how to avoid jetting when injection molding
When the melt flow through a nozzle at high speed, runner, sprue or other narrow area, enter into the open areas, and there is no contact with the wall and die, it will produce jetting. Snake-like jetting makes contact with the melt equivalent to each other, give rise to small-scale sutures, as shown in Figure 1. Jet stream will reduce the strength of plastic parts, resulting in multi-surface and internal defects.
how to avoid jetting when injection molding?
In contrast, the normal pattern of melt filling wave front won’t generate these problems. Improve the plastic parts of the jetting flawed methods described below:
Change mold design: usually jet problem occurs in the gate design; you can relocate or change the gate design to guide the melt surface contact with the mold wall. Use overlapping gate or submersible gates, as shown in Figure 2. To the gradual expansion of the melt flow area to reduce the flow rate; using tabs or fan gate, as shown in Figure 3, you can provide melt into the mold cavity from the gate smoother transition, reducing the melt shear stress and shear strain. Increase the gate and runner size, or shorten the gate length. Review whether cold slug well designed properly or not.how to avoid jetting when injection molding
Adjusting molding conditions: Adjust for Best screw speed curve, so that the wave front melt through the gate at low speed, until the melt glue stuck outside the gate to further increase the rate of fire to eliminate the jetting, as shown in Figure 4. Barrel temperature may be also adjusted to increase or decrease by the amount of melt temperature of each section, to eliminate the jet stream, the reason for this improvement remains uncertain, but may be there is a relationship of nozzle and melt properties (such as viscosity and surface tension etc.). For most plastic materials, reducing the temperature increases a die swell effect; however, there are some plastics (e.g. PVC) at elevated temperatures because of increasing nozzle expansion effect.
Hot runner system has advantage of material-saving,time-saving,improving products appearance etc.
Hot runner manifold is a center components in hot runner system.
Hot runner manifold leaking will damage mould.
We should solve manifold leaking problem from hot runner manifold leaking reasons.
Thermocouple thermo-electric effect
Hot runner temperature control system is control manifold and nozzle.
Thermocouple purpose is detect temperature then reflect the achieved signal to temperature control.
Thermocouple thermo-electric effect is a closed loop circuit that make up by two different material metal A and B.
Please see the following picture:
Under the condition of material is same,current size is proportional to temperature T and T0.
Anole is a Chinese agent of German heating elements.
Valve gate hot runner needle motion
With respect to common hot runner system, valve gate hot runner system has higher technical content. The common main problem is valve gate hot runner needle motion not smooth.
When appear this phenomenon, firstly, engineer should check whether the pressure enough or not. Also need check gas route and tightness is good. Secondly, check concentric of cylinder, manifold and nozzle. if not, needle won’t move smoothly. Thirdly, examine material leakage problem between valve gate needle and guide bushing. If the other is without problem, check the machining sizes. At least, injection molding machine signal connection incorrect and sprue bigger problem will cause this problem.
Anole hot runner is a research and development, production line and service line of integrated technology-intensive enterprises, which will help you solve hot runner professional problem. Welcome consultation.
Automotive mold hot runner choice
Automotive mold hot runner occupied a very big portion in hot runner market, more and more main engine plants always adopt hot runner to inject automotive parts. Due to the strong competition in the 21st century, product requirement become more demanding, the testing of processing become particularly important. when choose supplier of automotive mold hot runner they have high standard of hot runner professional degree.
Here I list a simple analysis: auto part included interior trim part and outer part. relatively speaking, interior trim part has low requirement of its appearance, but it has strict requirement to the assembling parts. We always make use of open gate hot runner system, small product will choose pinpoint gate nozzle, direct gate nozzle will be chosen by big products certainly. What’s more, some undemanding parts can use cold runner expect luxury vehicle. Outer parts has high demand of welding line problem don’t exclude a small number of interior trim part. Some key position must not be allowed to exist welding line. At this time, hot runner manufacturer will use sequence valve gate hot runner system to adjust welding line position.
Many clients vibrated between open gate and valve gate. Of course, open gate has an abuse that in case welding line turn up, there is no method to adjust it. But sequence valve gate is much more advanced than open gate. Of course, valve gate system is much more expensive than open gate, so benefit-risk balance is very important.
