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

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) materials 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 light weight, 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 have 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 end product, molds are basic processing equipment that are 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 less 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.

 

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 catalogue 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 increase 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 rise. 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 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 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.

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International Mold Supply Chain Further Leans Towards China Mold Companies

When compared to the past, the technological level of the Chinese mold industry has been greatly improved, but the proportions of high, medium and low-end molds produced by Chinese manufacturers are extremely imbalanced, which severely hampers the development of the Chinese mold industry. Over the past few years, tremendous changes have taken place in the industrial structure as well as the system of the Chinese mold industry, which are mainly represented by: medium- & high-level molds, large sizes, precision, complexity and long lifecycle, but the self-sufficiency rate of medium- & high-end molds falls below 60%, due to the fact that China has an enormous demand for medium- and low-level molds. It is easy to see the irrationality lying in this situation.

The industry has pointed out that the proportions of high, medium and low-level molds produced by Chinese manufacturers are extremely imbalanced, which severely hampers the development of the Chinese mold industry. The pace of restructuring needs to be quickened urgently with emphasis on development of the high-end market segment, so as to keep pace with the international market.

How to keep pace with the international market? The mold industry in China needs to speed up restructuring, while at the same time making efforts to improve technological level.

It is mainly reflected in the following aspects: i. Restraints, such as mold steel; ii. The level of standardization needs further improvement; iii. Top-level mold talents need to be cultivated desperately; iv. Quicken the pace of mold product restructuring; v. Increase investment to enhance innovation capability; vi. Promote consolidation and restructuring among mold enterprises; vii. Further deepen the exploration of overseas market.

The downstream suppliers, especially the automotive industry, have a high degree of dependence on importation when the key and core molds are concerned. As a result, a host of key and core injection molded parts that OEM products need are also supplied by these world-renowned mold enterprises.

In recent years, Chinese mold companies have continuously improved mold technologies and products. Therefore, some plastic molds and injection molded parts start to be distributed internationally, have successfully made it to the supply chain system of some high-end industries and even replaced some imported products, dependence on importation is thus eliminated. However, it is undeniable that, the companies that have got into international high-end market are few in number.

In the Chinese mold industry, along with the improvement of technological level and gradual increase of product lines, some international OEM industries are now further leaning towards Chinese companies, which presents not only an opportunity, but also a challenge. It is believed that by 2015, the mold self-sufficiency rate in the Chinese market will reach 85%, among which the self-sufficiency rate of high-end molds will witness a remarkable increase.

According to experts, in addition to continuous improvement of productivity, the Chinese mold industry needs to pay more attention to internal restructuring, as well as technological advancement. The focus is mainly on realization of a more specialized enterprise structure; a product structure that is oriented towards higher end molds; improvement towards the import & export structure; molding analysis & structural improvement of medium- & high-end automotive panels; application of multifunctional composite mold, combined machining technology and laser technology in design and manufacturing of molds; as well as the development orientation towards high-speed cutting, ultra-precision processing, polishing technology and informationization, etc.

With the thorough transformation of the machine tool industry, the Chinese mold industry is experiencing technological innovation and product upgrade, while also proactively exploring the international market. In the competition with international competitors, the Chinese mold industry is making the most of its strengths, in an attempt to secure a place in international market. So, what advantages does Chinese mold industry have over the international mold industry?

Advantage 1: Strong national policy support should not be ignored;

Advantage 2: Gradual improvement of infrastructure creates possibilities for the ever increasing market demand;

Advantage 3: Transfer of world mold industry center to China, as well as the wide application of e-commerce will create extraordinary business opportunities for the Chinese mold industry;

Advantage 4: Compared with European and American countries, the low labor and material costs will make China the center of attention under the current circumstances that there’s an urgent need to bring down cost in the international market.

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More Plating Tips for Plastic Injection Molded Parts

There are many, many plating tips and secrets of the trade that one learns throughout the years.  You may have heard some of these, but following are a few key pointers to keep in mind.  They could save you a lot of time and aggravation down the road.

Avoid using chrome when molding with polyvinylchloride (PVC).  Chloride is a component used to strip chrome off of steel; therefore the chrome will slowly dissolve due to the gases emitted from the chloride in the PVC.  There is an old school of thought that chrome is better than nickel.  Don’t believe it in this case.

Polytetrofluoroethylene, or PTFE, breaks down at 550xF.  If you are using a molding application requiring mold temperatures that exceed this level, avoid PTFE and go with nickel or chrome.  The PTFE, though useful for release, will break down and shut you down. It is not a bad idea to occasionally use different combinations of plating.  Depending on what kind of performance you require from your mold, consider having more than one plating material for optimum efficiency.  For example, if you require abrasion and corrosion protection, a base layer of electroless nickel (for corrosion) and a top layer of hard chrome (for abrasion) are recommended.  The two work together very well.

