Plastics offer several advantages over metals in industrial applications, including lightweight properties, corrosion resistance, design flexibility, excellent electrical insulation, and lower processing and maintenance costs. As modified and high-performance engineering plastics continue to evolve, many traditional metal-dominated applications are now being partially or fully replaced by plastics. Among these, ABS stands out due to its well-balanced mechanical strength, toughness, processability, surface finish potential, and cost-effectiveness. It occupies a significant position within the plastics family, acting as a bridge between commodity plastics and engineering plastics.
This article explores what ABS plastic is, its benefits and challenges in machining, typical applications for ABS parts, and expert tips for effective machining. Continue reading to learn more!
What Is ABS Plastic?
ABS (Acrylonitrile Butadiene Styrene) is a low-cost thermoplastic polymer, made by combining its three monomer constituents—acrylonitrile, butadiene, and styrene, along with any other desired additives. Some of its key properties are as below:
Maximum Temperature: 176°F ~ 212°F (80°C ~ 100°C) for continuous use
Thermal Insulation: 0.14 - 0.20 W/m.K
The synergistic combination of the three monomers in ABS provides toughness (B component), hardness (A component), and processability (S component). The properties can be fine-tuned by adjusting these ratios. Beyond this flexibility, choosing machined ABS plastics for prototypes and products offers the following benefits:
Resists breaking under impact and maintains toughness even at low temperatures.
Provides stable structural strength and wear resistance.
Offers reliable electrical insulation.
Tolerates dilute acids, alkalis, and greases.
Delivers excellent cost-effectiveness, meeting most general requirements while being significantly more affordable than high-performance plastics.
Has a high surface gloss, supports easy coloring, and allows secondary treatments like painting, electroplating, vacuum coating, transfer printing, and screen printing for diverse aesthetic effects.
Supports versatile forming processes, including injection molding, extrusion, 3D printing, and CNC machining.
Allows for modification by blending with other plastics (e.g., ABS/PC alloy, ABS/PBT alloy) or adding glass fiber, mineral fillers, flame retardants, and toughening agents to enhance mechanical, thermal, and flame-retardant properties.
However, it is important to note that ABS is sensitive to high temperatures. Prolonged exposure to heat may cause deformation or aging. When used outdoors, it can degrade or fade over time, requiring UV stabilizers for protection. ABS also has limited resistance to certain chemicals, such as aromatic compounds, ketones, and esters.
Benefits of CNC Machining ABS
While ABS is often associated with injection molding and 3D printing, particularly in large-scale production or rapid prototyping. However,CNC machining offers distinct advantages in certain applications. Here are the key benefits of choosing CNC-machined ABS:
It is a cost-effective method for producing ABS parts with complex geometries and tight tolerances since you don’t have to create expensive mold.
CNC machining does not involve melting or curing processes, ensuring ABS retains its full mechanical properties like strength and toughness.
CNC machining produces ABS parts with smooth surfaces and minimal visible tool marks, reducing the need for post-processing. Unlike 3D printing, which often leaves layer lines, or injection molding, which can result in weld lines, flow lines, or sink marks, CNC machining delivers consistent surface quality and precision.
For small batches or prototypes, CNC machining ABS offers quicker turnaround times compared to the lengthy process of designing and producing injection molds. This speeds up the development and testing phases.
Challenges of ABS in CNC Machining
As with other machined plastics, two very common machining defects in ABS plastic are distortion and a poor surface finish.
1. Distortion in ABS occurs when the material warps, bends, or deforms during or after machining. This typically happens due to the following reasons:
ABS has a relatively low heat deflection temperature and poor thermal conductivity. As a result, heat can quickly build up at the machining site, softening the material and causing it to deform.
Relative to commonly machined metals, ABS plastics experience significant thermal expansion when heated. This can cause an inexperienced machinist to remove too much material, which will be evident when the part cools and shrinks.
Using improper cutting speeds, feed rates, or dull tools can generate excessive heat and lead to deformation.
Inadequate fixturing can cause the part to move or flex during machining, resulting in distortion.
2. Another common challenge in CNC machining ABS plastic is achieving a high-quality surface finish. Compared to metals or harder materials, ABS is more prone to tooling marks and chatter lines during machining. Improper machining parameters or tool vibrations often exacerbate these issues. These imperfections can compromise the integrity of ABS fittings, leading to potential leaks, or cause transparent ABS parts to appear foggy.
Tips for Effective CNC Machining ABS
To avoid the pitfalls associated with machining ABS plastic, here are some helpful tips for achieving efficient and high-quality results:
Use Machine-Grade ABS Plastic
By adjusting the ratio of the three monomers, molecular weight, and additives, several different grades of ABS plastic can be produced. Machine-grade ABS is specifically engineered for machining. Unlike extrusion-grade and injection-molding-grade ABS, which are optimized for melt flow, machine-grade ABS is formulated with heat stabilizers to prevent deformation caused by frictional heat during cutting processes, demonstrating low internal stress, high rigidity, and dimensional stability. Always use machine-grade ABS when milling, turning, or drilling to ensure high-precision parts and a superior surface finish.
