Difference Between two plate mold and three plate mold

Three plate mold VS Two plate Mold

Appearance difference Between two plate mold and three plate Mold

With regard to appearance, the biggest difference between the two plate mold and the three plate mold is that there is a stripper plate between the upper clamping plate and the cavity plate of the three-plate mold.

The appearance difference between three plate mold and two plate mold

Structures difference Between 2-plate  mold and 3-plate Mold

The main difference in the structure of the molds lies in the location and orientation of the guide pin, and that the three-plate mold has a small tie bar and a nylon lock on parting surface or latch on the side of the mold to control mold opening sequence and stroke.

The structure difference between 3 plates mold and 2 plates mold

Applications difference Between 2-plate mold and 3-plate Mold

2-Plate Mold 3-Plate Mold
Mold Size Average Larger
Mold Production Cost Low High
Molding Machine Capacity Requirements Low High
Structural Strength Strong Weaker
Automatic Production Semi-automatic / Automatic Semi-automatic / Automatic
Molding Cycle Short Long
Molding Pressure Low Higher
Runner weight Small Larger
Gate Trimming Dependent on Gate Type Unnecessary

Comparison of the Two Mold StructuresGate location in two plates mold

We can clearly see from the comparison in the above table that a two-plate mold is better than a three plates mold in most aspects, but why is there a three-plate mold in mold making and design? How to make a choice during design?

A three plates mold mainly exists in response to the appearance and production requirements of plastic products. For the finished product on the drawing, if the design is implemented through a two plates mold, the following two filling methods are available:


  1. The first filling method is to directly inject material through the large points on the finished product surface.
  2. The second method is to fill material from the non-appearance surface of the finished product (there is a location for consideration).

We can clearly see in the three mold flow analysis diagrams on the right that there are such problems as uneven flow, uneven pressure and short shot. There is no need to explain the short shot. Under uneven plastic flow and uneven pressure, though the mold is completely filled, the finished product will be severely deformed after molding. Next, it is necessary to consider the trimming problems of the finished product after molding (the trimming of the gate and the finished product) and whether the residue gate interferes with other matching components due to protruding from the product surface, which in turn affects assembly.

moldflow analysis on two plate mold

As can be clearly seen from the drawing, mold filling is directly carried out from the side of the finished product. At this time, in addition to obvious short shot, there is still a situation in which the flow is uneven.short shot on 2 plate mold

During mold trial, the molding factory will increase the injection pressure and accelerate the injection speed in order to fully fill the finished product. At this time, the excessive injection pressure will most likely cause the mold to overflow. If so, this will greatly affect the service life of mold production.

In addition, because of the lateral feeding, the finished product must be placed in a location away from the mold core; in order to reduce the size, the mold must be designed into an eccentric one; as a result, in addition to mold cost rise, it may cause an increase in the capacity of the molding machine, which indirectly increases the production cost of the molding factory.

In the three diagrams on the right, we can clearly see the difference in its injection molding conditions with that of the two-plate mold. The material flow is also obviously more even than the single point filling, and the short shot phenomenon is gone. Although pressure distribution is still not even enough, we can adjust the pressure distribution by controlling the size of the filling point.

In terms of molding pressure, the injection pressure of the three-plate mold is not much higher than that of the two-plate mold under the situation of complete filling. The main reason is that for the finished product, single-point filling is more difficult for plastic feeding.

moldflow analysis on three plate mold

Lifter Design for Plastic Injection Mold


  • In essence: a combination of the ejection mechanism and the side-core pulling mechanism.
  • Stroke:S=undercut+(1~3)mm
  • Thickness:8~12mm
  • Angle:not more than 15°
  • Ejectors are allowed to place near the lifters.but not too many.

mold lifter design

1、【lifter without base】

mold lifter design

mold lifter base design
mold lifter base design


Thickness (D)=S (undercut)+(2/3Ø)mm

Width (W)≥12

(If the width less than 12mm,use lifter with base)

2、【Lifter with base】

Stop block:Steel 738

Base:can install several lifters




mold lifter design
mold lifter design

mold lifter design

【lifter material】

  • if main inserts use pre-harden steel,then lifter use 1.2344 for plastic injection mold
  • if main insert use harden up steel,then lifter need azotizing process (718H、2316H)

lifter design

Below is a mold lifter animation from our relative company,their website www.ecomolding.com

All copyright reserved by plastic injection mold maker Sositar Mould



PC/ABS plastic injection molding resin

PC/ABS plastic injection molding resin

What is the PC/ABS?

PC/ABS is a blend of PC (polycarbonate) and ABS (acrylonitrile-butadiene-styrene copolymer), and a thermoplastic made of the polycarbonate and ABS alloy, offering the most desirable properties of the two materials – the processability of ABS and the mechanical properties, as well as resistance to impact, temperature and UV of PC. It can be widely used in automotive internal parts, business machines, communication equipment, home appliances and lighting fixtures. Typical applications include computer and business machine housings, electrical equipment, lawn & gardening machines, automotive parts / dashboards, interior finishes, and wheel covers).

