When the Chair Mould(FURNITUREMOULD) is operated at high hardness, the mould steel has high yield strength and low fracture toughness. High yield strength is beneficial to delay the generation of fatigue cracks, but low fracture toughness accelerates the expansion rate of fatigue cracks, reduces the critical length, and greatly shortens the fatigue crack growth cycle. Therefore, the fatigue life of the cold work dies mainly depends on the fatigue crack initiation time.
Hot work dies are typically used for medium or low hardness conditions, and chair mould fracture toughness is much higher than cold work dies. Therefore, in the hot work die, the fatigue crack growth rate is lower than that of the cold work die, and the critical length is greater than the cold work. The subcritical expansion period of the hot mould fatigue crack is much longer than that of the cold mould. However, the surface of the hot work die is susceptible to rapid cooling and rapid heating. The fatigue crack initiation time of hot work die is much shorter than that of cold work die. Therefore, the fatigue fracture life of many hot moulds mainly depends on the time of fatigue crack growth.
Common forms of fracture failure are: fragmentation, caries, splitting, fracture, cracking, etc. The driving force for different mould fractures is different. Cold working dies are mainly subjected to mechanical forces (impact pressure). In addition to mechanical forces, hot moulds also have thermal stresses and microstructure stresses. Many hot working dies have higher operating temperatures and forced cooling. Internal stresses can far exceed mechanical stresses. Therefore, the fracture of many hot moulds is mainly related to excessive internal stress.
There are two types of chair mould fracture processes: one-time fracture and fatigue fracture. A one-time break is a mould that sometimes breaks suddenly during the stamping process, and once cracks begin, it becomes unstable and expands. The main reason for this is the severe overload or severe embrittlement of the mould material (eg overheating, insufficient tempering, severe stress setting and severe metallurgical defects).
The design of the gate is related to the size of the plastic part, the shape and the mould structure of the Crate Mould(FURNITUREMOULD), the conditions of the injection moulding process and the performance of the plastic part. However, in terms of basic functions, the gate portion should be small and the length should be short, as this is the only way to increase flow rate, rapid cooling and sealing, separation of plastic parts and minimal residual marking.
Regardless of whether the product is filled or not, the flow length determines the injection pressure, and the clamping force and shortening of the entire flow length reduce the injection pressure and clamping force.
The gate position will affect the pressure holding pressure, the pressure holding pressure and the pressure maintaining pressure balance. Keep the gate away from the stress position of the product (eg bearing position) to avoid residual stresses. Exhaust gas must be considered at the gate location to avoid wind accumulation.
If there is no balanced runner system, the following gate balancing method can be used to achieve the goal of uniform injection moulding. This method is suitable for crates moulds with a large number of holes.
There are two ways to balance the gate: change the length of the gate trench and change the cross-sectional area of the gate. In another case, the balancing door is also required when the chambers have different projected areas.
At this point, in order to determine the size of the gate, it is necessary to determine the size of one of the gates, find the ratio of its gate volume to the corresponding cavity volume, and apply the ratio to the gate and the corresponding gate comparison cavity, and then calculate The size of each door.
Proportional thickness criteria must be observed when constructing ribs and gussets. Longer cycle times can be expected if the ribs or gussets are also relative to the voids, component walls, sinking, warping, weld lines (all resulting in a large amount of compression stretch). The position of the ribs and gussets also affects the Crate Mould(FURNITUREMOULD) pattern of the assembly. Maintain the position of the door in the mind when designing the ribs or gussets.
Ribs that are well positioned within the flow line, also as gussets, can be used to enhance component filling by acting as an interior. Ribs and gussets that are poorly positioned or have the wrong purpose may result in the poor filling of the crate mould and may result in burn scars on the finished part. These problems usually occur on isolated ribs or gussets, just where air entrapment becomes a problem of ventilation. Note: This is an additionally recommended rib.
In extreme positions, the thickness of the intersection with the nominal wall does not exceed half of the nominal wall. The ribs from the intersection of the nominal walls should not exceed half the nominal wall. Encounters indicate that violating this rule greatly increases the risk of rib reading (partial gloss gradient differentiation). Bolts are used in parts with inserts, self-tapping fasteners, drive pins, enlarged inserts, reduced threads, and joints or force fits. Stay away from independent bosses anytime, anywhere.
More specifically, the boss is attached to a wall or rib to connect the ribs. If the boss is too far from the wall, connecting the ribs is unrealistic. Used to establish the size of the boss at a distance or at a distance. a wall. Keep in mind that these bosses are the core of all methods from the boss to the bottom. The formed thread can be developed into a part made of an engineering thermoplastic resin. The thread should normally have a rounded root and should not have a feathered edge - to prevent tension build-up. For example, a large pattern for moulding internal and external threads.
