Views: 0 Author: Site Editor Publish Time: 2026-05-25 Origin: Site
ABS (Acrylonitrile Butadiene Styrene) is one of the most widely used engineering plastics in the injection molding industry. Thanks to its excellent hardness, surface gloss, impact resistance, and low cost, ABS dominates consumer electronics, home appliances, automotive interiors, toys, and daily plastic products.
However, many mold makers and molding technicians encounter common issues: parts that run perfectly with PP or PE often suffer from silver streaks, bubbles, weld lines, shrinkage, and warpage when using ABS.
In fact, ABS molding quality depends mainly on mold structure design and precise process control. This blog systematically explains ABS material characteristics, mold design standards, injection parameters, and common defect solutions for mass production.
ABS is a non-crystalline plastic with stable shrinkage but high sensitivity to moisture, temperature, and mold ventilation. Its key properties determine all molding rules:
High moisture absorption: Easily absorbs water in the air, causing silver lines and bubbles
Medium fluidity: Requires moderate injection speed and pressure
Stable shrinkage rate: 0.4%–0.9%, ideal for high-precision appearance parts
Stress-sensitive: Easy cracking or whitening due to uneven ejection or excessive speed
Easy to burn and carbonize: Poor ventilation leads to black spots and burnt marks
A good product starts with a qualified mold. Unreasonable mold structure will cause repeated defects that cannot be fixed by machine adjustment alone.
The gate directly affects filling balance, surface appearance, and shrinkage control.
Thin-wall & high-gloss parts: Use pin-point gate (0.8–1.5 mm) for automatic cutting and no gate residue
Thick-wall structural parts: Use side gate or fan gate to increase feeding volume and prevent shrinkage dents
Design rule: Avoid gates on visible surfaces and stress-bearing positions
Poor ventilation is the No.1 cause of burnt marks, weld lines, and incomplete filling for ABS.
Standard vent size: 0.025–0.05 mm depth, 4–6 mm width
Open vents at melt flow ends, weld line positions, and dead corners
Effectively exhaust compressed air and decomposed gas inside the cavity
Uneven cooling is the main cause of ABS warpage and dimension deviation.
Water channel distance from cavity: 10–15 mm
Water pipe diameter: 8–12 mm with uniform layout
Control mold temperature difference within 5℃ to ensure stable cooling speed
Adopt circular runners and high polishing to reduce flow resistance and carbon deposition
Common mold steel: P20, 718H, which supports high-gloss surface polishing
These mature parameters are widely used in factory mass production:
Hopper section: 180–190℃
Compression section: 200–220℃
Metering section: 220–235℃
Nozzle temperature: 210–225℃ (prevent drooling)
Mold temperature: 40–60℃ (normal parts); 60–80℃ (high-gloss parts)
Injection pressure: 50–100 MPa (80–120 MPa for thin & complex parts)
Injection speed: Medium-high speed 30–80 mm/s
Holding pressure: 50%–70% of injection pressure (anti-shrinkage)
Back pressure: 5–10 MPa (uniform melting & stable color)
Drying is mandatory for ABS! Dry at 80–90℃ for 2–4 hours, moisture content ≤0.03%. Undried ABS will definitely produce silver streaks and bubbles. No recycled material is allowed for electroplating and high-gloss ABS.
Causes: Wet raw material, excessive barrel temperature, poor ventilation Solutions: Extend drying time, properly lower melt temperature, clean and deepen mold vents
Causes: Insufficient holding pressure, small gate size, uneven wall thickness Solutions: Increase holding pressure and time, optimize gate position, improve cooling balance
Causes: Low mold/melt temperature, slow injection speed, poor exhaust Solutions: Raise temperature, increase injection speed, optimize venting and gate layout
Causes: Unbalanced cooling, internal stress, uneven ejection Solutions: Optimize water channels, reduce injection pressure, balance ejector pins
Causes: Blocked vents, ultra-fast injection speed, local overheating Solutions: Clean vent slots, reduce injection speed, lower partial barrel temperature
Causes: Insufficient clamping force, excessive pressure, mold parting surface wear Solutions: Increase lock force, reduce injection/holding pressure, repair mold surface
Causes: Too low melt temperature, sharp corners stress concentration, mixed materials Solutions: Properly raise temperature, optimize sharp structures, use pure ABS material
Home Appliances: TV, air conditioner, washing machine, remote control shells
Electronics: Chassis, power banks, earphone parts, instrument housings
Automotive: Interior panels, dashboards, lamp housings, decorative trims
Daily Products: Toys, storage boxes, suitcases, plastic household items
Electroplating Parts: Chrome decoration panels, metal-looking trim parts
ABS is a basic but highly skill-testing plastic material. Stable ABS injection production relies on scientific mold design and standardized process debugging.
To sum up: Mold quality determines the upper limit of yield, and process parameters determine the stability of mass production. Mastering ABS mold and process logic can solve more than 95% of daily molding defects.
