Design idea of a plastic injection mold designer!

Time:2019-06-26 08:22:54 / Popularity: / Source:

precision mold 
First of all, after we got a product, don't rush to split mold. The most important thing is to check product structure first, including mold making, thickness and other molding problems. Of course, this may be difficult for a plastic injection mold designer who has just been engaged in mold structure design. Because they may not know how to use products that are more suitable for molding design, it doesn't matter. it is just a process that they accumulate daily. When you analyze draft, wall thickness, and where there is a buckle in direction of mold, you basically know direction of mold parting surface and position of gate. Of course, these are ultimately confirmed with customer.
Some people say that after I analyzed product structure, I can start molding design. Answer is of course NO. If you want to take less detours during molding design, some items that affect mold structure must be confirmed. Details are as follows:
  • Tonnage and model type of injection molding machine used by customer. If this confirmation is not good, you can't confirm inlet diameter of gate sleeve of your mold, diameter of positioning ring, size and position of ejection hole depth of injection molding machine that can be inserted into mold, even size of mold base, closing height and so on. You have worked hard to design a mold structure with a cylinder core. You also have a sense of accomplishment. But mold can't be produced by customer. Because customer only has electric injection molding machine, there is no additional neutron, it is estimated that you will have feeling of crying and tears.
  • Customer's injection molding machine's code mode, commonly used is pressure plate code, screw code mode, hydraulic code mode, magnetic code mode and so on. If this confirmation is finished, you know if it is necessary to design pattern screw hole or code slot for precision mold when molding design.
  • Problem points of products we analyzed just now, as well as product clamping, product materials and shrinkage. Do not take it for granted that PP plastic shrinkage must be 1.5%, this must be confirmed with customer, to know what grades they are ultimately used for production, whether to add any modified materials and so on.
When conditions permit, it is best to be familiar with assembly relationship of product and use of product etc. This information is very helpful for future mold structure design. Because only you understand this, you know which ones are appearance and which are non-appearances. Where are draft angles that can be easily increased and which areas cannot be changed. Even including structure of some products, if you understand actual assembly relationship and use of product, you know which reverse structure can be canceled or changed to another simple form.
It is important to keep in mind that process of mold making is a process of simplifying complex problems. I often see that some plastic injection mold designer are proud of how complicated structure is for precision mold, and I think it is very ignorant. Because many product engineers may design some unreasonable structures due to their own experience, if they can't correct them as a downstream process, they may always think that design is okay. Then progress of our product engineers will be very slow.

External parameters of mold water circuit, oil circuit, circuit, gas path.

Only after understanding customer's requirements before design, you can have a predictable design of waterway oil circuit. When you have worked hard to molding design, you will find that customer needs to connect oil circuit inside mold finally. Then you change it, you will be tired and half dead, because your waterway, ejector, screws and anything are not easy to arrange.
Design sequence of these four roads is generally to ensure oil circuit first, because oil road should be distributed and balanced, especially mold structure that needs cylinder to be ejected. If oil circuit is unbalanced, action of cylinder will be ejected in succession, and it is easy to eject imbalance. Of course, gear oil separators can also be used, but that is even more complicated. Secondly is waterway. Because waterway needs to ensure cooling effect, uneven distribution will affect product quality and mold life. The last is gas path and circuit. Order of placement on mold is that circuit closest to TOP direction, then water circuit, gas path, bottom is oil line connector.
precision mold 

Other unfinished matters.

With this information in hand, we can start designing mold. The first is split mold. This process is estimated to be a process that everyone likes. Because of sense of accomplishment. Principle of pulling profile is simple, that is it can be stretched out and not scanned, or with other advanced commands. Secondly, when you want to pull profile, you should have a big picture. Try to simplify parting surface. If it is not a precision mold, those 0.1-0.5 insertions can be avoided. In addition, parting surface must follow a principle, that is try to follow product trend. Parting surface that is made in that way will be beautiful.
When you are learning a three-dimensional software, you must remember that principle of each command is clear, then you know when you can use that command. Many times it's important that you don't use software, but you won't learn to how to use software. Same command, experienced people will have a variety of flexible usage, which is most obvious in UG. In a word, important thing is idea, not tool itself. When doing parting surface, you only need to know that angle of insertion surface can be large, area of collision surface can be large, and width of pillow can be wide. It is necessary to fully consider parting surface that you are pulling now. After actual mold is made, master who is responsible for fit mold will not be jealous of you. If you don't think it's going to be embarrassing, then OK, keep going, when you are really being paralyzed in the future, these are your experiences.