Threads are also a type of undercut, and when the assembly is removed from the crate mould, it should be handled by providing a demolding loosening assembly, folding the core, and the like. Every job should find external threads around the parting line of the crates, and economics and mould reliability are most appropriate.
Heating and maintenance of the control system are especially important for hot runner Chair Mould(FURNITUREMOULD). At the end of each production cycle, a multimeter should be used to measure the rod heater, thermocouple, and troubleshoot in time. The operator should remove the residue in time, keep the mould inside and outside the injection moulding machine clean and tidy, and do a good job in resettlement management and civilized production.
When working continuously, the debris should be removed regularly. For the high surface quality requirements of injection moulded plastic parts, the surface should be treated with skin texture to increase the cleaning frequency and ensure the surface of the cavity is smooth.
Strengthen the life cycle management of chair moulds and strictly implement the mould recovery card system. Used as a record for plastic moulding manufacturing, testing, use, repair, improvement, and scrapping, detailing the information in the above process. The contents of the card include plastic molding manufacturing records (characteristics of the mold itself, such as mold name, mold number, mold size, etc.), initial test mode, mold ejection mechanism and cooling circuit description, process adjustment point in mass production process, use And maintenance records, mold improvement records, mold waste records, etc. The mould history card transfers the information of the moulding workshop to the mould shop during the mould repair process, and records the mould.
The basis of the chair mould overhaul comes from three aspects: the content of the mold history card (according to the recorded data, this is the most common damage of the mould, which parts are most susceptible to mould damage, which mould is the most vulnerable, the most common mould reasons Damage, which damage has the most serious consequences). The first-line technicians and operators summarized the problems and problems that may arise during the moulding process of the injection moulded parts. The technical department summarized the problems of the plastic structure according to the requirements of the injection moulding manufacturer. The mould recovery card is mainly used for two aspects: one is the direct or indirect cost of monitoring; the other is a special analysis of the mould problem. Of course, people are not only interested in the damage of the mould, but also find the cause, find a solution, and try to prevent similar problems from happening.
The mould temperature of the Crate Mould(FURNITUREMOULD) at the interface with the part is important. It is generally recommended to use a separate cooling circuit. A more viable temperature regulation solution is usually a water jacket insert. These are sometimes custom made, but can also be used as typical products for many manufacturers. These usually result in observations around the entrance, which may require attention. Special care should also be taken to ensure that the valve stem is well secured for certain contact. Even with acceptable cooling and good contact, you will find a limit on the size of the gate. An inlet size of 3.10 mm (0.125 in.) and below usually produces the best appearance.
Doors larger than this are often difficult to cool and the door looks poor due to stickiness. Another aspect that affects the aesthetics of door space is crystallization. The crystallization phase will vary, using different polymers and crystallization tendencies. Consult a technical service representative to determine if this is relevant to your particular polymer supplier.
If possible, a valve method is required when running the polymer. This has several advantages over other hot melt transfer methods. For valve gates, the melt channel is externally heated and the mechanical shut-off function allows for better inlet trace manipulation.
Gate sizes are typically larger than other available technologies. The valve needle is retracted throughout the filling process, reducing operational obstructions. The end result is a reduction in shear heating and pushing.
Steel is the industry standard material for the manufacture of the Crate Mould(FURNITUREMOULD). It is considered a good all-around material that embodies many of the ideal features we are looking for.
There are many different types of steel available for a variety of general applications, and many special sheets of steel are available for more extreme applications. However, for our purposes, we will limit our discussion to those steels that are commonly used in crate mould manufacturers.
Many sheets of steel are used in the construction of crates moulds. All steels contain carbon. Generally, the higher the carbon content, the stronger the strength of the steel. Low-carbon ordinary steel or low-carbon steel is sometimes used, and in other cases, steel with higher carbon content is usually alloyed with other elements to improve the performance of the steel. Carbon steel alloyed with other elements to improve its properties is commonly referred to as tool steel or alloy tool steel.
For almost all mould steels, the most common alloying elements are chromium, nickel molybdate, tungsten cobalt and vanadium. For most mould steels, four of these components are typically used.
Chromium: Improves surface wear resistance and corrosion resistance.
Nickel: Improves low-temperature toughness and enhances fatigue resistance:
Vanadium: Improves strength, hardness and impact resistance.
Tungsten: Improves strength, toughness and higher temperature performance.
Although these alloying elements are intended to improve certain properties, care must be taken that they also adversely affect other properties, for example, as the chromium content increases, the thermal conductivity of the alloy steel also decreases.
Crate Mould(FURNITUREMOULD) finishing - Finishing is required for almost all cavity and punches forms. This may be a polished surface treatment, a photo-etching treatment or a plating treatment. However, for some technical components, surface finish is not critical and often requires fine EDM surface treatment. If special surface treatment is required, a variety of processes can be used, including:
If a very high surface finish is required on the core/cavity, the correct steel must be selected. It must be free of impurities and stresses and has a low sulfur content (usually added to improve processability).
