This is a frequently encountered problem, but it is also relatively easy to solve. When it is really not solved by technological means, it can be improved from the design and manufacture of molds, which can generally be solved.
Month: April 2021
What should I perform if plastic material injection molding is imperfect?
This is a frequently encountered problem, but it is also relatively easy to solve. When it is really not solved by technological means, it can be improved from the design and manufacture of molds, which can generally be solved.
1 . Equipment:
(1) The capacity of the injection molding machine is small. When the quality from the product exceeds the actual maximum injection quality of the injection molding machine, it is obvious that the amount of material supplied will not make ends meet. If the top quality of the product is close to the actual injection quality of the shot molding equipment, there is a problem of insufficient plasticization. The heating time of the material in the barrel is usually insufficient. As a result, the appropriate melt cannot be provided to the Cnc Machining mold in time. In this case, the problem can only become solved by replacing the injection molding machine with a large capacity. Some plastics such as nylon (especially synthetic 66) have a narrow melting range and a large specific heat. An injection molding machine having a large plasticizing capacity is required to ensure the supply of materials.
(2) The temperature displayed by the thermometer is not true, the bright high is definitely low, and the material temperature is too low. This is because the temperature control device such as thermocouple and its wiring or the temperature difference millivoltmeter fails, or because the heating coil far away from the heat measurement point is aging or burned, heating failure has not been found or has not been repaired and replaced with time.
(3) The diameter in the inner hole of the cnc turning nozzle is too large or perhaps too small. If it is too small , due to the small flow diameter, the specific volume of the strip will increase, which will easily be cooled, block the feed channel or consume the injections pressure; The condition of low force. At the same time, plastic materials such as uhmw machining cannot reduce the viscosity because of the lack of large shear warmth, which makes it difficult to fill the mold.
The nozzle can be not well matched with the inlet of the main runner, as well as the overflow with the mold plus the filling on the mold are often unsatisfactory. The nozzle itself has high flow resistance or is blocked by foreign matter, plastic carbonized deposits, etc .; the spherical surface of the nozzle or the primary runner inlet is damaged or deformed, which affects the good cooperation with the other party; edm Machining faults or deviations cause the nozzle and the main runner axis to have an inclination displacement or the axial pressing surface area to separate; the nozzle ball diameter is certainly larger than the main runner entrance ball diameter, due to the gap at the edge, the nozzle axis gradually increases under the squeeze of this overflow The pushing pressure will cause the plastic gear to be dissatisfied.
(4) The plastic material frit blocks the feeding channel. Because the plastic is normally partially melted and agglomerated in the hopper dryer, or the temperature inside the feed section of the barrel is too high, or the plastic grade is going to be not selected properly, or maybe the plastic contains too much lubricant, the clear plastic will enter the feed port or screw at the reduced diameter position. Premature melting in the deep groove of your screw end, the pellets and the melt are bonded to each other to form a “bridge”, which blocks the channel or envelops the screw, and slides circularly with the mess rotation, and cannot move forward, causing interruption of feeding or irregular fluctuations. This situation can only end up being fundamentally resolved after the passage is cut through as well as the material blocks are eliminated.
(5) The nozzle cold material enters the mold. Injection molding machines usually only install straight-through nozzles due to pressure loss. However , if the temp of the front end of the barrel and the nozzle is too large, or there is too much material at the front end of the barrel or clip under high pressure, “salivation” will occur, which will cause the vinyl to accidentally enter the key runner entry before the injection is started and the plastic mold is open. And it becomes hard underneath the cooling effect of the template, which usually prevents the melt from entering the cavity smoothly. At this time, the temperature belonging to the front end within the barrel plus the nozzle should be lowered, the storage capacity for the barrel must be reduced, and the back pressure ought to be reduced to avoid excessive dissolve density at the front end of the barrel.
(6) The treatment cycle is actually short. Due to the short cycle, the material heat is too late to keep up, which will also cause material shortage, especially when the voltage fluctuates greatly. The period should be adjusted accordingly according to the supply voltage. Generally, the injection and holding pressure time are not considered during the adjustment. The main consideration is to adjust the time from the completion of the holding pressure to the return from the screw, which in turn does not affect the filling and molding conditions, and can extend or shorten the preheating time of the pellets in the barrel.
