Views:13 Author:Site Editor Publish Time: 2019-11-26 Origin:Site
Although the process of producing laminated MDF does not seem so complicated, but because some manufacturers' technology is not mature enough, there will still be many problems in the production process of laminated MDF. When we have problems in the production process, the first thing is to analyze the problems that arise and then solve them.This also applies to Laminated Plywood and Laminated particle board.
Laminated MDF bubbling
Laminated MDF bulging
Crack on the laminated MDF surface
Common reasons are:
1. The water content of the slab is too high (>12%), causing the steam pressure in the plate to be greater than the bonding force during the hot pressing process, and the steam in the plate that has not been exhausted after the pressure relief is backflushed to form bubbling or direct stratification;
2. The fiber moisture content is low, but the speed of the press is fast, and the adhesive of the core layer of the slab is not fully cured to cause delamination;
3. Spraying water due to the alarm of the spark detector, resulting in high moisture content of the local fiber, bubbling after hot pressing;
4. In fiber form, the ratio of coarse and fine fibers is quite different. Under the same conditions, the coarse fiber bundle in the slab is easy to produce bubbling, especially in the production of thick plates;
5. The steel strip has been repaired, especially after large-area excavation. Due to the thickness of the steel strip and the change of heat transfer, the heat transfer effect is affected and the slab is bubbling or bulging.
Different measures should be taken for different bubbling: when the water content of the slab is high, the moisture content of the fiber should be reduced, and the process parameters should be adjusted appropriately to reduce the pressure and temperature, prolong the pressurization time, and discharge the steam in the plate as much as possible; For the fiber with lower moisture content, measures such as heating and pressure increasing should be adopted to meet the curing requirements of the adhesive; in fiber form, the ratio of controlling coarse fiber, qualified fiber and fine fiber is 10:75:15. For defects on the steel strip, adjustments should be made according to production conditions.
The reasons are as follows: First, the irregularity of the steel strip itself causes the finished board to bulge or dent; secondly, there are fiber clusters in the inlet section, or there are debris falling on the surface of the slab; in addition, the fibers accumulated in the drying pipeline When the group enters the press, it will also cause bulging.
It is recommended that in addition to the regular cleaning of the production equipment, a protective layer should be added above the paving area where many debris falls, and the fiber mass and debris are strictly prevented from falling on the surface of the slab.
Laminated MDF surface crack refers to the linear damage of the surface of the sheet produced by external force, and the hand feel is more obvious. It is mostly found in the production of thin sheets, concentrated in the pre-pressing, hot-pressing section and post-processing cutting section. The reason for this:
1. The speed of the press does not match the speed of the prepress. There is a speed difference between the production of the medium press pre-press and the paving line. When producing plates of the same specification, the transmission ratios of high-speed operation and low-speed operation are different. If the press is accelerated, the speed ratio must be adjusted in time (recommended value is about 1.5%) to ensure the matching of the front and rear process speeds to avoid slab breakage. The phenomenon.
2. The axis offset of the upper and lower rollers of the pre-press is offset, which can form shear force on the slab and cause cracks in the slab. In the production process, it is necessary to ensure that the error of the position of the upper and lower rollers of the pre-press is controlled within 10 mm.
3. The pressure setting at the inlet of the press is unreasonable. During the inlet exhaust process, the slab is easily broken to form a crack, and in severe cases, the slab at the entrance may be discounted. For presses with a long hot press section (40.3 m), the pressure at the inlet is preferably 2.0 to 2.5 MPa.
4. Differences in fiber morphology and moisture content. If the proportion of the qualified fibers is less than 75%, the toughness of the slab is poor at the time of paving, and it is easily pulled at a high speed. Further, the fiber moisture content exceeds 12%, and the slab has a large adhesion to the conveyor belt, and may crack the plate surface during high-speed conveyance; when it is less than 8%, the interlacing force between the fibers is lowered. Therefore, to ensure the proportion of qualified fiber, and according to the actual production situation, the moisture content of the control fiber is in the range of 8.5% to 11%.
5. External force bruises. Due to the low strength of the thin plate relative to the thick plate, in the high-speed running production line, the transportation and stacking process of the plain plate is prone to bruises and bumps, and the sand light and the sawing line are also problem-prone sections. Therefore, in the production process, pay attention to inspections and eliminate problems in time.
If you have more questions about the production process of laminated MDF, you can consult us!