Injection Mold WIKI

Types of Food Grade Plastic Materials

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food grade plastic

PET

  1. PET

Usually, this plastic is used in the production of plastic bottles, beverage bottles and the like. The plastic water bottles and carbonated beverage bottles people often buy are packaging products made from PET, which is a food-grade safe plastic material.

  1. Potential Risks:

PET is only suitable for the packaging of room temperature or cold drinks, rather than overheated food. If the temperature is too high, the bottle will release toxic substances, which may cause cancer. If the PET bottle is in service for a long time, it will automatically release toxic substances, so the plastic beverage bottles should be disposed right away after use, and should not be used to contain other foods for a long time, so as not to affect health.

PP

The PP plastic is one of the most common plastics, and can be used to produce plastic food packaging, such as special plastic food bags, plastic food boxes, food grade straws, and food grade plastic parts, etc. It is safe, non-toxic and resistant to low and high temperatures. PP is the only plastic that can be placed in a microwave oven and boasts a strong folding endurance (50,000 times). When falling from a high altitude under -20°C temperature conditions, it will not break.

PP plastic bag: Polypropylene

Characteristics: Harder than OPP, stretchable (two-way stretch), able to be stretched into a triangle, bottom or side seals (envelope bag), and barrel. Its transparency is not as good as that of OPP.

HDPE

  1. HDPE

The HDPE plastic is commonly known as high-density polyethylene, which enjoys a high application temperature, hardness, mechanical strength and chemical resistance. It is a non-toxic and safe material that is often used to produce plastic containers for food.

High-density low-pressure polyethylene feels crispy, and is often used to produce plastic bags.

  1. Potential Risks:

Plastic containers made from HDPE are difficult to clean, so it is not recommended for recycled applications. It is better not to microwave it.

food grade plastics            food grade plastics

 LDPE

  1. LDPE

Low density polyethylene, commonly known as LDPE, is soft to touch.

The products made from LDPE are odorless, tasteless, non-toxic and matte. They are commonly used in food grade plastic parts, food grade composite packaging film, food wrap, medical and pharmaceutical plastic packaging.

  1. Potential Risks:

LDPE is not highly heat resistant, and usually melts when the temperature exceeds 110°C. For instance, don’t heat food wrapped with the household food wrap film, to prevent the oil contained in the food from dissolving the harmful substances in the wrap film.

 PS

  1. PS

It is often used to produce bowls of instant noodles, fast food boxes, disposable food packaging boxes, etc., and is very cold resistant.

  1. Potential Risks:

The PS box cannot be microwaved, so as to prevent the release of toxic substances caused by excessive temperature. It also features poor resistance to acid and alkali, so not suitable for containing acidic foods, to avoid release of carcinogens.

 PC

  1. PC plastic resin

This plastic material can be used to produce sports water bottles, etc., and is widely used in the production of plastic containers as a safe material.

  1. Potential Risks:

There is residual bisphenol A (hazardous substance) contained in PC.  The higher the temperature, the more and faster it releases. Therefore, do not use PC water bottles to contain hot water, so as not to increase the speed and density of bisphenol A (if any) release.

 PVC

  1. PVC：

Currently, PVC plastics is rarely used for food packaging, so it is better not to buy it.

  1. Potential Risks:

When this material is used under high temperature conditions, or even during the manufacturing process, it is easy to produce and release harmful substances. When toxic substances enter the human body along with food, it may cause such diseases as breast cancer and birth defects. At present, containers made from this material is seldom used for food packaging. If you are using it, don’t get it heated.

How to control the cost of plastic injection molding?

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The cost control of plastic injection molding also involves many factors. It must be controlled from the equipment, application process, raw material, as well as management and technology to achieve the optimal efficiency at the lowest cost.

Plastic injection molding company from China

Tools and Components Control:

Tools – All screws, nuts, nylon hoses and hose clamps, etc. in the packaging workshop must be controlled with a corresponding method, or great waste will be caused!

 

Mold Application Control:

Production Process:

  • Appropriate clamping pressure during the adjustment process – It is appropriate as long as the product meets the requirements, and the clamping force is able to ensure that the injection pressure does not force the core and the cavity open to cause flashing.
  • The ejection speed needs to be properly controlled. The ejection system itself is a system that should avoid as much friction as possible. If the speed is too fast, the system will inevitably be damaged.
  • Make full use of the low-pressure protection feature of the injection molding machine, so that there is chance for the mold to be damaged.
  • Too-high or uncontrolled injection pressure, speed, holding pressure and back pressure are also important factors that cause damage to the mold or affect its service life!
  • Mold temperature control is also very important. Excessive mold temperature will cause the individual parts inside the mold to swell and the compatible space to change, thus finally damaging the mold. The too-low mold temperature is not able to ensure the mold temperature to reach a relative balance after the mold absorbs the heat generated by the melting of the plastic, thus eventually causing rust and damage due to long-term moisture in local areas!
  • Human factors: Especially when such issues as mold adhesion or scratches and other common mold issues occur, a specialist is required to handle them. Do not arbitrarily authorize anyone to handle them casually.