Technology now allows us to skillfully and effectively mask off even the most remote areas of a mold so that very localized plating can be applied.  Selective plating with electroless nickel, for example, is a great way to correct size on threaded cores or slides for ring necks threads.  This application is good for corrections under .004 inch per side. Need just abrasion protection?  Go for hard chrome with a heavy flash of between .0004 and .0006 inch – especially if you are using glass-filled materials.

If corrosion protection is needed, an electroless nickel .0002 to .0004 inch deposit is an excellent choice.  If corrosion protection and release is needed, a co-deposit of electroless nickel and PTFE – 25 percent by volume – is a proven combination.

When selecting electroless nickel for rubber molding, we have seen sulfur-cured materials still unwilling to release, so a heavy topcoat of PTFE is usually required.

An effective use for chrome is shimming or correcting for size on inserts, cavities and cores.  You can mask and selectively plate the parts up to a .020 inch deposit, finishing it with either grinding or EDM.

As always, when choosing plating you need to know what type of steel grade and what plastic material will be molded.  Communicate these details to your experienced plating house and, based on your molding requirements, you will have the ultimate finish on your molding surfaces, saving you time and money and producing the high quality parts your customer expects.

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Polishing Pointers-Saving Time On Ribs

Ask most shop owners what the number one reason is for new molds failing their first sample and you will most likely hear “material sticking in the ribs.” It is not uncommon for a tool to have its ribs and slots repolished two, three or more times before the tool works cleanly. The following is a list of different polishing techniques along with the pros and cons of each – and some tips and secrets to not only cut polishing time, but ensure a smooth-running tool every time.

The Problem

EDM is the primary reason material sticks in ribs. Not only can the surface be extremely rough, its hardness (the white coat) ranges about 72 Rockwell due to the combination of heat, oil and carbon – which are primary elements of heat treating steel. The combination of surface hardness and roughness leads to long hours of polishing, which despite the polisher’s best efforts, may still result in a poor performing tool. Undercut ribs due to cutter flexing also is an issue, but this article will deal solely with EDM-related problems and its solutions.

Disking

The technique of disking ribs is probably the fastest way to remove EDM from ribs; however, the downside can easily outweigh the benefits. Disked ribs can become undercut extremely easily – in a matter of only a second – and this technique should only be used by an experienced polisher with many years of “feeling with his fingers” – or discarding the block and starting all over again is a real possibility. Young and inexperienced polishers – often intent with impressing the owner with their great speed and who are totally ignorant of the severe consequences possible – are the least qualified people to use this technique, but are often the first to do so. Ironically, the older, more experienced polishers – who are the most capable of handling this technique – are the least eager to use it because of well-founded concerns about damaging the block. They opt to use other slightly slower, but safer methods.
Several methods of disking ribs include:

Putting a two- or three-inch disk in a one-inch disk holder and reaching down into the rib.

Tearing off the attached center mount from a disk and then backing up the disk with a homemade thin steel disk, while using a cut-off wheel arbor to hold it all together. This allows both increased depth and pressure to be applied to the disk at once.

Cutting an extra-large diameter steel disk from a sheet of galvanized steel -as in duct-working material – and mounting this disk onto a quarter-inch screw, then adding sticky-back strips of abrasives all along the cutting surfaces. These strips are easily replaced when they become worn out and allow for the disking of extremely deep ribs.

If disking is your choice, please be careful to leave 10 percent of the EDM on all of the surfaces to guarantee no damage to draft angles or the thickness of the rib.

Diamond Files

Diamond files are the next fastest cutting tools available for removing EDM from ribs after disking. Diamond files can be used in profilers, heavy-duty air profilers and by hand. One advantage is that the diamond’s hardness is ideal for cutting through EDM’s outer surface. Unfortunately, the cost of diamond files can be prohibitive – especially on larger jobs, which may require dozens of such files. Unwary polishers also have destroyed these files carelessly by pushing down on them too hard. They think that pressure makes them cut faster when in reality they were simply breaking the diamond particles off of the file. By embedding the particles into the steel they were exceeding the limits of the braze that holds the diamond onto the file – resulting only in stripping the file clean and wasted time and money. The ultimate tool would be something that stays sharp forever and holds diamond without the particles breaking off.

