What should be paid attention to when water jet cutting equipment is used to process fiber plate die?

Cutting and processing fiberboard die with water jet (MDF/plywood commonly used in plastic suction die and carton die) is completely different from laser cutting. Water jet belongs to high-pressure water+abrasive cold cutting. There are many key points that must be paid attention to when using it as a die. I will sort out the matters needing attention in practical operation for you, which can be used directly:

A, plate and knife seam key points for attention

Fiberboard is easy to absorb water, expand and deform.

Water jet is wet cutting, MDF and fiberboard will swell, warp and soften when exposed to water, and the size will change after cutting.

Note: The thicker the die plate (18mm/20mm/25mm), the more obvious the water absorption deformation.

Suggestion: After cutting, it must be fully dried before loading the knife, otherwise the blade will not fit in or become loose.

The slit is wider than the laser, which is not suitable for precision small slit knife die.

The slit of water jet is usually 0.8–1.2 mm, or even wider, while the common slit of knife die is only 0.45, 0.71 and 1.05 mm..

Note: The narrow slit can't be directly cut by ordinary water jet, and it is easy to make the slit too large, which will lead to the blade loosening, knife dropping and glue leakage.

Suitable for: rough die and simple die; Not suitable for high-precision plastic suction knife die.

Trimming verticality is not as good as laser.

Water jet cutting thick plate will have a slight taper (wide at the top and narrow at the bottom).

Knife die requires vertical seam, otherwise the blade will be inclined and uneven after being embedded.

Suggestion: Try to use small light spot, slow feed and reduce swing arm compensation.

Second, the cutting process and equipment parameters.

Abrasive selection

Just use pomegranate sand for cutting fiberboard, and don't use too coarse sand, otherwise the trimming will be rough and slag will fall off.

Coarse sand will make the inner wall of the knife gap rough and it is difficult to install the knife.

Pressure and speed control

Excessive pressure → edge collapse, pilling and delamination of the plate edge.

Too fast → it can't be cut through, and the slit is irregular.

Too slow speed → more serious water absorption and greater deformation.

Experience value: thick fiberboard should be medium and low pressure and slow cutting.

Must add plate, fixed firmly.

Fiberboard is soft and light, and the impact of water jet is large, so it is easy to shift and shake.

Failure to fix can lead to:

Knife gap dislocation

Graphic size deviation

Sharp angle deformation

Suggestion: Use batten+fixture to fix, and the bottom pad should be flat with wooden board or aluminum-plastic board.

Third, the quality of the die and the attention to the subsequent treatment

There will be burrs and fuzz when trimming.

The fiber material will be fuzz after being washed by water, and the inner wall of the knife seam is not smooth.

Before loading the knife, it needs to be polished and trimmed, otherwise the blade will be difficult to knock in.

The problem of water content directly affects the life of the die.

Wet fiberboard:

Easily moldy

Long-term use will shrink and deform.

Blades are easy to rust and loosen.

Treatment: drying → sanding → reloading.

Sharp corners, small circles and thin grooves perform poorly.

The inertia of water jet is large, and small circles and sharp corners are easy to fillet and not sharp.

Many plastic suction knife molds need sharp corner positioning, and water knives are not dominant.

IV. Applicable Scenarios and Non-applicable Scenarios (very critical)

Suitable for water knife.

Simple shape knife die

Large-size, thick-seam cutter die

Special plate that cannot be heated and is afraid of laser burning.

Occasionally machining, not pursuing ultra-high precision.

Not suitable/recommended

Precision plastic suction knife die

0.45/0.71mm standard narrow slit

Multi-cavity, dense fine figure

Mass production of knife dies (low efficiency and large deformation)

Five, safety and environmental protection attention

Water jet is dangerous in high pressure, so it is forbidden to approach the cutting area with your hands.

Fiber+water+abrasive → mud is too much, so drainage and filtration should be done well.

Humidity in the workshop can easily lead to rust of other equipment.

If you want to make a plastic knife mold, my straightforward suggestion is:

Pursuing precision, efficiency and standard of knife gap → choosing laser knife die cutting machine.

Only occasionally cut thick plates, simple die → you can use water knives, but you have to accept the problems of seam width, deformation and trimming.