Maintenance & Storage:

  • During the production process, the moving parts such as the lifter, the side pin, the slider, the guide pin and the ejector pin must be thoroughly lubricated at least once a day, or more than twice a day in special circumstances.
  • During hot-oil production, it is necessary to pay attention to the clamping of the mold and the partial swelling of the slider. During cold-water or icy-water production, the coolant must be cut off at least 15 minutes before shutting down the machine!
  • Pay special attention to the matte-surfaced mold and the polished mold – don’t damage or scratch them, or it will be quite troublesome to repair them!

 

Application of the Injection Molding Machine:

Plastic Injection Options:

  • Injection Volume:During the production process, the choice of injection molding machine is usually to ensure the molding quality. The weight of the product should be 25-75% of the total weight of the injected plastic, which is the recommended ratio. If the best product volume is required, the range should be lowered to 40- 60%.
  • Wear- / Corrosion-resistant Barrels and Screws:If the glassfiber-reinforced hard plastic is selected, it is better to choose wear- / corrosion-resistant alloy barrels and screws. Wear tends to occur when common nitrided screws are employed: choose corrosion-resistant alloy screws and barrels for acidic materials, such as PVC and POM.

Cost Control during injection molding Machine Adjustment:

  • Reduce wear and tear:If abnormal wear and tear is caused due to improper operations or other accidents during the adjustment process, the machine will not be able to operate properly for 12 years. Eventually, the daily wear and tear will increase greatly, and at the same time lead to incalculable and serious maintenance costs! To reduce abnormal wear and tear, it is necessary to strengthen the technical level of the technicians, as well as the knowledge of other workers.
  • The choice for the switch point between injection and pressure holding is able to reflect the actual operation level of a technician in an injection molding workshop. When realizing that the most fundamental purpose of pressure holding is to compensate for the shrinkage, the injection time and pressure can be minimized to reduce wear and tear, as well as power consumption, thus finally achieving the requirements for cost control!
  • The mold opening and closing process also reflects the actual operation level of a technician in a plastic injection molding workshop, because it fully reflects the connection between speed, time and energy consumption!

 

Material Cost Control:

The key to the cost control of a plastic injection molding workshop is the material control. If material control fails to reach the target, it will directly lead to a serious decline in profit. Any carelessness may lead to loss of profit.

Starting from the plastic materials release, control every detail to ensure zero material waste.

  • The machine cleansing process: Firstly, the machine scheduler must schedule the production from light to deep colors, so that it is possible to eliminate the discoloration that may occur by using a deep color to cover a light color. When cleansing the machine, first try to cleanse the machine with prepared sprues or recycle materials, and then adjust the machine using the sprues of the material to be used. When the product reaches the required quality, the production officially starts.
  • Machine adjustment process: Try to use the parameters and instructions provided by the flowchart, making the adjustment process a process of copying the book or inputting the parameters, thus simplifying the general adjustment process.

Surface finish of plastic injection molding product

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surface finish of VDI3400 texture
VDI 3400 texture

Different physical and chemical properties of the polymer blends, as well as the different parameters of the plastic injection molding process cause the surface finish on the plastic composites to vary greatly.

For a plastic injection molding service provider that offers custom-made products, the first goal is to work in collaboration with the client to determine the importance of surface finish for the exterior appearance, as well as the performance of the injection molded product, or to be specific, is the final product an eye-catching piece or simply a functional one? Your answer to this question determines the choice of material and the option of surface finish, based on which the plastic injection molding process is set, and the secondary finishing operations are accordingly required.

Available Surface Finish Types

Before making your final decision on the surface finish type for your plastic injection molded product, you should first have a clear idea in mind of what type of mold you need on the basis of your production volume, as well as the type of the material that your mold is going to be made of. Usually, a steel mold is of a higher hardness than an aluminum one, thus able to offer more surface finish options, because the steel material possesses the benefit of being able to be polished for a surface finish that is smoother than other materials, which is also helpful for such secondary finishing operations as painting aimed to enhance your final molded products.

