We investigated the question and interviewed 4 specialists:

• Franz Schachner –  Founder and CEO of systron and patent owner of a special waterjet cutting technology for vertical glass processing
• Thomas Haan – Head of Sales at systron with 17 years of experience in the glass and automation industry
• Christoph Schmitt – Specialist for high-pressure pumps from Uhde High Pressure Technologies
• Daniel Haslinger – Head of Sales at ALLFI Group AG

of the 3 companies mentioned above that deal intensively with the topic of waterjet cutting:

systron GmbH

We are manufacturer of vertical glass processing systems. Since 2014 we have been using this technology in our glass machines – systron proHD glass processing centre and the systron HD waterjet cutting machine – to cut glass.
Company headquarters: Wolfsbach in Austria, 60 employees

Uhde High Pressure Technologies GmbH

High pressure pump manufacturer; active in the business segment of high-pressure technologies since 1930.
Company headquarters: Hagen in Germany, 350 employees, additional locations on every continent

ALLFI Group AG

Manufacturer of high-pressure components for waterjet cutting.
Company headquarters: Stans in Switzerland, 40 employees, other locations in Austria, Japan, China, the USA and Brazil

Christoph Schmitt: Waterjet cutting was introduced in the 1950s by Dr. Norman Franz at the University of Berkley in California, but initially only relatively soft materials such as cardboard and paper were cut and then only with a pure waterjet. The aim was to develop a more efficient method for cutting wood. In the 1970s, waterjet cutting was introduced by Dr. Mohamed Hashish who further developed abrasive water jet cutting, with which harder and thicker materials could be cut due to the significantly increased cutting energy.

Thomas Haan: How it works: The high-pressure pump, which works with fresh water, generates a water pressure of 3000-4000 bar using a hydraulic unit and the pressure intensifier. The water pressure is conveyed to the cutting head using thick-walled, solid high-pressure pipes and valves. Due to the speed of the water (more than 1000m/sec) a vacuum occurs in the mixing chamber. This sucks the set amount of sand coming from the dosing unit to mix it with the water. A diamond or sapphire, when combined with the focusing tube, can concentrate this into a beam with approximately 0.8mm diameter.

Christoph Schmitt explains the function of the high-pressure pump in more detail: Traditional high-pressure generators operate on the principle of a pressure intensifier, where a hydraulic drive draws water into a high-pressure pump head through different surface ratios, and then, using the displacement principle, builds pressure against resistance (such as a cutting nozzle). In order to avoid pressure drops, the high-pressure pump works with a combination of a double-acting high-pressure booster and a pulsation damper, which reduce pressure fluctuations to a minimum.

Franz Schachner: As a technician and machine designer, I was familiar with the needs of the flat glass industry in German-speaking countries. There was no manufacturer of vertical processing systems that combined external and internal edge processing with the  waterjet cutting technology. With a small but very strong team behind us, we were able to install the first prototype at a well-known Austrian glass finishing company in a few months. This machine is still in use there.

 Thomas Haan:

1. The Waterjet makes the most difficult jobs easy. Flexibility is the main argument. There is no complicated tool management and the system is very easy to operate.
2. The most complex contours are cut quickly and can go on to the furnace without post-processing – no grinding and polishing are necessary for tempering.
3. High precision with tolerances of +/- 0.2mm, allowing for precise cuts and fine details.
4. No special tools are required, which will never be needed again after a special job.
5. Waterjet cutting works with a “cold” tool, the waterjet and thus avoids negative influences that mechanical or thermal processes have. Such as destroying the structure of the glass or causing burns and fusions at the cutting edges as well as stresses, micro cracks and structural changes. Where you heat up and cool down quickly, the glass can break more easily – there is an increased risk, especially with shapes. The precise and cold cutting technology ensures a clean cutting edge and preserves the original structure and strength of the glass.
6. Faster processes with Stocksheet Laminated Safety Glass: The waterjet can relieve the load on the LSG cutting table. With our proHD, the special shape is cut from the rectangle using a waterjet and completely finished in the same pass.

Christoph Schmitt: Up to 400mm stainless steel can be cut with up to 6000 bar. In terms of materials, everything is possible from grandma’s cherry pie to hard aluminium oxides or composite materials. And of course the material glass in all its facets.

Thomas Haan: With our systron proHD Glass Processing Centre or the systron HD Waterjet Cutting Machine, our customers cut glass up to 30mm thickness, as well as ceramics or natural stone, the smallest hole is 2-3mm.

