The ML-1200 flat indentation and cutting machine is a specialized equipment used for cutting various cardboard, leather, plastic products, etc. Our factory produces beer boxes and other packaging boxes with a large business volume, and uses multiple such equipment.
Once, a malfunction occurred during the use of an ML-1200 flat pressure indentation and cutting machine, causing the rectifier supplying 24V DC power to the electromagnetic clutch solenoid coil (with the component code VC on the simulation sheet) to burn out. During operation, the electromagnetic coil of the clutch has no current, and the electromagnetic clutch does not operate, resulting in the inability of the press frame of the machine to operate.
According to the structure and working principle of the machine, it can be seen that the machine is mainly composed of a base, a pressure frame, a high-power bidirectional electromagnetic clutch transmission mechanism, and electrical control departments. The action of pressing and cutting paper products is achieved by the electric motor installed on the right side of the machine seat driving the transmission shaft through the flywheel, and driving the press frame to reciprocating motion through the secondary gear transmission link. If the ribs between the splines and grooves on the electromagnetic clutch experience severe wear during operation, causing the width of the ribs to decrease and the fit between the splines and grooves to become very loose, the copper sleeve of the splines will rise during the clutch action, causing deviation and jamming during the axial clutch action of the splines, preventing normal axial clutch sliding. At this moment of jamming, Often, the rectifier is damaged (or some of the circuit's fuses are blown), causing the electromagnetic coil of the clutch to have no current and preventing the clutch from acting. Flat press die-cutting machine
Based on the above analysis (similar situations have also occurred in the past), we removed the friction wheel and inspected the spline copper sleeve. The results showed that there was a lot of wear in the width direction of the spline sleeve rib, and the fit was very loose. At the same time, the clutch compression spring uniformly distributed in the four holes on the friction wheel surface has worn out and broken, and the friction plate on the friction wheel has also worn to its limit and needs to be replaced.
Based on the above situation, the spline copper sleeve and the four compression springs of the clutch were replaced, and new friction plates were also installed. Subsequently, the machine was turned on for a trial run, and only one cycle was activated, causing the fuse of the rectifier circuit (code: FU3) to melt again. At first, we believed that the poor quality of the fuse was the cause, so we increased the capacity of the fuse appropriately before starting the test. However, the result was still that only one cycle of action occurred, and the fuse burned out again.
After all, where is the question? Through in-depth analysis, we believe that the recurrence of such faults after replacing the aforementioned parts should be attributed to an electrical fault. So a detailed inspection was conducted on the control circuit of the electromagnetic clutch. Firstly, measure the DC resistance of the electromagnetic coil of the clutch using a multimeter, and then compare the DC resistance value of the electromagnetic coil on another normally used model machine. The result shows that the DC resistance value of the electromagnetic coil on the clutch of the faulty machine is significantly lower than the normal value. This indicates that the fault is caused by the electromagnetic coil and its circuit. There are several main reasons for the analysis:
1、 Short circuit between turns of electromagnetic coil; 2、 Poor insulation of electromagnetic coil to ground; 3、 Short circuit or poor insulation between the slip ring and the spindle.
We will separate the wiring of the electromagnetic coil and the slip ring, and first measure the DC resistance of the electromagnetic coil separately. The result is that its DC resistance value is the same as the normal value. The magnetic force generated when the solenoid coil avoids the slip ring (also known as the Slip ring) and is directly energized is also normal. On site, through these two tests, it can be assumed that the electromagnetic coil is normal. So, the insulation resistance of the slip ring to the ground (i.e. the insulation between the slip ring and the spindle) was measured, and the result was that the resistance value was close to zero. This indicates that there is a short circuit between the slip ring and the spindle, and it is necessary to remove the slip ring for inspection and handling.
The insulation and assembly between the slip ring and the main shaft are as follows: an insulation sleeve ring processed with insulation bakelite is fixed on the step end face of the main shaft with four evenly distributed internal hexagonal screws, and the cylinder of the assembled internal hexagonal screws sinks (i.e. is lower) into the insulation ring sleeve; The end face of the insulation ring sleeve is also evenly distributed with 4 to 6 screw holes. In this way, the screws pass through the screw holes on the end face of the sliding ring and screw into the screw holes on the insulation ring end face to fix the ring on the insulation ring sleeve. Under normal circumstances, the sliding ring is fixed on the end face of the insulation ring sleeve and insulated from the main shaft. Flat press die-cutting machine
However, during the prolonged operation of the machine, it may be due to the incomplete tightening of the bolts fastening the insulation ring sleeve during assembly, which gradually loosened and exposed the end face of the insulation ring sleeve, causing it to come into contact with the sliding ring attached to the end face of the insulation ring sleeve. The sliding ring touched the main shaft and caused a short circuit, resulting in the above fault. After handling the short circuit fault normally, the machine immediately resumed normal operation. This is a case where both mechanical and electrical faults exist simultaneously.