Available surface finish types include:

  • Geometric shapes / patterns
  • Grains, e.g., the leather texture
  • Secondary finishes, e.g., paintings, print, etc.
  • Etching
  • Sand blast
  • Glossy, matte, or satin finishes
  • Mirror polishing or lens finishes

CATEGORIES of SURFACE FINISH

The Society of the Plastics Industry (SPI) has standardized the surface finishes for plastic injection molds. According to the finishing process selected, the following grades are determined:

Finish SPI* standard Finishing Method Typical surface roughness Ra (μm)
Super High Glossy finish A-1 Grade #3, 6000 Grit Diamond Buff 0.012 to 0.025
High Glossy finish A-2 Grade #6, 3000 Grit Diamond Buff 0.025 to 0.05
Normal Glossy finish A-3 Grade #15, 1200 Grit Diamond Buff 0.05 to 0.10
Fine Semi-glossy finish B-1 600 #Sand Paper 0.05 to 0.10
Medium Semi-glossy finish B-2 400# Sand Paper 0.10 to 0.15
Normal Semi-glossy finish B-3 320#Sand Paper 0.28 to 0.32
Fine Matte finish C-1 600 Grit Stone 0.35 to 0.40
Medium Matte finish C-2 400 Grit Stone 0.45 to 0.55
Normal Matte finish C-3 320 Grit Stone 0.63 to 0.70
Satin Textured finish D-1 Dry Blast Glass Bead #11 0.80 to 1.00
Dull Textured finish D-2 Dry Blast #240 Oxide 1.00 to 2.80
Rough Textured finish D-3 Dry Blast #24 Oxide 3.20 to 18.0
Machined Marks – – 3.20 (with visible machining marks)
surface finish SPI standard
SPI standard

AESTHETICS or FUNCTIONALITY

In surfacing finishing, a balance needs to be achieved between aesthetics and functionality, because the surface finish is able to affect not only the friction coefficient, but also the resistance to wear and tear; if these are considered to be important characteristics for the product performance, the design team is then required to choose the material and process that helps create a well matched finish effect. A skilled plastic injection mold maker is equipped with tremendous scientific data with regard to material chemistry, material behavior, and process conditions, so as to get the reference for accurate choice of surface finish process on the basis of specific parameters.

It is of critical importance to decide the surface finish type as early as the design stage, because it has a great influence on your selection of material and tooling, as well as your choice of the finishing process. The surface finish of a product is limited by the textures on the tool steel. From time to time, the imperfections, such as sink mark, on a surface can be covered by a rougher texture pattern. In addition, the draft required on a molded part can also be affected by the surface finish – if the draft is not appropriately designed, the surface finish could probably be destroyed during the ejection process.

SELECTION of PLASTIC MATERIALs

Your choice of the material, the additive, and the different plastic injection molding parameters, such as the fill rate, as well as the injection pressure and temperature affects the 2 key surface characteristics of glossiness and roughness. What is of special importance is the type of the material, e.g., the higher the melt temperature of the products made from reinforced crystalline resins, the more glossy and less rough the surface is, thus creating a smoother effect. However, when being plastic injection molded, a higher mold temperature is able to improve the glossiness and reduce the roughness of the reinforced amorphous resins.

Also, with regard to surface finish, another critical consideration is the additive that is applied to the resin material. At this point, the knowledge of material science is truly brought into play, e.g., the addition of contents containing fiberglass will lead to a lower glossiness. On the other hand, such additives as the carbon black and mica are able to reduce surface roughness, meaning if you have to maintain a certain degree of surface roughness out of considerations for product performance or appearance, you need to avoid or at least find substitutes for these additives. Also, if you add particulate fillers, the surface roughness might be increased. To produce a specific surface finish, a qualified engineer should be able to mix and match the proper combination of resins with additives.

China mold manufacturing business status compare to other countries

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Over the past decade or so, China mold manufacturing technology has made a qualitative leap, and the mold manufacturing industry has grown rapidly from small to large, making China one of the biggest mold manufacturing countries in the world. Along with the development of China’s automobile industry, the rise of domestic auto brands to the middle and high-end market segments, and the emergence of new energy vehicles, the market has put forward new demands for us, which requires us to move from low-end molds to high-end molds, and from a large mold manufacturing country to a mold powerhouse.

injection mold manufacturer in China

At present, the mold production value of the six mold manufacturing countries, i.e., China, the US, Japan, Germany, South Korea and Italy, occupies an absolute position in the world, among which the mold production value in China is the highest of all.

  1. The US

At present, there are about 7,000 mold manufacturers in the US, most of which produce automotive molds. Factories with less than 15 workers account for about 60% of the total, those with 15-50 employees account for 30% of the total, and the rest account for 10%. In spite of the small number of workers, thanks to its advanced automation and process technologies, it is now already one of the leaders in the world. According to authoritative statistics in 2014, the output value per capita of the US mold industry is around CNY 1.27 million.

  1. Japan

At present, there are about 10,000 mold enterprises in Japan, most of which produce automotive molds. Among them, individual companies with less than 20 workers account for 91% of the total. This is quite a shocking number, from which it is not difficult to see that the Japanese mold factories are usually small in size, and they mainly develop towards modularization. For example, a car needs 8,000 stamped parts, and each factory produces several fixed parts, which are then assembled, so as to lower the cost and improve efficiency.