2 . Mould:
(1) The mildew casting system is defective. The flow channel is too small , too thin or perhaps too long, which will increases fluid resistance. The primary runner should increase the size, and the athlete and branch runner needs to be round. The runner and also the mouth is too large, as well as the injection force is inadequate; the jogger and gate are clogged by impurities, foreign matter or carbide; the runner and door are rough with scars, or have sharp angles, plus the surface roughness is poor, which impacts the material circulation;
The athlete does not have a cold slug well or the chilly slug well is too small , and the opening direction is without question wrong; for multi-cavity molds, the jogger and gate size distribution should be carefully arranged, otherwise there will be only the main runner or the thick and short gate. The situation where the cavity can be filled but other cavities cannot be filled. The diameter in the runner need to be increased appropriately to reduce the pressure drop of the burn flowing towards the end with the runner, and the gate on the cavity farther from the main runner should be enlarged to make the injection pressure and materials flow velocity of each tooth cavity basically the same.
(2) The mold design is unreasonable. The mold is too complex, with many turns, improper selection of the feed inlet, too narrow runner, limited number of gates or improper form; the partial portion of the product is very thin, the thickness of this entire product or part should be increased, or an auxiliary must be set near the insufficient filling Runner or gate;
It is not uncommon intended for inadequate venting measures inside the cavity to cause dissatisfaction with the parts. This defect mostly occurs in the corners of the item, deep recesses, thin-walled parts surrounded by thick-walled parts, and thin-walled parts formed simply by side entrance. The bottom of your bottom shell, etc .
The design to eliminate this defect includes opening effective vents, selecting a reasonable door position to help make the air easy to discharge in advance, and when necessary, deliberately making a certain part of the trapped area of the cavity into an insert to make the air escape from your insert. Gap overflow; to get multi-cavity forms that are prone to unbalanced gateway distribution, the number of injection cavities should be decreased if necessary to ensure that other cavity parts are qualified.
(1) Improper give food to adjustment, lack of material or perhaps excessive material. Inaccurate nourishing metering or abnormal feeding control system operation, abnormal injection routine caused by hypodermic injection molding machine or form or operating conditions, low pre-plastic back pressure, or low particle density in the clip or barrel may cause materials shortage. For large particles, Pellets with many voids and plastics with large crystalline specific volume changes, such as polyethylene, polypropylene, nylon, etc ., as well as materials with higher viscosity, including ABS, ought to be adjusted to a higher volume. If the temperature belonging to the material is undoubtedly high, the volume should be modified.
When there is certainly too much material at the end within the barrel, the screw will certainly consume extra injection pressure to compress and push the excess stock in the gun barrel during injection, which greatly reduces the effective shot pressure for the plastic entering the mould cavity. The product is hard to fill.
(2) The injections pressure is actually low, the injection time is brief, and the plunger or twist returns too early. Molten plastic has larger viscosity and poor fluidity at lower working temperatures, so it needs to be injected at higher pressure and speed. For example , in the production of ABS color parts, the high temperature resistance of the colorant limits the heating heat range of the barrel, which has to become compensated by simply higher treatment pressure and longer hypodermic injection time than usual.
(3) The injection speed is slow. The injection speed is of great significance for some products with complicated shapes, huge thickness changes, and long processes, as well as plastics with high viscosity, such as toughened ABS. When the product can not be filled with ruthless, high-speed shot of ptj machining parts should be considered to overcome the problem of filling discontentment.
(4) The material temperature is too low. The temperature of the front end from the barrel is low, as well as the viscosity in the molten materials entering the cavity rises too early to the point where it is difficult to flow as a result of cooling a result of the shape, which hinders the filling of the far end; the rear part of the barrel or clip is a plastic with low temperature and substantial viscosity Difficult flow slows the forward movement with the tsmachining screw. As a result, it seems that the pressure displayed by the pressure gauge is sufficient, but the melt actually enters the cavity in low pressure and low speed;
If the nozzle temp is low, it may be that the nozzle is in contact with the cold black mold for a long time throughout the fixed feeding and loses heat, or perhaps the nozzle heating system ring is usually insufficiently heated or has poor contact, resulting in cold, frigidity, frigidness, coldness of the material, which may block the feeding channel on the mold; if the mold does not have cool material Well, with self-locking nozzles and post-feeding procedures, the valve can maintain the necessary temps; the nozzle is too frosty when it is just turned on, and sometimes a flame gun can be used for external heating to accelerate the temperature of this nozzle.
