Jackie, Author at Ecomolding.com

Surface finish of plastic injection molding product

March 9, 2020October 18, 2019 by Jackie

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

March 9, 2020October 17, 2019 by Jackie

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.

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.

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.

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.

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.

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

March 9, 2020October 16, 2019 by Jackie

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.

Wall thickness and mesh statistics in moldflow analysis

Thickness are uniformed

Plastic material information

Initial Nozzle/Gate Locations and Circuit

Filling

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

Deflection of Z direction is large NG

2)2 gates injection

Deflection of Z direction is large NG

3)One gate hot runner injection

Deflection of Z direction is large NG

4)Change material to ABS Chimei PA757,4 gates

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?

March 10, 2020October 14, 2019 by Jackie

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.
What kind of plastic materials will you use for product? their price and characters are totally different when you choose different plastic resins.
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.
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.
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.
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
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
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.
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
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
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

March 10, 2020October 12, 2019 by Jackie

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?

March 10, 2020October 10, 2019 by Jackie

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.

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:

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.
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.
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

November 3, 2020December 4, 2018 by Jackie

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.

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 20^th 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 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

November 3, 2020December 3, 2018 by Jackie

What is the 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.

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

Nylon(PA) injection molding properties and conditions

November 3, 2020November 29, 2018 by Jackie

What Is the Nylon Material, and What Are Its Purposes?

Nylon plastic injection molding material can be used in a great diversity of application projects, including clothing, rubber material reinforcement such as car tires, applications as a rope or a thread, as well as a great number of plastic injection molded vehicle parts and mechanical equipment. It is especially strong, resistant to abrasions, moisture absorption and chemicals, as well as durable, elastic and easy to clean. Nylon is able to be used to replace the low strength metal materials. By virtue of its strength, temperature resilience and chemical compatibility, it is the ideal plastic material for production of vehicle engine components.

The Nylon plastic injection molding is also able to be used in conjunction with a great number of additives for production of various variants with an extensive range of different features and properties. Now, let’s take a look at how a composite gear is made by combining both Nylon and carbon.

Nylon, usually referred to as “PA” (chemical designation, e.g. PA 6 or PA 6/66), often comes in black, white or its natural color (off white or beige). Nylon 6/6 is perhaps one of the most commonly seen variants for engineering applications. Thanks to the fact that it can be extruded, nylon 6/6 is a good choice for both plastic injection molding and 3D printing. Its high melting point makes the material an ideal replacement for metals in applications under high temperature conditions (e.g. in the engine compartment of a car).

What Plastic Injection Molding Characteristics Does Nylon Have?

Since we have already known the purposes of the nylon plastic injection molding material, now let’s take a look at some of its key properties and features. The Nylon plastic is a condensation copolymer that consists of several different types of monomers combined with each other. It is able to be produced in many different ways, usually starting with distillation from crude oil, but is also able to be made from biomass. Nylon falls into the thermoplastic (as opposed to “thermoset”) material classification, which describes how the material responds to heat. When heated to their melting temperature, the thermoplastic materials will liquefy (a temperature as high as 220 degrees Celsius for the Nylon plastic). One of the major advantages of the thermoplastic materials is that there will be no significant degradation after they go through the process of heating to their melting temperature, cooling and reheating. Thermoplastics like the ABS plastic will not burn. Instead, they will become liquid, so they can be easily injection molded and then recycled. On the contrary, the thermoset plastic materials only allow for one-time heating (especially during the plastic injection molding process). When being heated for the first time, the thermoset materials will set (like a 2-part epoxy), leading to a chemical alteration that is impossible to reverse. If you ever try to heat a thermoset plastic material to a very high temperature for a second time, it will burn. This is the characteristic that defines the thermoset plastics.

What Are The Different Variants of the Nylon Material?

Despite the fact that the Nylon injection molding plastic was first discovered and patented by Dupont’s Wallace Carothers, it was not produced (as Nylon 6) until 3 years later in 1938 by a German research chemist, Paul Schlack who then worked at IG Farban, by employing a different approach. At present, it is now produced by a great number of companies worldwide, each usually having their own manufacturing processes, exclusive formulas and trade names.

