How to choose the appropriate water jet pressure and speed to cut the die cushion?

Guide for selection of water jet pressure+cutting speed for die cushion (PU polyurethane, EVA, rubber, foam)

Core principles of soft elastic materials: low pressure, medium and low speed, soft cutting, high pressure easy to cut rotten, pilling, delamination, too fast notch sawtooth, too slow extrusion deformation, whitening. Matching premise: pure water cutting (without sand), soft materials do not need emery at all, only pure water jet is used.

First, distinguish material+hardness (key classification)

Classification of commonly used soft elastic pads for knife dies:

PU knife die spring pad (polyurethane 60–90 Shore A)

EVA foam, high elastic foam (30–55)

Natural rubber/silica gel pad (40–70)

Composite elastic cushion with adhesive backing (with sponge and adhesive layer)

Second, the standard parameters of each material 【 pressure+walking speed 】

1. Medium-high hardness PU knife die spring pad (70–90 mainstream model)

Working pressure of water jet: 25–35 MPa.

Cutting speed: 800–1500mm/min.

Key points of detail:

The higher the hardness, the higher the pressure and the lower the speed. Thick material (15–30 mm) pressure+5MPa, speed drop 20%.

2. Ordinary soft PU/rubber spring pad (50–70)

Working pressure: 18–25mpa.

Cutting speed: 1200–1800 mm/min.

Key points: the material is soft and the pressure should not be high, so as to prevent the jet from pulling the incision and causing waves at the edge after breakdown.

3. EVA foam and super soft foam (30–50)

Working pressure: 10–18 MPa (low pressure in the whole process)

Cutting speed: 1500–2200mm/min.

Taboo: it is forbidden to exceed ＞20MPa, which may easily collapse the foam pores, collapse the incision, and delaminate the chips.

4. Composite elastic pad with adhesive backing

Pressure: 3-5MPa lower than the corresponding material.

Speed: down by 10%

Objective: To prevent the back glue from melting, overflowing and delamination caused by high temperature water pressure and impact.

Three, according to the thickness of the rapid adjustment rules (universal formula)

Thickness ≤10mm: low pressure+high speed.

Thickness 10–25mm: standard intermediate parameter.

Thickness > ＞25mm: the pressure rises by 10% ~ 15%, and the speed must be reduced by 20% ~ 30% to ensure that the cutting is not burr.

Four, servo water knife exclusive fine-tuning skills (for servo models)

Angular deceleration

At the corners of abnormity, round hole and wave, start the servo angle to slow down (by 30%), so as to prevent the corner from tearing and chipping.

Tool-raising/cutting buffer

The impact of soft materials is the biggest at the moment of cutting. Set the slow pressure increase+low speed feeding to avoid edge rot at the feeding position.

Nozzle selection and matching

Fine nozzle for soft wood: 0.8 ~ 1.0 mm, with more concentrated jet and vertical section, and no divergence and paste cutting.

V. Common Bad Problems → Pressure/Speed Rectification Scheme

form

Adjustment scheme for the causes of bad phenomena and problems

When the incision is white and the material flattening pressure is too high, it will be reduced by 5-8MPa, and the speed will be increased appropriately.

The speed of edge burr, wire drawing and cutting is too fast, slow down by 30%, and slightly increase the pressure.

Incision wave, high deformation and pulling pressure+insufficient rigidity, pressure reduction and deceleration of opening angle.

Back glue overflow, layered heat+high and low pressure of water pressure impact+slow acceleration, reducing stopping cutting.

Round hole is not round, abnormal deformation servo corner speed is too fast, opening corner speed is limited, trajectory is smooth and optimized.

Six, novice debugging the simplest starting parameters (directly applied)

The vast majority of ordinary knife die PU spring pads (10–20 mm) are directly used first:

Pressure: 30 MPa

Speed: 1150 mm/min

Try to cut one piece and see the incision:

Hard to cut through →+3MPa, slow down;

Cut and blanch →-5MPa, speed up, fine-tune for two or three times to achieve stable mass production.