How to Find A Good Mold Maker in China?

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

 

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

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

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

 

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

Large, medium or small sized mold manufacturer?

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

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

 

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

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

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

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

Meet our customer in London UK

customer in London UK

 

Visit our customer in Birmingham UK

customer in Birmingham UK

 

Visit our customer in Kleve Germany

customer in Kleve Germany

Visit our customer in Rotterdam Netherland

customer in Rotterdam Netherland

 

Visit our customer in Milan Italy

customer in Milan Italy

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

 

Meet customer in Des Moines USA

The customer from Australia visit us in Shenzhen

The customer from Canada visit us in Shenzhen

The steels for plastic injection mold

Due to the enormous diversity of plastic materials and the widely varied requirements for plastic products, various requirements for the performance of plastic injection mold steel have been laid down. Therefore, many industrially developed countries have created an extensive range of plastic mold steel series, including carbon steel, carburized plastic mold steel, aging hardening plastic mold steel, corrosion resistant plastic mold steel, free machining plastic mold steel, through-hardening plastic mold steel, maraging plastic mold steel and mirror polishing plastic mold steel, etc.

 

Plastic injection Molds can be classified into 5 classes by service cycle, and they impose the following requirements on steel materials:

 

According to the length of mold life, molds can be classified into 5 classes. Class 1 mold runs 1 million or more shots, class 2 mold runs 0.5 – 1 million shots, class 3 mold runs 0.3 – 0.5 million shots, class 4 mold runs 0.1 – 0.3 million shots, and class 5 mold runs less than 0.1 million shots.

 

Class 1 and class 2 molds require the steel materials that can be harden up, with a hardness around HRC50, or the molds will wear easily, leading to out-of-tolerance injection molded products. As a result, the selected steel materials need to possess good heat treatment properties and machinability despite the high hardness. Of course, there are some other considerations, too.

 

Usually, the steel choices include Swedish 8407 and S136; American 420 and H13; European 2316, 2344 and 2083 and Japanese SKD61. For strongly corrosive plastics, S136, 2316 and 420 steels are normally chosen. In addition to S136, 2316 and 420 steels, low corrosion plastics can also choose SKD61, NAK80, PAK90 and 718M steels. Product appearance also has a great influence on the mold materials. S136, 2316, 718S, NAK80, PAK90 and 420 steel materials are suitable for transparent and mirror polishing products, while highly transparent products should primarily select the S136, and secondarily the 420 steel materials.

 

Class 3 molds mostly use pre-hardened steels, such as S136H, 2316H, 718H and 083H, with a hardness ranging from HB270 to 340.

 

Class 4 and class 5 molds usually use the P20, 718, 738, 618, 2311 and 2711 steel materials. For molds with extremely low requirements, S50C and 45# steels may be used, i.e. creating a cavity directly in the mold base

 

The spec. of plastic injection mold steel

1.USA standard:  AISI

Code:

P1-P19:Low Carbon Steel

P20-P39:Low Carbon, High Alloy Steel

2XX,3XX,4XX,6XX:Stainless Steel

H1-H19:Chromium base

Wx:Water Hardening Steel

Sx:Shock Resisting Steel

Ox:Oil Hardening Steel

Ax:Air Hardening Steel

Dx:High Carbon, High Chromium Steel

Mx:Molybdenum base (H.S.S.)

2.German standard:  DIN

Code:

1.2738:Low carbon, high alloy (P20)

1.2311:Low carbon, high alloy (P20)

1.2312:Low carbon, high alloy, free Machine (P20)

1.2083:Stainless Steel (420)

1.2316:High performance stainless Steel (420)

1.2343:Chromium base (H11)

1.2344:Chromium base (H13)

1.2510:Low alloy steel (O1)

1.2379:High carbon, high chromium steel (D2)

3.Japan standard: JIS

Code:

SxxC:Plain Carbon steel(S55C)

SUSxx:Stainless Steel (420)

SCrx:Chromium Steel

SCMx:Chromium Molybdenum Steel(P20)

SKx:Carbon Tool Steel

SKSx:Low Alloy Steel (- O1)

SKD11:Medium High Alloy Steel(D2)

SKD6:Medium High Alloy Steel(H11)

SKD61:Medium High Alloy Steel(H13)

SKHxx:High Speed Steel (M 2)

SUMx:Free Cutting Steel

SUJx:Bearing Steel

Common imported mold steels and their parameters & performance

 

ASSAB STAVAXESR-S136 – Highly abrasion/corrosion resistant pre-hardened mirror finish steel