Use Appropriate Cutting Tools
Tools designed for machining high-strength steel and titanium alloys is not the best choice for ABS plastics. When machining ABS, high-speed steel (HSS) and carbide tools are the commonly used. Maintaining sharp cutting edges is essential to minimize cutting resistance, reduce heat buildup, and prevent softening or melting of the material.
For optimal results, use tools with a positive rake angle of 10° to 15°, a relief angle of 5° to 10°, and a small edge radius to facilitate efficient chip removal and reduce heat generation. Typically, uncoated carbide tools are preferred to minimize friction, but in cases where adhesion is a concern, tools with low-friction coatings like TiN (Titanium Nitride) or DLC (Diamond-Like Carbon) can help prevent chip sticking and improve surface quality.
Adapt Your Cutting Parameters
ABS is sensitive to heat, and excessive cutting speeds can cause localized overheating, causing the material to soften or melt. It is generally recommended to use spindle speeds between 1,000 and 3,000 RPM, depending on the tool diameter and depth of cut. By comparison, metals like steel or aluminum can tolerate much higher cutting speeds, often ranging from 5,000 to 10,000 RPM or more.
Feed rates that are too high can result in chatter or a rough surface finish, while rates that are too low may cause friction between the tool and the workpiece, generating excess heat. When machining ABS, it's crucial to balance the feed rate to prevent the plastic from stretching or developing burrs. Additionally, taking deep cuts in a single pass can increase localized heat, causing deformation or melting. Instead, opt for multiple shallow cuts to effectively control heat buildup and maintain dimensional stability.
Use an Appropriate Coolant
ABS plastic is prone to overheating and deformation during machining if coolant is not properly applied. However, not all coolants are suitable for ABS. The material is sensitive to certain aromatic solvents, which can cause surface cracking or degradation. To avoid these issues, always choose non-aromatic, plastic-specific coolants.
Unlike machining metals, which often relies on oil-based or emulsified coolants, ABS requires low-temperature, efficient cooling due to its relatively low melting point (approximately 220°C). Water-soluble coolants are highly effective for machining ABS, as they effectively dissipate heat while preserving the material’s integrity.
Plastic-specific coolants can be applied in various forms depending on the cutting intensity. Options include a jet of pressurized gas for light cooling, a continuous mist for moderate cooling, or a flowing liquid for heavy-duty cooling in more demanding operations.
Anneal the ABS plastic
To relieve internal stresses and improve dimensional stability, consider annealing ABS plastic before machining. Annealing involves gradually heating the material in a heat treatment oven, holding it at the appropriate temperature, and then cooling it slowly.
This controlled process ensures that internal stresses are evenly relieved, enhancing the material's machinability and stability. It is especially beneficial for parts with complex geometries or thin walls, as it reduces the likelihood of cracking or warping during machining.
Common Applications of CNC Machined ABS Parts
ABS is popular for applications that need a strong, stable plastic with ease of forming ability. CNC machining provides unique benefits for low-volume, high-precision, and custom parts. Here are some typical applications of CNC machined ABS:
Custom Housings and Enclosures: ABS is frequently used for crafting custom electronic housings, instrument enclosures, and protective casings that demand exact dimensions and reliable performance.
Automotive Components: In the automotive industry, ABS is machined to produce interior trim pieces, dashboard components, and specialized fittings requiring precision and high-quality finishes.
Consumer Product Accessories: ABS is used to make customized consumer accessories like headphone parts, mounts, and other specialized gadgets .
Toys: The smooth finish of ABS make it a preferred material for toys including action figures, board game pieces, and puzzles. A well-known example is LEGO bricks, which are made from ABS due to its durability and precise machinability.
Medical Prototyping: ABS serves as a material of choice for prototyping medical devices, including customized brackets, fixtures, and enclosures for medical instruments and tools.
Jigs and Fixtures: For manufacturing operations, ABS is used to create durable jigs, fixtures, and tooling aids that facilitate assembly and production processes.
Educational Models: CNC machined ABS is often used for educational models and demonstration tools, valued for its ease of machining and durability in interactive learning environments.
Low-Volume Production: For small-batch production runs, ABS provides a cost-effective solution where creating molds for injection molding would be impractical or too expensive.
Create Custom Machined ABS Parts with Chiggo
At Chiggo, we deliver premium plastic CNC machining services at competitive prices. Our expert engineers and machinists, with over 20 years of experience, specialize in working with materials like ABS to ensure your parts meet — or exceed — surface finish and tolerance requirements. Partner with Chiggo today and let us help make your next ABS machining project a resounding success. Contact us now to get started!
