Basic methods and tasks of process control
For the sake of narration, let's take one. An example of a bicycle fleet crossing a wooden bridge: When a fleet of several bicycles passes through a single wooden bridge, how can we cross the bridge most quickly and safely? Not difficult to know:
a. When the speed of each car is fast, the bridge is the fastest, and the slowest car determines the time and speed of the team crossing the bridge;
b. The car and the car always keep the same speed and the same distance as the bridge is the safest.
Therefore, increasing the speed of each vehicle and maintaining the same distance at the same speed is the only way for the fleet to travel the bridge most quickly and safely.
The process control of plywood production is based on this principle. Based on the weakest production link, the output of the semi-products (or mid-way products) of the same working period is calculated and quickly transferred to the next section. Organize production in a way of 'synchronous advancement', not only to eliminate equipment and other materials, but also to eliminate the phenomenon of backlog on the way of processing semi-finished products, so that the plywood can be processed in an orderly production and effective control.
With this understanding, you can have the ability to target the device. Design "synchronous production of the production section of the production (limited to the length and relevance of the previous processing of the glue does not add to the text. Assume that a business main equipment is a hot press two doors 15 layers), three pre-presses; coating machine Two sets of production and production plans are prepared by taking three layers of plywood as an example. The hot press is used as the basis for calculation, and the hot pressing cycle is set to 3 minutes (hot press time 2 minutes/time, auxiliary time average 1 minute/time). The output under normal conditions is:
60/3 X 15X2=600 (sheets/hour)
Then it is determined that the output of each section is 600 sheets/hour, that is, one time of coating, one pre-pressing, repairing, secondary coating, secondary pre-pressing, and all the six sections of hot pressing are determined to have a yield of 600 sheets/hour. Process control:
1, one time glue
Calculated by 450 grams of glue on one side of each board, 270 kilograms of glue is used for 600 sheets per hour, and the amount of glue is 100 kg/time. It is stipulated that the glue will be glued every 20 to 25 minutes. Change; thus controlling the stability and sustainability of the production of 600 sheets per hour.
2, a preload
If two pre-presses are used for one pre-press, each pre-press must complete 300 pre-compression production per hour. When each plate is 300 sheets, the pre-pressing cycle is 60 minutes; when each plate is 500 sheets, the pre-pressing cycle is 100 minutes; according to the pre-pressing process requirements, the rubberizing process is determined to ensure that the two pre-presses take turns The average output is 600 blanks per hour.
3, repair (repair, core cutting)
The number of personnel in the repair section is reasonably arranged at a repair rate of 600 sheets per hour to ensure simultaneous output.
4, secondary coating
It has the same requirements as one-time gluing, but it should be noted; firstly, because there are different process requirements for two gluing, it is better to have two gluing machines to complete one time and two times; second, according to the previous design The second pre-pressing machine has only one pre-pressing machine, and its pre-pressing cycle will be shorter than one-time pre-compression. In view of the fact that the secondary pre-pressure bonding requirement is lower than the one-time pre-compression, and the secondary pre-compression is completed, the hot pressing can be performed. Pre-curing occurs less on the surface, so the secondary glue can generally adjust the cavity to gel faster to meet the requirements of secondary preloading.
5, secondary preload
It is possible to accelerate the preload by the second pre-pressing through the rubber. When the sheet is 300 sheets per sheet, the pre-pressing cycle is 30 minutes. The process of determining the secondary rubber is carried out according to the process requirements. Of course, the production organization allows Under the conditions, it is feasible to mix three pre-presses without division of labor. It is more appropriate to add a pre-press.
6, hot pressing
The secondary preload guarantees an average output of 600 slabs per hour. The two hot presses must guarantee a normal production rate of 300 sheets per hour (with a hot pressing cycle of 3 minutes). Avoid shortening the hot pressing cycle. When leaving a "rest", the adhesive layer is not fully cured by hot pressing. This is the "equal distance, equal speed" extension of the plywood production "synchronous" process control.
