How to scientifically plan production capacity and intelligently control board entry?
Faced with PCB of different sizes, thicknesses, weights and materials, how should the production capacity be allocated to meet the quality requirements and achieve the maximum production capacity?
Production capacity planning requires scientific basis instead of planning based on experience, imagination, and production tasks. We must study the heat absorption and supplementary heat conditions of each board in each temperature zone in order to correctly plan production capacity.
As shown in the figure below, you can use the veneer to pass through the furnace to understand the time required for the veneer to pass through each zone from heat absorption to heat recovery to the initial state, and to understand the thermal compensation capability of this zone. In this way, through the "capacity planning" function, you can grasp the thermal compensation capacity of each heating zone and understand the time required for each zone to reheat back to the initial state. Through comparison, find out the longest reheating time as the ideal boarding interval.
(Figure 9) Scientific capacity planning
But when the planned ideal boarding interval is too large, how should we choose to meet the maximum production capacity? Here are a few optimizations or trade-offs:
1) Increase the wind frequency, optimize the heating efficiency, and improve the thermal compensation ability of each temperature zone to reduce the compensation temperature return time;
2) Check whether the temperature probe of each temperature zone is at the air outlet, improve the temperature sensing sensitivity, shorten the feedback time, and then reduce the compensation temperature return time;
3) The compensation time for the important temperature zone is mainly used. If the first zone needs 90 seconds to warm up, and the other zones only need 60 seconds at most, then 60 seconds can be considered as the reasonable boarding interval.
With scientific capacity planning, can it be done once and for all? In fact, it is not. So, who can control the infeed of each production board at a reasonable interval? People always make mistakes, so it is especially important to control the board signal of the welding furnace through SMEMA and automatically control the board feeding according to the different board feeding intervals planned for each board.
The above is a large introduction to temperature fluctuations, compensation, and planning, but it mainly focuses on the temperature level. In fact, in addition to temperature that affects welding quality and reliability, there are chain speed, fan and track vibration, etc. Do we have countermeasures in these areas?
4) How to monitor the three killers of speed, wind and vibration?
The aging problem that chain speed is most worried about? How to define the maintenance period? How about the long-term stability of CPK?
Through the following statistical analysis of the chain speed aging trend, this information can be grasped to fully understand the chain speed variation process.
(Figure 11) Chain speed aging analysis
For hot air reflow ovens, in addition to the "heat" factor, "wind" plays a key role. "Heat" needs to be transferred to the board, and the medium of "wind" is indispensable. The size of the wind directly affects the heat transfer. How much, fast or slow, directly affect the strength of the thermal compensation ability. Therefore, real-time monitoring of the actual fan speed and trend analysis of the aging data help us to judge the health of each fan, understand its working status in time, and avoid the occurrence of poor quality.
(Figure 12) Actual fan speed monitoring
(Figure 13) Fan fluctuation analysis
At present, the poor quality abnormalities caused by track vibration account for the majority, and they are usually hidden and difficult to monitor. The impact of vibration on products has become the most critical factor in quality problems, so how much do we know about vibration ?
By understanding the real-time vibration of the track and analyzing historical vibration data, we can understand the working status of the equipment and the time of strong vibration caused by changes in the surrounding environment, so as to filter out specific vibration sources.
(Figure 15) Track vibration analysis
In view of the vibration sources that may cause strong vibrations, several situations currently encountered on the client are summarized:
1) Vibration from the pick and place machine;
2) Vibration from the cooling fan;
3) Vibration from chain transmission;
4) Vibration from rail deformation squeezed through furnace carrier
As long as you find the source of the vibration, the solution to the vibration will be different!
In summary, we have conducted a comprehensive analysis and monitoring in terms of temperature, chain speed, wind, vibration, etc.; Only by achieving comprehensive monitoring of the process and sufficient data support can it move to the final intelligent self-adjustment stage of intelligent closed-loop control.
5) Are you ready for smart closed-loop manufacturing?
