How to Select a Good Mold Manufacturer in China?

After a new product is designed, a lot of companies would be ready to develop the plastic injection mold for small-scale trial production, to see how the market will respond before making a decision on massive production. At this point, it will be of great importance to select a proper plastic mold manufacturer. Personally, I’ve been working in the mold making industry for many years, and have known no less than 100 mold manufacturers, big or small. In this article, I am going to sum up my years of understanding and experience in the profession and would be happy to share it with all of you.

 

(1)Which type of mold manufacturer is a better choice for cooperation?

Currently, there is a diversity of mold manufacturers available in the China market, including foreign-funded companies, Taiwan invested firms, Hong Kong enterprises, and domestic ones. The pros and cons comparison between each type of mold makers are stated as below:

  1. Foreign-funded mold manufacturers are characterized by standardized management, robust processes, strong service awareness, as well as assured quality and service, but their overhead costs and selling expenses are pretty high, meaning that mold development charge will be accordingly higher. If you have a strong financial capacity and would like to seek a company that is able to provide assured product quality, a large size foreign-funded mold manufacturer will be your choice of cooperator! However, in practice, large sized foreign-funded companies often have regular clients, so their prices will often be in line with the international market, which is not easy for many enterprises to accept. A set of large precision automotive mold usually costs hundreds of thousands or even millions dollar – the direct cause that discourages many buyers.
  2. Chinese privately owned mold manufacturers are mostly established by the first batch foreign enterprise employees who first accessed the mold industry. Dubbed up-and-coming stars, one of the biggest inherent advantages of such enterprises is the relatively low material, overhead and selling costs. The mold and product prices they offer are definitely lower than those of foreign, Taiwan and Hong Kong mold manufacturer, so they are always able to attract the attention of a large number of mold buyers.

 

(2)What size mold manufacturer is a good choice for cooperation?

Large, medium or small sized mold manufacturer?

Personally, I think the choice in this regard is dependent on the circumstances. From the perspective of factory size, everyone will preferentially choose the largest one, because the large ones are usually fully equipped and thus more competent! Potentially, their sizes also reflect the level of customer’s choice. But, on the other hand, the larger the size, the higher the overhead costs will be, so the price will not be as competitive. In particular, the prices offered by large-sized foreign-funded mold manufacturers are literally unacceptable for most buyers. It is of critical importance that whether the mold manufacturer you select treat you as a VIP, i.e. whether they respect you. As a matter of fact, looking for a supplier is like choosing a partner, a suitable match is required. If your company does not have a strong financial capacity and your purchase volume is not big enough, looking for cooperation with large-sized mold manufacturers will only lead to the result that you are not respectfully treated despite the money you spend because you are not able to meet their requirements, be it order amount or volume. That is to say, they cannot benefit from your orders.

Under such circumstances, most people will choose SMEs. As a matter of fact, it is now a common practice in the industry, after all the mold and product prices appear to be more acceptable. However, you will soon find other concerns arising – can the mold be produced punctually with assured quality, how will the mold perform in the process of mass production and what is the life cycle of the mold? At this point, I would suggest you pay attention to the general knowledge that you have to select a fully equipped mold manufacturer, i.e. it has to be equipped with supporting precision CNC machines, slow wire cut machines, EDM, high-speed high-precision injection machine and 3D/2D measuring instruments that are necessary for mold processing, production, and testing. This is the point that should be taken as the key element for inspection, evaluation and final selection of a mold manufacturer.

 

(3)Meet mold manufacturer face to face, or ask for some reference customers before place order.

When you search “China mold manufacturer “or” Chinese mold maker” in Google, you will get a lot of contacts from mold manufacturers in China, I suggest you send RFQs to 5 or more mold makers, then you can compare their price, they react speed, their professional support. Normally the mold manufacturer arranges an engineer or a sales who have the engineering background to contact you, it will be much better than a sales girl without any engineering experience. because mold making is a customize and professional service, mold experience will help a lot in communication and avoid misunderstanding in engineering. it will save lots of time and cost. when you decide to work with one mold manufacturer, I suggest to visit them on site, then you can check their facility and talk to them face to face. if time or budget is limited, then you can ask for some reference customers from your own country who are dealing with them, the people who live in the same country and culture are always more trustworthy.

