CNC Water Jet Cutting Machines: Safety Operation Guidelines | MachineMFG

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CNC Water Jet Cutting Machines: Safety Operation Guidelines


Safety Operation Guidelines

Safety Precautions

  • Non-staff members are prohibited from entering the water cutting operation room.
  • It is strictly prohibited to extend any part of the body into the high-pressure water spray area.
  • During work, operators must wear protective goggles and work clothes.
  • It is strictly prohibited to disassemble the fastening hydraulic system under pressure or connect the threaded connection of the high-pressure pipeline under pressure.
  • During the operation, prevent collisions between the body and the high-pressure water pipeline.
  • When the machine is running, no one is allowed to stand on either side of the ultra-high pressure generator.
  • In case of pipeline leakage, first cut off the power supply and then deal with the leaking part to prevent electric shock.

I. Startup Preparation

Check whether the oil tank is short of oil, add oil to the upper limit of the oil level gauge in the oil tank, and tighten the oil tank cap. Loosen the oil pipe at the return port of the plunger pump and pour oil into the plunger pump until it is full, then tighten the return oil pipe.

Turn on the power of the air pump and turn on the air gun switch when the pressure at the outlet of the air pump is ≥0.4 MPa. Air spraying out indicates that the gas supply is normal.

Start the power supply of the water supply pressurization pump, observe the water pressure indicator ≥0.2 MPa, and water flows out at the joint of the cutter head and the connecting rod, indicating that the cutting water supply is normal.

II. Debugging of Hydraulic System

Turn on the electrical main switch on the side of the high-pressure generator, the power switch of the industrial computer, and after the industrial computer enters the WINDOWS startup interface, click the waterjet cutting software to enter the software control interface.

Momentarily press the “Oil Pump Switch” button to check that the motor rotates in the same direction as the arrow on the oil pump body.

Start the oil pump motor and adjust the control pressure of the relief valve to a low value.

Open the double one-way throttle valve at both ends of the electric-hydraulic reversing valve, adjust the magnetic switch to the appropriate position, and the booster is in idle running state. Run for 5-10 minutes, observe that there is no abnormality in oil temperature and pump head temperature, and turn off the oil pump by pressing the “Oil Pump Switch” button to complete the debugging of the hydraulic system.

III. Debugging of High-Pressure Generator System

Install the energy converter (gem), press the “Oil Pump Switch” button to turn on the oil pump, press the “Air Valve Switch” to turn on the high-pressure water switch of the cutting head, and press the “High Pressure Switch” to start the high-pressure generator. The cutting head will spray high-pressure water.

Note: When operating in manual interface mode, first turn on the air valve switch, then turn on the high-pressure switch, otherwise it may cause dangerous pressure buildup in the system. When shutting down, turn off the high-pressure switch first, and then the air valve switch.

Adjust the relief valve knob to gradually increase the pressure in sections. Keep it at 1-2 minutes for every 1MPa increase. During the adjustment, pay attention to check for any oil or high-pressure water leakage, abnormal vibration, and noise. Stop adjusting when the pressure gauge pointer is at 15 MPa and the swing range is ≤3 MPa.

Adjustment of electric-hydraulic reversing valve: Check whether there is any impact sound in the hydraulic cylinder. If so, determine which side it is on and adjust the double one-way throttling valve on that side clockwise until the impact sound disappears.

Repeat turning on and off the high-pressure water switch. If the high-pressure water switch is sensitive, the debugging of the high-pressure generator system is completed.

III. Cutting Operation

Hoist the steel plate onto the cutting platform and adjust the bottom and side of the steel plate to be parallel to the X and Y axes of the platform, respectively.

Load cutting sand into the sand bucket and connect the sand pipe.

Copy the DXF graphic file into the computer.

Load the graphic file to be cut in the cutting interface.

Move the cutting head to the origin of the graphic file setting, adjust the distance between the cutting head and the steel plate height, set the current coordinates to “0,0,0” in the “Manual” interface, and set the “Cutting Speed” and “Relay Delay” in the “Parameter Settings” interface.

In the “Auto” interface, press the “Start from Beginning” button to start cutting.

IV. Precautions and Treatment for Abnormal Situations during Cutting Process

Pay close attention to the distance between the cutting head and the plate during the cutting process. The best cutting height of the cutting head from the workpiece is 3mm-5mm. It is strictly forbidden to run without supervision, which may cause the sand pipe to break, serious damage to the cutting head and the machine’s walking mechanism.

If sand breaks during the cutting process, immediately press the “ESC” key to stop the machine, and handle the sand valve and sand delivery pipe. Re-cut any uncut part. The method is to press “Begin Any Section” in the “Auto” interface, enter the program section number, and press “OK” to start cutting from a previous program section.

Before replacing the workpiece after cutting one workpiece, move the cutting head to the far end to prevent the cutting head from being damaged during loading.

The oil temperature during cutting should be controlled below 65°C. Immediate cooling measures should be taken if the oil temperature exceeds this value.