Four, raw materials:
Plastic has poor fluidity. Plastic Machining Service often uses recycled components, and recycled materials often reflect a tendency to increase viscosity. The experiment pointed out that the unit volume denseness of molecular chain scission generated by oxidative cracking increased, which increased the viscosity of your flow in the barrel and cavity, plus the regenerated scraps promoted the production of more gaseous substances, which caused the injections pressure to get lost. Increased, causing difficulty in filling the mold.
In order to improve the fluidity of the plastic material, it should be considered to add exterior lubricants just like stearic acid or its salts, preferably silicone oil (viscosity 300~600cm2/s). The addition of lubricants not only improves the fluidity of the clear plastic, but also improves the stability and reduces the air level of resistance of gaseous substances.
How to set the low pressure and high pressure clamping positions?
The clamping process is generally divided into three or four stages, generally fast-slow-high pressure; fast clamping, according to the structure of the mold,
Analysis of several important injection molding process parameters
The effect of plastic viscosity and conditions on viscosityThe nature of the friction between macromolecules when the molten plastic flows is called the viscosity of the plastic. The coefficient of this viscosity is called the viscosity, so the viscosity is a reflection of the fluidity of the molten plastic.
Safeguards for the appearance of plastic-type molds
Safeguards for the appearance of plastic-type molds
one particular: The content of your nameplate should be printed together with the mold amount, mold pounds (KG), and mold size (mm). The characters are all marked with 1/8 ” code, as well as the characters are clear and perfectly arranged.
a couple of: The nameplate ought to be fixed on the mildew and mold leg near the rear format and the guide corner (15mm away from equally sides), set with several rivets, fixed reliably, and not easy to peel off.
3; The cooling drinking water nozzle should use a plastic-type block to insert the nozzle, ￠10 tube, the specification can be G1/8″, G1/4″, G3/8″. Whenever there are particular requirements in the contract, you should follow the agreement.
4: The cooling normal water nozzle ought to extend from the aluminum cnc parts surface, and the head of the water nozzle sunken into the exterior surface should not exceed 3mm.
5: The diameter belonging to the cooling water nozzle elimination hole should be ￠25, ￠30, ￠35mm three specifications, the outer edge within the hole has a chamfer, the chamfer is greater than 1 . 5×45, plus the chamfer is the same.
6th: The a / c water nozzle must have an entry and exit indicate, the inlet water is at, the outlet drinking water is OUT, and the sequence number is added after Out-and-in, such as IN1 and OUT1.
7: Draw English heroes and amounts ought to be capitalized (5/6″), the location is 10mm directly below the tap, the handwriting is clear, beautiful, nice, and evenly spaced.
almost eight: The inlet and outlet nozzles as well as the inlet and outlet nozzles should be the same as the conditioning water valve, and add G (gas) and O (oil) with a bare character just before IN and OUT.
hunting for: There are drinking water nozzles within the upper and lower attributes of the shape installation way, which should end up being built-in, and open the diversion groove or have a support column beneath it meant for protection.
twelve: The lube nozzle or water nozzle that cannot be built-in should be protected by a support steering column.
11: Machining uhmw mold bottom part will need to have a reference direction symbol for each template, made a fortune English DATUM, the word level is 5/16″, the location is definitely 10mm from the side, the writing is very clear, beautiful, cool, and equally spaced.
12: Each web template must have a part number. The number is 10mm from the bottom directly under the reference point of view symbol, and the requirements will be the identical to No . 11.
13: Mold components should affect the lifting and storage for the mold. For example, there should be support legs to protect the ceiling fan oil tank, normal water nozzle, and pre-reset device that outflow underneath during installation.
13: To install the support calf, use screws to pass through the support knee and fix it on the mold base, or to fasten the excessively extended support limb to the mildew base by simply turning external threads.
15: Machining uhmw plastic black mold ejection ditch must meet the specified shot molding machine, except for tiny molds, in principle, a single center can’t be used for ejection (when the distance or thickness of the form is higher than 500mm), the ejection cup diameter ought to be larger than the top The fishing rod is 5-10mm larger.
of sixteen: The placing ring should be reliably set (usually 3 M6 or perhaps M8 hexagon socket screws), the size is generally ￠100 or ￠150mm, 10mm higher than the very best zone. If you will discover special requirements in the deal, the same shall apply.
18: The increasing hole of the positioning wedding ring must be a counterbore, and it is not allowed to get directly attached to the top surface area of the form base.
