Nine tips, 13 influencing factors, and solutions for ABS plastic injection molding

• Nine tips, 13 influencing factors, and solutions for ABS plastic injection molding
  • Performance of ABS injection molding materials
  • What is injection molding?
  • A simple understanding of the working principle of ABS injection molding
  • injection molding ABS plastic parts
    • Plastic processing
    • Combining Plastic Characteristics with Injection Molding Steps
    • Mold Design Techniques
    • Heating temperature control recommendations
    • Recommended barrel temperature
    • Infusion rate control recommendations
    • Recommendations on back pressure
    • Injection pressure recommendations
    • Retention time
  • Factors to be considered and solutions during ABS injection molding
  • Elimold provides expert ABS injection molding services
  • in conclusion

ABS plastic is an indispensable engineering material in manufacturing. As a durable and economical thermoplastic polymer, it plays a vital role in numerous key industries, ranging from automotive and home appliances to consumer electronics and building materials. Furthermore, ABS injection molding is a revolutionary process, playing a crucial role in the production of plastic parts across various industries. To successfully complete an ABS injection molding project, it is essential to understand the relevant manufacturing technologies required to produce ABS plastic parts. Based on Elimold’s many years of experience, this article summarizes the manufacturing technologies for ABS plastic injection molding projects, aiming to help you obtain high-quality ABS plastic components.

Performance of ABS injection molding materials

ABS plastic is a solid plastic material; ABS stands for acrylonitrile butadiene styrene. It is a thermoplastic polymer without a real melting point. This means that ABS plastic does not burn when heated, but rather liquefies, making it easy to mold. This plastic is amorphous and thermoplastic. It also means that unlike other materials, it reacts differently to heat. Unlike thermosetting plastics, which are only heated once for injection molding, ABS plastic can be repeatedly heated. Thermosetting plastics will burn upon reheating after the first heating. ABS plastic melts once heated to 221 degrees Fahrenheit, and then you can use injection molding to reshape it. Therefore, they are a good recyclable material, meaning you can reuse ABS plastic, which also demonstrates that ABS plastic is an environmentally friendly material.

What is injection molding?

Injection molding is a manufacturing process for producing plastic parts, enabling the mass production of complex-shaped plastic products. The core principle involves injecting molten plastic material into a mold and allowing it to cool, resulting in a semi-finished product. This molten plastic takes shape according to the mold. Injection molding is primarily used for manufacturing large quantities of identical plastic products. It can typically be completed in a short time, thus saving time and effort in the production of plastic parts and products.

A simple understanding of the working principle of ABS injection molding

ABS injection molding requires a series of precise and well-defined steps. The first step is drying the ABS granules to remove any moisture that could affect the quality of the molded part. These granules are then placed in the hopper of the injection molding machine and fed into the barrel, where they are heated until the desired temperature level is reached. Molten ABS is then injected into the mold cavity at higher pressure through a screw or plunger injector. As the material fills the cavity, it cools and solidifies, forming the desired shape. After sufficient cooling, the mold opens, and the newly molded part made of ABS is ejected. This repeatability allows for the efficient production of large quantities of high-quality plastic parts.

injection molding ABS plastic parts

While ABS is a cost-effective, recyclable plastic, and despite its recyclability and lack of quality loss during large-scale production, there are several techniques you should be aware of and learn to make the process more time-efficient and achieve higher production volumes more quickly. Follow along to learn about several key details and solutions to consider when producing ABS plastic parts.

Plastic processing

The water absorption rate of ABS is approximately 0.2%-0.8%. For general-grade ABS, it should be dried in an oven at 80-85℃ for 2-4 hours or in a drying hopper at 80℃ for 1-2 hours before processing. For heat-resistant ABS containing PC components, the drying temperature should be appropriately increased to 100℃, and the specific drying time can be determined by air extrusion.