It is worthwhile to continue to explore the synchronous process control, even if "600 sheets per hour" has been determined. However, the production cycle will still have a big difference. Try comparing 300 sheets and 5,000 sheets per raft board as follows:
It can be seen from the above comparison that although the equilibrium production index of each section is 600 sheets per hour, the production cycle is still very different due to the difference in the amount of flow (the number of sheets per raft). When the flow is 300 sheets /åž›, the production cycle is 240 minutes, which is beneficial for the prevention of pre-curing of the rubber layer in summer production, but for the production of poplar core plywood in winter, it will be difficult to achieve this requirement in the pre-pressing section and affect the synchronization of the entire production process; The amount is 500 sheets / åž› production cycle is 400 minutes. When producing poplar core plywood in winter. It is more suitable for Taiwan, and when the wood core plywood is produced in summer, the risk of the adhesiveness of the rubber layer is greatly increased. The comparison data also tells us that properly adjusting the amount of flow (number of sheets per slab) can also alleviate the conflict between preload performance and production cycle.
Therefore, the central task of plywood production process control is to determine and strictly control the equalization and simultaneous production of each section. Ensure that the production line is smooth (no downtime and no semi-finished product backlog) and properly adjust the production cycle so that each plywood is produced in a controlled process range and quality-assured production cycle.
It is true that the plywood is stable in strength. Uniform and long-lasting is closely related to the quality of the adhesive, the glue adjustment process, the quality level of the veneer, ie the moisture content, the flatness, the smoothness, the material, etc., but under the same conditions, the process control is balanced, synchronized and smooth. Keeping the plywood in reliable technical measures, suitable production cycle, and the same process conditions, the production factors affecting the bonding strength can be greatly reduced, so that the plywood strength is stable, uniform and durable, and the bonding quality is guaranteed. .
For the sake of narration, let's take one. An example of a bicycle fleet crossing a wooden bridge: When a fleet of several bicycles passes through a single wooden bridge, how can we cross the bridge most quickly and safely? Not difficult to know:
a. When the speed of each car is fast, the bridge is the fastest, and the slowest car determines the time and speed of the team crossing the bridge;
b. The car and the car always keep the same speed and the same distance as the bridge is the safest.
Therefore, increasing the speed of each vehicle and maintaining the same distance at the same speed is the only way for the fleet to travel the bridge most quickly and safely.
The process control of plywood production is based on this principle. Based on the weakest production link, the output of the semi-products (or mid-way products) of the same working period is calculated and quickly transferred to the next section. Organize production in a way of 'synchronous advancement', not only to eliminate equipment and other materials, but also to eliminate the phenomenon of backlog on the way of processing semi-finished products, so that the plywood can be processed in an orderly production and effective control.
With this understanding, you can have the ability to target the device. Design "synchronous production of the production section of the production (limited to the length and relevance of the previous processing of the glue does not add to the text. Assume that a business main equipment is a hot press two doors 15 layers), three pre-presses; coating machine Two sets of production and production plans are prepared by taking three layers of plywood as an example. The hot press is used as the basis for calculation, and the hot pressing cycle is set to 3 minutes (hot press time 2 minutes/time, auxiliary time average 1 minute/time). The output under normal conditions is:
60/3 X 15X2=600 (sheets/hour)
Then it is determined that the output of each section is 600 sheets/hour, that is, one time of coating, one pre-pressing, repairing, secondary coating, secondary pre-pressing, and all the six sections of hot pressing are determined to have a yield of 600 sheets/hour. Process control:
1, one time glue
Calculated by 450 grams of glue on one side of each board, 270 kilograms of glue is used for 600 sheets per hour, and the amount of glue is 100 kg/time. It is stipulated that the glue will be glued every 20 to 25 minutes. Change; thus controlling the stability and sustainability of the production of 600 sheets per hour.
