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Hydraulic Guillotine Shear

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Fault Analysis And Troubleshooting Of Mechanical Shearing Machine

Shearing machine is one of the commonly used equipment in the machinery industry, mainly used for linear cutting of metal materials. Based on years of experience in faults and repairs that often occur in practical use, they are summarized for reference.

1. Transmission principle of mechanical shearing machine

As shown in Figure 1, the motor drives the large pulley through a small pulley.

The large belt pulley drives the big and small gears to rotate through the drive shaft.

The big gear drives the eccentric wheel to rotate through the main shaft.

The eccentric wheel drives the slider (upper tool carrier) to move up and down through the connecting rod to shear.

Schematic diagram of transmission principle of shearing machine

Fig. 1 Schematic diagram of the transmission principle of shearing machine

2. Analysis and troubleshooting of mechanical shearing machine

2.1 The width of shear parts is not consistent, and the repeated accuracy of batch parts is out of tolerance.

Cause analysis

1) The positioning of the baffle plate is not accurate and the gap is too large, which causes the scale to move when it is locked.

2) The movement of the baffle plate is not synchronous on both sides, and the gap between the transmission parts is large.

3) Improper adjustment of pressing spring force will lead to uneven pressing force and plate material moving during shearing.

4) The baffle plate is deformed and the straightness is out of tolerance, resulting in inaccurate positioning of parts.

5) The gap between the upper and lower moving guide rail of the shear blade slider and the pressing plate is not adjusted properly.

Elimination method

1) The clearance is eliminated to make the distance between the baffle plate and the shear blade consistent.

After locking, the repeated positioning error is within 0.30/1000.

2) The clearance of transmission parts is eliminated.

3) The gap between the pressing beam and the sheet metal should be adjusted at about 10 mm, and the compression force of the spring should be ensured to be 11kn and both ends should be kept even.

4) It should repair to make the flatness straightness error of the baffle plate within 0.02/1000.

5) The clearance is adjusted between the guide rail and pressing plate to ensure that it is within 0.03mm.

2.2 The surface straightness of shear parts is out of tolerance, with convex or concave phenomenon.

Cause analysis

1) The horizontal error of worktable installation is large, which makes the equipment distorted.

2) The flatness error of the vertical supporting surface of the upper and lower scissors is large, which makes the straightness of the shear blade exceed the tolerance after fastening.

3) The shear blade moves up and down, both sides of the guide rail surface are twisted (not in the same plane), or the guide rail is worn, and the straightness is out of tolerance.

Elimination method

1) Realign the installation level of the equipment to ensure the installation accuracy of 0.05/1000.

2) Correct the fitting bearing surface of the upper and lower shear blades, and ensure the flatness between 0.03/1000.

3) Repair and scrape the slide rail of the bed so that both ends are parallel to each other, and the straightness is guaranteed to be between 0.02/1000.

2.3 The burr at the cutting part of the part is too large.

Cause analysis

1) The gap between the upper and lower shear blades is not adjusted properly.

2) The cutting edge is worn and blunt.

3) The gap between the upper and lower shear blades is uneven, and burr will appear at the larger gap.

Elimination method

1) The gap is adjusted to 5% ~ 8% of the sheet thickness.

2) Replace or grind the cutting edge.

3) Adjust, check once every 500mm to ensure that the gap is even and no more than 0.05mm.

2.4 Narrow strip is sheared, and the parts are twisted and deformed.

Cause analysis

1) The clearance of the slide guide surface of the shear blade is adjusted too large.

2) Both sides of the guide surface of the shear blade slider are twisted or the straightness is out of tolerance after wear.

Elimination method

1) Adjust the pressing plate to ensure that the clearance of each part of the guide rail on both sides is within 0.03mm.

2) Scrape the slide block and bed guide rail to make the contact surface of the slide block and the bed guide rail to be (25 × 25) mm2, with 12 points, and the straightness is within 0.02/1000.

2.5 There are historical materials and pushing materials in the shear narrow strip parts

Cause analysis

1) The plane of the baffle plate is inclined and not perpendicular to the horizontal plane.

2) The parallelism of the vertical support surface fitted with the upper blade is out of tolerance.

Elimination method

1) Repair the plane of the baffle plate to ensure that it is perpendicular to the horizontal plane.

2) When the upper turret moves downward, the distance between the two vertical surfaces which fit the upper blade and the lower blade can only be increased.

The error is within 0.02/1000.

2.6 The clutch of single stroke fails to engage and the shear blade does not act.

Cause analysis

1) The rotating part of the rotating key and the triangular notch of the buffer sleeve is worn, which causes the clutch to slip when contacting with the crankshaft.

2) The control spring of the turning key is broken or loose.

The force is not enough so that the rotation key action is not flexible.

3) The brake band and brake disc are adjusted too tightly, causing the clutch to slip.

Elimination method

1) Replace the rotary key and repair the triangle notch of the buffer sleeve, so that the rotation key can move flexibly, and the combination is good when the triangle notch is stuck.

2) Replace the spring and adjust the tension of the spring to make the turning key move flexibly.

3) Adjust the tightness of the brake band.

2.7 Continuous cutting occurs during single stroke.

Cause analysis

1) The pinhead and control block of the rotary key handle is worn, and the pinhead of the rotary key cannot be blocked.

2) If the position of the control plate is not adjusted properly, the pinhead of the turning key cannot be stuck when it is in place.

Elimination method

1) Repair welding, repair the pinhead of the rotary key and restore the original design size.

2) Adjust the mutual position and repair the control block.

2.8 There is an impulse phenomenon and abnormal noise in one stroke of the shear slider.

Cause analysis

1) The rotation key does not fit well with the triangle groove of the buffer sleeve, and the rotation angle of the rotating key is not in place after wear.

There are impact phenomenon and sounds in the reciprocating movement of the cutting edge.

2) The spring force of the turning key is too small to be pulled in place.

When the slider is from top to bottom, the impact phenomenon occurs.

3) The balance spring force of up and down movement of the shear blade slider is not adjusted properly.

Elimination method

1) Repair the contact surface between the rotating part of the rotary key and the triangular notch groove of the buffer sleeve to make the key rotate flexibly and reliably.

2) Adjust or replace the spring.

3) Adjust the spring force until the slider moves without shock and vibration.

2.9 When the flywheel is idling, the clutch makes a rhythmic sound.

Cause analysis

The rotating part of the rotary key does not completely come out of the triangle groove of the buffer sleeve, which makes a sound after one revolution.

Elimination method

Grind the mating surface of the rotary key and adjust the position of the turning key.

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