Needle punching machine is suitable produce nonwoven materials such as needle punched felt, asphalt felt substrate, geotextile,carpet etc. Three kinds of structure of this machine are pre-needle punching loom, upstroke needle punching loom and down-stroke needle punching loom. Middle speed needle punching machine or high speed needle punching machine can be select.
Principle
When the needle reaches a certain depth, it starts to rise. Due to the forward direction of the barbed hook, the displaced fibers are separated from the barbed hook and remain in the fiber net in an almost vertical state, just like many fiber bundles “pins” nailed into the fiber net, so that the compression of the fiber net cannot be restored. If the fiber net is repeatedly punctured dozens or hundreds of times per square centimeter, a considerable number of fiber bundles will be pierced into the fiber net, and the friction between the fibers in the fiber net will increase, the strength and density of the fiber net will increase. The fiber net will form a non-woven product with certain strength, density, elasticity and other properties.
Applications
The main applications of needle-punched nonwoven materials are carpets, decorative felts, sports mats, mattresses, furniture pads, shoes and hats, shoulder pads, synthetic leather base fabrics, coated base fabrics, ironing pads, wound dressings, artificial blood vessels, heat pipe sleeves, filter materials, geotextiles, papermaking blankets, linoleum base fabrics, sound insulation and heat insulation materials, and automotive decorative materials.
Currently, needle punching machines are widely used in high-temperature filtration products. The high-performance fibers of high-temperature filtration products mainly include glass fiber, Nomex fiber, P84 fiber, PPS fiber, and PETT fiber. Due to the characteristics of the first few fibers themselves, the scope of use has been affected to a certain extent. Glass fiber is relatively brittle, Nomex fiber has poor oxidation resistance, P84 fiber is easy to hydrolyze and age, and PPS fiber has a low operating temperature. PETT fiber is resistant to chemical corrosion and high temperature, can be used in various harsh environments and achieve better results, and has a longer service life than filter media made of other fibers.
Although PETT has good heat and chemical corrosion resistance, it is expensive and has no advantage in filtration efficiency compared to filter media made of other fibers. For this reason, some companies add an appropriate amount of ultra-fine glass fiber to it, which does not affect the heat resistance, but can improve the filtration efficiency of the filter material and reduce the price of the filter material, and also expand the scope of application and extend the service life.
Types
Striped needle punching machine, general pattern needle punching machine, special needle punching machine, annular needle punching machine, round tube special needle punching machine, four-plate positive position needle punching machine, barb needle punching machine, double drum needle punching machine, double spindle needle punching machine, pile needle punching machine, jacquard needle punching machine, high-speed needle punching machine, computer automatic jump needle punching machine, needle punching and spunlace compound machine, etc.
Process forms
Pre-needling, main needling, pattern needling, ring needling and tubular needling, etc. (Pre-needling and main needling are the most common.)
Pre-needling process
Pre-needling: The main transmission of the needle punching machine drives the needle beam, needle plate and needles to reciprocate up and down through the crank-connecting rod mechanism. The fluffy fiber web is fed into the needling area under the clamping of the feeding curtain. When the needle plate moves downward, the needles pierce the fiber web, and the fiber web is close to the net support plate. When the needle plate moves upward, the friction between the fiber web and the needles causes the fiber web and the needles to move upward together, and the fiber web is close to the stripping plate. The feeding and output speeds are matched, and can be intermittently stepped or continuously. After the fiber web passes through the needling area, it has a certain strength, density and thickness, and then it is sent to the main needling.
Main needling reinforcement process
Main needling is to needle the pre-needled fiber web to increase the needling density.
(1) Main features
The distance between the stripping plate and the supporting plate is small;
The frequency of needling is high;
The range of needling is small;
The density of needles on the needle board is high and the needles are short.
(2) Needle board movement direction
The direction of needle board movement is usually perpendicular to the fiber web, but there is also upward or downward oblique needling. Oblique needling can increase the needling depth. For example, 60° oblique needling increases the needling depth by 13% compared with vertical needling. The resulting product has greater strength, lower elongation at break, greater density and less air permeability, and can also improve dimensional stability. Commonly used inclination angles are 45°, 60° and 75°.
Needle board
Due to the wide variety of needle punching machine, the functional structures are different. Therefore, there are great differences between needle plates of acupuncture machines.