Sositar mould is a professional plastic injection mold manufacturer in Shenzhen China. We have more than 100 customers all over the world. most of them come from European and US.

Let us share some interaction between Sositar mould and customers all over the world.

Meet our customer in London UK

Visit our customer in Birmingham UK

Visit our customer in Keleve Germany

Visit our customer in Rotterdam Netherland

Visit our customer in Milan Italy

Meet our customer in Florida USA and trial the product we made in Mexico bay

Meet customer in Des Moines USA

The customer from Australia visit us in Shenzhen

The customer from Canada visit us in Shenzhen

Hot runner types and their application in plastic injection mold

1,How the Hot Runner Works?

The cold runner of a plastic injection mold refers to the section between the mold 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 mold, 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 mold

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.

2,The advantage of Hot Runner Molds compare to cold runner molds

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 the traditional injection molding is always associated with the following disadvantages:

  1. Hard to fill; b. thin-walled large size parts easy to deform; c. material waste in the runner; d. 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:

■ 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.

■ Material saving

In a complete hot runner mold, material waste will not occur thanks to the absence of a cold runner. This is of a 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.

■ 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 a higher quality, so after mold release, the part produced will have a 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.

■ Eliminating 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.

3,The Hot Runner types

  1. The mold that employs a hot sprue for direct or indirect material feeding, is referred to as a hot sprue mold.

 

2,The mold that is designed with a hot runner manifold and a secondary hot sprue, is referred to as a hot runner mold.

Examples of hot sprue molds

(1) The hot sprue mold structure that feeds materials through the point gate. It is only suitable for the single-cavity mold, and is limited by the gate location.

2) The hot sprue mold structure with the end surface engaged in injection molding. It is suitable for the single-cavity mold, but sprue marks will be left on the part surface. The end surface of the hot sprue is machinable.

(3) The hot sprue/cold runner mold structure with a bit of the traditional runner features. This structure is able to produce multiple plastic parts at the same time, but some cold slugs will be produced.

Besides open gate hot runner as above,Now people start to choose valve gate hot runner for high class product.

What is valve gate hot runner?

Mount the hot sprue and the manifold into the injection mold, and then by way of heating, keep the fluidity of the plastic material after it is out of the barrel. The result is, the product gate seems to be able to contact with the nozzle directly. So, when releasing the product, the sprue is closed under the action of the needle valve. The application of one or more cold runners is thus avoided, realizing wasteless production.

The advantages of the valve gate hot runner include:

  • Shorten production cycle, improve production efficiency;
  • Since the cold runner is replaced, cold slugs will not be produced, thus saving a large amount of raw materials;
  • Improve product consistency, free from obvious gate marks;
  • Remarkably improve product appearance;
  • Help reduce product stress, minimize product deformation and structural brittleness, so the production capacity and life cycle of complex products are improved;
  • Offer more process control, allow accurate adjustment to the injection molding process;
  • Not limited by the change of plastic injection molding materials.

Why the venting is so important for a plastic injection mold?

The venting slot serves two purposes: 1. Expel air from the plastic injection mold cavity during the injection process of the molten plastic material; 2. Get rid of the various gases produced during injection molding processing. The setup of venting slots is of great importance, especially for thin-walled products or the locations far away from the gate. In addition, close attention should also be paid to venting slots for the production of small-size or precision parts, because they are able to protect the products from surface burns, insufficient filling, as well as other defects.

So, what is sufficient air venting for plastic injection molding? Generally speaking, if no burn marks are left on the product at the highest molten plastic injection speed, then the venting effect of the mold cavity will be considered sufficient.

 

Venting Methods:

There are lots of ways to vent the mold cavity, but each of them has to guarantee that: while performing venting functions, the size of the vent slot needs to be able to prevent material from entering the slot, as well as clogging at the same time. However, if there are too many slots, it will do more harm than good, because if the clamping force against the mold cavity parting surface area without vent slots is too high, the cavity material will be prone to cracks, which is very dangerous. In addition to being designed on the parting surface of the mold cavity, the vent slot can also be machined in the end section of the runner system. The clearance around the ejector can also act as a way to let the trapped air out. If the height, width and position of the vent are not appropriately defined, flash will be caused, thus affecting product aesthetics and precision. As a result, the clearance design should be able to prevent flash from occurring around the ejector pin. In particular, it is worth noting that molded parts like gears expect no flash at all. Therefore, the following venting methods should be employed:

  1. Completely eliminate the air in the runner;
  2. Apply peening treatment to the parting surface with the 200# silicon carbide abrasive, and open vent slots in the end section of the runner system, mainly referring to machining slots in the end section of the sub-channel, of which the width should be equal to that of the sub-channel while the height may vary from material from material.