If one of the following situations occurs, stop the machine immediately for maintenance:

  • The high pressure is running normally, but there is no high-pressure water spraying out from the cutting head.
  • The high-pressure water intermittently comes out of the cutting head, and the pressure gauge swings between 0-15 MPa.
  • Cracks, twists, deformations, and medium leakage occur in high-pressure parts and pipelines.

V. Shutdown

After all the work is completed, exit the system, shut down the computer in the WINDOWS interface, then turn off the electrical main switch on the side of the high-pressure generator, and finally turn off the power supply of the cutting water pressurization pump and the air pump power supply.

Waterjet Cutting Machine Process Parameters

1. Relationship between Cutting Plate Thickness and Cutting Speed

Cutting Speed
Cutting Pressure
Steel Plate

Stainless Steel Plate       


(The pointer shakes, according to the center value)
Note: The lower the cutting speed, the better the quality of the cut.
Cutting Speed
Cutting Pressure
Aluminum Plate 2

(The pointer shakes, according to the center value)
Note: The lower the cutting speed, the better the quality of the cut.

The following image shows a cutting cross-section, which guarantees a normal cutting effect of 3 roughness and cannot be lower than this.

2. Inspection Points and Normal Values when the Machine is Operating Normally.

Oil Temperature: ≦ 65℃

Secondary Pressurized Pump Outlet Water Pressure: 6~8 kgf/cm2

2. Normal Service Life of Machine Consumables

Jewel Service Life: 50~80 hours

Sand Pipe Service Life: 200 hours

Common Faults and Maintenance of CNC High Pressure Waterjet Cutting Machine

Serial numberFault phenomenonCause of occurrenceElimination methods
1Oil pump noise1) Blocked suction oil filterClean or replace the oil filter core with a new one
2) The viscosity of the oil is too highUse lubricating oil with specified grades according to seasons
3) The fuel tank is not breathableClean the oil tank air filter element
4) Low fuel tank levelFill to the upper limit of the liquid level gauge
2There is foam in the oil1) Oil suction pipe leakingEliminate air leakage or replace with a new pipe
2) Oil pump shaft seal leakageReplace the sealing ring
3Excessive heating of the oil pump1) Oil pump worn or damagedRepair or update
2) The viscosity of the oil is too low, too high, or deterioratedReplace with new oil
4Overflow valve whistlingDamaged spring or valve core or blocked damping holeReplace damaged parts or clean them
5Oil temperature too highExcessive overflow rate of the overflow valveReduce overflow to match high pressure
6Hydraulic system without pressure1) There is air in the pump head of the oil pump, and the oil has not come outRemove the oil return pipe for inspection and fill the pump head with oil
2) The solenoid overflow valve core is stuck or has no signalClean the overflow valve or restore the electrical signal
7No high-pressure water spraying from the blade1) Hydraulic system has no pressure outputReference hydraulic system without pressure treatment
2) Cutting water not suppliedCheck the water supply pump and booster pump
3) High pressure filter cloggedClean the filter screen
4) Blade gemstone blocked or water switch not turned onCheck the above components
8Booster does not change direction1) Blade gemstone blocked or water switch not turned onCheck the above components
2) The valve core of the electro-hydraulic directional valve is stuckClean the valve core
3) Electrohydraulic directional valve not receiving signalEliminate faults and ensure that the electro-hydraulic directional valve receives a signal
9When reversing, the pressure gauge needle swings excessivelyIf one side returns to zero 
1) Check for leakage (overheating) of the one-way valveReplace the high-pressure valve core and spring
2) Check the plug assemblyCheck if the low-pressure valve core is loose
3) Damaged high-pressure sealing rubber ringReplace the high-pressure sealing ring
4) Damaged sealing ring of hydraulic cylinder pistonReplace
If both sides return to zero 
1) Is there no energy converter installed (gemstone)Install
2) Check the high-pressure pipeline for leaksEliminate leakage
3) Insufficient or leaking hydraulic pressureTroubleshooting
10There is a knocking sound from the left and right turbochargers at different reversing speedsThe dual one-way throttle valve is not adjusted properlyAdjusting the dual one-way throttle valve
11The pressure gauge indicates that the pressure cannot be relieved1) Blocked energy converterreplace
2) High pressure water switch not turned onTurn on the high-pressure water switch
3) Relief valve solenoid has no signal or is stuckCheck the signal circuit and overflow valve
12Water leakage at the interface between the high-pressure cylinder end cover and the high-pressure cylinderHigh pressure cylinder end cover or high pressure cylinder damagedReplace the high-pressure cylinders at both ends,
13Water leakage from the observation hole of the cylinder end coverHigh pressure ring damageReplace
14Water and oil leakage from the small hole of the cylinder end coverDamaged piston rodReplace the Y-shaped sealing ring of the piston rod and D3
15Water leakage from the observation hole of the water switch valve bodyDamaged sealing ring or pressure ringReplace the sealing ring or pressure ring

Note: Water or oil leakage in droplets can be temporarily ignored, but continuous water or oil leakage in a line must be stopped for maintenance.

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