(1) Materials include wooden needle plates, rubber-plastic needle plates, epoxy resin needle plates, copper needle plates, magnesium alloy needle plates, aluminum-magnesium alloy needle plates, lithium-magnesium alloy needle plates, etc.
(2) Needle eye arrangement is also very different, generally divided into herringbone, double herringbone, messy shape, etc. A reasonable needle arrangement order needs to be formulated according to the purpose.
Needle
The needle of the needle punching machine consists of a needle handle with an elbow, a needle waist (some have no needle waist), a needle blade and a needle tip. The needle blade is the working section of the needle and is the main section of the needle.
(1) The shape of the needle tip can have many variations, such as standard needle tip, sharp needle tip, micro-ball needle tip, ball needle tip, blunt ball needle tip, polar ball needle tip, etc.
(2) The structure of the barb can also have many variations. Such as standard barb, rounded barb, non-protruding barb, and medium-protruding barb.
(3) The relative bending direction of the needle handle elbow can also have several variations.
(4) The cross-sectional shape of the needle blade includes round, triangular, square, diamond, etc.
(5) The geometric size of the needle is an important parameter to express the specifications of the needle. The thickness of the needle blade, needle waist and needle handle are expressed by the needle blade number, needle waist number and needle handle number respectively. The larger the number, the thinner it is. The needle blade number (sometimes referred to as the needle number) is often mentioned in production. The size of the ordinary needle blade number corresponds to the height of the needle blade cross-sectional triangle.
(6) The arrangement of the barbs varies, generally divided into standard type (RB), medium type (MB), encrypted type (CB), etc.
The needle and the needle plate are almost statically matched. The diameter and length of the needle, the arrangement form and various specification parameters are determined according to the purpose.
Nonwoven performance approach
1.Mixing high shrinkage fibers
Mix high shrinkage fibers, such as polyvinyl chloride fibers, into the fiber web. After needling, they are treated with hot air, steam or hot water to increase the density of the needle-punched nonwoven material.
According to the product density requirements, the content of high shrinkage fibers in the fiber web can vary greatly. For example, if the content of high shrinkage fibers in the fiber web is 80%, the shrinkage rate can reach 50% after heat treatment.
This method can increase the density of needle-punched nonwoven materials, reduce surface needle puncture marks, and have good resistance to multiple bending and delamination, which is suitable for synthetic leather base fabrics.
2.Mixing thermal bonding fibers
Mix thermal bonding fibers into the fiber web. After needling, they are treated with hot rolling to improve the strength and dimensional stability of needle-punched nonwoven materials, but the hardness of the nonwoven material increases and the resistance to multiple bending decreases.
This method cannot usually be used independently as a reinforcement for needle-punched nonwoven materials, and can only be used to additionally reinforce the needle-punched nonwoven materials on which the base fabric is laid.
3.Laying the base fabric
Laying a light and thin base fabric can greatly improve the initial elastic modulus of the nonwoven material, but it is not very helpful to improve the breaking strength. Laying a high-strength thick and heavy base fabric can greatly improve the breaking strength of the nonwoven material, but attention must be paid to the damage to the base fabric caused by the needles.
Studies have shown that when the needling depth is 13mm and the needling density is 200 needles/㎝², the single-edge hook needles are arranged in the longitudinal position, and the longitudinal strength of the base fabric after needling is 90% and the transverse strength is 28%; the single-edge hook needles are arranged in the transverse position, and the longitudinal strength of the base fabric after needling is 10% and the transverse strength is 90%. Reasonable setting of the arrangement angle of the needle hooks can take into account the longitudinal and transverse residual strength of the base fabric after needling. If the angle between the hook edge of the single-edge hook needle and the feeding direction of the fiber web is set at 40°, the longitudinal and transverse strength of the base fabric after needling can remain about 50%.
The influence of density on quality
The needling density refers to the theoretical number of needlings received by the fiber web per unit area (1 square centimeter). Needling density is the most important process parameter. Generally speaking, the greater the needling density, the greater the strength and tougher the product. However, if the fiber web is tight enough, needling again will cause fiber damage or needle breakage, which will reduce the strength of the product. Needling depth is the length of the needle protruding outside the fiber web after piercing the fiber web, in mm. Within a certain range, as the needling depth increases, the entanglement between the fibers is more complete, and the strength of the product is improved, but if the needling depth is too deep, the fibers will break and the strength of the product will be reduced. Usually the needling depth is controlled between 3 and 17 mm.