Combining Plastic Characteristics with Injection Molding Steps

When performing injection molding, considering the material’s composition and properties will help you make correct settings. This means you will use sufficiently precise steps in the injection molding process, reducing errors caused by human factors. For example, if a higher surface finish is required, more heat will be needed. You will need to control the injection speed. Additionally, ABS plastic has an absorption rate of 0.2–0.8%. Furthermore, the recycling rate of ABS plastic should not exceed 30%. If it happens to be electroplated ABS, do not use recycled materials in the molding process. It may cause unnecessary damage to your product.

Mold Design Techniques

When designing injection molds for producing ABS plastic products, the design of the mold gate and runner system must be considered, as this will determine the final product molding result. Although designs vary from product to product, we provide some basic standards for your reference.

First, you can set the mold temperature to around 60-65 °C. The runner diameter can be adjusted to 6-8 mm, and the thickness should match the product. In addition, the mold gate is also important to consider. The gate length should not be less than 1 mm, and the width should be 3 mm. Its vent hole thickness should be 0.025-0.05 mm, and its width should be 4-6 mm.

Heating temperature control recommendations

The heating temperature of ABS is important because the amount of heat determines the melting rate. However, it’s important to know that while the heating temperature is determined by the product, it also depends on the air injection. Below are some suggestions from Elimold regarding considering melting temperature; but please note that the temperature depends on the product. For example, products with high surface areas require higher heating temperatures.

• Regarding impact resistance, we recommend choosing 250 °C. However, the temperature range can also be between 220-260 °C. For heat resistance, the range can be between 265 °C and 270 °C, or 240 °C to 280 °C.
• The temperature range for the transparent grade is 230°C to 260°C. However, some may recommend sticking with 245°C. The electroplating grade ranges between 250°C and 275°C. Alternatively, you can choose 270°C.
• For flame retardant and glass fiber reinforced grades, the first range is between 200 °C – 240 °C or 220 – 230 °C. The second range is between 230 – 270 °C.

Recommended barrel temperature

ABS is an amorphous plastic with no distinct melting point. Its melt flow temperature is not very high; it achieves sufficient fluidity above 160℃, but excessively high temperatures do not increase fluidity. There are many types of ABS, and the barrel temperature varies depending on the type. The barrel temperature for general-purpose ABS is 180~230℃; for heat-resistant ABS, it’s 190~240℃; and for flame-retardant ABS, it’s 170~220℃. The nozzle temperature is 20~30℃ lower than the temperature at the front of the barrel.

Infusion rate control recommendations

When manufacturing ABS plastic products, different injection speeds are used depending on the product. For example, for products requiring high surface finish, high-speed control is recommended. Furthermore, the injection speed should be fast when injecting heated ABS, as the ABS is already heated.

Recommendations on back pressure

Back pressure is crucial in ABS plastic injection molding because it ensures that additives and colorants can be thoroughly mixed. Additionally, it reduces porosity in the material. Ensuring greater uniformity in the ABS is very important. Plastic pressure is key to achieving thorough material mixing, reducing bubbles, and increasing gloss.

Generally, higher back pressure reduces internal air bubbles, resulting in a more uniform appearance for the material. Excessive pressure can cause fiber breakage in the reinforcing resin, while lower pressure may increase pores and create spots. Therefore, finding the proper balance is crucial. We typically recommend a pressure of 5 bar, but this should be adjusted during the molding process based on specific conditions.

Injection pressure recommendations

The injection pressure depends primarily on the structure and wall thickness of the plastic part. Generally, the injection pressure for general-purpose ABS is 50-70 MPa; for heat-resistant ABS, it’s 60-85 MPa; and for flame-retardant ABS, it’s 60-100 MPa. If the flow resistance during mold filling is high, a higher injection pressure should be used; conversely, a lower injection pressure should be used.

Retention time

The holding time here refers to the time ABS is heated during the manufacturing process. This duration will affect the quality of the final product. It can also alter product color changes, degradation, and weak points, and it affects machine performance, thus influencing melt temperature. It can also overflow and affect everything in ABS plastic injection molding.

