Joy Technology Co.,Limited

1. Failure analysis
1） fault description: the production process suddenly a few pieces, flying parts, part of the nozzle and head automatically shield.
2） on-site inspection: the machine without alarm, the machine is completed, the manual came out has been found on the PCB board pieces of random pieces. Also found in the machine there are some nozzle (NOZZLE) scattered.

2. Troubleshooting
 consider the nozzle off may cause the head to leak, and finally sucking bad, resulting in fewer pieces, flying. Will be missing the nozzle to re-fill, do the head height and alignment calibration, do vacuum detection, all qualified. Continue to produce, found or the occurrence of fewer pieces, flying parts, nozzle off, and the falling nozzle and head are not fixed.

consider the X / Y movement table uneven, may affect the component placement height, resulting in flying, less occurred. As the running process suddenly occurs, this may be very small. Use the dial gauge on the track and the table to do horizontal longitudinal detection, all within the qualified range.

consider the placement of the head Z-axis mounting height tolerance, may affect the component placement height, resulting in flying, less pieces occur. Use the dial gauge to detect the height of each placement head and the movement stroke, all within the qualified range.

 consider the machine head control vacuum off valve failure, resulting in the placement of components when the valve can not be closed in time, the components away, resulting in fewer pieces. But after checking the disposal of the box, did not find the placement of the paste with solder paste components. For safety reasons, continue to experiment, consider the valve can not fail at the same time, the head in accordance with the odd evenly divided into two parts, respectively, shielding experiments, failures have occurred. Divided into four parts to continue the test, the fault remains the same.

 Consider that it may be too fast, leading to some institutional failure. The speed from 0.1 s down to 0.3 s, 0.5 s, and 1.0 s, the fault remains the same. Check the machine vacuum pump operation, normal.

 reanalyze the working principle of each machine head station (Figure 1-1). Consider the possibility of an abnormality in the 13th station action. No. 13 station has three functions. First, the control nozzle to accommodate the cylinder solenoid valve open, all the nozzle to the highest position. Second, release the selected nozzle cylinder solenoid valve open, the selected nozzle to release. Third, the control nozzle to accommodate the cylinder solenoid valve closed, hold the release of the nozzle down to the bottom. Suspected failure for the control nozzle to accept the cylinder failure, in the nozzle to the bottom of the release, can not drag the nozzle, resulting in automatic nozzle off. SANYO 3000 nozzle installation is mainly relying on the tip of the nozzle opening of the four claws stuck in the demolition, relying on their own spring elasticity and inertia, the release of the nozzle can be hook. Due to the failure of the cylinder, in the 13th station is equivalent to the nozzle disassembly, resulting in nozzle off, while the machine's overall vacuum leak, reducing the vacuum running of other nozzles, forming a small, flying pieces.

After the above analysis, and continue to do experiments. The machine turret to a certain angle, and the touch screen to switch to a separate action interface, a separate action control nozzle intake cylinder, step by step operation, cylinder action orderly. After pressing the action button quickly, found that the cylinder has lost the phenomenon. After replacing the solenoid valve of the control cylinder, the fault disappears.

3 Conclusion
Due to the control of the cylinder action solenoid valve spool action is not smooth, resulting in the control of the cylinder in the fast movement can not be normal action, and ultimately the nozzle storage board can not be in place, the machine nozzle off, working nozzle vacuum reduced, resulting in machine operation When a few pieces, flying pieces.

4. 
We carry out all kinds of maintenance and preventive maintenance (PM) of the machine on time. All the maintenance points of the machine are done in accordance with the instructions required. But with the increase in the number of years, some maintenance-free spare parts should also be added to the inspection project. Especially for the mechanical structure to be given special attention, lubrication maintenance is indispensable. After this failure, the maintenance of the various solenoid valve spool has been added to the preventive maintenance list, reducing the occurrence of similar failures. In addition, the maintenance of the machine is concerned, the working principle analysis is very important, the circuit control map also have a deep understanding.

Figure 1-1 Description of the job of the placement head station
2. Analysis of Common Problems in SMT Production Process
2.1. Problem description of the placement of small pieces, dislocation
2.1.1 Possible causes of the problem
a. solder paste tin is insufficient or the furnace stay too long
b. Machine mounts are uneven or lack of support
c. Incorrect coordinate of the machine or the abnormality of the parts database error caused by machine identification
d. The machine is dirty, clogged, worn, damaged, and the size is not equal
e. Machine Vacuum System Problem (Vacuum Pump Damage, Air Leakage Vacuum, Filtering Cotton Blocking, Vacuum Valve Operation Abnormal)
f. The appearance of the parts is quite different, the machine identification is unstable, the process is lost
g. Production substrate bending or size difference is large, the substrate in the placement of work surface instability

Analysis of the problem
a. Tin or brush with tin plate
b. Adjust the table or increase the support pin to stabilize
c. adjust the coordinates or database
d. Clean or replace the nozzle
e. Clean the vacuum system or replace the problem parts
f. Replace the parts or adjust the machine database
g. increase support or adjust the work surface and track, adjust the substrate plane
2.2 Problem Description Placement components Flip, stand (tombstone effect)

Causes of the problem
a. solder paste tin is insufficient or the furnace stay too long
b. The machine sucks the reverse piece or the piece directly
c. The machine uses the feeder problem, causing the feed to turn over
d. nozzle used wrong, jam, wear, dirty and so on
e. Part consistency or infiltration is not good
f. Machine work surface uneven or poor substrate support
g. The component database is set incorrectly, resulting in unstable machine identification

Analysis and resolution of the problem
a. Tin or brush with tin plate
b. Adjust the detection sensor or adjust the database
c. Replace the feeder of the machine
d. Clean or replace the problem nozzle
e. Replace the problem material
f. Adjust the work surface or increase support
g. Adjust the database precisely

5. Summary
SMT production is a complex integrated systems engineering, involving materials, processes, processing, assembly, testing and other factors. Therefore, in the production or equipment abnormalities, from the people, machine, material, law, ring several aspects to consider, targeted analysis of the problem, solve the problem, thereby enhancing our production efficiency