Design Approach:

Based on the years of injection mold design and mold trial experience, this article is aimed to generally explain the design principles of several slot types. For parts with complicated geometric shapes, the vent slot positions should be identified after several mold trials. If a mold design adopts the integrated structure, poor ventilation will be its biggest disadvantage. So, for molds with integrated cavity and core, the following venting methods can be adopted:

(1) Make use of the slot or insert location in the mold cavity;

(2) Make use of the lateral insert crevice;

(3) Machine the local part into the spiral shape;

(4) When it is extremely difficult to expel the air out of the mold, an insert should be adopted. If it is not easy to machine a vent slot in some locations of a mold, such as in the corners, the insert molding process may be appropriately applied on condition that product appearance and precision are not affected. This method not only helps with venting, but is also able to lower the difficulty level for machining, and convenient for maintenance, too.

Vent Slot Design Dimensions:

The width of the vent slot ranges from 1.5 to 6mm, while the depth design should be able guarantee that the plastic material will not get into the slot to cause flash. Its value is dependent on the viscosity of the molten plastic, but usually its applicable range is from 0.013 to 0.05mm.

 

Conclusion:

Appropriately designed venting slots are able to drastically reduce injection pressure, injection time, pressure holding time and clamping force, thus making the plastic injection molding process much easier by improving production efficiency, lowering production costs and saving the energy consumed by machine.

An Overview & Future Development Trend of the Chinese Plastic Injection Molding Industry

Recent years, plastic injection industry have a huge change in the environment of consumption upgrade. product requirements are getting an increase. In the past, large-scale production of precision-less plastic industry, now also need to rely on the mold industry to improve the accuracy of product demand.

The production of plastic products starts with the design and development of plastic molds, which are a basic tool for manufacturing of plastic products. As a result, the mold precision has a direct influence on the structural integrity and dimensional accuracy of the end plastic products.

The production of all plastic products has to go through the several steps that include design & making of plastic molds, injection molding, and surface finishing, among which the precision mold features a complex structure and therefore imposes high requirements for surface quality and technical standards.

Since it is a technology-intensive as well as capital-intensive product, many technologies need to be involved in its production process, including high-speed machining, super-finishing, rapid prototyping, automatic control, processing and applications of polymeric materials, etc., covering the areas of machinery, metal materials, polymeric materials, electronics & electrics and automatic control, imposing high comprehensive requirements on technologies.

 

1.Overview of the Plastic Industry

Plastics are malleable (seldom non-malleable) material that are consisting of synthetic or natural high molecular compounds. They are produced under certain temperature and pressure conditions, assisted with additives of plasticizer, filler, lubricant, injection agent and more.

 

Plastics are widely used in modern society thanks to its lightweight, high plasticity, low production cost and diversified functions. Currently, as one of the four basic materials that support the development of modern society (the other three are steel, wood, and cement), the high molecular compound material has become a new material that is indispensable to human life.

Its application covers the many areas of information, energy, industry, agriculture, and transportation, etc. In recent years, the plastic manufacturing industry of China has witnessed a rapid development with an ever-increasing scale – it is now one of the essential parts of the Chinese economy.

 

  • In 2013, production of Chinese plastic products totaled 61.886,6 million tons, representing a year-on-year increase of 8.02%;
  • As of December 2014, the number of above-scale plastic manufacturing enterprises reached 14,062;
  • Prime operating revenue hit 2,039.239 billion CNY, representing a year-on-year increase of 8.92%;
  • Total profit reached 118.286 billion CNY, a year-on-year increase of 4.24%;
  • Export delivery value reached 226.066 billion CNY, a year-on-year increase of 2.82%.

Therefore, it is obvious that the production scale of the Chinese plastic manufacturing industry is being continuously expanded and production is increasing year by year, though year-on-year increase rate slows down a little bit over the past two years.

