Romeo
Engineering, Inc.
Waterjet
FAQs
Why buy from Romeo Engineering Inc?
Our engineers
have been designing and manufacturing waterjets for a quarter of a century. Our
machinery has a reputation for being rock solid, easy to use and performing well
for a very long time. The equipment is fabricated at our multiple factories
located in Fort Worth, Texas USA. We have a full engineering staff complete with
degreed & licensed professional engineers, mechanical engineers, electrical
engineers, and nano-particle engineers. Need something different? We build much
more than X-Y tables. We offer a broader product line of waterjets and factory
automation than any other manufacturer in the world.
1. All machines are
precision ground on the world's largest grinding machinery. It starts with an
all-steel construction that is stress relieved and precision ground flat,
straight, and perpendicular in one setup. Our stress relief process has been
proven through independent research to be equal or actually better than thermal
stress relief. Lesser quality machines may have milled ways which is not as
flat, resulting in nozzle movement. Further, many competitve brands are machined
in multiple setups because their machine tools are too small to make large
machines in one setup. Or, even worse, they may use aluminum extrusion or not
even be machined at all. All REI machines are gantry style. They are built to
stand on their own without relying on the customer's floor.
2. Vendors
often publish static positioning accuracy, which is not as good of a machine's
true accuracy becuase machines are expected to move. A better measure of machine
accuracy is dynamic accuracy. Less quality machines, such as cantilever design
or those anchored to the floor, will be cheaper to build but cannot hold dynamic
accuracy at the same acceleration. Most of our models are ball screw driven with
2 pre-loaded nuts for maximum life. Less quality machines will use a single nut
with oversize balls or phased tracks, both of which wear prematurely. Even
worse, less quality machines will use rack & pinion which have severe
backlash problems.
3. Our control system is designed and built by REI
from the ground up. Being Microsoft Windows based, hardware and software
upgrades are easy. As part of the base model, all of our controllers include air
conditioners, pendants, and other necessary items that others consider to be
"optional."
4. On the high pressure system, we only use hydraulic-type
waterjet pumps. We do not sell or recommend crank pumps (aka direct drive pumps)
for several reasons. Our abrasive delivery system (patents pending) is digitally
controlled and has excellent feed performance. Our machines are available in
2,3, and 5 axis and are available with multi-head dynamic centerline as an
option.
Why run at 60,000 psi and not higher or lower?
Below
45,000 psi, a waterjet will not cut metal or other hard materials very well. The
industry standard is 60,000 psi operating pressure. Pumps are available that are
capable of reaching much higher pressure. So why not run at higher pressure?
First is safety. The materials and design of 60 KSI components are well
understood and commercially available. A failure in a high pressure system at
that pressure would be catastrophic and expensive to replace high pressure
cylinders. Second is fatigue life. Remember, a waterjet pump must go from a
vacuum to full operating pressure several times per minute. It is impossible to
prevent fatique forever. Faster cyclic loading and higher pressure cause shorter
fatigue life. A KMT brand pump has the longest stroke plunger in the industry
(8-inches), so it typically strokes 50 times per minute. Competitive brands have
shorter stroke (usually 4 or 8 inches), and so their stroke much faster at over
75 to 100+ strokes per minute. Again, faster stroke means shorter life. Third,
pressures higher than 60 KSI causes faster wear on nozzle and other consumable
parts. Finally, the cut quality is not much improved and in some cases is worse
for several reasons. If you have a need for speed in your waterjet, contact
Romeo Engineering Inc for a smarter way.
What makes a good application for a
Waterjet?
Waterjets are ideal for any application that requires
intricate cutting all the way through the material. They are exceptional for
cutting a variety of materials ranging from very hard to very soft. There are
few materials that a waterjet is not able to cut (such as diamond and carbide).
You can think of waterjets as a liquid grinder that continuously erodes the
material. The decision about cutting speed usually concerns the quality of the
cut versus speed. The cut will usually have striation (“rooster tail”) along the
edge where the water/abrasive eroded away the material. Striation is a function
of material, thickness, speed, and nozzle size. Slower cuts usually result in
less striation. Faster cuts usually result in more striation.
Good
Applications:
1. Soft materials like rubber, thin plastic,
or leather
2. Hard materials like steel, tool steel, or
stone
3. Exotic materials like ceramic, composites, and
glass
4. Food products like pizza, cheese cake, and
vegetables
5. Energetic materials like extruded
propellant
6. Gummy materials like elastic and cookie
dough
7. Multiple layers like stacks of sheet metal or
fiberglass
8. Programs that have contoured corners like letters
in signs
9. Multiple nozzles to improve production
volume
10. Nested parts to reduce scrap waste
Why use a Waterjet instead of saws, plasma, laser, EDM, or
milling machines?