  • The status of Ex-factory︰ HB215
  • Equivalent to Buderus standard︰ 2316
  • Equivalent to Bohler standard︰ M310
  • Equivalent to Hitachi standard︰ HPM38
  • Equivalent to DAIDO standard︰ PAK90
  • Abrasive resistance︰ ★★★☆☆
  • Tenacity︰ ★★★☆☆
  • Dimension stability︰ ★★★☆☆
  • Machinability︰ ★★★☆☆
  • Polish︰ ★★★★★
  • Corrosion Resistance︰ ★★★★☆
  • Product Description: The high grade stainless tool steel that possesses excellent anti-corrosion, polishing, anti-abrasion and machining properties. Electrical discharge machining (EDM) can create good mirror finishing effects and high quality surface finish; great stability will be showed when hardening. The cavity is able to maintain the original smoothness despite long-term mold production. Special care is not needed when the mold is operated or stored in a moist environment. So, it is recommended for molds that have high polishing requirements, as well as corrosive plastic molds.

 ASSAB 8407 – High grade hot-work tool steel

  • The status of Ex-factory︰ HB 185
  • Equivalent to Buderus standard︰ 2344ESR
  • Equivalent to Hitachi standard︰ DAC
  • Equivalent to DAIDO standard︰ DHA1
  • Abrasive resistance︰ ★★★☆☆
  • Tenacity︰ ★★★☆☆
  • Machinability︰ ★★★★☆
  • Product Description: The Cr-Mo-V tool steel is a high-purity fine steel material that is produced via special steelmaking technologies and under stringent quality control. The isotropy (physical properties are identical in all directions.) of the 8407 steel is better than the conventional H13, which brings great benefits of mechanical fatigue resistant and thermal stress fatigue resistant properties to the molds like die casting molds, forging molds and extrusion molds etc. As a result, the hardness of the 8407 molds is 1 – 2 HRC higher than that of the ordinary H13 without comprising the toughness. The high hardness is able to reduce the occurrence of crazing, thus improve mold life cycle. So, it is applicable for various die casting metal molds, extrusion molds, and plastic molds that have requirements for high quality.

 ASSAB 718HH — High-polishing pre-hardened precision plastic mold steel

  • The status of Ex-factory︰ HB 330-370
  • Equivalent to Buderus standard︰ 2711
  • Abrasive resistance︰ ★★★☆☆
  • Tenacity︰ ★★★☆☆
  • Machinability︰ ★★★☆☆
  • Polish︰ ★★★★☆
  • Corrosion Resistance︰ ★★★☆☆
  • Product Description: The pre-hardened Cr-Ni-Mo plastic mold steel that is produced under vacuum melting for improved properties. Before leaving the factory, it has undergone the hardening and tempering processes, so there is no risk of quenching cracks or heat treating deformation, because it does not need heat treatment, but employs nitrogentreatment and flame hardening treatment to enhance the surface hardness and abrasion resistance of the molds. The excellent polishing and anti-abrasion properties allow it to be used for thermal plastic injection molds and extrusion molds, high polishing plastic product molds, as well as blow molds, forming molds, structural components and shafts, etc.

 DAIDO NAK80 – Pre-hardened mirror surface precision plastic mold steel

  • The status of Ex-factory︰ HRC37-43
  • Equivalent to Hitachi standard︰ HPM50
  • Abrasive resistance︰ ★★★☆☆
  • Tenacity︰ ★★★☆☆
  • Machinability︰ ★★★☆☆
  • Polish︰ ★★★★☆
  • Corrosion Resistance︰ ★★★☆☆
  • Product Description: The pre-hardened steel (36-43 HRC) can be machined directly without heat treatment. Its hardness is quite uniform from the surface to the core with great machinability; possesses excellent electrical discharge machinability, and very easy to grind after EDM because the uniform surface hardness and lower white layer hardness are ensured after EDM; good mirror polishing features; excellent welding performance; great etching properties; and dimensional stability, making it suitable for precision parts production as well as mass production. As restricted by its chemical components, this steel material is quite brittle. When used for complicated molds, cracks tend to appear on the area where processing stress concentrates. Due to its high thermal sensitivity, preheating, heat reservation, post weld heat treatment (PWHT) and stress relieving treatment are required during welding, or weld failure might occur. What’s worth noting is that when treating temperature exceeds 520℃, dimensional changes can take place.

