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ABS Machining: Properties, Challenges, and Best Practises

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Hey There, I’m Caro!

I am the author of this article and a CNC machining specialist at RICHCONN with ten years of experience, and I am happy to share my knowledge and insights with you through this blog. We provide cost-effective machining services from China, you can contact me anytime if you have any questions!

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In less than a century, plastics have taken over the manufacturing sector due to their low cost and versatile mechanical properties. Among them, ABS is one of the most used thermoplastics – both in prototypes and end-use products. 

Like most plastics, ABS parts are often produced through injection molding, blow molding, or 3D printing. However, CNC machining is essential for applications requiring tight tolerances and precision. Although ABS is machinable, machinists commonly encounter warping and rough surface finishes when working with it.

This article explores the key aspects of ABS machining, covering the common challenges and best practices to counter them. It provides insights into machining techniques, surface finishing methods, and ways to produce high-quality ABS components.

ABS Composition: Physical and Mechanical Properties

ABS Composition Physical and Mechanical Properties

ABS stands for acrylonitrile butadiene styrene. It’s a thermoplastic polymer that constitutes three monomers, mentioned in its name. The three monomers are present in different proportions: 15 – 35% acrylonitrile, 5 – 30% butadiene, and 40 – 60% Styrene. 

Each one of of monomers gives it different characteristics. The nitrile groups are polar, bind together, and give it a higher strength.  Acrylonitrile gives it chemical resistance and hardness. The butadiene gives impact resistance and ductility at low temperatures. While styrene is responsible for its overall shiny outlook.

Physical Properties

ABS is opaque with the original color being white or grey. However, pigments can be added to give any color. It’s an amorphous plastic, so there’s no sharp melting point. It transitions to a glassy state at about 106 and begins at 106°C. Its melting and decomposition fall between 190 to 320°C, depending on the exact composition. Like plastics, ABS is also lighter with densities ranging between 1.00 to 1.2 g/cm3.

Mechanical and Chemical Properties

ABS has several desired properties, but for manufacturers, the key ones are strength, hardness, chemical resistance, and insulation. These properties define its suitability for various applications and highlight potential challenges during machining.

ABS is a tough plastic. Its hardness value lies between 68 to 118 on the Rockwell scale. The tensile strength goes up to 65 Mpa. ABS also boasts good chemical resistance. It can withstand diluted acids, alkalis, and oils. However, it is vulnerable to aromatic solvents like acetone and benzene. And lastly, it’s a good insulator.

ABS Key Properties

Density1.00 – 1.02 g/cc
ColorWhite/Grey
Melting Temperature190 – 320°C
Hardness (Rockwell R)68 – 118
Tensile Strength (UTS)13 – 65 MPa
Thermal Conductivity0.150  – 0.200 W/m.K

How is ABS Machined: Top Techniques

How is ABS Machined Top Techniques

Apart from blow molding, 3D printing, and FDM, machining is one of the major processes used to shape ABS plastics. CNC machining aids in precise material removal, making it ideal for functional prototypes that require tight tolerances. 

Here’s a list of primary machining techniques used for ABS.

Milling

Milling is a subtractive machining process where cutting tools remove material from a solid ABS block to create the desired shape. It is ideal for producing complex geometries, flat surfaces, pockets, slots, and intricate 3D contours that would be difficult to achieve through molding or 3D printing.

Turning

Turning is performed on a lathe, where a rotating ABS workpiece is shaped using a stationary cutting tool. This process is used for cylindrical and symmetrical parts such as rollers and shafts.

Drilling

Drilling is the primary method for creating holes in ABS components for fasteners, wiring, or fluid passageways. Unlike metals, plastics like ABS can develop burrs, melted edges, or stress cracks if drilled at incorrect speeds or with dull bits.

Challenges in ABS Machining

Challenges in ABS Machining

Compared to metals, the machining of plastics is relatively easier. But still, plastics present their own set of challenges.

Surface Roughness

Like other plastics, the machining of ABS can result in scratches. One of the reasons is its amorphous nature. Its surface is more prone to micro-abrasions when exposed to cutting tools, improper feeds, or excessive tool pressure.

