Jackie

Jackie Lau, Senior Tooling Engineer and Expert of plastic injection molding, experienced in plastic injection molding and tooling for more than 15 years. The founder and Director of Eco Molding & Sositar Mould.

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

Nylon(PA) injection molding properties and conditions

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

Nylon(PA) injection molding plastic pellets

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.

Nylon(PA) injection molding parts in China

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.

PP injection molding properties and conditions

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What Is the Polypropylene (PP) injection molding Material ?

Polypropylene/PP injection molding material ,  is a thermoplastic addition polymer made by combining several propylene monomers. It 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.

PP plastic material plastic injection moldingPP injection molding plastic resin pellets

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 thePP injection molding .

What Advantages Does Polypropylene PP injection molding Have?

PP plastic injection molding product in China

PP 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.

PP is very resistant to fatigue.

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.

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 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.

ABS injection molding properties and conditions

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What Is the ABS injection molding Material?

Commonly known as ABS injection molding material, Acrylonitrile Butadiene Styrene is an opaque thermoplastic polymer. ABS is amorphous and therefore has no true melting point. Thermoplastic (VS “thermoset”) describes how the ABS plastic responds to heat. A thermoplastic material becomes liquid when heated to a certain temperature level (105 degrees Celsius in the case of ABS material). Significant degradation will not happen after they go through the process of heating to their melting point, 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 1injection 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.

ABS injection molding plastic materialABS injection molding plastic pellets

Why Is ABS So Commonly Used?

The ABS plastic is strongly resistant to chemical corrosion, as well as physical impacts. It allows very easy machining and features a very low melting point, making it a perfect fit for the plastic injection molding process and 3D printing via a fused deposition modeling (FDM) machine. And, relatively speaking, ABS is inexpensive, of which the cost usually falls between those of Polypropylene (PP) and Polycarbonate (PC). Because of its low melting temperature, the ABS material is usually not applied in high heat conditions. By virtue of these properties, ABS can be widely used in a great number of project applications across an extensive range of trades.

What Are the Purposes of the ABS Plastic?

The ABS material can be used in a wide range of applications, among which the most commonly seen ones are computer keyboard keys, housing of a power-tool, the plastic protective covering of wall sockets (usually a blend of PC and ABS) and LEGO parts.

Is ABS Toxic or Harmless?

ABS is deemed relatively harmless, since it does not contain any known substances that cause cancer, and exposure to it does not result in any known adverse effects on health. However, ABS is usually not a good fit for production of medical implants.

What Properties Does the ABS injection molding Material Possess?

As its name indicates, ABS is composed of 3 monomers: acrylonitrile, butadiene and styrene, each of which passes on different properties: hardness, and resistance to chemical & heat from acrylonitrile; processability, surface gloss and strength from styrene; toughness and resistance to impact from butadiene. With regard to morphology, ABS is amorphous.

Through polymerization, the 3 individual monomers combine into a terpolymer with 2 phases: a continuous phase of styrene-acrylonitrile (SAN) and a dispersed phase of polybutadiene rubber. The ratios of the 2 monomers and the molecular structure of the 2 phases affect the properties of the ABS material, which allows product design great flexibility, and subsequently, hundreds of different grades are made available on the market. Thanks to these available grades, varied characteristics, such as low to high impact resistance, low to high surface gloss and low to high heat distortion are made possible.

In the paragraphs that follow, we would like to dive deeper into the ABS injection molding process. ABS features a fluidity that is between that of PS and PC .This influences the injection molding temperature and injection molding pressure, and vice versa. As a result, to lower melt viscosity and improve the cavity filling performance, a higher injection molding pressure is usually applied.ABS plastic injection molded product in China

What Are the Injection Molding Processing Conditions of ABS?