  1. Germany

Germany is a country with very developed machinery and one of the first countries in Europe and America to start making molds. Its mechanics is almost invincible in the world, and the same is naturally true with mold making. Most of the factories produce automotive molds. There is a jargon in Germany: coordination, teamwork, technological innovation, learning from each other’s strengths, making progress together, giving full play to the overall advantages and jointly becoming the industry leader. You know, many countries may probably stand in awe before this sentence of courage and insight.

  1. China

Throughout the past decade, it can be said that the China’s mold manufacturing industry has undergone earthshaking changes. China boasts the highest number of mold factories, about 30,000 in total, among which state owned companies account for 5%, JVs account 10%, while the rest are privately owned. At present, there are about 3 million people involved in the mold industry.

Although the Chinese data seems amazing, with regard to production capacity per capita, we can see that the annual production capacity per capita in Germany is 2 CNY million, that in the US and Japan are respectively CNY 1.27 million and CNY 1.2 million, but that in China is only CNY 335,000. The comparison result is really shocking. The annual output value per capita of the mold industry in the US and Japan is 3-5 times that of China, and the annual output value per capita in Germany is 5-9 times that of China.

In recent years, with the continuous upgrading of household consumption, the development of China’s automotive industry has been accelerated. The development of automobiles has driven the rapid development of the automotive mold industry, and many enterprises have transformed towards the automobile industry. So, the China’s automotive mold industry is booming, with great prospects.

Moldflow Analysis Report for plastic injection molding

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Moldflow analysis is the plastic injection molding simulation software that obtains data and results  through the computer-aided simulation to simulate the plastic injection molding process, based on which, the feasibility of the mold solution is to be evaluated, in a bid to improve mold and product designs.

plastic product for mold flow

Product description

Wall thickness and mesh statistics in moldflow analysis

mesh thickness diagnostic moldflow

Thickness are uniformed

Plastic material information

Plastic material information for moldflow

injection molding process analysis for moldflow

Initial Nozzle/Gate Locations and Circuit

Gate location for moldflow analysis

Filling

filling moldflow analysis

The filling process is balance

Distortion, all effects at Z Component

In this plot a scale factor of  2X was added to overstate the magnitude of the warpage to make the trends easier to understand。

1) 4 gates injection

4 gates Distortion analysis

Deflection of Z direction is large  NG

2)2 gates injection

distortion analysis

Deflection of Z direction is large  NG

3)One gate hot runner injection

distortion moldflow analysis

Deflection of Z direction is large  NG

4)Change material to ABS Chimei PA757,4 gates

deflection analysis

Deflection of Z direction is small  OK

Conclusion:

As can be seen from the above results of moldflow analysis, four-point glue injection is smaller than two-point glue injection, but the deformation is not significantly improved. After replacing PP with ABS, the deformation is significantly reduced. It is suggested to use ABS material forming to reduce product deformation.

Quests to know the plastic injection mold price?

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Plastic injection mold price in China

  1. Do you have engineering design or physic samples? if you provide drawing, the most mold factories prefer 3D data in step or IGES format. If the design is complicated or large, the mold design should also be complicated and more cost. if you have physical samples, the mold factory will copy it and made the mold for you.
  2. What kind of plastic materials will you use for product? their price and characters are totally different when you choose different plastic resins.
  3. How many cavities will the injection mold have? how many parts will it make per shot(cycle)?it depends on the quantity you forcast to produce. if you plan to produce a huge quantity, then need more cavities in the mold.
  4. What mold life will it be? how many parts it can make during its lifetime. The higher class steel use for the mold, the mold life will be more longer, then more parts will be made. Cheaper steel or soft steel will cause shorter mold life.
  5. what is the tolerance of your plastic parts.if the tolerance is too tight,then the plastic injection mold price will be higher.because it bring more risk to adjust the dimensions.Normally the tolerance is +/_ 0.05mm for general plastic parts.
  6. Will the injection mold stay in China for production after manufacturing? if your quantity is not so high, it will save the shipping cost and import duty
  7. Will you own the injection mold? Or the mold factory? if the mold factory own the mold, they will quote the mold with non-profit price, but they want to get some profit from mass production
  8. If the mold factory will own the mold, How much will you need to pay when you get your mold from them? Normally the mold factory will charge 20% mold price for compensating. of course you can request 100% ownership of the mold, then you need to pay higher price at the beginning.
  9. Will the injection mold be made with American standard or Europe standard components? if they are made in china standard. it will take long time or high cost to wait for the mold components from china when they damage or wear out
  10. Do you need hot runner for your mold?Hot Runner Molds are usually more expensive.it affect plastic injection mold price a lot. But not all of molds should be hot runner. It depends on the structure of the part, the part size, the wall thickness, the required quantity, etc
  11. What is the finish of your plastic product? If transprent plastic material(such as PC,PMMA), the mold polishing should be with a higher level which leads to more cost. if need special texture on your product surface, then it will cause some cost, which depends on the texture spec. if need MT or Nihon standard,it will be much more expensive than normal requirement.

if you prepare all the information for above questions,Then you will easiy get the price of plastic injection mold from mold factory.

