Frequently Asked Questions (FAQs)

Company

Why was OMAX started when there were so many other waterjet companies around?

Because nobody else made a waterjet that was precise, easy to use, fast to setup and program. Traditional waterjets have been used for applications such as cutting diapers, but nobody made a machine tool for the machine tool market. The abrasivejets that were available for machine tool work were very low tolerance, and built from a variety of custom configurations. OMAX brought precision, ease of use, and a standard product line to the market.

Materials

Are there special considerations for making glass parts?

Yes. Dual pressure piercing allows for piercing of glass with minimal risk of cracking. OMAX JetMachining Centers come standard with dual pressure capabilities. OMAX Machines also have a special "brittle mode" that works in conjunction with low-pressure piercing to slowly raise the pump pressure during the pierce to avoid a sudden shock to the material by a rapid change in pressure. Using these techniques reduces the risk of cracking, making glass cutting into a very profitable venture.

What is the thickest material the OMAX JetMachining Center can cut?

There is a practical limit, and a physical limit. (The Grand Canyon was essentially created with a natural abrasivejet.) The practical limit for most materials and conditions is about four inches thick. Thicker than that, and tolerances drop while machining times increase. For some projects, however, OMAX users have found it practical to machine material eight or more inches thick. Cutting titanium is one such application where OMAX customers report great profits at these high thicknesses.

The physical limit is the maximum Z-axis travel, which is typically around 8 inches (20 cm) for most OMAX machines. The actual Z-axis travel will vary depending on options installed. Note that it is possible to cut parts that are thicker or taller than the maximum Z-axis travel by removing the slats and submerging the part in the catcher tank.

How is the material fixtured?

There are many methods of fixturing the material down. The simplest is to place a plate of material on the machine, and anchor it with weights. Handi-grips are also used to secure the plate in the X and Y directions. More advanced fixturing can be employed if needed for specialty applications or secondary machining.

Pumps

What size pump would be best?

This depends on the kind of work you want to do. If working in very thick metal, get a pump that is capable of putting a lot of horsepower to the nozzle. Although a smaller pump can machine thick metal, a larger pump will be faster, and therefore more practical. If cutting mostly thin metal, or doing water-only cutting, get a smaller pump. Smaller pumps are often cheaper, cost less to run, are easier to maintain, more reliable, and are quieter. Bigger pumps, however, allow faster cutting.

Note: It is very important to understand that it is horsepower at the nozzle that is important, not the size of the motor turning the pump. This is important because many pumps have big motors driving inefficient pumps, while other pumps have smaller motors running efficient pumps.

For example, a 50 hp (37 kW) intensifier pump will typically only put 30 hp (22 kW) to the nozzle, while a 30 hp (22 kW) crankshaft pump will put 28 hp (21 kW) to the nozzle. Examine the price and maintenance differences between the two types of pumps, and the lower horsepower pump quickly starts to look like the better choice:

Comparison with English units 50 hp intensifier = 30hp at nozzle = 20 hp lost to inefficiencies
30 hp crankshaft pump = 28 hp at nozzle = only 2 hp lost

Comparison with Metric units
37 kW intensifier = 22 kW at nozzle = 15 kW lost to inefficiencies
22 kW crankshaft pump = 21 kW at nozzle = only 1 kW lost

The amount of electricity lost as efficiencies can have a significant effect on operating cost. For example, if electricity costs $0.10 per KWH, and you are wasting 15 KWH per hour, then you are losing $1.50 per hour to heat. In addition, because Intensifiers require additional cooling water, you are losing even more in the cost of cooling water.

What is the difference between an intensifier and a crankshaft pump, and why did the inventor of the modern style Intensifier decide that direct drive pumps are better?

The two share the same basic pumping principal: a plunger is pushed into a closed chamber to raise pressure and expel fluid through an outlet check valve; as the direction of the plunger is reversed, low pressure fluid enters the chamber through an inlet check valve. The difference between them is only how the plunger is moved. The crank or direct drive pump uses a crank similar to the one in an automobile engine. The intensifier drives the plunger with a hydraulic cylinder usually with oil.

The intensifier pump is not as efficient and is more costly to operate than the direct drive pump. It has pressure ripples and is noisy, but it does have a longer seal life and is more suited to 24-hour operations using multiple independent nozzles. The crank drive pump is quieter, uses less water and power and is more straightforward to maintain. It is the better option for environments where operating costs and profitability are important.

What other differences does a different size pump make?