The most commonly used types of nylon are Nylon 6, Nylon 6/6, Nylon 66 and Nylon 6/66. The numerals in the nomenclature indicate the quantity of carbon atoms between acid and amine groups, while the single digits, such as 6 mean that the plastic is produced from a single monomer in conjunction with itself (i.e. the molecule in general is a homopolymer), the two digits, such as 66, mean that the plastic is produced from several monomers in conjunction with one another (comonomers), and the slash means that the plastic is made up of multiple comonomer groups in conjunction with one another (that is to say it is a copolymer).

In addition, the nylon material is also able to be negatively affected by exposure to UV rays mainly from direct sunlight. As a result, before the plastic injection molding process, a UV stabilizer is usually added to the plastic.

Conditions of Nylon plastic Injection Molding Process

Dry	Since the PA6 material is prone to moisture absorption, we need to guarantee its dryness before the plastic injection molding process. When the material is shipped or delivered in waterproof packages, the containers should be tightly closed.
Melting Point	230 – 280 degrees Celsius (446 – 536 degrees Fahrenheit); 250 – 300 degrees Celsius (482 – 572 degrees Fahrenheit) for reinforced nylon grades
Mold Temperature	80 – 90 degrees Celsius (176 – 194 degrees Fahrenheit). The mold temperature has a significant influence on the crystallinity level of the material, which in turn greatly influences its mechanical properties. For parts which require a high degree of crystallization, like structural parts, the recommended mold temperatures are 80 – 90 degrees Celsius (176 – 194 degrees Fahrenheit). As for thin-wall parts with long flow lengths, higher mold temperatures are recommended. Although the strength and hardness will Increase with the mold temperature, the toughness will reduce. If the thickness of the wall is larger than 3 mm, we will recommend a cold mold (20 – 40 degrees Celsius / 68 – 104 degrees Fahrenheit), so as to ensure a higher and more uniform level of crystallinity. For glass reinforced materials, the recommended mold temperatures are always higher than 80 degrees Celsius (176 degrees Fahrenheit).
Plastic Injection Molding Pressure	Usually between 75 and 125 MPa (dependent on material type and product design)
Plastic Injection Molding Speed	High (a little bit lower for reinforced grades of nylon materials)

Chemical & Physical Properties

With regard to unfilled nylon grades, the shrinkage rate is usually between 0.01 and 0.015 mm/mm (1 – 1.5%). The addition of glass fibers is able to limit the shrinkage rate to 0.3% in the flow direction (but may be up to 1% in the cross-flow direction). Mainly, the crystallinity and moisture absorption levels are the 2 factors that affects the post-molding shrinkage rate, while the actual shrinkage rate is a result of multiple combined conditions, including part design, wall thickness and processing environment.

Polypropylene Injection Molding: Properties and Conditions

August 12, 2024November 28, 2018 by Jackie

What Is the Polypropylene (PP) injection molding Material ?

Polypropylene/PP injection molding material is a plastic polymer made by combining several propylene monomers. It is widely used in food containers due to its safety, as it is free from BPA. This thermoplastic polymer features a wide range of applications that include packaging of consumer products, plastic components for such industries as the automotive industry. Relatively speaking, the surface of the PP plastic is very slippery, so in some low-friction applications, it can be used to replace some plastics like polyacetal (POM), or used as a contact point for furniture. One of the weaknesses of this property might be that it is not easy to adhere PP to the surface of other materials (it does not bond ideally with certain types of glues, so sometimes it needs to be welded when it is required to form a joint). PP is slippery at the molecular level, but it has a relatively high friction coefficient. As a result, POM, nylon or PTFE will sometimes be used instead of it. When compared with other common plastics, PP also has a relatively lower density, meaning weight reductions for producers and sellers of injection molded PP products. The features described above and below demonstrate that the PP material can be used in a great number of applications: safe plates of a dishwasher, food trays and cups, etc., as well as opaque to-go containers and an extensive range of toys.

Conditions of the Polypropylene PP Injection Molding Process

Dry	Usually unnecessary when properly stored
Melting Point	220 – 280 degrees Celsius (428 – 536 degrees Fahrenheit); no higher than 280 degrees Celsius
Mold Temperature	20 – 80 degrees Celsius (68 – 176 degrees Fahrenheit); suggested: 50 degrees Celsius (122 degrees Fahrenheit). The mold temperature is the factor that determines the crystallinity level.
Plastic Injection Molding Pressure	As high as 180 MPa

Plastic Injection Molding Speed

Generally speaking, for PP injection molding process, a fast speed is usually adopted to keep the internal stresses at the lowest possible level; in case of surface defects, it is preferred to use a slower molding speed at higher temperature conditions. It is strongly recommended to employ machines that are able to provide profiled speed.