Factors Affect Plastic Injection Molding Cost

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plastic injection molding cost china

The involvement in a plastic injection molding project will surely enable you to understand that the mold can easily become the most expensive part in a project. Among the multiple factors that affect the cost of a plastic injection molding product, the top three ones are undoubtedly the dimensions and complexity of the part, the quantity of the part, as well as the effort required to build the plastic injection mold.

As we know, the cost of all manufactured products is dependent on that of the raw material and the labor required. Therefore, the cost of a plastic injection molding product is also dependent on the costs of the plastic material and the labor involved throughout the production process. Here, we would like to focus on one of the most influential factors throughout our operation, i.e., the plastic injection mold tooling. Later on, we will have a brief discussion on the vast diversity of plastic material options.

Mold tooling size and design

Among all the items built to produce a plastic product, a plastic injection mold, also referred to as a die or an injection mold tooling, stands out to be the most expensive one that’s built specifically to produce the plastic part via a very simple plastic injection molding process, which works as follows: the molten plastic material is first fed into a mold via the pressured injectors, and then, as the mold cools down, the plastic part is formed before the mold opens in two halves to release the part. A molding cycle consists of the closing, injection, and opening operation of a mold.

But, the devil is in the detail, as the saying goes. In the plastic injection molding process, the complicated and instantaneous motion of numerous moving components are involved, among which, some are designed with micron-level tolerances. Hence, a plastic injection mold plays a key role in this process. Molds are available in a diversity of different dimensions and designs, each of them is built to produce an integral part of a complete product, and each with a cavity (or more cavities to produce more than one parts in a single cycle) that holds the molten plastic. To ensure precision, the cavity needs to be created to extremely tight tolerances.

To build a mold for a particular project, the first thing to do is to work on an engineering table, to define the most effective size and number of mold cavities. In the process of mold making, the main factors include the size and shape of the entire mold. For plastic parts that are large-sized and sophisticated, the cavities need to be intricately machined and polished, though the most commonly seen and less costly ones are those having two halves that simply open and close against each other. However, there are also very complicated molds that are designed with such additional features as the slide, the lifter, and the cam, so as to facilitate the handling of the undercut.

Mold steel material

Next, we have to consider the cost of the mold  material. Steel is the most common material for the plastic injection mold, of which the type and grade are of great importance. As there are extremely tight tolerances for the part, all the cavities of a plastic injection mold must be able to last long without any wear, deformation or pits.

Therefore, hardened or pre-hardened steels become the best choices for making molds, so as to minimize mold deformation or wear. There are different reasons for the wear of steels and other metal materials, i.e., heat, friction, thermal change, pressure and fatigue. The number of parts to be produced determines what kind of material you choose for your mold. The greater the number of parts, the higher-grade steel (better quality and therefore more expensive) should be selected. Remember that, the material cost is only one of the factors, while the steel machining and finishing cost is dependent on the characteristics of the material you choose.

Plastic Material types

Throughout the globe, we have countless products that feature plastic parts. Thanks to its benefits of high strength, light weight and infinite design possibilities, plastic is more and more widely used.

Different plastics are regularly used in different industries that impose different requirements for the material. For example, The cost of plastic injection molding material used in different industries also varies a lot. Similar to other goods, when purchased in large quantities, the unit price of the material might drop. Yet, the ingredients of the material can be either simple or complicated, depending on its specific application, because the plastic materials are created to different specific needs, such as precision cutting, as well as resistance to chemicals, electricity, heat and more.

Manufacturer size and expertise

The cost of the tooling used for steel machining also varies greatly. In addition, the plastic parts are greatly varied in size and shape, so a mold manufacturer needs a large number of cutting tools, abrasives and more in storage for finishing the mold. Usually, a mold manufacturer enjoys the expertise necessary for the recommendation and manufacturing of various plastic injection molds. However, you might have to ask a mold company to build a product that they have never built before. This can cause the cost and risk to significantly rise.

Conclusion

As we all aware, the cost of plastic injection molding is composed of a string of items: the resin material, mold tooling, engineering and manufacturing, etc.The cost of plastic injection molding also includes other manufacturing factors, such as maintenance and utilities.  So, we need to have a great design first and then optimize it for manufacturability from the beginning, so as to help the customer save time and money throughout the whole process.

