Yes, polycarbonate can be injection molded. In fact, injection molding is a preferred manufacturing process for polycarbonate parts and products thanks to the material’s exceptional balance of optical clarity, high strength, durability, and heat resistance.
In this complete guide, as a professional plastic injection molding manufacturer, we’re going to dive into everything you need to know about polycarbonate injection molding.
You’ll learn:
- What is Polycarbonate?
- Polycarbonate Injection Molding Applications
- Polycarbonate Injection Molding Process
- Polycarbonate Injection Molding Design Guidelines
- Troubleshooting Common Polycarbonate Injection Molding Issues
So if you want to leverage polycarbonate injection molding for your next project, you’ll find this guide invaluable.
Let’s get started!
What is Polycarbonate?
Polycarbonate (PC) is an amorphous thermoplastic material known for its optical clarity and high impact resistance. It combines strength and durability with lightweight properties and heat resistance up to 135 ̊C.
In its pure form, polycarbonate is optically clear with light transmission up to 89%. This exceptional clarity makes polycarbonate a popular choice for transparent applications.
Polycarbonate is available in a wide range of specialized grades tailored to specific needs:
- Optical-grade polycarbonate for maximum clarity
- UV-blocking grades with light stabilizers
- Flame-retardant grades meeting UL94 V-0
- High-heat grades for improved thermal performance
- Healthcare grades that are biocompatible and sterilizable
- High-flow variants for thin-wall injection molding
This versatility allows polycarbonate to meet the demands of diverse applications across industries like automotive, medical, electronics, and more.
Now let’s look at the major benefits that make polycarbonate well-suited to injection molding.
Why Choose Polycarbonate for Injection Molding?
Polycarbonate offers exceptional properties that make it an ideal candidate for injection molded applications:
Strength & Toughness
With a tensile strength of 60-70 MPa, PC withstands high stresses without fracture or deformation. This durability suits it well to demanding applications.
Heat Resistance
PC retains strength and stiffness up to 135 ̊C. This allows use in hot environments and helps molded parts resist warping.
Optical Clarity
The amorphous structure of clear PC grades allows light transmission exceeding 85%, rivaling glass.
Dimensional Stability
Low moisture absorption helps PC parts maintain accuracy. Parts show minimal shrinkage of 0.5-0.7%.
Flame Retardancy
PC compounding can achieve UL94 and UL746 flame retardancy ratings for electronics and medical devices.
This impressive property profile makes PC a versatile choice for injection molding intricate, robust, transparent parts cost-effectively on a mass production scale.
Polycarbonate Injection Molding Applications
Thanks to its exceptional balance of optical, mechanical and thermal properties, polycarbonate finds widespread use across industries.
Automotive
Lightweight PC glazing with 250 times the impact strength of glass improves passenger safety. Headlamp lenses withstand years of UV exposure.
Healthcare & Medical
Sterilizable, biocompatible PC suits medical equipment like dialyzers. Radiolucent grades visualize flow in IV tubing during X-rays without interfering.
Electronics
With heat and flame resistance suited to electronics plus electrical insulation, PC makes ideal housings for devices and components.
Consumer Goods
From baby bottles to food processors, PC’s food contact compliance and toughness suit household items seeing daily wear and tear.
And many more – scientific equipment, safety wear, lighting, etc!
Now that you know the major polycarbonate injection molding applications let’s look at the actual molding process.
Polycarbonate Injection Molding Process
Polycarbonate injection molding involves injecting molten polycarbonate into a mold cavity, where it cools and hardens to the final part shape.
Though similar to other thermoplastics, molding polycarbonate has unique requirements to produce quality parts.
Let’s walk through the standard injection molding work flow:
1. Dry the Polycarbonate
Like most plastics, polycarbonate resin absorbs ambient moisture. Water content over 0.02% creates defects like streaking, splay marks or bubbles.
Hopper dryers use desiccant beds to lower moisture levels below 0.02% prior to molding. Typical PC drying parameters are 80-120 ̊C for 2-4 hours.
2. Insert the Polycarbonate Into the Injection Machine
Once dried, polycarbonate pellets are gravity fed from an integrated hopper into the injection machine’s heated barrel.