Distortion

ABS has a low thermal conductivity i.e. heat generated during machining tends to concentrate in localized areas. This heat buildup, combined with ABS’s relatively low melting point, causes the material to soften or deform, leading to dimensional inaccuracies. 

Furthermore, the internal stresses within the material may be released during machining, which results in the warping or bending of the part.

Surface Finishing Options for ABS

Since ABS is prone to tool marks and scratches proper finishing techniques help achieve aesthetic appeal and improved performance. Common polishing options for ABS are:

As Machined

This is the natural finish of ABS after machining. The surface retains visible tool marks, cutting lines, and potential rough textures, which may be acceptable for internal components where appearance is not a priority.

Bead Blasting

Bead blasting involves propelling fine abrasive media (glass beads or plastic beads) onto the ABS surface to achieve a uniform matte texture. It is ideal for aesthetic applications and grip surfaces.

Acetone Smoothing

Acetone smoothing is a chemical vapor treatment to create a glossy, polished finish on ABS. ABS is soluble in acetone – a controlled exposure causes the surface to soften and reflow, eliminating fine scratches. This method is quite known for 3D printing as it removes those layer lines.

Metal Plating

ABS can be electroplated with metals like chrome, nickel, or copper to improve its mechanical strength, electrical conductivity, and corrosion resistance. In this process, the surface is pretreated with a conductive coating or etching, which allows metal adhesion.

Best Practises for Machining ABS Plastic

Machining ABS plastic requires a balance of cutting efficiency, heat control, and precision to achieve high-quality parts. We have a few suggestions that can help optimize the machining process of ABS.

Machine Grade ABS

ABS comes in different grades and compositions, each for specific applications. For machining, machine-grade ABS should be used, as it is formulated to have better dimensional stability and lower residual stress.

Cutting and Clamping Setup Tools

Avoid excessive clamping pressure, as ABS is softer than metals and can deform under pressure. For machining, use sharp carbide or high-speed steel (HSS) tools to minimize cutting resistance and prevent melting. 

Standard roughing end mills work well for bulk material removal. For finishing jobs, we recommend 2- or 4-flute mills.

Best Design Practices

When designing ABS parts, keep in view tool accessibility, stress distribution, and machining feasibility. Small end mills and drills are necessary for fine details, but excessively small tools increase machining time and tool wear. A minimum end mill size of 0.8 mm (0.03 in) and a minimum drill size of 0.5 mm (0.02 in) should be maintained to balance precision.

Wall thickness is another critical factor in ABS machining. Thin walls can deform under cutting forces or vibrate. Keep a minimum wall thickness of 0.5 mm to maintain structural integrity.

To avoid tool deflection, the general rule is that: the depth of drilled holes should not exceed 12 times the drill bit diameter. While end mills should not exceed 10 times their tool diameter in depth.

Choice of Coolants

ABS is chemically resistance to aqueous acids but highly sensitive to aromatic coolants, which can cause swelling and deformation. So, use non-aromatic, water-soluble coolants such as pressurized air and spray mist.

Applications of Machined ABS

Plastics are in fact common in multiple industries and ABS, being a member, also shares the same popularity. The table illustrates applications of ABS Machined parts:

IndustryABS Applications
AutomotiveInterior trim, dashboard components, sensor housings, brackets
ElectronicsEnclosures, switch housings, insulating components
MedicalMedical device casings, diagnostic equipment housings, sterilizable trays
Industrial EquipmentMachine guards, conveyor components, structural supports
AerospaceMostly Prototype parts

How RichConn Can Help with ABS Machining

Working on a plastic product that requires precise machining, especially with ABS? You can count on RichConn Plastic CNC Machining Services.

Our team of experienced machinists specializes in working with a wide range of plastics, including ABS, PC, PP, PEEK, PMMA, PEI, HDPE, PVC, POM, PTFE, and Nylon. From CNC milling to turning, we ensure your parts are machined to exact specifications and delivered on time.

Contact us today for an instant quote and allow us bring your designs to life with precision and expertise!

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