At the same time as parting surface, it is necessary to consider arrangement of slider and slanting top, because those also involve modification of parting surface.

Typical slider structure is a trigonometric function relationship. This is fine if you calculate it yourself, but make sure that angle of oblique guide column is not too large and try to be 30 degrees or less. Principle of inclined guide column is that it can be thick as much as possible, not too small, because inclined guide column is subject to force. In addition, slider is also divided into many variant structures, for example, uphill slider, downhill slider, inner suction slider, cylinder pumping, front die slider, slider with slider, slider with anti-top, slider belt Inclined tops, etc., these special structures make full use of trigonometric function relationship, purpose is to achieve release of product buckle, and normal opening and closing of mold. Calculation formula of slider has a detailed introduction in each major forum, and I will not go into details here.
precision mold 

Followed by sloping top.

Slanting top is more flexible, but angle of typical slanting top is not too big, try not to exceed 15 degrees, of course you have to do 20 degrees, but life is difficult to guarantee, and action will not be very smooth, specific principle refers to trigonometric functions and theoretical mechanics. There are many evolutions of shape of sloping roof, for example, uphill sloping roof, downhill sloping roof, sloping neck, large sloping roof with slanted ram, large sloping roof with round bar, splicing platform, small sloping roof, slanting top under top block, slanting top on slider, slanting top on slanting top, anti-top on slanting top, etc.
All these structures are a purpose, using trigonometric functions to make product back-offs. This shows how important it is to learn trigonometric functions! So as for all kinds of special structures, people think of it. You can make full use of your imagination. No matter what kind of structure, you can just think about it. Then go to bold design. There are maybe new inventions, but after molding design, it is necessary to verify relationship of lower trigonometric function, which is to simulate opening and closing of mold under actual simulation, and to consider whether there will be problems during injection molding.
After parting is completed, next step is ranking of mold structure. These contents are to be sorted out in advance. According to actual situation of product, different types of mold structures are selected, for example, two-plate mold, three-plate mold, hot runner, IMD, IML, two colors, stacking and so on. All mold structure types are designed for precision mold to be able to achieve mass production of product. When choosing a mold base, we must fully consider four points that just mentioned.
precision mold 

We have to consider mold frame now.

Principle of inlaying is to simplify processing, save materials and facilitate product molding, such as exhaust. You think that there is a particularly thin place on mold, it must be set separately and easy to replace in the future. When inlaying, consider strength of insert, workability, and designability of waterway in the future.

After inlay is finished, it is necessary to add standard parts.

Principle of adding standard parts is to focus on back part and try to arrange balance symmetry. Generally, it is necessary to add a ejector first. When adding a ram, it is necessary to consider arrangement of waterway. Under normal circumstances, it is necessary to give priority to arrangement of ejector pins, and then design waterway, and adjust waterway ejector according to actual situation to balance these two. Principle of topping out is place where holding force is large. In addition, it should be added to the place where strength structure of product is better, such as squatting, table and edge, so as to avoid whitening or topping out imbalance.
Principle of drainage road is to principle of ejector, because in general, place where product is tight is also hot spot of product, and it is necessary to strengthen cooling part. This contradiction needs to be adjusted. As for whether to use a ejector or a top block or a push plate, specific analysis is needed. This should be analyzed in combination with structural characteristics of product. For example, if product is easy to stick to front mold, it is necessary to consider whether back mold is added with a reverse buckle, or front mold plus top mold. These are natural things, but many engineers do not think comprehensively for precision mold and what is reason? It is because there is no adequate analysis of product structure, and there is no practical consideration of state of product during injection molding process. This is key to problem. Plunging waterway has been added, and rest are standard parts that are messy. Everyone tries to consider the symmetrical balance when they are adding.
precision mold 

After design of the whole set of molds is completed, following checks must be done.

First is draft analysis of inserts to see if there is any undercut, and interference check of parts of mold is the most important. Today's 3D software has this feature, which is very convenient. Then there is simulation of mold opening and closing action. If mold is not too clear, it must be actually simulated. In addition, moldability of parts of mold and assembly process of mold. Do not work hard to design a clever structure, theoretical calculations are no problem. After processing, results can not be loaded, or not well assembled.
precision mold 
In fact, molding design is a matter of contradiction. If you want to design a perfect one, cost of mold will be high. If you want to design a simple one, you may have to change product or strength of mold, and service life will have an impact. So molding design is not absolute. As long as you find balance point, mold you designed is successful. Therefore, structure designed by others may not be suitable for you. As long as above molding design points are followed, it is estimated that everyone can design a more reasonable mold structure.

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