This article is designed to help reduce the learning curve for first-time water jet users. First we must make some assumptions (yes, we know what happens when you assume, but we feel we're on solid ground here) to create this guide.
Pretty straight-stick stuff, right? Now it's time to start.
Water jets are industrial cutting tools operating at high voltage and are capable of inflicting severe injuries in the blink of an eye. Ensure you know how to use your water jet system safely as outlined in the owner’s manual and your company’s safety policies. Here are a few extracts from our upcoming blog on system safety:
Here are some important tips and best practices to getting started.
Best operating practices recommend using an orderly start-up process every time you prepare your system. Creating a check list to work from creates consistency between operators and ensures you will not miss any steps. The brand and/or manufacturer of the system you are using may require different or additional steps so adjust these as needed. A helpful checklist should include:
Note: Your operating manual will have a start-up routine that should be followed. Observe the routine and report any unusual or unexpected results before proceeding.
Important: Keep in mind that the time your start-up takes will grow shorter with experience. Be patient, learn the process and the idiosyncrasies of your setup and, above all, never skip steps.
Setting up your water jet cutting system for its first cut involves these steps:
Usually, the part design that creates the part geometry is done via CAD (computer aided design) software run on a separate IT platform. The CAD files are converted to machine code via a CAM (computer aided manufacturing) process and an .NC part file is created. The resulting .NC part file works with the water jet’s control software to position the cutting tool, regulate the cutting tool height, define feed rates, activate the required pump pressure, and begin the garnet delivery system. The part file may be delivered to the water jet’s controller over the shop’s network or downloaded onto a flash drive and plugged in. Either way, navigate to the proper file and load it into the machine controls. Manual programming or program modifications can be made at the controller unless the operator is locked out and prevented from making changes per process control guidelines.
Ask the engineers to provide a paper copy of the part design that details the raw material being cut, the part number, the part dimensions, and program name. Ideally, set up instructions are included, standard run times estimated and key features details like finish quality are highlighted. The following affects the quality of the finished cut, cutting speed, and the cost of abrasive usage:
The material being cut must be placed in the cutting envelope defined by the table size of the system and there must be adequate distance from the table sides so no damage is done to the catcher tank. For ease of positioning, the front side closest to the controller is often the preferred placement. The material orientation may not be critical as long as the piece being cut is fully within the blank size.
The water jet cutting operates at high pressure and may cause the material to move if not secured with fixtures or clamps. Large heavy materials may not need to be secured. Smaller, lighter materials may need to be secured so they do not move during cutting or bounce into the catcher tank when the cut is complete. For high precision cutting, fixtures are often designed and integrated into the catcher tank for quick setup and higher process control. When cutting very small parts or parts that may be prone to sagging, water jet bricks may be used.
Best practice: Ensure your part hold down method is defined and does not interfere with the cutting path.
Tool movement is accomplished using servomotors, ball screws, ball nuts, and linear bearings in the cross beam, side beams, and z-axis assembly. The cross beam, side beams, and z-axis assembly are assembled together to produce the three planes of movement (x-, y-, and z-axes) of the mid rail 3-axis motion control system. The length of the cross beam and side beams determines the work envelope in which a tool can operate.
The operator needs to establish the X and Y plane “Home” (x=0; y=0) as the cut's starting point, most commonly set at the lower left corner of the stock. To establish home, lower the cutting head to .25" - .5" above the stock surface and jog to the point in which the program is intended to begin. Lower the cutting head to 1/8" from each edge for the fine adjustment of the starting point. Set that current position as home.
A home also needs to be established for the Z-plane (Z=0). To establish home for the nozzle height, utilize a gauge between the stock surface and nozzle tip to ensure the desired standoff distance is achieved. Slide the gauge back and forth under the nozzle while slowly lowering it. You want a snug fit but no resistance to the gauge moving. In other words, you want to feel when the gauge touches the nozzle without impediment. Set that height as the home value.
Best practice: The cut’s starting point is referred to as the lead-in. Beginning the cut in the scrap area of material and "leading-in" to the actual geometry to cut is standard operating procedure in most applications. This avoids placing a blemish from the initial cut. At the end of a cut, a lead-out may be required to remove any "nib" from the lead-in area. Various types of lead-ins and lead-outs can be experimented with for different materials and thicknesses.
The dry run feature executes the part program axis movement with the cutting heads turned off. The dry run is typically set to run the program as fast as practical. The dry run feature helps validate the program path and will ensure there is no interference from clamps or uneven parts. Raise the cutting head 2" and select the "dry run at full rapid traverse speed" command. Return the head to its correct cutting height following a successful test. Surface detection options like laser mapping or using a height sensor further assists in managing the cutting of non-flat materials. Parameters including feed rates and dwell times can be changed or adjusted based on the results of the dry run.
Select the program, set the controls to computer control (not manual), ensure the pump is on and delivering the required pressure, the abrasive flow is metered appropriately and then hit run. Note that while running a part program, situations can occur that require you to stop the part program to address a problem. When an issue is detected use the stop cycle switch on the control panel to end the program and then address the issue. In the event of an emergency use the emergency stop to immediately shut down the motion system. The following are some of the reasons for suspending a part program:
At the end of the cycle, retrieve your part and rinse it with clear water to remove any garnet residue. Congratulations, you've completed your first cut.
When the cutting has been completed and the motion system has returned to its safe, end point position, it is safe to remove the part. Remove any clamps, wash the part with clean water, inspect the finish quality and part geometry to confirm the first article.
Obviously, this is just a generic high-level overview of water jet cutting with each system having its own unique operating procedures. However, this guide does cover the basics of cutting your first 2D part. It is essential to train your operators in safety and operation before attempting to operate your system. Create and follow a structured start-up/shut-down process each time and always make sure to secure your stock properly. Do these things, and you're well on your way to becoming a master of water jet cutting systems.
Every Jet Edge water jet system includes unlimited lifetime hands-on training. Water jet training is free when taken at Jet Edge’s headquarters. You also can arrange to have training at your facility for a fee. Register for classes online or call 1-800-JET-EDGE to schedule custom training sessions for your business
If you do not have a copy of your Jet Edge Owner’s Manual that outlines the safety protocol and operating procedures, please request one right away from our technical support page. If you would prefer to speak with our Technical Service Team regarding a specific issue please contact a team member.
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