China manufacturer and company for Packaging – Food/Beverage plastic crate mould,turnover box mould making with P20 steel
plastic crate mould
Currently，the crate applied to the field of logistics, such as beer crates, milk crates, food boxes and all kinds of cargo turnover box used in workshop is basically made of plastic.Plastic crate owns the features like anti-bending, anti-aging,heavy loading, tensile resistant, compression resistant, tearing resistant, high temperature resistant and so on.Often ,these Crate Dimensions are large and also require good mechanical properties, low temperature performance and durability. To meet these requirements, HDPE is used as a raw material and design a number of criss-crossing ribs on the outer surface and the bottom of the plastic crates, in order to increase its strength and stiffness. For good plastic injection molding, on crate mould structure design, the crate mould often adopt 4 or 6 hotrunner drops gate (or 3 plates crate mold)due to the large size ,complex shapes; due to four side walls with a lots of ribs perpendicular to the turnover box mold open direction ,4 sliders are need to form those ribs and make the crate release away from the mold. If you adopt point gate molds which require a three-plate structure, sequence and automatic stripping off the gate, etc., this kind of crate mould is with complex structure, large dimensions, long processing manufacture…
We use hot runner technology, injection molding flow analysis software to design and make crate mold.the crate mold is with reasonable structure, reliable operation, easy molding process control, crate quality assurance. Use hotrunner system technology to improve the quality of plastic parts, reduce production costs and save time.
- plastic crate mold
- Hotrunner:4 drops with “HOTSET” heating coils
- mold cavity steel:DIN 1.2738
- mold core steel:DIN 1.2312
- Plastic material:HDPE
- Cycle time:40 Secs
- Delivery time:45 days.
the maintenance of the crate mould before production
1.clean the mould surface for the oil, rust, check mould cooling hole for foreign material.
2.check the sprue if there is residual material.
3.check the fixed mold plate and confirm if the screw clamp is tightened.
4.After crate mould fixed on the injection molding machine ,injection operation should be carried out first. Observe the movement of each part of the operation :whether there is abnormal phenomenon, the moveable parts such as the guide pins, the ejection pins,sliders whether there is wear, lubrication is good,the stroke…
Hot Runner Systems
Advantages Over Cold Runner Moulds
There are numerous advantages in using hot runner system to make crate mould as opposed to a cold runner crate mould. A selection of the most obvious ones is listed below:
- There is no runner system to be removed from the mould.
- With no cold runner to be cooled, there is a shorter cycle time.
- Crate Mould opening stroke is reduced.
- Cost of storing and regrinding runners is eliminated.
- Risk of material contamination is lower as no reground material is used.
- Gates may be balanced more easily.
- Hot runner diameters can be larger than cold runners; thus lower injection pressures may be used.
- Cooling times are reduced.
- Better part quality can be achieved owing to a more consistent cyclc.
- A greater number of impressions may be used, as less injection pressure is necessary.
- Smaller shot weight means shorter metering times and injection times.
- Lower injection pressure means that smaller machines may be used.
These are powerful reasons for using hot runner moulds but the crate moulds are significantly more expensive than equivalent cold runner moulds. In view of this they are normally used for large quantities of at least 500 000 parts but, exceptionally, smaller quantities are sometimes produced.
The disadvantages are few hut worth mentioning:
- 24-hour operation is required for maximum economic production.
- Heat-sensitive materials may be difficult to process.
- Gate blockages can be time consuming and expensive to remedy.
hot runner systems have almost universally replaced the older insulated runner designs where high volume production is required. With only minor design changes it is possible to obtain much better temperature control, less pressure drop, and higher quality of parts moulded.
the modern designs make use of heated manifolds.these are separate units that carry the runner and nozzle gating systems. They are separate units insulated from the main body of the tool by stand-off buttons or feet. Note that the manifold does not touch the main tool at all, to prevent heat transfer from the manifold. The stand-off buttons and the lock screws are the only contact between the two. These types of tool are also sometimes referred to a shot runner unit tools.
Cartridge or tubular heaters are used to maintain melt temperature in the manifold and thermocouples are used to monitor it. These are connected to temperature controllers that switch the heaters on and off at predetermined values.
This design is ideally suited to moulding in non-heat sensitive materials and is very widely used where the quantity requirements justify the cost. Once melt temperatures have been reached after startup, very little additional energy is required to maintain the material temperature at this level owing to the insulating properties of plastics materials in general.Above illustrates the basic design of a modern manifold design hot runner tool.
Above shows a more detailed full hot runner tool moulding two different components. This clearly shows the manifold located into the tool at the top and insulated from the rest of the tool by stand off buttons. Note also that the tool is equipped with adequate water-cooling both in the cores and the cavities. This is important with hot runner tools to counter the inevitable transfer of heat from the manifold to the rest of the tool.
The mould incorporates a stripper plate, which gives maximum support to the two mouldings during ejection. This is important in this case to provide even, all round support for stripping the undercuts on the mouldings as ejection takes place. Another important feature of this tool is the length of the guide pillars, which must be long enough to guide the stripper plate throughout the ejection stroke. In this design, the length of the ejection stroke is controlled either mechanically with a stop as shown or with a hydraulic ejector.
When large components are being moulded, these may require a hybrid hot runner/cold runner system. the below shows such a design for a suitcase half, which uses a flash gate along most of the length of the moulding. This ensures that the melt stream is directed uniformly through the cavity with even flow. It also ensures that the relatively large volume of air is progressively displaced towards the split line furthest away from the gate. The direction of flow is very important to achieve this displacement of air to prevent burning and to prevent distortion associated with multipoint overhead pin gating.
Note in particular the position of the moulding with respect to the mould centre line of the mould tool. It is positioned dead centre on the mould. This ensures that the main projected area and hence the force is evenly spread with respect to the mould centre, thus avoiding out-of-balance forces on the machine platens.
To achieve this, the hot runner manifold has to be placed off centre. This does create a small out-of-balance force blit it is very small compared to that of the cavity area.