Hot runner system in plastic outdoor square dustbin mould
The cold runner of a plastic injection mould refers to the section between the mould inlet and the gate. The molten plastic maintains its fluidity inside the runner by virtue of the injection pressure and its own heat. However, as a part of the molding material, the runner is not a product. As a result, when designing a mould, we need to consider not only the filling effects but also the material-saving effect produced by shortening or downsizing the runner; but in actuality, it is not easy for us to have the best of both worlds, this is why we need hot runner mould.
Also known as the runner-less system, the hot runner is a system in which the molten plastic is not solidified after each injection, so when releasing the plastic part, the gate inside the runner does not have to be released. Since the plastic inside the runner is not solidified, the runner still stays unblocked when the next injection takes place.
The advantages of using a hot runner system
Why has the hot runner system been developed? What benefits can the hot runner system bring us?
Engineers familiar with the plastic injection molding process all know that traditional injection molding is always associated with the following disadvantages:
1. Hard to fill
2. Thin-walled large size parts easy to deform
3. Material waste in the runner
4. Inconsistent plastic part quality when using a multi-cavity mold, and so forth
The appearance of the hot runner system has provided an almost perfect solution for these problems.
Generally speaking, the hot runner system offers the following benefits:
1. Shorter cycle time
As it is not limited by the runner cooling time, the plastic part can be ejected in a timely manner after being molded and solidified. For the production of thin-walled small parts, the molding cycle can be kept within 5s.
2. Material saving
In a complete hot runner mould, material waste will not occur thanks to the absence of a cold runner. This is of greater significance to the application projects of the more costly plastic materials. As a matter of fact, global major hot runner manufacturers had witnessed leap forward development during the years when world crude oil and raw plastic materials were expensive. This is because the hot runner technology is an effective way to reduce waste materials and thus lower raw material costs.
3. Reducing defective products, and improving product quality
The temperature of the molten plastic inside the runner system can be accurately controlled during the hot runner injection molding process, so that the plastic is able to flow into each cavity in a more consistent manner, thus guaranteeing consistent quality products. The hot runner gate is of higher quality, so after mold release, the part produced will have smaller internal stress, leading to a smaller part deformation. Therefore, many high-quality products in the market are all produced with the hot runner mold.
4. Eliminating the following steps, helpful for production automation
After being molded with a hot runner mold, the part will be the final product, so there will be no follow-up steps like gate trimming, recycling, and runner cooling, thus helpful for production automation. Many manufacturers from both home and abroad have combined the hot runner system with automation, so as to greatly improve production efficiency.
Plastic outdoor square dustbin mould trial steps
1. Before the mould trial, dry the raw materials first. All materials need to be dried except PE/PP. It is a standard practice to perform the trial with new materials.
2. Mount the mould onto the center hole and keep it aligned. It is enough to set the clamping force at 1/3 of the rated capacity (tons). During the injection process, if burs occur due to some reason rather than too high injection pressure, the clamping force can be gradually increased until burs disappear, and such a practice is able to improve mould service life.
3. Mould opening speed, pressure and position should be appropriately adjusted, and in particular, low-pressure protection should be well adjusted, because it is a new mould, of which the molded product is unknown. If a mould is equipped with slides, the opening speed cannot be too fast. For a core-pulling mould, the first thing to do is to try it manually to see whether it functions well. Or else, the mould will be damaged in case of a mistake.
4. Clean the barrel with PP or PMMA, which are used for viscosity and friction respectively. The material temperature should be kept between 220 – 240℃. Make the travel as short as possible, and apply some backpressure to cleanse with fast injection. Apply some reasonably proportioned detergent if it is not easy to clean.
5. Condition setting/material injection volume/pressure & speed/time/quantity/position, etc. Injection pressure/injection speed/quantity are set from lower to higher according to product conditions. Cooling time/injection time should be gradually shortened as the product is taking shape, so as to prevent sticking and overfill.
6. Packing pressure must be applied, mainly with packing material of 5 – 10mm.
7. For molds with a straight hydraulic clamping system, it is necessary to see whether the clamping force is sufficient; for the toggle type, it is necessary to check whether the crosshead is straightened, to prevent the mould from being pushed backward during the injection process, thus avoiding mold damage caused by leakage of large burs.
8. Since the molding conditions are unknown, release agents are needed for the first several runs. If the product is released smoothly without any ejection marks, a release agent will not be necessary.
9. Each parameter should be gradually adjusted according to the molded product. Effect of pressure/speed change will show within 2 runs; effect of material/mold temperature change will show in at least 5 minutes.
10. The trial molded products should be stored in different bags, with defects and suggestions for improvement noted down. It is better to work in collaboration with the plastic injection mould manufacturer.
11. Pay attention to mould temperature increase. During multiple mould runs, mould temperature should be controlled via coolant or oil temperature/water temperature/electric heating tube – select different mould temperature controls for different materials, such as hot mould (60℃ and above): nylon/PBT/POM/PPS/PET/PMMA/PC/NORYL, and cold mold (60℃ and below): PE/PP/PS/AS/ABS/PVC/PU.
12. Air blow can be used to determine how water circulates within the mould. With regard to water pipe installation, the inlet pipe should be installed at the lower end; and the return pipe, the upper end.
13. The machine can only be stopped after raw materials in the barrel are completely injected. Then, remove the water pipe and blow air into the mould to expel water from it. Apply anti-rust agent to the inside of the mold and clean material trifles at the same time.
Plastic outdoor square dustbin mould trail instructions
1. Backpressure should be adjusted according to product conditions, usually between 2 to 5kg/cm2, to achieve an even material feeding. As a precondition, backing off should not allow entry of air.
2. When melting plastic, the rotational speed can be faster for low viscosity and should be slower for high viscosity.
3. The setting of a cycle must ensure that the material can be fully melted for the next round of injection. If this purpose cannot be achieved, material temperature/backpressure/cooling time and change for a bigger machine will be among the important considerations.
4. If the raw material for the mould trial is PVC/POM/PBT, they need to be cleaned with PP or PE after the trial.
5. Keep records of molding conditions and several molded products after the trial, which will be used as a reference for the next trial run, saving both time and materials for the plastic injection mould company.
6. For products that have high requirements for precision, another measurement is required on the following day, for confirmation of mould modification.
7. We have to be clear that there are rings in mm thread (thin thread), such as 10mm, 12mm, 16mm and 20mm, etc., and rings in inches (thick thread), such as 3/8〞, 1/2〞, 5/8〞 and 1〞, etc. There are also thick and thin water pipes (pipe thread), but only the application of quick joint is able to save labor hours.
About plastic outdoor square dustbin mould making company
SWY MOULD was established in 2015 with around 30 staff. SWY is located in Huangyan city which is known as "the country of mould'. Our company occupies 1200 square meters and provide moulds and plastic products to lots of areas all over the world.
SWY MOULD has a strict quality control system and high-efficiency work team; the workshop is well equipped with the latest machines and production facilities of the injection moulds, with setting up a perfect CAD/CAM/CAE NX-UG system. We have a strong technical team, advanced mould processing system, professional workers.
We wish to provide you with the best service at a minimum cost.
Welcome you to create a nice future with us.