Therefore, we recommend that the repetition time for ABS should not exceed 5-6 minutes. This will help prevent degradation, especially at high temperatures of 265 °C. The flame retardant time should also be shorter. However, if you require a longer retention time, the temperature must be adjusted to 100 °C to achieve equilibrium. You don’t want your product to decompose. It would be a disgrace after all your efforts.

Factors to be considered and solutions during ABS injection molding

To obtain high-quality ABS plastic products, strict humidity control, stable thermal management, reasonable mold design, and optimized pressure profiles are required during the injection molding process. Only by systematically addressing these factors can defects such as warpage, diffusion, burn marks, and weak weld lines be reduced, while also improving part consistency and mechanical properties. Below is a summary of the influencing factors to consider during the injection molding of ABS materials and their solutions.

No.	Process Factor	Typical Issues / Risks	Recommended Solutions and Controls
1	Material Moisture Content	Splay marks, silver streaks, bubbles, reduced strength	Dry ABS at 80–90 °C for 2–4 hours; keep moisture <0.1%; use sealed hoppers
2	Melt Temperature	Poor flow, burn marks, degradation, weak weld lines	Control melt temperature at 210–260 °C; use uniform barrel heating; avoid long residence time
3	Mold Temperature	Flow lines, poor surface finish, internal stress	Maintain mold temperature at 40–80 °C; use temperature controllers; raise temperature for cosmetic parts
4	Injection Speed & Pressure	Short shots, jetting, flash, burn marks	Use medium-to-high injection speed; optimize pressure; apply multi-stage injection profiles
5	Packing / Holding Pressure	Sink marks, voids, warpage, internal stress	Set holding pressure at 50–80% of injection pressure; hold until gate freeze-off
6	Cooling Time & Cooling Design	Warpage, deformation, unstable cycles	Design uniform cooling channels; ensure sufficient cooling time; avoid overcooling
7	Mold Venting	Burn marks, short shots, gas traps	Provide vents at flow ends (0.02–0.04 mm depth); clean vents regularly; consider vacuum venting
8	Gate & Runner Design	Weld lines, uneven shrinkage, flow hesitation	Use properly sized gates; locate gates in thicker or non-cosmetic areas; balance runner systems
9	Shrinkage & Warpage Control	Dimensional inaccuracy, part distortion	Maintain uniform wall thickness (1.2–3.5 mm); optimize packing and cooling; use proper rib design
10	Weld Line Quality	Reduced strength, visible lines	Increase melt and mold temperatures; raise injection speed; optimize gate location
11	Surface Finish & Gloss	Flow marks, dull or uneven appearance	Increase mold temperature; polish mold surfaces; stabilize injection parameters
12	Thermal Degradation	Yellowing, black specks, odor	Avoid excessive temperatures; reduce residence time; control back pressure; purge regularly
13	Post-Molding Stress & Cracking	Stress cracking during assembly or solvent exposure	Reduce residual stress via optimized packing and cooling; avoid sharp corners; apply annealing if needed

Elimold provides expert ABS injection molding services

Elimold is at the forefront of the ABS injection molding service industry, offering comprehensive services that emphasize precision, scalability, and innovation. Our state-of-the-art facilities are equipped with the latest injection molding technologies, ensuring that every part is molded to specifications and of consistent quality. Furthermore, we offer a consulting approach, working closely with clients to optimize manufacturability design, streamline production, and minimize costs without compromising quality. Get a quote today and you’re guaranteed to receive high-quality ABS injection molded parts at a competitive price.

in conclusion

Please remember that ABS has a different composition. It exhibits properties different from other thermoset plastics. Exercise caution when melting it. ABS is a plastic suitable for any industry, from which you can obtain the highest quality products. Also note that it is a strong yet fragile material. Therefore, it must be processed using the correct molding process. This is why these tips can ease your stress. For best results, please use the tips above.