How to choose cost effective plastic injection molding supplier from China?

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What kind of injection molding supplier is a better choice?

With regard to this question, people believe that it depends on the specific situation. When considered from the only perspective of factory size, it is better that you choose the larger one, because a large size is often an synonym of strength, meaning that the comprehensive strength of the factory is better. Besides, the size also indirectly reflects how popular the factory is among customers! However, conversely, the larger the size, the higher the management cost is, so there will not be noticeable cost advantages. It is very important to know whether the injection molding supplier you choose regards you as an important customer, i.e., whether you are important to them.

injection mold supplier from China

If your purchase volume is small, due to insufficient company strength or whatsoever, blindly choosing a large-sized mold manufacturer sometimes costs you extra money just because they don’t treat you as an important customer. Currently, a lot of large-sized mold manufacturers refuse to take small amount orders, nor do they take responsibility for this state of mind, simply because you are not able to meet their requirements for order amount or order quantity. To you, it may feel like showing excessive passion to a cold person. Though the metaphor may be inappropriate, it shows quite the reality.

In such circumstances, most businesses prefer to choose small / medium-sized mold factories from China. As a matter fact, that’s what every player in the industry is doing right now. Anyway, these factories offer molds and products at a more acceptable price, which means it is a good deal for the customer. However, your concerns will soon come back: are they able to make the mold on time and with great quality; what is the production volume, and how long is the service life of the mold.

To respond to your concerns, we recommend you to focus on the horse sense, i.e., choosing the injection molding supplier with a complete set of facilities. It is what we usually refer to as the mold manufacturer with “Five Sets”, that is,  the CNC machining center, the slow speed wire cutting machine, the EDM mirror spark machine, the high-speed high-precision plastic injection molding machine, the 3D / 2D measuring instrument, as well as other necessary equipment for mold machining, making and testing. This should be taken as the key indicators to evaluate and finally select a injection molding supplier, because without these machines, The injection molding supplier would need to outsource the mold manufacturing process.

If so, negative impacts will be exerted: First, it increases the mold manufacturing cost; Second, it takes time for the mold manufacturer to repeatedly discuss and coordinate the transfer of workpieces during the outsourcing process, which, in turn, will extend the molding cycle, thus very easily causing delays of mold and product delivery. Although you may have the delay clauses well stipulated in the Purchase Agreement or Contract, the penalty will not be able to make up for the actual and long-term losses of your company in case of a delay, which will put the purchaser on a bed of thorns.

How to effectively minimize the cost of mold purchase?

From my experience, we firstly need to understand how many orders of the new product we can expect – is it big enough. In the review stage of the new product development, if the order amount cannot reach 500,000 or above, I will not recommend the hard mold. Just simply develop a soft mold, which is what we usually refer to as the mold for test. Thanks to the low cost of a soft mold, if the market reacts unfavorably, it’ll help save the unnecessary high cost of hard mold development; if, later the sales of the product booms with sharply increased demands, the hard mold can be developed at any time during the first round of mass production. Since it is just a hard copy of the soft mold, production and shipment schedule of the product will not be affected.

Also, there is another benefit in this practice – the injection molding supplier is able to learn something from the design, development and production experience of the first mold set (soft mold). When applied to the development of the second mold set, such experience will help make significant improvements. Even without you asking for it, the injection supplier would certainly like to do it for you, because it takes less efforts for them to copy a mold design. However, if the order amount of the product cannot be predicted, developing a hard mold at the very beginning of your project will increase your mold purchase cost by at least 1/3. Moreover, you need to take the mold cost into consideration as early as the engineering design stage. For instance, the selection of mold core materials, e.g., S136H and NAK80, as well as other components, such as the fine nozzles, will also cause the mold price to increase to different levels, except that the customer specifies higher requirements, or which material to use for the product.

Last but not the least, the following several points must be given special attention to if you want to select the most proper injection molding supplier:

  1. You get what you pay for, so don’t believe in low prices blindly, because there are often some traps that are unknown to us hiding behind the low price, be it shoddy or cut corners. We have to know that a injection molding supplier has to pay a lot for rent, water, electricity and the workers, while earning profits for itself.
  2. I prefer to select a well-equipped, most preferably, a medium-sized and above mold manufacturer. This year, due to the low price, I learned a lesson during my purchase process. I selected a small-sized China mold factory, which only employed a few dozen people in the entire mold division. And, inside the factory, there is even no CNC, with incomplete mechanical equipment, but only a few pieces of out-of-the-date equipment. Unsurprisingly, the final result was that though the factory developed the mold, mass production was not possible at the end.
  3. At last, it is recommended that you select a injection molding supplier by comprehensively analyze the overall situations and characteristics of each respective factory. Make a rational choice after making an objective evaluation of your own needs with regards to your mold and product positioning, so as to achieve a satisfactory result!