 

If viewed from the different segments of the plastic manufacturing industry, the most widely used plastic products are plastic pipes & fittings, plastic wires, and plastic weaving products, followed by plastic films and plastic packaging containers, while household plastic products and plastic parts rank third.

Among them, the prime operating revenue and export delivery value of plastic parts has reflected a rising trend over the past five years. The increase rate was particularly high during the 2010-2011 period, with prime operating revenue increasing from 237.282 billion CNY to 709.559 billion CNY,

representing an increase of nearly 200%, while export delivery value increased from 63.579 billion CNY to 191.426 billion CNY;

from 2012 to 2014, though increase rate slowed down slightly, the prime operating revenue was still on the rise, which hit 939.413 billion CNY as of 2014.

 

2. Overview of Mold Manufacturing Industry

As an intermediate product used for the production of the end product, molds are basic processing equipment that is machined by using a wide range of materials, such as plastic, rubber, metal, powder, glass, and FRP, etc.

Mold processing is one of the most important ways of material molding. Compared with machining, its benefits include fewer process steps, higher material utilization ratio, less energy consumption, ease of production, higher profitability and more. Thus, it is widely used in the manufacturing of automobile, energy, machinery, electronics, information, aviation, as well as household commodities. According to statistics, 75% parts of the rough processing industry and 50% parts of the precision processing industry are molded, while 80% parts of the home appliance industry and over 70% parts of the ME industry are also mold-processed.

As the mold industry is helpful for driving the development of other related industries, it is often dubbed the profit amplifier.

injection molding market

image: injection molding market

Though the mold industry of China had an early start, it was kept as an affiliate of downstream production-oriented enterprises, which restricted the development of molding enterprises, and molds were not listed in the ME product catalog until the year of 1987. At that time, there were approx.

6,000 mold factories in China, which yielded a total production value of 3 billion CNY. After more than two decades of development, the Chinese mold industry has made a remarkable progress. As of 2013, the number of mold companies had reached 30,000, with a total output value of approx. 220 billion CNY and an annual export value of nearly 5 billion CNY.

Currently, the largest markets of Chinese molding lie in the following industries of automobile, IT, home appliance & office equipment, machinery and building materials. Along with the rapid growth of national economy and improvement of people’s income level, there is a growing demand for automobiles, consumer electronics, and home appliances, allowing these industries to embrace a speedy development phase in recent years. This constitutes one of the most important reasons for the rapid development of China’s mold industry.

The following diagram shows the 2007 – 2013 mold production value of China. We can see that the production value of China’s mold industry has witnessed a rapid growth in recent years, increasing from 87 billion CNY in 2007 to 210.6 billion CNY in 2013, with an increased rate much higher than the overall level of the world mold industry.

 

3. Development Trend of the Mold & Plastic Industry

Along with the gradual industrial transformation and upgrade, as well as the increasing proportion of high-end products and continuous improvement of basic supporting services, there’s still much value in plastic production. Though it is witnessing a slower increase rate of production, the output value is still increasing at a relatively fast pace.

We can tell that the plastic processing industry still shows a sign of rising. As one of the indicators to measure the development level of a country’s plastic industry, the ratio between plastic and metal is only 30:70 in China, falling far behind the world average (50:50) and the developed countries like Germany (63:37) and America (70:30). Hence, with technological advancement and consumption upgrade, the plastic industry of China will maintain a steady development pace.

 

The mold industry which forms a basic industry in the national economy, is specifically involved in machinery, automobile, optical industry, electronics, chemistry, metallurgy, building materials and more industries, representing a very wide and comprehensive scope of application. China’s industry is developing rapidly, among which, the development of automotive manufacturing, IT and the medical device offers a great development opportunity for the entire mold industry.

 

Currently, China is experiencing an industrial restructuring, with national objectives for emerging industries planned as: by the year of 2020, the increased value of strategic emerging industries is aimed to account for about 15% of GDP. To achieve this 15% target, among all the seven strategic emerging industries, as the pillar of national economy, the high-end equipment manufacturing industry will be vigorously developed, so the mold industry which is dubbed “the mother of modern industry”, will definitely benefit from the development of high-end equipment manufacturing.