 DAIDO DHA1 – High performance hot-work tool steel JIS SKD61

  • The status of Ex-factory︰ HB229
  • Equivalent to Buderus standard︰ 2344
  • Equivalent to Bohler standard︰ W302
  • Equivalent to hitachi standard︰ DAC
  • Equivalent to ASSAB standard︰ 8402
  • Abrasive resistance︰ ★★★☆☆
  • Tenacity︰ ★★★☆☆
  • Dimension stability︰ ★★★☆☆
  • Machinability︰ ★★★☆☆
  • Polish︰ ★★☆☆☆
  • Product Description: The DAIDO DHA1 steel is widely used for Mg & Al die casting molds. As a common hot-work mold steel, it possesses great machinability and balanced heat resistant features. DHA1 is mainly used for Mg & Al die casting molds, related parts of die casting molds, hot stamping molds, hot extrusion molds and hot shearing blades, etc.

 

All copyright reserved by injection molded tooling company Sositar Mould

 

Hot runner types and their application in plastic injection mold

1,How the Hot Runner Works?

The cold runner of a plastic injection mold refers to the section between the mold inlet and the gate. The molten plastic maintains its fluidity inside the runner by virtue of the injection pressure and its own heat. However, as a part of the molding material, the runner is not a product. As a result, when designing a mold, we need to consider not only the filling effects, but also the material-saving effect produced by shortening or downsizing the runner; but in actuality, it is not easy for us to have the best of both worlds.this is why we need hot runner mold

Also known as the runner-less system, the hot runner is a system in which the molten plastic is not solidified after each injection, so when releasing the plastic part, the gate inside the runner does not have to be released. Since the plastic inside the runner is not solidified, the runner still stays unblocked when the next injection takes place.

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

Why has the hot runner system been developed? What benefits can the hot runner system bring us? Engineers familiar with the plastic injection molding process all know that the traditional injection molding is always associated with the following disadvantages:

  1. Hard to fill; b. thin-walled large size parts easy to deform; c. material waste in the runner; d. inconsistent plastic part quality when using a multi-cavity mold, and so forth.

The appearance of the hot runner system has provided an almost perfect solution for these problems. Generally speaking, the hot runner system offers the following benefits:

■ Shorter cycle time

As it is not limited by the runner cooling time, the plastic part can be ejected in a timely manner after being molded and solidified. For the production of thin-walled small parts, the molding cycle can be kept within 5s.

■ Material saving

In a complete hot runner mold, material waste will not occur thanks to the absence of a cold runner. This is of a greater significance to the application projects of the more costly plastic materials. As a matter of fact, global major hot runner manufacturers had witnessed leap forward development during the years when world crude oil and raw plastic materials were expensive. This is because the hot runner technology is an effective way to reduce waste materials and thus lower raw material costs.

■ Reducing defective products, and improving product quality

The temperature of the molten plastic inside the runner system can be accurately controlled during the hot runner injection molding process, so that the plastic is able to flow into each cavity in a more consistent manner, thus guaranteeing consistent quality products. The hot runner gate is of a higher quality, so after mold release, the part produced will have a smaller internal stress, leading to a smaller part deformation. Therefore, many high quality products in the market are all produced with the hot runner mold.

■ Eliminating following steps, helpful for production automation

After being molded with a hot runner mold, the part will be the final product, so there will be no follow-up steps like gate trimming, recycling and runner cooling, thus helpful for production automation. Many manufacturers from both home and abroad have combined the hot runner system with automation, so as to greatly improve production efficiency.

3,The Hot Runner types

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

 

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

Examples of hot sprue molds

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

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

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

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

What is valve gate hot runner?

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

The advantages of the valve gate hot runner include:

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

All copyright reserved by injection molding company Sositar Mould

Plastic injection molding gate types

For plastic injection mold design, one of the most important factors is how and where the gate should be located. As the mold opening, the gate is where the molten plastic flows into the final part. It serves as the boundary between the part and the scrap, so its location, size, and shape play an important role in how everything should be constructed, from structural integrity to exterior appearance of the finished product.Below is gate type we often choose:

Direct Gate(Sprue gate):

Pros:  
1. Little pressure loss;
2. Easy preparation.

Cons: 
1. High stress around the gate;
2. Gate (runner) needs to be trimmed manually;
3. Obvious gate scars will be left on the surface.

Application:
1. Suitable for production of large and deep barrel-shaped plastic parts. However, warping can easily occur due to contractibility   and stress when applied on shallow and flat plastic parts.

2,For plastic parts that do not allow gate marks on the exterior, the gate can be designed on the inner surface of the parts.

 

Side Gate:

Pros:
1. Simple structure, easy processing;
2. Easier to remove the gate.

Cons:
1. Automatic separation of the part and the gate is not allowed;
2. Gate marks are easily left on the plastic part.

