Waterjet Options: Diamond, Ruby, or Sapphire?
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!
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