Every cutting technology has advantages and
disadvantages. Waterjets are best known for cutting speed and versatility in
cutting a wide variety of materials. They are easily adaptable to automated
material handling. Like every cutting tool, however, there will be costs
associated with tool wear plus the cost of consumable abrasive (if
applicable).
Saws vs.
Waterjets
* Band saws and scroll saws are best for
rough cutting tubular sections
* Unlike waterjets, saws
cannot cut intricate contoured shapes or very hard tool
steels.
* Saws do not allow nested
parts
* Saws cannot cut from the center of a plate.
Plasma vs.
Waterjets
* Plasma offers extremely fast cutting
of steel & aluminum
* Plasma offers low cost & no
consumable media
* Plasma leaves molten slag leaves very
rough edge quality
* Plasma produces a heat affected zone
(HAZ)
* In stainless steel, HAZ is a chromium depletion
zone and will rust if not heat treated.
Laser vs. Waterjets
* Lasers can cut faster
and more accurately on to ˝" thick or less steel
* Lasers
provide a clean cutting process
* Lasers cannot cut 4 - 6
inch thick steel
* Lasers cannot cut shiny surfaces
because the molten slag burns the optics
* Lasers cannot
powder coat laser cut parts without chemical removal of
organics
* Lasers cannot cut some combustibles like
corrugate & foam (toxic isocyanate)
* Lasers introduce
a heat affect zone and degrades material
* Lasers are
expensive to support multiple nozzles
* Lasers costs start
at $350,000 to $900,000. Waterjets cost $100,000 to $180,000.
EDM vs.
Waterjets
* EDM is more accurate than
waterjets.
* Waterjets cut much
faster.
* Waterjets cut a much larger variety of materials
including non-conductive materials.
Milling Machines vs. Waterjets
* Milling
machines can cut a variety of materials with very close
tolerance.
* Milling Machines allows accurate depth of cut
(X,Y,Z)
* Milling Machines are less expensive to operate
(No consumable media)
* Milling Machines are less
expensive to buy than waterjets ($45,000 to $100,000)
*
Milling Machines cannot nest parts as closely (typical cutter is 3/8" - 1"
diameter)
* Must deal with chips
*
Milling Machines require substantial clamping or the rotating tool will move the
part
* Tool contacts the part, so may have tool breakage
and wear
* Must be careful not to distort thin
parts
* Milling Machines are less adaptable to automatic
feeding because of clamping
How do I decide the best Waterjet vendor?
Here are
a few guidelines for choosing a Waterjet System vendor:
1. CNC Chassis
Accuracy
There are many ways to produce high pressure water. But the key
to accuracy is in the CNC chassis. You must ensure that a machine tool's
accuracy is tightly controlled so that the overall desired shape will be
dimensionally accurate. Otherwise, circles will be elliptical and squares will
be trapezoidal to some degree. If the machine tool is not "tight", then edges
will not be straight and there will be poor cut quality. This is especially a
problem with cantilever designs or machines driven from one side only. In
general the finished part accuracy of most materials will be around 0.005". It
is difficult to achieve better due to the nature of high pressure jet mechanics
and inherent 21/2 degree draft angle. Here a few guidelines when selecting the
chassis.
Buy a mid-rail gantry - Romeo Engineering uses electronic
gearing to drive a master motor and a slave motor for smooth accurate motion.
Mid-rail means that the guideways are halfway between the floor and the nozzle.
High rail machines are prone to high frequency vibration and are generally
anchored to the floor. Just .001 inch of amplitude or thermal grown at the floor
can mean .005 or more inaccuracy at the nozzle.
Don't buy a
cantilever chassis - Cantilever designs, high-rail gantries, and single-side
drives are never accurate. Cantilever arms have notoriously poor "chatter"
during rapid acceleration/deceleration. This causes excessive "rooster tail
washout" especially in smaller circles and corners. Cantilevers are less
expensive than gantries because the manufacturer saves costs of the additional
motor, amplifier, rails, etc. But YOU pay the penalty of low accuracy.
Don't get a chassis with rails bolted to the tank - With a dial
indicator, you can see that a tank will swell up to 0.015" as the jet cut.
Bolting to the tank puts precision rails in a bind. All Romeo Engineering
machines have the drive train detached from the tank to prevent distortion.
Ensure the chassis is ballscrew driven - Romeo Engineering
designs include ballscrews which have been certified to be matched sets. Avoid
single nut designs or those that use oversize ball bearings or phased tracks.
Definitely avoid rack & pinion systems are only accurate to around 0.015
inches.
Get closed loop servo motors only - Do not accept open
loop stepper motors. Avoid machines that use servos with so-called "follower
rack & pinion" which are just as worse. Try to determine if the vendor knows
why they use the motor they use. Their are a lot of brushless and brush motors
cog at less than 3 RPM, which is the prime speed for a lot of waterjet cutting.
Our power train runs at the speed of light, whereas other brands are limited to
conventional clock frequency speed.