Electroslag refining (ESR) is a process used by mould steel suppliers to reduce the number of impurities in steel. Vacuum degassed steel is also used to prevent the formation of localized impurities or pits on the steel surface which can damage the polished surface.
The polishing process is a slow and laborious process involving three different phases:
Rough: Use sandpaper, emery or mechanical reciprocating polishing equipment such as I profile.
Intermediate: Use fine grinding stone.
Surface treatment: hand polished with diamond paste and orange bar or with a mechanical reciprocating hand tool.
All Crate Mould(FURNITUREMOULD) is expensive and can be easily damaged and corroded if not properly maintained. In most injection moulding shops, crate mould storage areas typically require considerable capital investment and typically require millions of pounds.
Before storing the crate mould, check for any repairs that should be made before the next use of the mould. Some simple precautions will ensure that the crates are in good condition the next time they are needed. The basic list is as follows:
Crate moulds should be cleaned and repaired.
The waterway should be blown out with air.
The crates mould should be lubricated.
The vents should be cleaned.
All moulded surfaces should be protected by a spray mould.
All safety switches should be inspected for damage and proper function.
The safety and function of all circuits should be checked and, if possible, the crate mould should be kept closed and, if not possible, a wooden or similar cover should be used to protect the two moulds from damage.
It is foolish to wait for the machine to fail before performing maintenance. It may also be unwise to perform large maintenance work because the planned maintenance plan indicates the date the maintenance work has been completed. However, Murphy's demanding law states that failures always occur at the most inconvenient time, and if the failure results in a large and profitable order, the losses incurred may be much greater than the cost of performing planned maintenance.
At the position that is opened before the Daily Necessities Mould(FURNITUREMOULD) unscrewing operation, the workpiece will remain on the displaced portion of the daily necessities mould. In this case, it is important to shape the keying features at the bottom of the part.
For the practice of loosening when the daily necessities mould is opened, any type of keying function is acceptable, including those described above. This may be an active feature or a feature that needs to be specifically introduced. If the keying feature cannot currently be accessed as part of an off-the-shelf design, the appropriate design must be arranged with the product design engineer. A simple rectangular or triangular type extending along the exterior of the moulding is typically used.
A valuable rule is to carefully examine the design of the daily necessities mould, determine which type of keying is required and combine it with the design so that it can withstand the loosening function without damage. With this design, the loosened core moves axially outside the mould to expel it. This allows the moulded part to be placed in the cavity, depending on the design. Additional jetting capabilities may be required with regard to part geometry and basic tool design. Longer threads can be demolded with this design compared to the stripper method. The figure below shows a common shift core layout. In this configuration, as previously mentioned, it is natural to add a key around the bottom of the moulded part. This again provides resistance to the moulded article that rotates throughout the unscrewing stage, but in this case, it is not necessary to maintain the peeling plate. This is because the core is being screwed out from the moulding, so the keys are not pushed away like a fixed core structure.
The different forms of plastic production that are used occasionally are the removal of the moulded article before the mould of the daily necessities is opened. This may require the generation of splines and other keying features into the cavity. However, this creates another problem in that the component stays in the cavity after the demolding phase. This, therefore, indicates that some fixed half jet may be required to remove the moulded part from the mould cavity. While such structures typically require parts with complex geometric features, it is always best to ensure that the mould rests on the moving parts of the daily necessities mould. This makes the design and construction of the mould easier.
The polishing process of Daily Necessities Mould(FURNITUREMOULD) is a very important step in the manufacture of the entire mould.
Mechanical polishing: Mechanical polishing is accomplished by cutting and removing protrusions and obtaining a smooth surface. Polishing methods generally use oil stone, wool wheel, sandpaper, etc., mainly by hand. Some special parts of the rotor surface require the use of a turntable, and if other tools require high surface quality, ultra-precision polishing may be required. Ultra-precision polishing uses a special abrasive. The polishing liquid contains abrasive pressure on the surface of the workpiece to be processed and rotates at high speed. This technology can achieve a surface roughness of Ra0.008μm, which is the most accurate polishing method.
Chemical polishing: Chemical polishing refers to first dissolving a material in a chemical medium having a convex portion to obtain a smooth surface. The main advantage of this method is that this method does not require complicated equipment, the complex shape of the workpiece can be polished, and many workpieces can be polished at the same time with high efficiency. The main problem is how to formulate a suitable chemical polishing solution. The chemical polishing surface roughness is generally 10 μm.
Electropolishing: Electropolishing and chemical polishing have the same basic principle of smoothing the surface by selectively dissolving small convex portions on the surface. It eliminates the effects of the cathodic reaction compared to chemical polishing.