Armoured Glass Waterjet Cutting: Solutions for Bullet-Resistant Glazing

Security architecture has evolved rapidly in the last decade. The demand for transparent materials that can withstand ballistic impacts or forced entry is higher than ever. Manufacturers face a specific challenge: how to shape these incredibly durable materials without destroying them. The answer lies in armoured glass waterjet cutting.

Bullet-resistant glass is not a single piece of material. It is a “sandwich” of multiple layers. Typically, it involves alternating layers of glass and polycarbonate or other plastics, bonded together with interlayers like PVB (Polyvinyl Butyral). Traditional glass cutting methods, such as scoring and snapping, are impossible to use on these laminates. Diamond saws generate too much heat, melting the plastic layers.

This leaves waterjet technology as the primary solution. It utilizes a high-pressure stream of water and abrasive to erode the material. Because it is a cold process, it cuts through the glass and plastic layers simultaneously without thermal stress. Companies like VICHOR provide the industrial-grade machinery required to handle these heavy, expensive, and sensitive composite materials with the necessary precision.

The Structure of Armoured Glass

To understand the complexity of the cutting process, one must understand the material. Armoured glass, often called bulletproof glass, is designed to absorb energy. The hard glass layers flatten the projectile, while the soft plastic layers absorb the shock and prevent spalling (glass shards flying inward).

When a waterjet stream hits this material, it encounters changing densities. It moves from hard, brittle glass to soft, gummy plastic, and back to glass. Each transition presents a risk. The plastic can absorb the jet’s energy differently than the glass, potentially causing the stream to deflect or spread.

Successful armoured glass waterjet cutting requires a machine that can adapt to these variables. The operator must maintain specific parameters to ensure the edge quality remains consistent across all layers.

The Problem of Delamination

The biggest risk when cutting laminated glass is delamination. This occurs when the water pressure forces the layers apart. If the water stream penetrates the bond between the glass and the PVB, it creates unsightly bubbles or large separation zones. This ruins the structural integrity and visual clarity of the panel.

This usually happens during the piercing stage. When the jet first impacts the surface, the water has nowhere to go but sideways until it breaks through to the bottom. This lateral pressure is the enemy.

To combat this, modern machines use a low-pressure pierce technique. The pump starts at a very low pressure to gently bore a hole through the layers. Once the stream has fully penetrated the material, the pressure ramps up to high operational levels to begin the cut path.

Vacuum Assist Technology

Another critical tool in armoured glass waterjet cutting is the vacuum assist unit. This device is attached to the cutting head. Its purpose is to draw the abrasive and water through the nozzle before the water is fully pressurized.

By pulling the stream through, the vacuum reduces the air pocket that initially hits the glass. It creates a more coherent stream instantly. This significantly reduces the shock of the initial impact, further mitigating the risk of cracking or delamination.

High-end systems, such as those engineered by VICHOR, often integrate these features to ensure that expensive sheets of security glass are not scrapped due to piercing errors.

Abrasive Selection for Optical Clarity

The edge quality of security glass is vital. In many architectural applications, the edge is exposed. A rough edge acts as a stress riser, which can lead to spontaneous breakage later. The choice of abrasive plays a massive role here.

For cutting thick steel, 80-mesh garnet is standard. However, for glass, this might be too aggressive. Many operators prefer 120-mesh or even finer garnet for armoured glass waterjet cutting. The finer particles produce a satin-smooth finish.

The flow rate of the abrasive must also be consistent. Any pulsation in the abrasive delivery will show up as striations (lines) on the cut edge. Precision metering systems are essential for achieving a polished look directly off the machine.

Submerged Cutting Techniques

Cutting glass creates a lot of noise and splash. More importantly, the spray from the surface can scratch the face of the glass. Security glass is expensive, and surface scratches can cause a panel to be rejected by the client.

Submerged cutting involves raising the water level in the tank until the glass is underwater. This serves two purposes. First, it silences the noise of the supersonic stream. Second, it contains the abrasive spray.

However, operators must be careful. Cutting underwater can obscure the view of the nozzle. Reliable collision detection software and rigid gantry construction from manufacturers like VICHOR give operators the confidence to run submerged operations without fearing a crash.

