ABS vs Polycarbonate: Which Plastic Is Better for CNC Machining Service?
Feb 09, 2026
● Choose ABS for lower cost, faster machining, and stable tolerances (non-transparent parts).
● Choose PC for impact resistance and transparency, but expect higher machining risk and cost.
● For thin walls + tight tolerances, ABS is usually safer.
● For clear guards/windows, PC is the only practical option (often needs polishing).
This guide compares ABS and polycarbonate specifically from a CNC machining perspective, helping engineers select the right plastic based on machining behavior, tolerance risk, and end-use requirement
ABS vs Polycarbonate for CNC Machining — Quick Definition
ABS is a cost-effective, easy-to-machine thermoplastic widely used for CNC-machined housings, brackets, and functional parts where dimensional stability and surface finish are more important than transparency or extreme impact strength.
Polycarbonate (PC) is a high-impact, transparent engineering plastic used for CNC-machined guards, covers, and structural components, requiring stricter control of heat and cutting stress to avoid distortion or cracking.
Quick Comparison: ABS vs PC for CNC Machining
Quick Takeaways:
ABS: Lower cost, easier machining, and better dimensional stability for most non-transparent parts.
Polycarbonate (PC): Higher impact resistance and optical transparency, but more prone to stress whitening, cracking, and heat-related distortion if parameters are not controlled.
Choose ABS when: cost, speed, and stable tolerances are the priority.
Choose PC when: transarency or impact resistance is a hard requirement, and the process can support more conservative cutting and fixturing.
The table below summarizes the key CNC machining differences between ABS and polycarbonate, focusing on machinability, tolerance control, surface finish, and cost impact.
ABS vs Polycarbonate for CNC Machining: Comparative Analysis
If machining speed and cost dominate, ABS usually wins.
If impact resistance or transparency is non-negotiable, PC becomes necessary despite the higher machining risk.
Factor
ABS
Polycarbonate (PC)
Machinability
Easy to cut and stable
Harder to cut, higher cutting forces
Tool Wear
Low, forgiving on tools
Higher wear with aggressive settings
Heat Sensitivity
Softens if the feeds are too slow
Builds internal stress from heat
Risk During Machining
Smearing and edge melt
Cracking, stress whitening
Surface Finish
Smooth, matte finish
Clear or glossy but harder to polish
Tolerance Control
Good for general tolerances
Challenging for thin or tight features
Cost Sensitivity
Lower material and machining costs
Higher material and processing cost
Typical CNC Use
Housings, brackets, prototypes
Guards, covers, impact-resistant parts
CNC Machinability and Stability: ABS vs Polycarbonate
CNC Machining Behavior
ABS and polycarbonate behave very differently under CNC cutting forces and heat, which directly affects machining stability and process reliability.
ABS is generally forgiving during machining. It tolerates higher cutting speeds and more aggressive toolpaths with a lower risk of stress cracking. Chips evacuate cleanly, cutting forces remain stable, and the material dissipates heat relatively evenly. This makes ABS suitable for complex geometries and repeated production runs without tight process tuning.
Polycarbonate is more sensitive to localized heat and stress concentration. During CNC machining, internal stress tends to accumulate rather than dissipate, especially near sharp internal corners or thin sections. If feeds, speeds, or tool geometry are not carefully controlled, polycarbonate may show edge whitening, surface cracking, or post-machining distortion.
As a result, machining polycarbonate typically requires reduced cutting speeds, sharp tools, conservative depths of cut, and carefully planned toolpaths to maintain consistency and avoid damage.
Dimensional Stability After Machining
Dimensional stability refers to a machined part’s ability to maintain its intended geometry after cutting forces are removed and clamping is released. Loss of dimensional stability typically manifests as warping, bowing, or delayed deformation after machining.
ABS generally maintains dimensional stability well. Its lower sensitivity to residual stress allows parts to relax more uniformly once unclamped, reducing the risk of warping in thin walls or large flat areas.
Polycarbonate, while mechanically stronger, is more prone to internal stress buildup during machining. If cutting heat, tool pressure, or uneven clamping is not well controlled, this internal stress can release after machining, leading to warping, edge curl, or stress whitening. Proper fixturing, conservative cutting parameters, and uniform wall thickness are essential to minimize these risks.
Surface Finish, Cosmetic Quality, and Cracking Risk
Surface appearance and cosmetic expectations differ significantly between ABS and polycarbonate.
ABS supports aggressive finishing passes and produces smooth, matte surfaces with minimal post-processing. It machines cleanly and is well-suited for visible housings, enclosures, and painted or textured parts. Minor tool marks are easy to remove with light finishing.
Polycarbonate requires more controlled finishing, especially for clear or optical parts. Tool marks, scratches, or stress whitening are more visible due to transparency. Clear polycarbonate often needs careful polishing, buffing, or coating to meet cosmetic or optical standards.
While both materials can show surface defects if machining parameters are incorrect, polycarbonate demands tighter control to preserve clarity and long-term appearance.
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