By Richard Ward, March 2008

Waterjet Cutting Tips

Although I knew nothing about waterjet cutting 16 years ago, I believed it had a great future, and would one day be a sought-after production tool by many industries.  Today waterjet cutting has passed even the most optimistic predictions, with what appears to be an unlimited future.

The capabilities and applications of waterjet cutting systems have done a quantum leap and they are easier to operate, program and service.  Initially they were viewed with skepticism; just the thought of trying to cut a piece of stainless with water seemed ridiculous.  This technology is now seen as a precision machining tool, and has opened up innovative ways of addressing old and new challenges.

As advanced as waterjet technology becomes, there are still certain aspects that have to be understood.  Who would ever think a blockage causing a shut down of a $200,000 piece of equipment was caused by a bead of sweat that dropped into the abrasive as it was being loaded into the hopper?  We must pay attention to the details.

Here are some of the helpful tips one should know when looking to own and operate a waterjet system: 

The most important decision

·         People are everything.  Get the right person to oversee and to run the machine.  It is often better to have the right characteristics in the individual, than previous experience.

·         Look for reliability, a willingness to learn and retain the new knowledge, and someone who is interested – ideally fascinated with waterjet.  When everything is running great, anyone can be in charge.  But when something stops working, you suddenly need a depth of knowledge and understanding.

·         Find someone who is inquisitive. 

·         Get as much training as you can lay your hands on.  Every minute will pay for itself hundreds of times.

Safety

·         Very few safety issues are a must with waterjet and recorded injuries with CNC waterjet cutting are rare, but the consequences are devastating.  If your staff are not prepared to follow the rules, don’t get a waterjet.

·         Most important is eye protection.  You will never be able to blink in time. 

·         Ear protection could be important if sound levels are above the acceptable limit.

·         Observe all electrical and safety rules

·         Remember you are working with high pressure.  Keep a medical explanation for the attending physician in your wallet, and have it attached to the machine in case of an emergency.  The manufacturer of your equipment should provide this for you.

Is waterjet the right process?

·         Make sure you look at other processes, specifically laser, oxy-fuel and plasma.  Many times a perception after watching a TV show where waterjet is used is that waterjet is better than other processes for the application.  This may not always be the case.  We can all be sure the guys on TV are being compensated in some way for using whatever tool is being promoted, or should we say used.

·         Look at other methods such as stamping and punching. 

·         Compare prices of different processes and do a time and motion study.

·         Calculate the return on investment of the different processes.

·         Look at the opportunities waterjet offer that other processes don’t.  Remember, waterjet may not necessarily the best solution to a specific application, but it can do the work of a handful of other processes.  So where you may end up compromising on cut speed for say 1/8” steel when compared to a laser, you could cut the other 40 materials that go into the product with the one waterjet system.  So the overall result could be waterjet is the best solution.

·         Check cutting speeds, edge quality, tolerances, side effects such as a heat affected zone and the affect of getting the parts wet.

·         Waterjet cuts most aerospace materials and composites, nearly every alloy and steel, the entire range of stones, glass, laminated materials, plastics, wood, leather, foams, rubber, cloth, most food products frozen or not, and the list goes on. 

·         If your company thinks outside the box, makes or modifies anything, waterjet could be the most valuable and versatile tool your facility could own.

Get the right machine and options

·         Waterjets come in a wide range of sizes, with an exhaustive and growing list of options to tackle virtually any application.  Get a clear understanding of what options are available.

·         Check all options can be added at a later stage with ease.

·         Can options be installed without the manufacturer having to visit your facility with the accompanying hidden charge?

·         The largest obstacle you will face will be ‘up time’ in cutting.  Regardless of the color of the machine you own, when you are not cutting, you are not making money.  Make sure the manufacturer has thought about this and can show you how you can limit downtime with the way their machines are designed.

·         Get the right cutting envelope.  Look at permutations of different sizes of your raw material.

·         Check the sizes of your finished parts, and optimize the yield, which may render the need for a larger or smaller cutting envelope.

·         Presume you are going to grow, and want to add another cutting head, or 2 or 3 or 4.  A great thing about waterjet is you can double your production by adding a second head.  You still have one table, one operator, one program and the same space on the floor.  It may be necessary to increase your pump size along with adding more heads, but this may not be necessary depending on the original configuration of the system.  So good planning on the initial system, can make a world of difference later.

·         Some machines are built in such a way that one has to climb onto the table to load or unload the parts.  If a table like this is selected, make sure precautions are made to protect the person from falling or slipping.  It is possible to purchase machines where it is virtually unnecessary to ever climb onto the table.  You may want to consider this at the time of purchasing.

·         Check the limitations that will occur should you want to add a second cutting head to your table.  Will it reduce your cutting envelope?  What restrictions will you be limited by.  There are machines specifically built to address this point, with space to park the second head outside the standard cutting envelope.

·         Check if additional cutting heads can only be added onto a spreader bar, or if they can be mounted onto the same set of linear bearings and rails as the master cutting head.  This will make a huge difference to your productivity.