Ensure that the machine is
mechanically accurate first and foremost - Do not accept a machine that has
been electronic compensated to meet the specification. Electronic compensation
is a software trick used to map out position errors. That accuracy will be short
lived.
Witness the accuracy for yourself and get a written report -
For quality assurance, all Romeo Engineering machines are checked with one
of our high precision laser interferometers capable of measuring sub-micron
accuracy.
Ensure the structure is made of steel - Romeo
Engineering's waterjet chassis are built entirely of heavy structural steel and
not aluminum extrusion.
Ensure all guideways are precision machined
flat and straight - Romeo Engineering uses the world's largest surface
grinder. Our design dictates that the straightness and flatness are permanent
features of the rigid structure. Do not accept machines with shims or
spacers.
2. CNC Controller
Ensure that the controller
is RS-274 complaint - Our controller follows the United States standard for
CNC programming architecture. It is compatible with thousands of CAD/CAM
software packages. On the other hand, many competitive brands use proprietary
code that is not supported by any other format. Be aware if a vendor offers you
free software upgrades for life. That may be true only until the next operating
system is released. Then you are stuck with a proprietary machine or forced to
buy all new hardware.
Ensure the controller is right for you -
There are "traditional or conventional" type controllers and PC based
controllers. Traditional controllers have fast dedicated purpose processors.
However, most traditional controllers are adapted from milling machines and do
not include special software features desired for waterjet cutting. The vast
majority of controllers in the waterjet industry are now PC based because they
tend to cost less and are much easier to upgrade as technology changes.
If the controller is PC based, learn if the controller is a CPU
driven or DSP driven - CPU driven controllers are not stable. The Romeo
Engineering RE2000NT Waterjet Controller is digital signal processor (DSP)
driven using special microchips designed exclusively for servo motion control.
Romeo Engineering designed the RE2000NT Waterjet Controller from the ground up
dedicated for waterjet cutting. It runs on Windows 2000 platform and includes
all sorts of clever software functions exclusively for waterjet cutting.
Know how large a part program the controller can handle - Romeo
Engineering's RE2000NT allows unlimited part program size. Competitive
controllers are sometimes limited to less than 5,000 lines; that is simply not
enough if you want to scan and cut images.
3. Nozzle Design
Get the specifications about life cutting speeds for abrasive nozzles
- KMT Waterjet Systems focusing tubes use a special low binder formula of
carbide for long life and wear resistance. KMT Waterjet Systems focusing tubes
are also a full 3/8" diameter for durability. Some competitive brands have a
small diameter with weak thinner walls, which cause the carbide to fracture
easier.
Get prices up front for technician service and spare parts
- Spares include orifices, focusing tubes, valve packing, pump seals, and
check valves. Be aware that the bid price may not reflect the long term cost of
spare parts.
4. Abrasive Delivery System
Do not accept
vacuum orifice feeders - They tend to surge because light particles are
drawn first, then heavier particles. The result is more striation and wear on
the nozzles.
Do not accept vibratory feeders - They depend on
inconsistent in-coming source electricity voltage and frequency, so they cannot
be calibrated accurately. Romeo Engineering uses a special positive displacement
abrasive feeder design. It even has a display meter to illustrate the pounds per
minute of abrasive delivery. Accurate abrasive delivery is very important
because the consumable cost of abrasive is the highest percentage of operation
cost. Hence, the more accurate abrasive delivery, the less waste and less cost.
5. Service and Training
Determine if the vendor will
be able to support you operation over an extended period.
Does the
vendor have a history of rejected machines?
Does the vendor have used
machines available?
Is emergency service
available?
Do I need a water softener, de-ionizer, or reverse
osmosis?
In many areas of North America, tap water straight
from the municipal supply is fine to supply the intensifier pump. Most areas
however do have relatively "hard water", which means it contains calcium and
magnesium. A water softener is inexpensive and in general will increase the life
and performance of the intensifier pump.
When the amount of TDS (total
dissolved solids) is too high, then you have two options: De-ionization (DI) or
Reverse Osmosis (RO). Do not use a water softener with DI or RO systems. We
generally recommended the de-ionizer over reverse osmosis. The benefit of a DI
filter is that for every gallon of water input, you get one gallon output. For
example, a 25 horsepower intensifier pump requites 0.5 GPM of clean water. That
is equivalent to 720 gallons per 24-hour day. A suitable size reverse osmosis
unit will have about 35% recovery, so you would expect to loose 1,300 gallons
per day down the drain.
The main problem with DI systems is that the
resin beads will become depleted and must be regenerated. The regeneration
process uses powerful chemicals that you do not want stored on site. Therefore,
you typically use an outside company who can regenerate the resin for you.
Copyright ©
2012 Romeo Engineering, Inc. | All rights reserved
Address: 4217 Hahn Blvd, Fort Worth, TX
76117
Phone: (817) 656-0048 Fax: (817)
581-9332