Thomas Haan: Maintenance of the high-pressure system is usually carried out quickly and effortlessly by the machine operator or the maintenance person. Due to the high pressure, wear naturally occurs. In particular, the consumables such as sapphire, focusing tube and the mixing chamber must be replaced from time to time. We also recommend having annual maintenance carried out by the pump manufacturer Uhde. Each part can be exchanged separately and easily. We also recommend a certain level of storage of high-pressure parts (e.g. needle valves, high-pressure pipes, etc.).

Franz Schachner: The special thing about our patented systron water jet technology is the use of a patented valve. It allows the high-pressure pump to be started up or switched in just 1 second (instead of the previous minimum of 6″), thus ensuring an extremely fast waterjet cut.

We also have a special function to minimize the jet lag effect. What is that? The waterjet enters ahead, the exit lags – the thicker the plate, the more noticeable it is. Through tracking and circular movement, a cylindrical cut becomes a cone. This tracking effect is greatly reduced by automatic speed adjustments, which has a major impact on accuracy and tolerances.

We also work with breaking tabs for cut-outs larger than 10x20cm, which are adjusted depending on the glass thickness. Large internal cut-outs do not fall into the processing tower, but breaking tabs are created for a predetermined breaking point. This means that large internal cut-outs can be removed by a robot or the operator and the breaking tab is then levelled automatically and precisely using the waterjet.

We only use parts from well-known manufacturers such as Uhde and ALLFI. Daniel Haslinger: systron uses our ALLFI abrasive cutting head with spring-guided needle and patented sealing system. It allows to pierce the glass gently and with low pressure to avoid chipping. The electronically controllable abrasive dosage also allows the user to flexibly adjust the amount of abrasive during processing via the machine control within a range of 0 – to 1000 g/min.

Josef Gasperlmair (Glas Gasperlmair): „Waterjet processing is indispensable. This technology has enormous advantages, especially for complex glass products. Drilling is more difficult to adjust, not to mention the unattainable cycle times. In addition, waterjet holes and cut-outs do not have to be post-processed before tempering because no micro-cracks occur with this high-pressure process. We produce between 400 and 600 glass doors every day, the holes for metal fittings do not have to be grinded unless explicitly requested. We process all special shapes and cut-outs on our systron machines. The more complex the glass is, the more economically we work with it.“ To the full article

Matthias Baumgartner (Arbonia): “The waterjet is a productive technology for us because it can be used in a very versatile way for holes and cut-outs. Since it is expected that the desired glass will become even more complex in the future, there will be no way around waterjet cutting technology.” To the full article

Thomas Haan:

• After waterjet cutting it cannot be tempered directly
• The waterjet cut will scratch the ceramic rollers in the tempering furnace

Based on 10 years of customer experience, this can clearly be denied. The cut edge in waterjet cutting of glass is cloudy, rough and precise and therefore technically does not need to be processed before the tempering process. Additional grinding or polishing is of course possible and may be desired in order to obtain an even finer edge quality.

• Maintenance is difficult and intensive

The waterjet system is easy to service, only standard parts are installed. Often there is a lack of experience and there is a fear of new things. Of course, we provide training during commissioning and every customer receives free technician training from Uhde. Christoph Schmitt adds on the topic of maintenance: High-pressure technology is a reliable technology. In addition to the classic maintenance procedures for oil hydraulics, the maintenance work is essentially limited to the replacement of the high-pressure seals and non-return valves.

• High energy costs

Thomas Haan: Instead of buying diamond tools (and energy to operate the spindle), you have to invest in energy, water, cutting sand and wear parts. When compared directly, you can see that waterjet technology is faster, more flexible and cheaper. To calculate the exact costs, you have to take into account the price of energy, sand, water and maintenance costs. Basically, it can be said that for more complex cut-outs such as Mickey Mouse or socket cutouts, the waterjet is much cheaper and faster than conventional drilling and milling. This is the opposite for simple holes with countersinks. In comparison, you also have to take storage costs and tool management – sharpening, exchanging, testing – into account.

• High water consumption

For long-term use of water jet technology, fresh water is required, which is reused via an efficient water purification system – e.g. the systron SWR300. This sustainable reuse of water contributes to the environmentally friendly nature of the process.

Thomas Haan: For example, for large batch sizes with simple hole drilling, conventional drilling is faster and more cost-effective. You can drill and countersink from both sides at the same time. However, it is important to note: Who knows their products of the future? The waterjet is more flexible and simpler.

Thomas Haan: As far as I know, the only comparable alternative currently available is conventional drilling and milling with diamond tools. The alternative in the future will probably be the laser. However, this will still need some time to be able to process thick glasses (from 8mm) at the appropriate speed and without too much thermal load for the glass. Laser cutting technologies are already being used for thin display glasses, for example.

Franz Schachner: There will probably already be, but so far not a single systron customer.