retrieve it manually if something like that does happen. But searching for a small object in a large gantry is challenging, to say the least. So it’s always better to not let it drop through the gap in the first place.

3. Don’t Work Near the Edge

For large heavy-duty waterjet cutters with 5-axis cutting heads, you’ll need to place the material further in the middle before working on it. Setting the base material near the edge of the tank can cause damage to your tank itself. 

This usually happens if you angle the water stream too much and it faces the tank walls on the side instead of the bottom of the tank. This can cause the water stream to damage the sides and even potentially harm you if you stand too near.

That’s why it’s standard practice to have the workpiece placed further along the middle of the gantry so that the stray jets stay far away from the walls.

4. Secure The Workpiece Firmly Before Using The Cutter

While working with stones, you need to secure the thing onto the support ribs so it doesn’t move around when the water jet hits. The waterjet is not like a laser cutter which burns the material without applying force. The waterjet stream moves faster than the sound barrier, and has considerable power.

If your material is unfastened, it will move when the water hits and ruin the cut. That could lead to uneven cuts or even accidents. You should also get a small grip magnet to handle your material better, especially when working with metal. Magnets aren’t all that helpful when dealing with rocks, though.

5. Garnet Usage

There is a correlation between garnet quality and the final finishing quality. Larger garnet grains tend to have a stronger impact on the surface but are also more sparse. That leads to a slightly more coarse cut than using finer garnet.

Finer garnet with 80/90  mesh will give you significantly finer cuts. Such garnet is highly recommended for precision works like designing and sculpting. However,  the default low-quality coarse garnet also has its usage. 

Coarse, low-quality garnet has higher impact force and abrasion than the finer stuff. So it’s better to use them when cutting larger or thicker rocks because it gives more penetration power.

FAQ For Waterjet Cutting Stone

A few questions usually come up when folks see a waterjet demonstration. Here are some noteworthy ones:

Q. Can you recycle the garnet?

Yes and no. Yes, the garnet used for cutting can be recycled, but you can’t do that yourself. It’s not as simple as scooping up the garnet from the quagmire in the gantry. You need a particular processing facility to sort out the metal, rock shavings and other debris from the garnet.

The process requires dedicated machinery and infrastructure. So, buying a new batch of garnet is often better.

Q. How much water flow does it need?

Contrary to popular belief, waterjet machines do not use that much water. Five gallons per minute is generally enough to work with most machines. All of that water isn’t even used for cutting, either. A good portion of it is used for cooling down the pump instead.

Q. Does a waterjet cutter come pre-installed?

The smaller ones do, but something like a gantry will need to be shipped as separate components. You’ll then need to reassemble it on-site. Take this HEAD gantry model, for example. It weighs 4300 kg and is understandably quite huge. Most facilities can’t even fit it through their door.

Q. Does the nozzle wear out?

The nozzle will wear out with time, and you will need to replace it after every 300 operational hours or so. You will also need to replace the blast shield, too, for that matter. Waterjet cutters have a few other wear components in the pump itself.

You will often need to replace other parts like the cutting head, mixing tube, etc. Most of the replaceable parts are on the pump and the nozzle. You may occasionally need to change the abrasive dispenser pipe if it gets damaged, but that doesn’t happen too often.

Q. Do you need to change the support ribs?

Yes, you do need to change the support ribs. The support ribs help keep your material in place when the waterjet does the cutting. It often has to withstand the full brunt of the water pressure and wears out much faster than the regular wear components.

Conclusion

Waterjet cutters are excellent for dealing with stone and other mineral components. That’s why waterjet cutting stone has become a standard practice in many places. It is a versatile cutting technology that can work with various materials. Other than its rather bulky size, waterjet cutters have no downsides.

That said, if you are interested in waterjet cutters, you should check out our collection. We supply high-end waterjets and other industrial cutting machines on a global scale.