Hot runner mould design notes
Hot runner mould design should think about not only hot runner flow route of plastic, cooling system and plastic processing technical problems, but also mould manufacture equipments and structure issue. In summary, plastic product injection points as following:
1. According to plastic material rheological behavior and runner, cavity flow resistance to analysis mold filling order. In the meantime, designer should consider melted plastic would be bypass flow or fusion again and air venting problem, analysis parting line position to decide sprue quantity and position.
2. On the basis of melted material performance figure, cavity shape and cooling system route arrangement, by analyzing we know pressure holding and in the course of cooling the mold part temperature behavior to solve mold parts shrink problem. As far as possible to reduce buckling deformation problem which is caused by temperature, pressure, crystallization and orientation inconformity.
3. Mold parts demold and core-pilling problem can be solved by experience and analysis.
4. Decide mold parts parting lie and cavity inlaying assembly.
Hot runner system consist of hot nozzle,mainfold,temperature controller box and
accessories, etc.Spray nozzle generally includes pin point gate,direct gate,valve gate these three types.
Mainfold in a multi-cavity mould or multipoint feeding, single point feed but is used when a bias, material usually adopt P20 or H13, generally divided into two major categories of standard and non-standard, its structure is mainly composed of the distribution of cavity on the mold, the nozzle arrangement and gate location to determine.
Hot runner accessories usually include the heater and thermocouple, port sealing ring, plug and socket, terminal block, etc.
Hot runner mould technology development
Hot runner mould technology development is a big change in plastic injection mould. In plastic molding, it has quite a lot of incomparable advantages.This is mainly because of hot runner mould has the following distinctive features:
1. Shorten the molding cycle time. Because hot runner mould is no limit to the cooling time of gating system.
1. shorten the molding cycle parts ,because there is no limit to the gating system, cooling time, stamping
2. Saving plastic material.
There doesn’t have cold runner in the hot runner mould ,so hot runner mould doesn’t produce scrap. This is very important for a project that plastic is very expensive,such as PC material. Hot runner technology is a effective way to reduce the scrap and save material.
3. Hot runner mould technology development has been successfully used in processing all kinds of plastic materials. Such as PP, PE, PS, ABS, PBT, PA, PSU, PC, POM, LCP, PVC, PET, PMMA, PEI, ABS/PC, etc. Any can use in a cold runner mold processing plastic materials can be used hot runner mould processing.
Hot runner mould technology development is increasingly important to electronic, automotive, medical, daily necessities, toys, packaging, building industry.Anole is a professional hot runner manufacturer ,we supply hot runner system,heating elements etc.
Writen by Demi
CAD technology developing tendency
CAD is abbreviation of computer aided design . It is refer to a technology that designer design products in computer.
After decades of development,CAD technology is occupied of leading position and appear a batch of excellent and
Developing CAD software is order to apply CAD technology and purpose of CAD technology application is to improve the design
In the 21st century, the basic characteristics of the mould manufacturing industry is a highly integrated,
Anole hot runner is also professional mould manufacturer in China,our engineer and designer practice
Writen by Demi
In the injection molding process, hot runner plays a very important role. Hot runner function can be seen in the below mentionded.
For example, in the injection molding production of ultra-thin (such as mobile phone battery cover), through the use of hot runner can easily produce the high precision, high quality products;For illiquid injection molding raw material, through the use of hot runner can obviously improve the liquidity of raw material, ensure injection production smoothly; For some large injection molded parts, such as automotive bumpers and door plank, TV shell, air conditioners shell and so on, through the use of hot runner, to make injection molding has become relatively simple. In multi-cavity mould, the product can not form if lack of hot runner. It can say that the hot runner is the best technology for the runner balance.
For plastics processors, as long as there is a certain batch of injection molding production, using hot runner is very economic.
This is because the hot runner help enterprises eliminated gate in injection molding production.In most cases, the gate may not be reuse. Sometimes, the weight of the gate and products almost the same, if the traditional way of nozzle injection, means that the waste of raw materials and products used by as much as raw material. Extrapolate that using hot runner, you can save 30% ~ 50% of raw materials.
In addition, the hot runner also helps reduce mould wear, prolonging the life of the mould.
Post by Ashley