Polycarbonate Injection Molding for Optical & Structural PC Parts
What tolerances does Fecision hold on polycarbonate injection molded parts?
Our production PC molds are machined to ±0.01 mm on cavity dimensions using slow-wire EDM. Optical-grade cavities reach S136 mirror polish at Ra ≤ 0.012 µm. Molds run 500,000+ cycles before first resurfacing, at a clamping range of 80–350 tons depending on part area.
ISO 9001:2015
ISO 13485:2016
AS 9100 Certified
DFM Review
slow-wire EDM
first resurfacing event
optical-grade PC
time from DFM approval
Why Engineers Specify
Polycarbonate for Demanding
Injection Molded Parts
Polycarbonate's Izod notched impact strength of 640–850 J/m — roughly 40× higher than standard acrylic — is why it shows up in riot shields, aircraft cabin windows, and surgical instrument housings where component failure isn't an acceptable outcome.
We've been running polycarbonate molds since the early days of our medical division. What became clear quickly: most PC part failures we see at DFM stage trace back to wall thickness irregularities and gate position, not material quality. A 0.8 mm thin section adjacent to a 3.5 mm rib will always show stress whitening under load — not because the PC is weak, but because the mold design created a molecular orientation that the material can't carry.
PC also requires careful moisture management. Pellets dried below 0.02% moisture before entering the barrel — our process uses desiccant-hopper dryers running continuously at 110–120 °C. Skip that step and you'll see silver streaks in the first shot. The material tells you immediately when something in the process is off, which is either frustrating or useful depending on how you think about it.
More material available on our Material Services →
Impact Resistance
Izod notched strength 640–850 J/m (ASTM D256). Survives repeated drop impact at room temperature — essential for device housings, safety equipment.
Heat Deflection
HDT 120–130 °C at 1.82 MPa (ASTM D648). Survives autoclave sterilization cycles and continuous service in environments up to 115 °C.
Optical Clarity
Light transmittance 88–90% (ASTM D1003). Refractive index 1.586. Suitable for lenses, instrument windows, and display covers requiring near-glass clarity.
Dimensional Stability
Shrinkage 0.5–0.7% (uniform, amorphous). Low warpage versus semi-crystalline alternatives. Consistent across cavities in multi-cavity tooling.
Biocompatibility
USP Class VI and ISO 10993 compliant grades available (Makrolon 2458, Lexan 940). Suitable for medical device contact components under ISO 13485.
Flame Rating
UL94 V-0 flame-retardant grades available (Makrolon FR) for electronic enclosures, connectors, and electrical components requiring regulatory compliance.
PC Grades We Run —and Why Each One Matters
Not all polycarbonate performs equally under injection conditions. Viscosity, flame rating, fiber reinforcement, and biocompatibility requirements determine grade selection before the mold design begins.
Makrolon 2458 / Lexan 940
PrimaryThis is what we reach for on the majority of PC jobs — lens covers, display bezels, and enclosures where transparency and structural integrity both matter. Lexan 940 specifically has been the industry workhorse for 30 years for good reason: consistent melt flow (10 g/10 min at 300 °C), predictable shrinkage, and clean mold release.
Makrolon FR / Lexan 500R
Flame RetardantWhen the end-use product needs UL94 V-0 — power supply housings, EV battery components, electrical connectors — we switch to FR-grade PC. The flame-retardant additives don't meaningfully change the mold setup, but they do affect gate sizing (the material runs slightly stiffer) and surface appearance (slight haze vs unfilled PC).
PC GF10 / GF20
Glass-FilledGlass-filled PC trades optical clarity for stiffness. We run GF grades for structural brackets, camera mounts, and medical device chassis where creep under load is a concern. The tradeoff: glass fibers surface at the mold wall and create a textured finish — polished A-surface is not achievable without secondary operations. Also note: GF PC is abrasive; we use S136 hardened cavities rated for GF grades.
PC/ABS Blends
Blend — Cost BalancedPC/ABS sits in an interesting middle ground — it loses some impact and heat resistance compared to straight PC, but processes more easily (lower barrel temperature 230–260 °C vs PC's 280–310 °C) and costs 15–25% less per kilogram. For consumer device enclosures where ABS-level aesthetics are acceptable but PC-level structural rigidity is needed, it's the right choice.
Our Polycarbonate Injection
Molding Process
Six controlled stages, each with a documented checkpoint. PC requires tighter process discipline than commodity resins — barrel temperature, moisture content, injection speed, and mold temperature all interact in ways that show up immediately in part quality.
DFM Review
Wall uniformity, gate location, draft angles, and rib geometry reviewed before CAM programming. PC-specific red flags: wall transitions above 25% change, gate positions that create jetting on optical surfaces.
Precision Tooling
S136 cavity steel machined to ±0.01 mm via slow-wire EDM on critical dimensions. Optical surfaces diamond-polished to SPI A1 (Ra ≤0.012 µm). Mirror polish completed before any gate fitting.