Parameters:
1. Gate width W = (1.5~5.0)mm. Usually W = 2H, which may be appropriately increased for large and transparent plastic parts.
2. Height H = (0.5~1.5)mm. Specifically speaking, usually H = (0.4~0.6)d for commonly seen ABS and HIPS. Among them, d refers to the basic wall thickness of the plastic part; H = (0.6~0.8)d for materials with poor fluidity, like PC and PMMA; the suggested gate height for POM and PA is H = (0.6~0.8)d, so as to help avoid shrink marks and wrinkles by guaranteeing sufficient pressure holding, because though these materials possess good fluidity, they become solid very fast with larger contractibility; for materials like PE and PP, gate height H = (0.4~  0.5)d, because the small-sized gate is helpful for molten plastic shear thinning, thus reducing stickiness.

Application:
1. Suitable for production of plastic parts of various shapes, but it is will not be selected for slender barrel-shaped parts.

 

Tab Gate:

Pros:
1. It is a form evolved form the side gate, so it shares the various advantages of the side gate;
2. It is a typical impingement gate that can effectively prevent molten plastic jetting.

Cons:
1. Automatic separation of the part and the gate is not  allowed;
2. Obvious gate scars are easily left on the surface.

Parameters:
Refer to the side gate parameters for application.

Application:
Suitable for flat plastic parts that impose requirements on surface finish.

 

Fan Gate:


Pros:
1. The horizontal distribution of the molten plastic is more uniform when passing through the gate, helpful for reduction of plastic part stress;
2. Lower the possibility of air getting into the cavity, to avoid the occurrence of defects, like silver lines and bubbles, etc.

Cons:
1. Automatic separation of the part and the gate is not allowed;
2. Long gate marks are left on the edge of the plastic part, which need to be flattened by a tool.

Parameters:
1. The commonly used height H = (0.25~1.60) mm;
2. Width W = 8.00 mm to ¼ of the cavity width at the gate end.
3. The section area of the gate should be larger than that of the sub-runner.

Application:
Usually used for production of wide but thin plastic parts, as well as transparent plastic parts and those with poor fluidity, like PC and PMMA, etc.

 

Submarine Gate:

Pros:
1. Flexible choices of gate location;

Automatic separation of the part and the gate is allowed;
3. Smaller gate marks;
4. Applicable for both 2-plate and 3-plate molds.

Cons:
1. Plastic powder is easily dragged at the gate position;
2. Stress mark is easily created at water entry;
3. Plastic films need to be sheared manually;
4. Great pressure loss from the gate to the cavity.

Parameters:
1. Gate diameter d = 0.8~1.5mm;
2. The plastic flow direction and the vertical direction form an angle a between 30°and 60°;
3. The taper b is between 15° and 25°;
4. Distance to the cavity A = (1.5~3.0)mm.

Application:
Suitable for plastic parts that do not allow exposed gate marks on the exterior. For a multi cavity mold, the resistances from the gate to each cavity should be kept as close as possible, so as to avoid viscous flow and obtain better flow balance.

 

Banana Gate:

Pros:
1. Automatic separation of the part and the gate is allowed;
2. The gate area does not need additional processing;
3. No gate marks will be left on the exterior of the plastic parts.

Cons:
1. Stress marks may show on the surface;
2. Complicated processing;
3. Easily broken and thus blocking the gate if not appropriately designed.

Parameters:
1. Gate diameter at water entry end d = (Φ0.8~Φ1.2) mm, length = (1.0~1.2) mm;
2. A = approx. 2.5D;
3. Φ2.5min* refers to the gradual transition from the large end 0.8D to the small end Φ2.5.

Application:
Normally used for ABS and HIPS, suitable for neither crystalline materials like POM and PBT, nor high-rigidity materials like PC and PMMA, so as to avoid the curvy runner from being broken and thus blocking the gate.

 

Point Gate:

Pros:
1. Flexible choices of gate location;
2. Automatic separation of the part and the gate is allowed;
3. Smaller gate marks;
4. Low stress around the gate.

Cons:
1. High injection pressure;
2. Complicated structure, usually employing the 3-plate structure.

Parameters:
1. Usually the gate diameter d = (0.8~1.5) mm;
3.The gate length L = (0.8~1.2) mm;
4. To help pull the gate broken from the root, a taper should be set for the gate, a = approx. 15°~20°;

the gate and the runner are joined by arc R1 to ensure that the plastic part is not damaged when pulling the point gate broken; R2 = (1.5~2.0) mm; R3 = (2.5~3.0) mm; height h = (0.6~0.8) mm.

Application:
Usually used for the production of large plates and bottom cases. The proper distribution of gate can help reduce the flow distance of molten plastic and thus guarantee satisfactory distribution of melting marks; also able to be used for production of long barrel-shaped plastic parts to improve ventilation.

 

All copyright reserved by injection molding manufacturer Sositar Mould