How to select a Plastic Injection Molding Machine

When searching for effective methods to choose a plastic injection molding machine, one often finds that it is crucial to balance various factors such as size, functionality, and cost. According to Google search results, proper selection hinges on understanding the technical specifications and operational requirements of the machine, ensuring that the chosen model aligns perfectly with production needs.

Buying an injection molding machine represents a significant financial commitment. Investing in a machine that is either excessively large or too small can lead to inefficiencies and waste. Therefore, finding the right fit for your specific product is essential, and this process typically begins with guidance from the supplier. They play a vital role in identifying the most suitable machinery and providing insights into how to properly select it.

With an abundance of machines on the market today, it is inadequate to solely focus on the type of injection molding machine such as hydraulic or electric; one must also consider the clamping force and injection weight to make an informed choice.

Understanding Injection Weight

The injection weight of a machine is a critical parameter in determining its suitability. It can be expressed in grams or ounces. While the parameter might seem straightforward, it can be confusing. Once the type of plastic material is identified, determining the weight of the plastic part simplifies the selection process. However, it's important to note that injection weight refers to the maximum weight that can be injected by the screw at its maximum injection stroke, under the air shot state (not injected into the mold). This parameter indicates the processing capability of the machine and should be theoretically understood, often based on tests using standard PS plastic with a density of 1.05.

Steps to Determine the Injection Weight

1. Begin by calculating the product weight with the formula: W = product weight + gate system weight. This gives you the necessary injection weight.
2. For polystyrene (PS) products, calculate the required injection volume as follows: Wps = (1.3 ~ 1.1) × W (where W is the total weight determined earlier). Adjust the coefficient based on product requirements.
3. For other plastics, first calculate the theoretical injection volume as Wx = (1.3 ~ 1.1) × (product weight + gate weight), then convert to actual PS weight using the formula Wps = Wx × 1.05 / Vx.
4. Select an appropriate injection molding machine based on Wps and manufacturer's manuals.

Relationship Between Injection Weight and Injection Volume

Note that injection weight is not merely injection volume multiplied by PS density. The injection volume is theoretical—factors like the flow of plastic into the gaps in the barrel impact the actual injection weight and volume ratio.

• For products with low precision needs, like toys, the total weight should be around 85% of the injection weight; for higher precision like crystal products, it drops to 75%.
• Avoid using machines with excessive injection weight. The total weight of the plastic should remain between 35% and 85% of the injected weight to prevent issues such as plate bending and quality degradation.
• Consider injection speed, which can be crucial for ultra-thin products; use high fluidity materials for optimal results.

Calculating Clamping Force

The clamping force is another significant aspect of selecting an injection molding machine. Key factors involve:

1. The projected area (S) from the mold opening.
2. Determining cavity pressure (P), influenced by various elements like gate size and product thickness.

Well-Known Plastic Groups and Their Viscosity Characteristics

• Group 1: PS, PE, PP
• Group 2: PA6, PBT, PET
• Group 3: PU, soft PVC
• Group 4: ABS, POM
• Group 5: PMMA, PC/ABS, PC/PBT
• Group 6: PC, PEEK, rigid UPVC

Choosing the Right Supplier

Finding a reliable manufacturer is just as important as choosing the right machine. Numerous Chinese suppliers are available, and their equipment is often considered to be of high quality and reliability. Here are two reasons to consider Chinese manufacturers:

1. China features the most complete industrial network worldwide, achieving rapid development and hitting world-class standards.
2. Cost advantages in China come from lower labor costs, abundant skilled workforce, and well-established production technologies.

Methods for Finding Manufacturers

You can utilize several platforms and methods to find reputable injection molding machine manufacturers in China:

B2B Platforms

• Alibaba: A key foreign trade platform where various suppliers can be located.
• Made in China: Promotes Chinese products and connects buyers specifically to Chinese suppliers.
• Global Sources: Caters to foreign trade needs from Chinese small and medium-sized enterprises.

Conducting Searches on Google

Brand manufacturer websites are often informative and provide quicker responses than B2B platforms.

Final Steps

To select the best injection molding machine, evaluate each supplier carefully based on previous customer reviews, the reliability of their website information, and promptness in communication. Following these methods can streamline your selection process and will hopefully guide you to make the right investment.

For additional assistance or details on specific machines and manufacturers, you may reach out directly. We advise considering Log-Machine, a top manufacturer based in China, which offers competitive pricing and quality machines. Click here for more information.