MDF QC Inspection Checklist : Part 5 Common Quality Defects and Causes of MDF
Common Quality Defects and Causes of MDF
I. Appearance Defects
1. Three-storey structure is too obvious.
(1) too high water content;.
(2) The setting of the first peak position is too low;.
(3) The flow rate of small pump in the drying and plasticizing section is larger, and the second peak is not obvious or even has no second peak;.
2. Coarse fibers (1) bad raw materials, too much hardwood; (2) too low moisture content of raw materials; (3) too large shape of wood chips; (4) too low steam pressure; (5) too short cooking time; (6) unreasonable selection of grinding chips; (7) poor precision and quality of grinding chips; (8) too large deviation of parallel degree between moving disc and fixed disc; (9) too large dynamic disc. The clearance between disc and fixed disc is too large; (10) the pressure of pressurized cylinder is too low, and the disc moves along the axis; (11) the feeding quantity is too large or uneven; (12) the steam balance pipe of the grinding chamber is not put into use; (13) the discharge valve is too large or excessively worn; (8) the discharging valve is too open.
3. Rough surface (1) Coarse fibers; (2) Low moisture content of slab; (3) too high temperature of pressing plate and too slow closing speed of press; (4) unreasonable setting of hot pressing curve, small pump flow rate in drying and plasticizing section, too far away from the thickness of plate; (5) too little paraffin wax application; (6) pre-solidified layer can not be sand removed; (7) sand exists in sanding layer. Trace sand line; (8) too low sizing; (9) wool board control is too thick, sanding surface compact layer;
4. Surface foreign bodies (1) Wood chips contain foreign bodies (such as rubber, bundled ropes); (2) conveyor belt degumming falls into wood chips and slabs; (3) grinding chamber body and drying pipe coking; (4) equipment and site remnants enter into fibers during maintenance; (5) materials recovered from cleaning sites contain sundries; (6) equipment and environment cleaning is uncertain. Long-term deposits of dust and fibers fall to the slab to form local softness;.
5. Sand mark sand line (1) unreasonable distribution of cutting amount of coarse sand and fine sand; (2) unreasonable type and collocation of coarse sand and fine sand; (3) unqualified quality of abrasive belt, easy to drop sand grains; (4) not long enough cooling time of wool plate, sticky abrasive belt; (5) too long use time of abrasive belt, not replaced in time; (6) poor quality of graphite belt and wool pad or not replaced in time after wear and tear. (7) The contact rollers and conveyor rollers are worn seriously and the accuracy can not meet the requirements; (8) the horizontal deviation between the sand rack and the sand rack is too large; (9) the feeding speed of the conveyor roll is not synchronous; (10) the recovery of sand powder containing sand is too large; (11) there are problems in the installation of sand polisher and the vibration is too large; (12) the precision of sand polisher itself can not meet the requirements; (2) the sand polisher itself can not meet the requirements.
6. Local sand leakage (1) uneven slab after pavement; (2) partial damage of slab during conveying and loading; (3) failure of the same arm of press to adjust, local slab was washed out during rapid closing; (4) deformation of press; (5) insufficient thickness of slab; (6) excessive deviation of density of slab; (7) deformation of slab; (8) graphite belt. (9) The local wear of contact rollers and conveyor rollers is serious; (8) The quality of wool cushion is not good or it is not replaced in time after partial wear and tear; (3) The local wear of contact rollers and conveyor rollers is serious.
7. The thickness deviation of the blank is large (1) the deviation of raw materials is too large (2) the weighing of the blank is inaccurate (3) the weight of the blank is not stable (4) there are debris on the thickness gauge or the thickness gauge has been worn out (5) the position controller is not working properly (6) the deformation of the blank;
8. Slab delamination and bubbling (1) Slab moisture content is too high or uneven; (2) Adhesive quality and viscosity and solid content do not meet the requirements; (3) The first peak position of hot pressing curve is too small, pressure is too high, and surface dense layer is too thick;
4) Press unloading and pressing plate opening speed is too fast; (5) pressing plate temperature is too high or hot pressing time is too long; (6) density is too high;
9. Soft edges and corners (1) uneven pavement, low density of slab edge; (2) excessive vibration of equipment or low presser line pressure setting, collapse and fall of fibers in the corner during slab conveying; (3) serious deformation of push-pull board, collapse and fall of fibers in the corner during pushing; (4) unsatisfactory hot pressing process conditions, no guaranteed glue. Adhesive solidifies sufficiently; (5) Sanding edge-cutting saws last too long;
10. Rough edge (1) incorrect length of cross-cutting saw chain makes the slab shorter; (2) low presser line pressure makes the slab shorter in pushing process; (3) the surface of push-pull slab is not smooth, and the resistance of slab is too large and shorter in pushing process; (4) there are water or oil substances on the surface of push-pull slab; (5) improper adjustment of the travel of loading slab trolley, and the slab is not delivered in loading machine. Position; (6) improper adjustment of travel switch before loading horizontal cylinder, slab not delivered in press; (7) improper adjustment of fast closing stroke of press, serious deformation of slab; (8) improper adjustment of the same arm of press; (8) improper adjustment of the same arm of press;
2. Unqualified physical and chemical indicators
1. (1)(1)low product density; (2)slow closure and compression speed of press, low product density gradient; (3)insufficient application of adhesives, uneven distribution, too high or too low moisture content of slab, resulting in incomplete curing of adhesives; (4)poor quality of fiber raw materials or low separation of fibers; (5)long hot pressing time or not. Foot;
2. (1)(1)insufficient sizing capacity; (2)too fast pressure speed (too large product density gradient) and insufficient hot pressing time; (3)high moisture content in slab, low temperature and incomplete solidification of adhesive; (4)low density; (5)too large proportion of recycled waste fibers or sand powder; (6)insufficient cooling time of slab High stacking temperature and excessive curing degradation of adhesives;