Steel Laps

Steel laps are the tool of choice for most polishers. Steel can be ground to any thinness and still allow for heavy downward pressure. Steel laps can be used with diamond compound or silicon carbide lapping compound as the cutting medium. Lapping compound is only slightly slower than diamond, but considerably cheaper. Unfortunately, the downside to steel laps is greater than the benefits derived from them – steel laps often create deep, “zig-zag” lines in the side walls of the ribs, which are often far worse than the EDM with which they started. This is due to “scoring” between the steel rib wall and the steel lap. The only way to get around this uncontrolled scoring is to not push down so hard, but this also slows down the cutting process. Another big disadvantage to steel laps is the combination of downward pressure and the cutting action of the profiler, which often causes the diamond or lapping compound particle to simply shatter into fine grains. Shattering the rough grain and leaving a fine grain wastes time. The ultimate tool would allow downward pressure without shattering the larger size grains.

Two examples of steel laps are:

Pre-hard rod cut to thickness and length.
Stainless steel butter knives are often already the perfect thickness, blade length and strength for deep rib work and are the ideal width for mounting sticky-back, press-on paper abrasives. They also can be mounted into profilers and heavy-duty air profilers.

Brass Laps

Brass laps also are very popular for lapping ribs. While not quite as rigid as steel laps, brass laps are easier to work to thickness and shape and they don’t suffer nearly as much from the deep, zigzag scoring as steel laps do. Overall, brass laps may be the most finish control-orientated lap being used. The downside is the large grains of diamond and lapping compound are still shattering from the pressure and cutting action of the profiler, which results in slower times to finish.

Copper Laps

Although copper laps are hardly ever used, they are extremely valuable to the polisher. Their use offers a great improvement in time saved while polishing ribs. This is due to the softness of the copper itself. Copper laps are so soft that the rough grain of diamond or lapping compound never breaks into fine particles. Instead, the large particles embed themselves into the soft copper and become a truly aggressive cutting tool – causing more wear to the EDM than any other form of lap. Unfortunately, copper is so soft that dressing it down thinly enough for most ribs takes all of the strength out of the lap itself – making it practically useless except for the widest and shallowest of ribs. Whenever possible, copper laps should be used as a great timesaver.

Stones

Nothing else cuts EDM faster and has a more controllable finish than a stone. While diamond files start off as being faster than stones, they quickly wear down from use and do not replenish their cutting action with new layers underneath as stones do. The fastest of all stones is a medium, hard-bond, aluminum oxide, nonoil-filled, 220-grit stone. This type of stone, when used properly, is EDM’s worst nightmare. The secret to proper use is to cut it to thinness, dress it with 220-grit (mesh) natural diamond and stone by hand with a side-to-side sweeping motion – exactly like a windshield wiper on a car. This action will tear EDM out of a rib faster than any other method and allow the polisher to maintain total control over the final finish. The downside is that all stones break very easily when dressed down this thin. The cutting action is phenomenal, but when pressure is applied the stone always snaps off. The only thing this combination needs is the strength of steel or brass to become the ultimate rib polishing tool.

The Ultimate Rib Polishing Tool

Take a brass lap, dress it to half the thinness of the rib, take a 220-grit, medium, hard-bond, aluminum oxide, nonoil-filled stone and slice it to half the thinness of the rib. Then smooth off the tip of the brass lap, apply a drop of ethyl cyanoacrylate glue (instant nail glue available at any drug store) and glue the slice of stone directly to the lap. Wait about a minute, then apply just enough 220-grit natural diamond compound to impregnate the pores of the stone and start the sweeping action on the EDM – you are now using the ultimate rib polishing tool.

This combination offers the following benefits:

It accelerates controlled EDM stock removal like no other motion or technique.

The 220-grit diamond is not shattering at all because it’s embedded safely in the pores of the stone.

The diamond compound remains aggressive until it is completely worn out and then is easily refreshed by applying just enough compound so as to refill the pores in the stone.

It also may be used as “draw” in a profiler, but side-to-side sweeping is much faster; therefore, draw should only be used to finish and not to rough out.

The fact that the 220-grit diamond particles fall so neatly into the pores of the 220-grit stone creates nothing less than a “super” diamond file, which is glued to a brass lap that is unbreakable and will never wear out.

When the stone slice wears out, simply glue another one back on and you have a brand-new, super diamond file.

One five-gram tube of 220-grit (mesh) natural diamond applied properly is enough to easily polish all of the ribs most shops produce in six months or more.

Gluing a piece of stone onto a brass lap, charging it with natural diamond and using it in a sweeping side-to-side motion is nothing more than taking the best parts of several different techniques. This solution has worked very well over the years and has cut rib polishing time on some jobs by as much as 50 percent or more – without risking rib damage.

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