18: When a custom cnc aluminum mold considering more than 8000KG is installed on the injections molding equipment, the attach should be forced by perforation, and the area must not be shoved separately. In cases where the equipment uses hydraulic fastening molds, twist perforations must also be added to prevent the inability of the hydraulic mechanism.
20: The sprue bushing ball R is usually larger than the nozzle ball R from the injection molding machining.
20: The inlet dimension of the sprue bushing ought to be bigger than the diameter in the nozzle injections port.
twenty-one: The overall measurements of the form must conform to the specified treatment molding machine.
22: The surface of the mold starting will need to have pits, rust represents, unnecessary jewelry, water, gas, oil slots, etc ., and other defects that affect the looks.
23: Every plate of the mold base must have a chamfer greater than 1 . 5mm.
24: The mold should be convenient designed for hoisting and transportation, plus the mold parts should not be disassembled during hoisting ( aside from the important cylinder, which in turn needs to be manufactured separately). The lifting wedding ring interferes with the faucet, oils cylinder, pre-reset rod, etc ., and the position of the moving ring pin could be altered.
25: Every single mold part weighing a lot more than 10KG will need to have a suitable weightlifting eye tooth cavity. If certainly not, corresponding actions must be taken up ensure that the component is easy to disassemble and mount. The size of the ring and the positioning with the ring opening are designed according to the relevant organization standards.
21: If ejector mechanisms such as for example ejector supports and ejector blocks interfere with sliders, and so forth, there has to be a forced pre-reset mechanism, and the very best tag has a reset to zero travel swap.
27: The cylinder key and disposition should be handled by a travel around switch, and the installation is definitely reliable.
twenty eight: The mould oil separator ought to be fixed and trustworthy. The oily fat pipe hooking up the gas separator as well as the oil tube should use a rubber conduit, and the joint should employ standard parts.
29: There has to be trash toenails on the thimble plate. The clamping system should be mounted reliably, with positioning limits, symmetrical unit installation, no less than some (small forms can be 2).
30: In case the injection molding machine switches into an extended nozzle, there must be enough space inside the setting ring to ensure that the expanded nozzle with heating wedding band of the standard injection molding machine can easily extend in.
31: Most inclined surfaces could be removed from a gap that moves through underneath plate plus the thimble lower part plate and whose position is the same as the inclined leading angle.
thirty two: The bottom area of the screw mounting golf hole must be toned. Screws in this article M12 (including M12) should be (12. in search of grade).
Mold meets working conditions
1. Wear resistanceWhen the blank is plastically deformed in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, which causes the machining uhmw mold to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
Hardness is the main factor affecting wear resistance. In general, the higher the hardness of the mold parts, the smaller the amount of wear and the better the wear resistance. In addition, wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the material.
2. StrengthThe working conditions of the molds are mostly very bad, and some of them are often subjected to large impact loads, which leads to brittle fracture. In order to prevent the sudden brittle fracture of precision machining china parts during work, the mold must have high strength and toughness. The toughness of the mold mainly depends on the carbon content, grain size and organization state of the material.3. Fatigue fracture performanceIn the working process of uhmw machining mold, under the long-term action of cyclic stress, it often leads to fatigue fracture. Its forms include low-energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture, and bending fatigue fracture. The fracture performance of the mold mainly depends on its strength, toughness, hardness, and the content of inclusions in the material.
4. High temperature performanceWhen the working temperature of the mold is higher, the hardness and strength will decrease, leading to early wear of the mold or deformation and failure of the machining uhmw plastic. Because the mold material should have high anti-tempering stability, to ensure that the mold has a high hardness and strength at the working temperature.
5. Resistance to cold and heat fatigueSome molds are in a state of repeated heating and cooling during the working process, which causes the surface of the cavity to be pulled and pressure to change the stress, causing surface cracks and peeling, increasing friction, hindering plastic deformation, and reducing dimensional accuracy. Mold failure. Heat and cold fatigue is one of the main forms of failure of hot work molds, and this type of mold should have high resistance to cold and heat fatigue.
6. Corrosion resistanceWhen some molds such as plastic molds are in operation, due to the presence of chlorine and fluorine in the plastic, strong corrosive gases such as hci and hf will be resolved after heating, which will erode the surface of the mold cavity, increase its surface roughness, and aggravate wear failure.
Mold meets process performance requirements
The manufacturing of molds generally involves several processes such as forging, cutting, and heat treatment. In order to ensure the quality of mold manufacturing and reduce production costs, the material should have good forgeability, machinability, hardenability, hardenability and grindability; it should also have small oxidation, decarburization sensitivity and quenching Deformation and cracking tendency.