·         Think about where you could improve your own production and efficiency and make up a wish list of things you would like to do with a waterjet.  The following is already available:

o        taper cutting over 45 degrees for weld preps

o        remote monitoring of all aspects of the system from your cell phone

o        bar code recognition of part numbers that automatically load the programs in the machines

o        or how about tapping the holes after they have been cut with a waterjet – all with the same machine, in the same program, without moving the sheet of material off the table

o        etching part numbers and grain orientation onto the part prior to cutting

o        drying the parts after cutting, then applying adhesive beads (while still on the waterjet table), eliminating some stages in production

o        part calibration and measurement with built-in high focus cameras connected back to QC software

o        using your entire cutting envelope as a simple digitizer

o        and so the list is as long as your imagination – limited by the manufacturers ability to build the system to accommodate this kind of ‘out of the box – not just a waterjet’ thinking

Check your market

·         If you are looking at starting a waterjet job shop, you do need to take into account several other aspects as your survival will depend on the amount of cutting done on the machine.  If you don’t hear the ‘hissing sound, you are not making any money!’

·         Identify your competition, what machines they have, what their capabilities are, and how easy it is for them to expand.

·         Do a market research and target 1000 companies who are in businesses that are known to use waterjet services.  Contact them, quantify the need and potential work you could pick up offering them a service.  Remember, most large customers will go and buy a machine on their own, so don’t become too reliant on a few larger customers.

·         Plan how you intend to educate and service your customers – mailer, many open house events, internet, face to face visitation, sample parts, articles, local newspapers, advertising etc.

Installation

·         Install your machine in the right position in your building.

·         Presume you are going to grow, and will want to cut larger sheets than anticipated, larger parts, will add more cutting heads and ultimately, add more machines.

·         Some machines allow unlimited length sheets to be fed through the waterjet – take this into account when you position the machine on the floor.

·         Make sure you have enough power or can get more power.  It can be costly to increase the power later.

·         Get a full layout of the installation of the waterjet in your building.  Use this to plan into the future.  Many waterjet companies now have multiple machines.  Plan for the same success.

Do and don’ts of cutting

·         Waterjet cutting still relies on the same basic principles that were identified 20 years ago.  Make sure you are able to apply these consistently, no matter how advanced your system is.  A few basic principles to follow are:

o        Make sure you have dry compressed air

o        Keep all abrasive dry

o        Never allow moisture to mix with the abrasive outside the cutting head – not even a bead of sweat when loading the abrasive into the hopper

o        Keep all contaminates – such as a piece of paper ¼”  x ¼” out of the abrasive and only cut bags open with a knife.  Never tear them open.

o        Maintain the nozzle height approximately 1/16” above the part.  Height sensors can make this an easy task.

o        Check the speed of the Z-travel.  Make sure you can easily override this to limit breaking of nozzles.

o        Check anti-backflow devices are in place on the abrasive delivery system that inhibit water backing up into the mini hopper.  A simple but vital lifesaver.

o        Have a tub handy to put under the cutting head when working on a part.  It is easier to catch the parts in a tub then fish for them out of the tank.

o        Make sure all repair work is done in a clean environment.  Have the right materials on hand at all times to ensure this.

o        Check the pump regularly, and have the operator walk around the machine say once an hour just to look and see.  There is certainly no harm in doing this.

o        Keep the machine clean.  Waterjets can get dirty fast.  By keeping it clean, the pride in the machine will overflow into work ethics.

o        Keep the water level lapping the underside of the part you are cutting, or if possible cut under water.  This will keep air out of the process and cutting will be silent.  This is not easy to do if you don’t have a height sensor as you will risk breaking cutting nozzles.

o        Always clamp your work down to the table.  Many waterjets do not have an easy way of clamping the parts down, so identify how you will accomplish this.

Now the cutting is finished

·         Removing the material from the cutting table can be as important as how you put it on.

·         Have the right tools to lift the materials off your table.  This could range from straps, chains, vacuum lifters and of course by hand with the proper gloves.

·         Don’t stack wet parts on top of each other, especially aluminum.  Always dry the parts as soon as they are off the table, and a host of issues will simply not appear and Murphy will be kept at bay just a little longer!

Costing and efficiency

·         Institute easy ways to track production.

·         Make people accountable with ways to measure and reward progress.

·         Provide the correct clothing for the operator who will get wet occasionally.  Make sure he or she is comfortable.  This will affect the costs at the end of the day.

·         Constantly try to find new ways to improve production and controls. 

·         Try to maximize cutting time and limit dead time. 

·         Some systems are built to allow parts to be loaded and clamped down on one part of the table while cutting is maintained on another part.  Check if you can do this and how you might be able to configure your machine to allow such an opportunity.  Check too on safety limits etc that can be set to ensure safety for the operator.

·         Monitor as much as is practical.  Some new controllers allow tracking of the life of parts, along with use of consumables.  This facilitates the ability to evaluate cost per part etc that should be relayed back to the quoting department, or person.

Waterjet cutting has to be one of the most mesmerizing processes out there.  Having worked as an operator for my first 3 years, I know.  And yet 15 years later, I am still fascinated by the technology, the advances and the capabilities of what water can do.

If you were to visit me, don’t be surprised if you found me off in my own little world, gazing at a part being cut on a waterjet system as I watch in awe how this stream of water, under the control of software and hardware, is eroding its way through a 2” part of Titanium, reminding me of a sparkler on the 4^th of July.

Richard Ward is the founder and president of WARDJet, Inc., a manufacturer of waterjet cutting machines; www.wardjet.com;  330-677-9100; Tallmadge, Ohio.