Runners and Gates

With regard to the cold runner molds, the commonly used diameters is between 4 to 7mm. We recommend the application of full round sprues and runners. It is OK to employ all types of gates. Typically, the diameters of a pin gate is set between 1 to 1.5mm, but it is also possible to use diameters of as low as 0.7 mm. When it comes to edge gating, the depth of the gate should be kept no lower than half of the wall thickness, but it should be at least twice as wide as the thickness. On the other hand, the hot runner molds are able to be directly used for the PP injection molding.

The injection mold design is crucial for efficient production in the polypropylene injection molding process.

What Advantages Does Polypropylene PP injection molding Have?

Injection molding polypropylene is easy to access and not expensive.

PP possesses a high flexural strength by virtue of its semi-crystalline property.

PP is characterized by a relatively slippery surface.

PP is rather resistant to moisture absorption.

PP is chemically resistant to an extensive range of bases and acids. Despite this, its chemical resistance has limitations, particularly with substances like chromic acid. Additionally, PP’s low melt viscosity provides advantages in injection molding, facilitating quicker mold filling and reducing cycle times and costs.

PP is very resistant to fatigue. The use of living hinges in polypropylene injection molding showcases the material’s durability and ability to mold thin features effectively.

PP possesses great resistance to impact.

PP can act as a great electrical insulator.

What Disadvantages Does Polypropylene PP injection molding Have?

PP has a high thermal expansion coefficient which limits its high temperature applications.

PP is sensitive to UV.

PP is not strongly resistant to chlorinated solvents and aromatics. Compared to other plastics, PP’s resistance to these chemicals is relatively lower.

It is not easy to paint on PP, due to its poor bonding properties.

PP is highly flammable.

In spite of its weaknesses, PP is still a great injection molding material. It features a diversity of unique qualities that cannot be found in any other materials, making it an ideal choice for a diversity of application projects.

What Properties Does Polypropylene Have?

When producing polypropylene plastic through PP injection molding, propylene polymerization is performed by involving stereospecific catalysts. Usually, it is isotactic PP that is produced (the methyl groups is lying on one side of the carbon chain). Due to the ordered molecular structure, this linear plastic is semi-crystalline, which is stiffer and has a higher melting temperature than PE. The PP homopolymer will become fragile when the temperature is higher than 0 degrees Celsius (32 degrees Fahrenheit). For this reason, many grades of PP available in the market are random copolymers with 1 – 4% ethylene or block copolymers with a higher ethylene proportion. Copolymers possess a lower heat distortion temperature (approx. 100 degrees Celsius / 212 degrees Fahrenheit), less clarity, surface gloss and rigidity, but a greater resistance to impact. When the ratio of ethylene increases, this material will become tougher and tougher. Its Vicat softening temperature is about 150 degrees Celsius (302 degrees Fahrenheit). For these materials, the surface hardness and resistance to scratch are higher thanks to the higher levels of crystallinity.

The PP plastic is not prone to stress cracking. It is usually adjusted by adding glass fibers, mineral fillers or thermoplastic rubbers. The melt flow rate of the PP material ranges between 1 and 40; materials with a lower melt flow rate feature a better resistance to impact but a lower tensile strength. When compared with homopolymer of the same melt flow rate, the copolymer appears to be tougher. Its viscosity leads to more shear, while being more temperature sensitive than PE.

By virtue of its crystallinity, the shrinkage rate of PP is quite high (0.018 – 0.025 mm/mm or 1.8 – 2.5%), but its shrinkage is more uniform than that PE-HD (the variance in flow and cross-flow shrinkage is usually lower than 0.2%). Increase of glass by 30% is helpful with reducing the shrinkage rate to about 0.7%.

Both the homopolymer and copolymer PP injection molding materials are strongly resistant to moisture, as well as chemicals like acids, alkalis and solvents. But, it does not offer excellent resistance to aromatic hydrocarbons, like benzene, as well as chlorinated hydrocarbons, like carbon tetrachloride. And, under high temperature conditions, its resistance to oxidation is not as strong as that of the PE plastic.