3. Melt the Polycarbonate
Next, rotating screws inside the barrel melt the pellets using conducted heat and the shearing action of the screw.
Barrel temperatures of 250-320 ̊C melt the PC while minimizing material degradation from overheating during the process.
4. Inject Polycarbonate Into Mold
After sufficient melting, the screw injects the plasticized polycarbonate into the mold at high pressures of 1,000-2,000 bars.
Gate locations and profiles introduce the material smoothly while avoiding weld lines.
Specialized hot runner systems keep the material molten between injection cycles in high-volume molding.
5. Cool the Polycarbonate
Channels circulate coolant, helping molded parts solidify faster. Typical mold temperatures are 80-100 ̊C.
Adequate cooling time is critical to prevent stresses while ensuring dimensional accuracy and replication of fine mold details.
6. Eject the Solidified Parts
Once sufficiently cool, mold opening actuators separate the mold halves. Ejector pins then remove finished PC parts from the cavities.
Automated part removal robots collect and stack outputs, minimizing manual intervention.
7. Perform Secondary Operations
Secondary finishing steps prepare parts for shipment or assembly. This includes trim removal, drilling/tapping holes or applying decorative finishes.
Stringent quality checks validate part dimensions, material quality and cosmetics during this phase.
And that’s polycarbonate injection molding in a nutshell!
Proper processing is vital for defect-free, dimensionally accurate polycarbonate parts. Next, let’s look at some design considerations.
Polycarbonate Injection Molding Design Guidelines
Like any injection molded components, polycarbonate parts need certain design allowances to ensure manufacturability and function.
Below are some key PC injection molding design guidelines:
Wall Thickness
- Minimum wall = 1 mm
- Maximum wall = 3.5 mm
- Optimal = 2 mm
Thicker walls risk sink marks. Thinner walls make fill challenging.
Radii & Drafts
- Internal radii ≥ 3 mm
- External radii ≥ 1 mm
- Draft angles = 0.5-1 ̊
Smoother geometry lowers stress concentration. Draft assists part ejection.
Ribs
- Height ≤ 3x wall thickness
- Thickness = 0.5 x wall thickness
Excessive rib height risks sink marks. Overload can cause warp.
Gates
- Ø ≥ 2 x wall thickness
- Location controls orientation
Wider gates suit high viscosity. Gate position impacts cosmetics, strength.
Ejector Pins
- Ø ≥ 2 x wall thickness
- Locate off cosmetic areas
Ample pin area prevents damage. Layout avoids surface defects.
By accommodating these guidelines, your polycarbonate injection molding parts will meet functionality needs while maximizing cosmetic appearance.
Troubleshooting Polycarbonate Injection Molding Issues
Despite best efforts, defects can plague injection molded polycarbonate parts.
Here are some common PC injection molding issues and potential remedies:
Sink Marks
Indentations in thick regions from rapid cooling. Reduce wall thickness, increase temperature/pressure.
Warpage
Twisting from uneven cooling and residual stress. Optimize temperature and pressure, increase mold venting.
Weld Lines
Visible joints between separate melt flows. Raise temperature, alter gate position or style.
Flash
Excess material leaks from mold due to high pressure. Lower injection pressure and clamp force.
Short Shots
Incomplete filling due to low temperature/pressure. Increase temperature, pressure and injection speed.
Jetting
Flow front folds from rapidly-injecting high-viscosity melt. Lower injection speed, raise temperature.
With troubleshooting efforts guided by these defect insights, your team can consistently achieve high-quality polycarbonate injection molding output.
Can Polycarbonate Be Injection Molded?
Yes! As we’ve seen in this guide, polycarbonate is very well-suited to precision injection molding thanks to its exceptional balance of optical, mechanical and thermal properties.
Polycarbonate injection molding is integral from automotive glazing to medical devices and electronics enclosures. With an understanding of the unique needs of the material and process, engineers can mold intricate, robust and flawless polycarbonate parts at mass production scales cost-effectively.
So if your application calls for a clear, tough thermoplastic, injection moldable polycarbonate is an excellent fit!