Polycarbonates(PC) injection molding properties and conditions

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What is the PC injection molding material?

Polycarbonates, more commonly known as PC, are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Although PC are commercially available in a diversity of different of colors (either translucent or opaque), the raw material is able to transmit light internally in a capacity similar to that of glass. The PC material is typically applied to produce a wide range of materials and are especially useful when the product requires outstanding resistance to impact and / or good transparency (for example, when used in production of bullet-proof glass). The PC material is most commonly applied for production of plastic lenses in eyewear, medical equipment, plastic auto components / parts, protective gears, greenhouse material, digital disks (CD, DVD, and Blu-ray), as well as exterior lighting fixtures. PC is also very resistant to heat and is able to be mixed with flame retardants without causing significant degradation to the material. PC is a group of engineering plastic materials, since they are able to be used for more capable and robust applications, e.g. in “glass-like” surfaces that are strongly resistant to impact.

 PC(Polycarbonates)plastic injection molding materialPC(Polycarbonates)injection molding plastic pellets

What are the different variants of the PC material?

According to the publication, AZO Materials, the PC injection molding plastic material was invented in the middle of the 20th century at the same time by GE in the US and Bayer in Germany. In today’s society, the material is produced by a great number of companies worldwide, each usually having their own manufacturing processes, exclusive formulas and trade names, including well known variant resins, such as Lexan® by produced SABIC, or Makrolon® produced by Bayer MaterialScience.

In the market, many different industry grades of the PC injection molding plastic materials are commercially available, most of which are referred to by their generic name (PC). Usually, they are differentiated by how much reinforcing glass fiber they contain, as well as the difference in melt fluidity among them. Some PC materials are combined with additives, such as the “UV stabilizers” that help protect it from long period direct exposure to the sunlight. PC materials that are plastic injection moldable may contain some other additives, such as mold release agents that help lubricate the mold during the injection molding process. Finished PC materials are usually sold in rods, cylinders or sheets.

Is PC toxic or harmless?

During the hydrolysis (the chemical breakdown of a compound due to reaction with water) process, it is very likely that some types of PC materials can be harmful when contacting with food, due to the unwanted release of Bisphenol A (BPA). The most commonly produced PC types are created by combining BPA and COCl2, but there are BPA free PC materials available, which are especially marketable for applications that involve perishable water or food.

What Characteristics Does PC injection molding material Have?PC plastic injection molding part in China

PC is one of the polyesters of carbonic acid, and all of the general-purpose PC materials are produced on basis of bisphenol A (BPA). In the molecules, the BPA component leads to its relatively higher glass transition temperature of 150 degrees Celsius (or 302 degrees Fahrenheit), while the rotational mobility of the carbonyl group inside the molecules allows the material to be highly ductile and tough.

As an amorphous engineering material, PC features an exceptionally high resistance to impact / heat, great clarity, outstanding sterilizability, admirable flame retardancy, and good resistance to stain. The notched Izod resistance to impact of the PC materials is pretty high, with a low and consistent mold shrinkage rate of (0.1 – 0.2 mm).

PC injection molding materials that have a high molecular weight (meaning the melt flow rate is rather low) usually features higher mechanical properties, but it becomes more difficult to process such grades of PC. It is a good idea to choose the PC type for a specific application on basis of the desired requirements, e.g. for high impact resistance, choose a low-MFR (Melt Flow Rate) PC; on the contrary, for optimal processability, choose a high-MFR (Melt Flow Rate) PC.

The melt viscosities of PC are usually Newtonian up to shear rates of 1000 s-1 and reduce more than that. The Heat Deflection Temperature under Load usually ranges between 130 and 140 degrees Celsius (or 266 – 284 degrees Fahrenheit) and the Vicat Softening Point is usually around 155 degrees Celsius (or 311 degrees Fahrenheit).

Conditions of the PC Injection Molding Process

Drying Different grades of PC absorb moisture, so pre-drying is of great importance. It is recommended to dry it under 100 – 120 degrees Celsius (or 212 – 248 degrees Fahrenheit) conditions for 3 to 4 hours. Moisture content must be kept below 0.02% before the process starts.
Melting Point 260 – 340 degrees Celsius (or 500 – 644 degrees Fahrenheit); higher temperatures for low MFR PC grades, and vice-versa
Mold Temperature 70 – 120 degrees Celsius (or 158 – 248 degrees Fahrenheit); higher temperatures for low MFR PC grades, and vice-versa.
Plastic Injection Molding Pressure Keep the pressure as high as possible, to enable fast molding.
Plastic Injection Molding Speed Adopt slow plastic injection molding speeds when small-sized or edge gate is used; adopt higher speeds for the rest gate types

POM injection molding properties and conditions

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What is the POM injection molding plastic material?POM injection molding plastic material

Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is a naturally white semi-crystalline engineering thermoplastic used in production of precision parts that require high stiffness, low friction, excellent dimensional stability, as well as high resistance to abrasion, heat, water absorption and organic chemical compounds, such as hydrocarbons. It is a plastic material featuring a very high tensile strength, with an outstanding resistance to creep, allowing it to bridge the gaps of material properties between most of the plastics and metals. Typically, the applications of POM include small size gears, home electronics, molded plastic zippers, medical equipment, and components of furniture like the plastic feet of a couch.