The more horsepower that makes it to the nozzle, the faster you can cut. The trade-off with a higher horsepower pump is cost, efficiency, a larger kerf width, and sometimes a slight loss in precision. However, a high horsepower pump can almost always be run at lower pressures to reduce the operating cost and maintenance, and then run at higher pressures for special jobs that would otherwise try your patience.

Systems

Why are OMAX machines so much faster than others on the market, while at the same time being so much more precise?

There are four main factors that contribute to the exceptional speed and precision of OMAX JetMachining Centers:

1. Superior software
OMAX incorporates an advanced cutting model into the controller which automatically creates the optimal cutting path. It varies speeds and accelerations so that no time is wasted going more slowly than necessary. In addition, the OMAX controller automatically takes advantages of many speed-up tricks that would be too difficult and cumbersome for a human to program. For example:

The OMAX controller automatically adds corner passing on corners that will allow for it. This can result in speed increases from 5 to 25%, depending on the geometry of the part. This process is automatic, and does not require additional work or knowledge from the operator.

The OMAX controller automatically adjusts the speeds and accelerations around curves and corners to optimize the tool path for speed, precision, and square corners. This makes it very fast and easy to program the machine, and allows the parts to be machined as quickly as possible while still maintaining the highest tolerances.

The OMAX controller selects the optimal pierce speed, and length, based on an advanced piercing model. This greatly speeds up the otherwise slow process of piercing the material, automatically and optimally.

There are also tools such as the "optimal stack height calculator", which can be used to greatly speed up some categories of parts.

2. Superior X,Y positioning system

All OMAX JetMachining Centers are designed for high precision machining. A combination of precision mechanics, rigid construction, and precision velocity control from the software insures the highest degree of precision in the machined parts, even in shops where vibrations from other tools such as punch presses or fork-lifts driving by may exist.

3. Superior direct drive pump technology

OMAX pumps are highly efficient, so 33% more horsepower makes it to the nozzle than in the competing intensifier pump designs. This means that for the same horsepower rating, the OMAX system's pump will cut much faster, and at a significantly lower cost.

4. Superior nozzle technology

OMAX MAXJET® and MiniJet nozzles are designed for maximum precision, life, and cutting speed.

How hard is it to learn how to operate the OMAX?

After about one day of training, you can make simple parts. Three days of training are provided for extra proficiency (see Training). Optional follow-up training is available and recommended after a few months of use, to increase skills and productivity.

Can secondary machining operations on an existing part be done?

Yes. There are many ways in which this can be done. Here are some of the more popular methods:

The optional OMAX Precision Optical Locator (POL) makes secondary machining on existing parts easy.

You can also do secondary operations on existing parts by cutting a "square" from a plate of steel, then sliding the parts into the corner of the square, which provides a known reference point.

The OMAX Controller also allows up to 100 user-specified home locations, which provides multiple tooling locations on a single machine.

Why aren't cuts made at even higher pressures?

While it is technically possible to make equipment that can achieve pressures beyond 100,000 psi, there are fatigue limits to consider. This limits the practical range of pressures to be below 60,000 psi (414,000 kPa). Anything higher, and reliability drops very fast. For this reason, OMAX pumps all operate at below 60,000 psi (414,000 kPa).

What does it take to maintain an OMAX JetMachining Center?

When operating at high pressures, there is typically more maintenance required than for most traditional machine tools. However, the maintenance is relatively easy to do. Anyone with a basic mechanical aptitude should be able to properly maintain the machine.

What does it cost to run an OMAX JetMachining Center?

There are two models of pumps available, and cost depends on the model you choose.

Why are cuts made under water, and can I cut above water if I like?

Cutting under water is typically used to reduce the noise and splash and to eliminate airborne dust. However cuts can be made above water if desired, with no loss in performance.

What are the limiting factors in getting a precision part?

Typically as the thickness of the part increases, the ease of obtaining precision decreases.

Nozzles

What is the smallest kerf width that can be cut and how small can a part be made?

With the OMAX Mini-Jet nozzle, the kerf width is 0.020" (0.5 mm) wide, which is 0.010" (0.25 mm) smaller than a standard OMAX MAXJET nozzle. For even smaller cuts, the 7/15 MAXJET5 nozzle has a kerf width of only 0.015” (0.38 mm). You can make parts as small as you like, but exceptionally small parts may require special fixturing to prevent them from falling into the tank. OMAX offers several methods for fixturing such small pieces. OMAX "waterjet brick" is especially popular for detailed work.

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