Dry ABS tends to absorb moisture, so it is required to be dried prior to processing. It is suggested that the ABS is dried under 80 – 90 degrees Celsius conditions for at least 2 hours, so as to restrict the moisture content of the material to less than 0.1%.
Melting Point: 200 – 280 degrees Celsius; Aim: 230 degrees Celsius
Plastic Injection Molding Pressure: 50 – 100 MPa
Material Pre-treatment: The moisture absorption rate of the ABS plastic is around 0.2% – 0.8%. For common ABS grades, drying must be performed prior to processing. It needs to be dried under 80 – 85℃ conditions for more than 2 – 4 hours or baked in a drying hopper at 80℃ for 1 – 2 hours. Usually, the regrind material should be kept within 30%, while no recycled material should be used for the Plating Grade ABS material.

Gate & vent design: the diameter of the channel should be set at 3mm and the thickness is kept the same as the part, gate length should be less than 1mm, the width of the vents is set between 4 and 6mm, and the thickness between 0.025 – 0.05mm.

Speed of Injection Molding: For flame resistant grade ABS material, a slow injection molding speed should be applied. If product surface is highly required, a high speed or multi-stage injection molding should be applied.

Back Pressure

To avoid wear, the back pressure should be minimized as much as possible, usually 5 bar.

That said, a high back pressure is able to ensure a uniform mixing.

Secondary Operations: The ABS injection molding material can also be used in secondary operations, e.g. ultrasonic welding and decorated moldings, which follows the hot stamping, pad printing or laser marking processes.

Additional Information

After being melted, some grades of the ABS plastic (in particular, the flame retardant ones) strongly adhere to the screw surface, and it will break down after staying on the screw for a certain period of time. Therefore, you need to regularly clean the screw with PS.

That’s all about the ABS injection molding process and I hope this could be of help to you. We are a injection molding manufacturer offering a diversity of plastic mold products. Please don’t hesitate to contact us for more information.

Find a turnkey injection molding manufacturer in China

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To produce superior quality tailor made parts, an entire team of skilled professionals is needed; we have to verify and sourceturnkey injection molding manufacturer in china multiple service providers, such as design & engineering, tooling, troubleshooting, quality control, packaging and shipping providers, while facilitating and organizing the communication among different sides. However, if you choose to work with a turnkey manufacturer, all these sources of stress will be eliminated, which would lead to an all-around one-stop manufacturing solution from an experienced supplier.

The Benefits of working with a turnkey Manufacturer is one of our guides on how an experienced team of professionals is able to streamline all the aspect of a production project, as well as the many benefits that a turnkey injection molding manufacturer brings, such as cost savings and streamlined communication, etc. Now, let’s take a closer look at some of them.

High Efficiency of a turnkey injection molding manufacturer

In a turnkey team, all the members will be working collaboratively to achieve a single target – successfully create the design and build the ideal finished product for you. Without a turnkey supplier, you will have to go through the whole laborious process that includes management of multiple suppliers, sync of supplier schedules, as well as sending (and sometimes resending) plans / prototypes; however, a turnkey team is able to take full responsibility for the production project – from conception to completion –  and offer immediate updates upon a simple phone call.

Advantageous Design, Tool-making and Manufacturing Services

It is made much simpler to change the current designs, thanks to the fact that designers, toolmakers and manufacturers work in close collaboration under the same turnkey company. If you don’t choose to work with a turnkey company, you will have to contact your designer and manufacturer separately whenever something needs to be adjusted. On the contrary, handling a single turnkey company makes it easier and smoother to communicate and more quickly to make changes.

Also, a more unified and consistent process is likely to be guaranteed, because the manufacturing, design and tool-making teams might have prior experience working with each other.

Vested Interest in Your Business

In a turnkey team, all the members will be working collaboratively to achieve a single target – help you complete your project successfully. If you can find a trustworthy turnkey supplier, the overall quality across every aspect of the project can be ensured, since the inevitable quality variance associated with working with multiple different vendors can be eliminated. Usually, you’ll probably get a higher level of custom service, as well as a devoted contact for your project.

In addition, working with several supplier may lead to blames on each other if any setbacks take place, while a turnkey provider is definitely held to a higher level of accountability, so a smoother and less stressful process can be guaranteed for everyone involved.