Handling Thick Laminates

Some armoured glass can exceed 3 inches (75mm) in thickness, especially for military vehicles or government buildings. Cutting material this thick requires patience and power. The cutting speed drops significantly.

As the jet travels down through 3 inches of material, it naturally creates a taper. The bottom of the cut is narrower than the top. To fix this, 5-axis cutting heads are used. The head tilts slightly to compensate for the taper.

This ensures that the edge is perfectly perpendicular to the face of the glass. This is crucial if the glass needs to fit into a metal frame or butt joint against another panel.

Applications in Defense and Automotive

The primary consumers of armoured glass waterjet cutting services are the defense and automotive industries. Armored personnel carriers require custom-shaped windows that fit into complex vehicle geometries.

Civilian armoured cars also require precise glass cutting. The glass must fit seamlessly into the doors of luxury sedans or SUVs without altering the vehicle’s exterior appearance. Waterjets allow for complex curves and notches that accommodate window regulators and door mechanisms.

Banks and embassies utilize this technology for teller windows and transaction drawers. The ability to cut speaker holes and pass-through trays directly into the laminated block is a unique advantage of the waterjet process.

Software and Nesting

Armoured glass is sold in large, heavy sheets. It is extremely expensive per square foot. Waste reduction is a top priority for any fabrication shop. Advanced nesting software helps position parts to maximize yield.

The software must also manage the lead-ins and lead-outs. The cut should never start exactly on the part line. It should start in the scrap material and move into the part path. This prevents the pierce mark from damaging the finished edge.

Sophisticated control systems provided with VICHOR machinery allow for intricate path planning, ensuring that the nozzle speed slows down at corners to prevent “tail wash” (where the jet lags behind the head).

The Risk of “Blowouts”

Glass is brittle. Even with the best precautions, tension exists within the glass layers. A “blowout” creates a large chip or crack near the exit point of the cut. This is often caused by the support slats underneath the glass.

If the jet hits a steel slat and splashes back upward, it can shatter the bottom layer of the glass. To prevent this, operators often use a sacrificial material, such as brick or high-density foam, between the steel slats and the glass.

This sacrificial layer absorbs the flashback and supports the glass evenly, reducing vibration. It is a simple consumable cost that saves thousands in lost material.

Maintenance for Glass Shops

Cutting glass creates a fine silica paste. This abrasive sludge is very different from metal filings. It can harden like cement if left to dry in the tank or on the machine components.

Shops specializing in armoured glass waterjet cutting must be diligent about cleaning. Bellows and way covers must be inspected frequently. The fine glass dust can work its way into bearings if they are not properly sealed.

Using a machine with robust protection for the motion system, such as those designed by VICHOR, extends the lifespan of the equipment in these harsh abrasive environments.

Comparison with Polycarbonate Only

Some security glazing is purely polycarbonate or acrylic. These are easier to cut than glass laminates but present their own challenges. They are softer and can scratch easily during loading and unloading.

Pure plastics also tend to frost or whiten at the cut edge due to the abrasive impact. Flame polishing or mechanical buffing is often required after waterjet cutting to restore transparency to the edge.

However, the waterjet remains superior to saws for thick polycarbonate because it does not melt the material. Friction melting creates internal stress that can lead to crazing (tiny cracks) later on.

Future of Security Glass Fabrication

As ballistic standards become stricter, glass is becoming thicker and more complex. We are seeing new composite materials incorporating ceramics and transparent aluminum (ALON). These materials are incredibly hard.

The waterjet industry is responding with higher pressure pumps (up to 90,000 PSI) to cut these super-hard materials efficiently. The fundamental principle remains the same: erosion is the only way to cut without heat.

Automation in loading and unloading is also increasing. A sheet of UL Level 8 ballistic glass can weigh hundreds of pounds. Vacuum lifters and automated shuttles are becoming standard in high-volume shops.

For the security glazing industry, armoured glass waterjet cutting is not just an option; it is the manufacturing backbone. It provides the versatility to cut multi-material laminates without compromising their protective qualities.

Success requires a deep understanding of material behavior, careful parameter control, and reliable equipment. Partnering with experienced equipment manufacturers like VICHOR ensures that fabricators can meet the rigorous standards demanded by military and architectural clients.

Common Questions About Armoured Glass Waterjet Cutting