The most common press brake mistakes

Phenomenon :Non-parallel movement of the ram rapid down motion

Internal leakage in the hydraulic cylinder ,resulting from excessive clearance between the piston and the cylinder ,causing unequal leakage between the left and the right cylinders and asynchronous movement. 

Issues with the hydraulic oil supply lines:During the rapid descent of the press brake ,both oil lines supply oil to the upper chamber of the cylinder to achieve rapid downward motion.As the two hydraulic cylinders donnot start synchronously,the pressure in the upper chambers of the two cylinders differs,resulting in the uneven pressure differences before and after the check valves.Consequently ,the flow through the check valves into the two cylinders is also unequal .leading to asynchronous movement of the cylinders. 

Unequal damping in the return oil path during the rapid downward motion of the ram ,resulting in differential back pressure in the lower chambers of the cylinders and unequal flow rates during back flow,causing asynchronous downward motion of the cylinders.

Excessive friction in the guide rail or cylinder.

Excessive rapid downward speed.

Timing differences in the opening of the rapid descent valve.

Damaged servo valve.

CNC parameter settings such as acceleration distance ,servo valve delay time,etc.

Solutions:

Ensure the components such as left and right pistons,cylinders ,etc., are selected and matched with high precision(including dimensional accuracy ,positional accuracy such as coaxiality,roundness,etc.),and design the hydraulic circuits of the two hydraulic cylinders to be as similar as possible.

Ensure that the flow through the two check valves is equal ,and make the mechanical damping between the piston and piston rod,as well as between the pistopn rod and end cap,similar to ensure 

consistent mechanical damping during the rapid downward motion of the two cylinders.

Ensure equal flow rates during back flow by maintaining similar resistance in the return oil path,including similar pipe diameter,length ,number of bends ,and bend angles.

Check the guide rail and cylinder.

Reduce the speed

Replace the rapid descent valve.

Check the feedback voltage of the servo valve.

Adjust the parameters

Phenonmenon:Failure to achieve rapid descent spped

Possible causes:

Proportional valve not fully open.

Excessive flow in the lower chamber,proportion valve too small.

Excessive friction

Improper CNC parameter settings

Solutions:

Check feedback voltage.

Redesign the cylinder ,replace with a higher flow rate proportional valve,

Inspect the guide rail and cylinder,

Check the parameters for rapid descent.

Phenomenon :Rapid descent ram jitter

Possible cause:

Excessive gain.

Steep initial slope of the ram.

Inappropriate area ratio of the cylinder,

Solutions:Reduce the gain signal.

Increase the acceleration distance.

Recalculate the area ration

Phenomenon:Impact sound during rapid decent

Possible cause:

Impact sound caused by loose guide rail plates.

Incorrect position of the black strip on the grating ruler.

Too small value for the delay paraeter before rapid descent.

Phenomenon:No rapid descent action of the ram

Possible causes:

Rapid descent valve has no electrical signal or is stuck.

Electromagnetic proportional directional valve has no electrical signal or the spool is stuck (check feedback voltage)

Mechanical parts are connected too tifhtly ,such as the guide rail plates or cylinder.

Fill valve is closed and cannot open ,resulting in no oil suction

Issues with the grating ruler.

Check the condition of the foot switch and inspect the wiring.

After the slow descent valve is energized ,the fill valve is closed,causing the upper chamber to be unable to draw oil.

Phenomenon :No rapid descent action of the ram

Possible causes:

Rapid descent valve has no electrical signal or is stuck.

Electromagnetic proportional directional valve has no electrical singal or the spool is stuck (check the feedback voltage)

Mechanical parts are connected too tightly,such as the guide rail plates or cylinder.

Fill valve is clsoed and cannot open ,resulting in no oil suction.

Issues with the grating ruler.

Check the condition of the foot switch and inspect the wiring.

After the slow descent valve is energized ,the fill valve is closed ,causing the upper chamber to be unable to draw oil.

2.1 Phenomenon :Long pause time at the speed transition point of the ram

Possible causes:

Air suction in the upper chamber of the cylinder ,resulting in a long pressure buildup time(air leakage in the self-scution pipelibe).

Insuffient flow rate of the fill valve or self-suction pipeline,or rapid descent speed causing vacuum suction.

The fill valve is not fully closed ,resulting in slow pressure reduction in the upper chamber.

After the slow descent valve is energized,the fill valve is closed, causing the upper chamber to be unable to draw oil,

Incorrect mid- position of the proportiobal valve ,causing different openings and asynchronous movement.

Try reducing the rapid descent speed to see if there is any pause.

Adjust the pressure parameters during the pre-delay stage of the working feed.

Control circuit parameters(slow decent pre-delay).

CNC system parameters (slow descent pre-delay).

CNC system parameters(decrease in gain parameter for slow descent)

Phenomenon :Tilt of the ram during rapid-to -slow speed transition

Possible causes:

Insufficient gain during rapid descent

Too small deceleration slope.

Excessive friction

Default setting of rapid descent speed

Solutions:

Increase the gain.

Increase the deceleration distance

Inspect the guide rail and cylinder

Modify the default values.

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