Tag Archive for: transperant plastic molding

PMMA injection molding

 What means PMMA Injection Molding

PMMA injection molding, acrylic injection molding or Polymethyl methacrylate molding is a process where organic glass/acrylic is injected into a injection mold cavity to mold a particular product upon cooling and hardening. The PMMA injection molding parts are normally used to make some transperant components or parts, such  as car windows, LED lens, display box, and LED screens for some electric appliacnes. Acrylic is preferred to glass because it has better abrasion resistance. PMMA has excellent light transmission properties comparing to all of rest of plastic materials on the world today, making it an ideal material for applications where clarity is essential. Additionally, There are lots of thin wall clear plastic parts which select PMMA as molding material.

PMMA Injection Molding Technology

PMMA is the highest transperant plastic materils but PMMA is easy to break comparing to PC or ABS, so PMMA’s modification appears one after another such as copolymerization between methyl methacrylate and styrene and butadiene, a blend of PMMA and PC, etc. 372 PMMA is the copolymer of methyl methacrylate and styrene. If you add a small amount of nitrile rubber (about 50%) in the 372 PMMA, it will become 373 PMMA.PMMA injection molding parts

The fluidity of PMMA is poorer than that of PS, ABS and its melt viscosity is rather sensitive to the change of temperature. In molding, it changes the melt viscosity mainly from the injection temperature. PMMA is an amorphous polymer, the melt temperature is above 160 Celsius degree and the decomposition temperature can reach 270 Celsius degree.

  1. Processing of plastic
    PMMA has a certain degree of water absorption of 0.3-0.4%. The injection molding moisture must be less than 0.1%. Typically, it is 0.04%. The presence of moisture makes the melt bubbles, gas lines, and low transparency. So it should be dried. Dying temperature is 80-90 Celsius degree and drying time is 3 hours or above. In some cases, the utilization of recycled materials can reach 100%. The actual quantity depends on the requirements for quality. Usually, it can reach 30%, you should make sure there is no pollution of recycled materials, or it will influence the transparency and the nature of the finished products.
  2. Selection of injection molding machine
    The PMMA material doesn’t have special requirements for the injection molding machine. Due to the great melt viscosity, it requires the grooves deeper and nozzle hole a larger diameter. If you need higher strength requirements of products, you should use a larger aspect ratio of the screw to implement low-temperature plastics. In addition, PMMA must use drying hopper to store material.
  3. Design of mold and gate
    Mold temperature can be 60 -80 Celsius degree, The diameter of the sprue should match up with the internal taper. The optimum angle is 5 to 7, if the products of injecting molding are 4mm or more, the angle should be 7, the diameter of the mainstream channel is 8 to 10 mm, the overall length of the gate should not exceed 50 mm.
    For the products with wall thickness less than 4mm, the diameter of the flow channel should be 6-8mm. For the wall thickness is more than 4mm, the diameter of the flow channel should be 8-12mm. Depth of gate, fan-shaped and tabs-shaped gate should be 0.7 to 0.9t(t is the wall thickness of product), the diameter of pin gate should be 0.8to 2mm; The product with lower viscosity should choose the smaller size. The common venting hole’s depth is 0.05 to 0.07mm, width is 6mm, the stripping slope 30′-1, cavity portions are between 35′-1 and 30.
  1. Melt temperature
    You can use the air injection method to measure temperature ranging from 210-270 Celsius degree, which depends on the information provided by the supplier.
  2. Injection temperature
    You can use rapid injection to avoid generating a high degree of internal stress. It’s suitable to use multi-level injection, such as slow – fast – slow, etc. When injecting the thick parts, you should use the slow speed.
  3. Dwell time
    If the temperature is 260 Celsius degree, the dwell time is within 10 minutes. If the temperature is 270 Celsius degree, the dwell time is within 8 minutes.
PMMA injection molding

Applications of PMMA Injection Molding

There are many industries that needs PMMA injection molding parts, below are very few list components which use acylic injection molding parts:

  1. Eyeglass lenses: PMMA is one of the best materials for the eyeglass due to its excellent optical properties. It has the highest transparency from all other plastic materials, this is the best choice for eyewear.
  2. Plexiglass windows: PMMA, also known as plexiglass or acrylic glass, is a popular alternative to traditional glass windows due to its high impact resistance and optical clarity. It is commonly used in buildings, aquariums, and even airplane windows.
  3. Mobile phone casings: PMMA is used in the manufacturing of mobile phone casings due to its high impact resistance, scratch resistance, and optical clarity. It is also lightweight and can be easily molded into various shapes and sizes.
  4. Computer and electronics casings: Similar to mobile phone casings, PMMA is used in the manufacturing of computer and electronics casings due to its durability, impact resistance, and optical clarity. It is also lightweight and can be easily molded into various shapes and sizes.
  5. Vehicle windshields: PMMA is commonly used in the manufacturing of vehicle windshields due to its high impact resistance and optical clarity. It is also lighter than glass, which can improve fuel efficiency.
  6. LED lens: You see the light on the street and your house, that smal leens inside which is made by PMMA injection molding parts, this is very popular on all of light industry.
Below are a few of Acrylic injection molding parts we made before, if you have any project that needs PMMA molding products, welcome to send us your data, we will offer you the best quality with our expert experience of PMMA molding service.
PMMA plastic parts

PMMA plastic parts

PMMA injection moulding

PMMA injection moulding

 

 

Advantages of PMMA Injection Molding (acrylic injection molding)

1. It Produces Scratch-Resistant Products

Research has confirmed that acrylic injection molding materials are more scratch-resistant than other glass products. In this manner, the molding process generates products that can maintain their lustrous appearances for long without degradation.

2. It Produces Light Products

Acrylic has a density of 1.185 grams per cubic centimeters. On the other hand, glass has a density of 2.4 grams per cubic centimeters. As a result, PMMA plastic molding produces products that can be used as lightweight alternatives to glass.

3. PMMA Injection Molding Can Produce Complex Designs

The injection molding develops advanced shapes that cannot be generated by other injection molding processes such as metal injection molding. Furthermore, the PMMA injection molding process can reproduce a significant number of products that are identical in terms of shape, size, and weight.

4. High Production Efficiency

The PMMA injection molding process is faster than metal injection molding. As a result, more production units can be produced through this process in a given time. Technical analyses have confirmed that PMMA injection molding plants have shorter cycle times, which increase the overall production output of the industry.

5. Enhancement of Color Flexibility

Acrylic injection molding produces items that can be mixed with resins to create a wide variety of colored products. In contrast, this feature is not present in other processes such as metal/glass injection molding.

6, Special material for high requirement of transparent plastic molding.

PMMA material called Acrylic, or Plexiglass, Transmittance is up to 92%, is high then the glass, that means Acrylic molding is one of the best options for high requirement transparent injection molding parts, such as glass, Optical glass, lens, car lights, transparent pipes, etc.

PMMA plastic molding

PMMA plastic molding

Disadvantages of Acrylic PMMA plastic Injection Molding

Like any other molding manufacturing process, it has its own set of disadvantages that must be taken into consideration. below is some of the disadvantages of acrylic PMMA plastic injection molding.

  1. The materials produced have a lower resistance to impact compared to those produced by metal injection molding.
  2. The heat resistance of most products produced by the PMMA injection process is low (About 80 Degrees Celsius).
  3. Most items produced by the process have lower mechanical strengths, which limit their loading capacities.
  4. Some acrylic products have poor chemical resistance, which makes them prone to react with organic compounds.
  5. PMMA injection molding needs invert the special injection mold, which means the initial tooling cost is high, this is not benefits for low volume of production.
  6. Limited design flexibility. The process is best suited for producing products with simple and uniform shapes. Complex designs with intricate details may be difficult to achieve using acrylic PMMA plastic injection molding. This limitation can be a significant drawback for manufacturers looking to create unique and innovative products.
Conclusion
Given the above points, it is essential to understand how the PMMA injection molding works, its applications, advantages, and, disadvantages. Also, knowledge is vital at helping you appreciate the PMMA injection molding process.
If you want to see more transparent plastic molding parts please go to our transparent plastic molding page, if you have any project that needs PMMA injection molding or any other custom mold and molding parts, you are welcome to send us an email, we will offer you the best option solution.