2, a preload
If two pre-presses are used for one pre-press, each pre-press must complete 300 pre-compression production per hour. When each plate is 300 sheets, the pre-pressing cycle is 60 minutes; when each plate is 500 sheets, the pre-pressing cycle is 100 minutes; according to the pre-pressing process requirements, the rubberizing process is determined to ensure that the two pre-presses take turns The average output is 600 blanks per hour.
3, repair (repair, core cutting)
The number of personnel in the repair section is reasonably arranged at a repair rate of 600 sheets per hour to ensure simultaneous output.
4, secondary coating
It has the same requirements as one-time gluing, but it should be noted; firstly, because there are different process requirements for two gluing, it is better to have two gluing machines to complete one time and two times; second, according to the previous design The second pre-pressing machine has only one pre-pressing machine, and its pre-pressing cycle will be shorter than one-time pre-compression. In view of the fact that the secondary pre-pressure bonding requirement is lower than the one-time pre-compression, and the secondary pre-compression is completed, the hot pressing can be performed. Pre-curing occurs less on the surface, so the secondary glue can generally adjust the cavity to gel faster to meet the requirements of secondary preloading.
5, secondary preload
It is possible to accelerate the preload by the second pre-pressing through the rubber. When the sheet is 300 sheets per sheet, the pre-pressing cycle is 30 minutes. The process of determining the secondary rubber is carried out according to the process requirements. Of course, the production organization allows Under the conditions, it is feasible to mix three pre-presses without division of labor. It is more appropriate to add a pre-press.
6, hot pressing
The secondary preload guarantees an average output of 600 slabs per hour. The two hot presses must guarantee a normal production rate of 300 sheets per hour (with a hot pressing cycle of 3 minutes). Avoid shortening the hot pressing cycle. When leaving a "rest", the adhesive layer is not fully cured by hot pressing. This is the "equal distance, equal speed" extension of the plywood production "synchronous" process control.
It is worthwhile to continue to explore the synchronous process control, even if "600 sheets per hour" has been determined. However, the production cycle will still have a big difference. Try comparing 300 sheets and 5,000 sheets per raft board as follows:
300 sheets per processing time, 500 sheets per processing time, glue application 30 minutes, 50 minutes, pre-pressure, 60 minutes, 100 minutes, repair, 30 minutes, 50 minutes, secondary coating, 30 minutes, 50 minutes, second pre-pressure, 30 minutes, 50 minutes, hot pressing, 60 Minute 100 minutes production cycle 240 minutes 400 minutes
It can be seen from the above comparison that although the equilibrium production index of each section is 600 sheets per hour, the production cycle is still very different due to the difference in the amount of flow (the number of sheets per raft). When the flow is 300 sheets /åž›, the production cycle is 240 minutes, which is beneficial for the prevention of pre-curing of the rubber layer in summer production, but for the production of poplar core plywood in winter, it will be difficult to achieve this requirement in the pre-pressing section and affect the synchronization of the entire production process; The amount is 500 sheets / åž› production cycle is 400 minutes. When producing poplar core plywood in winter. It is more suitable for Taiwan, and when the wood core plywood is produced in summer, the risk of the adhesiveness of the rubber layer is greatly increased. The comparison data also tells us that properly adjusting the amount of flow (number of sheets per slab) can also alleviate the conflict between preload performance and production cycle.
Therefore, the central task of plywood production process control is to determine and strictly control the equalization and simultaneous production of each section. Ensure that the production line is smooth (no downtime and no semi-finished product backlog) and properly adjust the production cycle so that each plywood is produced in a controlled process range and quality-assured production cycle.
It is true that the plywood is stable in strength. Uniform and long-lasting is closely related to the quality of the adhesive, the glue adjustment process, the quality level of the veneer, ie the moisture content, the flatness, the smoothness, the material, etc., but under the same conditions, the process control is balanced, synchronized and smooth. Keeping the plywood in reliable technical measures, suitable production cycle, and the same process conditions, the production factors affecting the bonding strength can be greatly reduced, so that the plywood strength is stable, uniform and durable, and the bonding quality is guaranteed. .
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