Injection Molding Process Conditions: Drying before processing is a must. The humidity should be kept below 0.04%. The recommended drying condition is 90°C-110°C for 2-4 hours. Melting temperature: 230-300°C. Mold temperature: 50-100°C. Injection pressure: depending on the plastic product. Injection speed: as high as possible.

Chemical and Physical properties: the PC/ABS injection molding material combines the properties of both PC and ABS. For example, the easy processability of ABS, and the excellent mechanical properties and thermal stability of PC. The ratio of the two will affect the thermal stability of the PC/ABS material. The blend of PC/ABS also shows excellent fluidity. The shrinkage rate is around 0.5%. PC/ABS is a modified engineering plastic synthesized by blending. Among them, PC refers to polycarbonate, and ABS refers to the copolymer of acrylonitrile (A), butadiene (B) and styrene (S). This modified plastic boasts a better performance than pure PC and ABS, such as the improved resistance to impact and heat, as well as the increased hardness.

The characteristics of the PC/ABS injection molding  Material:

  1. The fluidity is a little lower than that of HIPS, but better than that of PMMA and PC, etc., while the flexibility is great.
  2. Highly resistant to impact and heat, flame retardant (V0 flammability rating), enhanced properties, and transparent.
  3. Great weldability with the 372 plexiglass, allowing production of two-color plastic parts, able to be chrome-plated and painted.
  4. Outstanding overall performance, high resistance to impact, chemical stability and great electrical performance.

Applications: Computer casings, computer components, typewriter casings, cameras, mobile phones & other business machine housings, electrical equipment, electrical & electronic parts, small household appliance components, hair dryers, connectors, word processors, medical equipment components, office supplies, cosmetic containers, food plates, lawn and garden machines, automotive headlamp frames, taillight covers, dashboards, interior finishes, and wheel covers, etc.

Plastic injection molding processing Conditions of the PC/ABS Material:

Drying Temperature: 104-110°C

Drying Time: 3.0-4.0h

Suggested Injection Volume: 30-80%

Suggested Max Water Content: 0.040%

Barrel Temperature: 60-80°C

Barrel Rear Temperature: 249-288°C

Barrel Center Temperature: 254-293°C

Barrel Front Temperature: 260-302°C

Injection Nozzle Temperature: 274-302°C

Processing (Melt) Temperature: 274-302°C

Mold Temperature: 60-87°C

Back Pressure: 0.345-0.689Mpa

Screw Speed: 40-70RPM

The amorphous thermoplastic blend of polycarbonate/acrylonitrile butadiene styrene (PC/ABS) is highly resistant to impact, with easy plasticity at low temperature. With excellent resistance to impact and heat, as well as excellent aesthetic and coloring effects, the Cycoloy resin blends can be tailored to meet the requirements for specific properties, so as to balance performance, cost and processability. The outstanding appearance and durability of the Cycoloy resin blends are very important for them to offer excellent design solutions.


PC/ABS is a injection molding thermoplastic made of PC and ABS alloy, combining the excellent properties of both materials. It can be widely used in automotive trims, lampshades, handles and other parts; consumer and commercial appliances, such as computers; and peripherals, such as mobile phones; able to replace PC for production of thin-walled products with long running processes; camera components, instrument panels, fan covers, hard hat housings, screw caps, radiator grilles, computer and optical instrument housings, hair dryers, and coffee makers, etc. PC/ABS manufacturers include SABIC Innovative Plastics, Bayer (Germany), Chimei (Taiwan, China), Teijin (Japan), LNP (the US), LG (South Korea), and Mitsubishi Engineering (Japan)

What is 3 plates molds?

1)The structure of 3 plates mold

3 plate mold

17.Locating ring    18.Dowel pin   19.Runner holder   20.Runners systerm    21.Return pin    22.Spring    23.stopper    24.Main runner     25.Nylon locker  26.Guide pin     27.Guide bush  28.Supporter   29.K.O holes

2) How the 3-plate mold works?

3 plate mold

  • When a 3 plate mold opens, the cavity and the core do not separate from each other at first, but the striper plate will be firstly separated from the cavity plate – the striper plate releases the molded product from the gate material, and then the cavity and the core separate from each other to eject the product.
  • Some variations of 2 plates molds are also applicable in 3 plates molds, but the molds are much more complicated.
  • One of the variations of a 3-plate mold is its combined application with the runner of a 2 plates mold.

The gate and runner systerm of 3 plate mold

3 plate mold gate   3 plate mold gate

  • Pros of a 3-plate mold:
    • A 3-plate mold only adopts the pin-point gate system.
    • A 3-plate mold leaves very minimal marks on the product; even mark-less injection molding is allowed;
    • The gate of a 3 plate mold does not need to be specially removed.
  • Cons of a 3-plate mold:
    • Since a 3 plates mold features a longer runner, cooling will take a longer time, thus leading to a longer injection cycle;
    • A 3 plates mold consumes more materials;
    • The structure of a 3 plates mold is relatively more complicated.

if you want to find a professional plastic injection mold manufacturer to make your 3 plates mold,please feel to contact us!