1. ForgeabilityIt has low hot forging deformation resistance, good plasticity, wide forging temperature range, low tendency of forging cracking and cold cracking and precipitation of networked carbides.
2. Annealing processabilityThe spheroidizing annealing temperature range is wide, the annealing hardness is low, the fluctuation range is small, and the spheroidizing rate is high.
3. MachinabilityThe cutting amount is large, the tool loss is low, and the machined surface roughness is low.
4. Sensitivity to oxidation and decarburizationWhen heated at high temperature, the oxidation resistance is good, the decarburization speed is slow, the heating medium is not sensitive, and the tendency of pitting is small.
5. HardenabilityAfter quenching, it has uniform and high surface hardness.
6. HardenabilityAfter quenching, a deeper hardened layer can be obtained, and it can be hardened by using a mild quenching medium.
7. Tendency of quenching deformation and crackingConventional quenching has small volume change, shape warping, slight distortion, and low tendency of abnormal deformation. Conventional quenching has low sensitivity to cracking, and is insensitive to quenching temperature and workpiece shape.
8. GrindabilityThe relative wear of the grinding wheel is small, and the limit of grinding without burn is large. It is not sensitive to the quality of the grinding wheel and cooling conditions, and it is not easy to cause abrasion and grinding cracks.
Third, the mold meets the economic requirementsWhen selecting materials for the mold, the principle of economy must be considered to reduce the manufacturing cost as much as possible. Therefore, under the premise of satisfying the performance, the first choice is the lower price, carbon steel can be used without alloy steel, and domestic materials can be used without imported materials. In addition, the production and supply of the market should also be considered when selecting materials, and the selected steel grades should be as few and concentrated as possible, and easy to buy.
Analysis of the advantages and disadvantages of PA6 nylon plastic raw materials
The main advantages of PA6 nylon plastic materials:
Nine common problems of color masterbatch
Under sunlight, there are striped pigment bands in the productThis question needs to be considered from two aspects: the physical and mechanical properties of the plastic and the plastic molding process:
High precision plastic mold processing steps
High-precision plastic mold processing steps 1. Heating and pre-plasticizing:Driven by the drive system, the screw conveys and compacts the material from the hopper. Under the combined action of the heater, screw and barrel outside the barrel, the material is gradually melted, and the material is gradually melted at the head of the barrel. The part has accumulated a certain amount of molten plastic machining. Under the pressure of the melt, the screw slowly retreats. The retreat distance depends on the amount required for one injection of the metering device to adjust. When the predetermined injection volume is reached, the screw stops rotating and retreats .
The most complete classification of polymer materials in history
Macromolecular materials, also called polymer materials, are materials composed of macromolecular compounds as the matrix and with other additives (auxiliary agents).Polymer material classification1. Classification by sourcePolymer materials are classified into natural polymer materials and synthetic polymer materials according to their sources.Natural macromolecules are macromolecule substances that exist in animals, plants and organisms, and can be divided into natural fibers, natural resins, natural rubber, animal glues, and so on. Synthetic polymer materials mainly refer to the three major synthetic materials of plastics, synthetic rubber and synthetic fibers, in addition to adhesives, coatings and various functional polymer materials.Synthetic machining uhmw have properties that are not available or superior to natural polymer materials-smaller density, higher mechanics, wear resistance, corrosion resistance, electrical insulation, etc.
2. Classified by applicationPolymer materials are classified into rubber, fiber, plastic, polymer adhesives, polymer coatings and polymer-based composite materials according to their characteristics. 3. Classified by application functionAccording to the classification of material application functions, polymer materials are divided into three categories: general polymer materials, special polymer materials and functional polymer materials. General polymer materials refer to machining uhmw plastic that can be produced on a large scale and have been widely used in major areas of the national economy such as construction, transportation, agriculture, electrical and electronic industries and people’s daily lives.These are divided into different types such as plastics, rubber, fibers, adhesives, and coatings. Special polymer materials are mainly uhmw machining with excellent mechanical strength and heat resistance, such as polycarbonate, polyimide and other materials, which have been widely used in engineering materials. Functional polymer materials refer to polymer compounds that have specific functions and can be used as functional materials, including functional separation membranes, conductive materials, medical polymer materials, liquid crystal polymer materials, etc.