More Savings

If you entrust your project to a dedicated turnkey injection molding manufacturer, you will save not only time, but also money. A full-service provider is able to offer more discounted rates for the services they offer, when compared with other firms who is only able to handle one step in the whole manufacturing process.

Furthermore, a single turnkey injection molding manufacturer can handle your invoicing in a consistent manner, so as to ensure less confusion and an easier job for your accountants.

Learn More about Us

The skilled engineering and designer teams at a turnkey  injection molding manufacturer are able to ensure faster production cycles, greater service & savings, and higher-quality work.

Enjoying a history of more than 18 years, the ECO molding is able to offer the best quality turnkey services. We work in close collaboration with each of our clients by leveraging our specialized expertise on high-precision and high-volume tailor-made plastic injection molding, so as to ensure a streamlined and effective process, while adding value to your business on basis our profound experience in the industry. Several of the designers at Eco Molding began as toolmakers, so they are able to accurately create a plastic injection mold for manufacturability.

How to design plastic wall thickness for injection molding product?

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When designing a plastic part, its wall thickness must be carefully identified by properly considering the balance among weight, geometry and budget. For instance, though the thick plastic walls offer greater strength, they tend to warp when cooled in the manufacturing process. Among all the design elements, the thickness of a wall exerts the largest impact on production cost, efficiency and the quality of the final product.

plastic wall thickness analysis

A Reasonable Wall Thickness for plastic injection molding

While thicker walls are engineered for additional strength, thinner walls are created for some other benefits. As a matter of fact, you can get more benefits by keeping the part thinner and lighter when the production runs longer. As a result, it is of particular importance to maintain the optimum thickness especially for large volume plastic injection molding projects. If you keep the wall as thin as possible, you can get the following benefits:

  • Greater warping resistance when cooling
  • Lower costs thanks to less material usage and faster production
  • Lighter overall weight, thus much easier for handling, management, packaging and shipping
  • Shorter cooling cycles for faster and more efficient production

The wall thickness of a part is subject to no restrictions at all, but generally speaking, our ultimate goal would be to create a wall that is as thin as possible while also taking the structural requirements, overall dimensions and the geometry of a part into consideration. Another factor to be considered is the flow behavior and qualities of the resin materials.

Ensuring a Uniform Wall Thickness

During the injection molding process, a consistent thickness is of critical importance to cooling; if some parts of a product are thinner or thicker than the rest, the product might not be strong enough to withstand warping, cracking, twisting and overall failure. A consistent wall thickness is able to minimize shrinkage rate, as well as residual stress of the final product.

If a fully uniform wall thickness is not possible, it is better to maintain gradual thickness variations, so as to maintain design stability. For a product made from high mold shrinkage plastic materials, the variations in wall thickness should not exceed 10%, even with gradual variations to cope with possible stress concentrations.

A consistent wall thickness is also able to guarantee that the resin flows through a tool in the most efficient and uniform way, so as to achieve ideal processing. On the other hand, if there are variations in the wall thickness, air trapping, unbalanced filling and weld lines might be caused, as the molten plastic tends to take preferential flows.

Recommended Wall Thickness By Plastic Resin Types

Resin Type Wall Thickness(mm)
Acrylic(PMMA) 0.635-3.81
Polypropylene(PP) 0.635-3.81
Acetal(Delrin,POM) 0.762-3.048
Polystyrene(PS) 0.889-3.81
Polycarbonate(PC) 1.016-3.81
Acylonitrile Butadiene Styrene(ABS) 1.143-3.556
Nylon(PA) 0.762-2.921
Polyethylene(PE) 0.762-5.08
Polyurethane(PU) 2.032-19.05
Polyphenylene Sulfide(PPS) 0.508-4.572
Polybutylene Terephthalate(PBT) 2.032-6.35
Rigid PVC 2.286-6.35
Soft PVC 0.635-3.81