Material Pre-Drying
PC pellets dried at 110–120 °C for 4–6 hours in desiccant-hopper dryers. Dewpoint monitored continuously (< −30 °C). Moisture must be below 0.02% — we verify with Karl Fischer titration on medical-grade runs.
Injection & Process Control
Barrel 280–310 °C, mold 80–110 °C. Injection speed profiled to reduce shear stress on PC chains and prevent optical distortion (birefringence). Scientific molding DOE used on first article to lock process window.
In-Process Inspection
First-article measured on CMM (±0.002 mm system accuracy). Optical-grade parts inspected under diffused 500-lux light box for surface defects. Birefringence checked via polarized light where specified.
Post-Process & Delivery
Optional annealing at 100–120 °C to relieve molded-in stress before shipment. Parts individually bagged in anti-scratch film. Full batch record and dimensional report shipped with every order.
PC Injection Molding DFM: Where Part Failures Are Prevented
Our DFM for PC parts runs through eight specific checkpoints before the mold design is locked. PC failure modes are predictable when you know what to look for.
Explore our injection mold tooling capabilities →
Common PC DFM Issues We Flag
Stress Cracking at Undercuts
PC doesn't flex during ejection the way PE or PP does. Any undercut above 0.8 mm per side requires a slider or lifter — forced ejection creates stress whitening or delayed cracking under load.
Max undercut: 0.8 mm/side without mechanismBirefringence in Optical Parts
Fast injection speed + low mold temperature + thin walls = molecular orientation that shows as rainbow banding under polarized light. Optical lenses require injection speed profiling and mold temperature ≥80 °C to allow molecular relaxation before freeze-off.
Mold temp ≥80 °C for optical-grade PCChemical Compatibility of Mold Release
PC has poor resistance to hydrocarbon-based mold release agents — they cause stress cracking within days of part production. Silicone-based internal lubricants or dry mold release only. This catches people by surprise on first PC runs.
Silicone release only — no hydrocarbon spraysHot Runner Nozzle Temperature
PC degrades at ≥340 °C. Nozzle tip temperature must stay 280–315 °C — too hot and yellowing appears in the first 50 shots; too cold and the gate freezes mid-fill. We calibrate per-nozzle on tool qualification.
Nozzle: 280–315 °C strict windowPrecision Control & Quality Assurance for PC Parts
Every metric below is measured, not estimated. PC's low shrinkage makes it possible to hold tight tolerances — but only if the measurement system resolution is high enough to verify them reliably.
- PC (Polycarbonate) is widely used in medical device housings, surgical instrument handles, and IV connectors due to its exceptional clarity, impact resistance, and ability to withstand sterilization cycles.
- At Fecision, we manufacture PC medical components with tight tolerances and full traceability, ensuring compliance with ISO 13485 and FDA requirements. Whether you need transparent fluid management parts or durable surgical tools, our medical injection molding services deliver the precision and biocompatibility your devices demand.
Industries That Rely on Polycarbonate Injection Molding
PC's combination of optical clarity, structural integrity, and regulatory-grade biocompatibility makes it relevant across industries with very different operating requirements — all of which we serve from the same tooling infrastructure.
Medical & Diagnostics
Microfluidic cartridges, IVD reagent housings, surgical instrument bodies, and transparent diagnostic chamber covers. ISO 13485 process, USP Class VI grade available, Class 10,000 cleanroom production cell for sensitive assemblies.
Consumer Electronics
Camera lens covers, LED diffuser plates, display bezels, and device enclosures where SPI A2 or better cosmetic finish is required. PC's scratch resistance (Rockwell M70) keeps surfaces presentable through production handling.
Aerospace & Defense
Instrument panel lenses, HUD covers, avionics enclosures. AS 9100 Rev D certified process. PC's combination of optical clarity and structural rigidity at −40 °C to +115 °C service range makes it one of the few amorphous polymers that satisfies aerospace qualification standards.
Industrial Electronics
Connector housings, sensor covers, terminal blocks, and switching enclosures requiring UL94 V-0 flame rating. PC/ABS blends handle the majority of these applications at lower cost while meeting most thermal and impact specifications.
Polycarbonate Injection Molding — Buyer Questions Answered
These are the six questions engineering and procurement contacts ask before they send us a drawing. We've answered them with actual numbers, not marketing language.
+
Need to discuss your polycarbonate injection molding project?
Our expert engineers can analyze your application requirements and recommend the optimal solution.
Start Your Polycarbonate Injection Molding Project
Upload your 3D file or 2D drawing.
Our engineers run a full PC-specific DFM review for you.
Related Services
PET Injection Molding
PEEK Injection Molding
PP Injection Molding
Nylon Injection Molding
PMMA Injection Molding