Why is POM so frequently used?

In applications that require low friction, POM is an especially useful plastic material. We choose to use POM when we need to produce strong, slippery and flexible parts (or maybe plastic parts with just one of these properties). Often, we employ the POM injection molding material to realize the reduction of friction. By nature, POM is such a slippery material, that it is a perfect fit for production of sliding mechanisms and gears. Just imagine the plastic feet of a couch sliding on the wood floor in your living room. It is very likely that these “feet” are POM parts made through the plastic injection molding process.

What other names does POM have?

POM is often referred to by several different names, either technical or industrial, among which the most commonly used one is Acetal. Other technical names are shown below:

  • Polyformaldehyde
  • Polyacetal
  • Polyoxymethylene glycol
  • Polymethylene glycol

Industrial names are adopted to indicate the slightly varied formulas for basically the same substances, and usually differ by the chemical firm who is involved in their production process. Please see the following for examples:

  • Celcon®: the POM Copolymer plastic made by Ticona (a subsidiary of Celanese located in Florence, Kentucky, the US);
  • Delrin®: the POM Homopolymer plastic made by DuPont, located in Wilmington, Delaware, the US;
  • Duracon®: the POM Copolymer plastic made by Polyplastics, a chemical company located in Taiwan, China;
  • Kepital®-POM: the POM Copolymer plastic made by Korea Engineering Plastics Company (KEP) located in Seoul, Korea;
  • Hostaform®: the POM Copolymer plastic made by the Celanese Corporation, Ramtal, Irving, Texas, the US;
  • Tecaform®: the POM Copolymer plastic made by Ensinger Company located in Washington, Pennsylvania, the US;
  • Tepcon®: the POM Copolymer plastic made by Polyplastics located in Taiwan, China;
  • Ultraform®: the POM Copolymer plastic made by BASF located in Ludwigshafen, Germany.

As a trademarked name of DuPont, the POM Homopolymer is often referred to as Delrin to indicate the specific resin material. Usually sold in the form of rods or sheets, Delrin is thought to be one of the most commonly used types of POM in the US market. It is the one and only Homopolymer on the list.

POM plastic injection molding parts in China

Is POM toxic or harmless?

The answer is no when the material is in a solid form. As a matter of fact, POM is frequently applied to food processing equipment and manufacturing. However, when absorbed and / or inhaled into the skin or eyes in the vapor or liquid form, POM can be toxic to people. In particular, you should be careful and follow the operation instructions closely when handling molten polymer.

What properties does the POM injection molding process?

POM is a strong and flexible material that shows a great resistance to creep, outstanding dimensional stability and impressive impact strength even at very low temperature conditions. With regard to grades, POM is either copolymers or homopolymers. Homopolymers usually feature better ultimate tensile strength, resistance to fatigue and ideal hardness, but it is not easy to process. Comparatively speaking, copolymers are better in terms of thermal stability, resistance to chemicals and processability. What they have in common is that both of them are crystalline and absorbs little moisture.

With regard to processing temperature, copolymers can be used continuously under temperature conditions of up to 100 degrees Celsius (or 212 degrees Fahrenheit); homopolymers are slightly more resistant to high temperatures. A great number of grades of the POM material are available in the market, allowing customization for different application projects.

Due to the relatively high crystallinity level of POM injection molding materials, higher shrinkage levels of 0.02 – 0.035 mm is caused. On reinforced grades of POM, differential shrinkage can be observed.

Conditions of the POM Injection Molding Process

Drying Drying is not usually required for POM, but it is better to store the material in a dry environment.
Melting Point 180 – 230 degrees Celsius (or 356 – 446 degrees Fahrenheit) for homopolymer; 190 – 210 degrees Celsius (or 374 – 410 degrees Fahrenheit) for copolymer.
Mold Temperature 50 – 105 degrees Celsius (or 122 – 221 degrees Fahrenheit); precision molding requires higher mold temperatures, because it can reduce post-molding shrinkage.
Plastic Injection Molding Pressure 70 – 120 MPa
Plastic Injection Molding Speed Medium to High