Yes, hollow plastic tubes can absolutely be produced using injection molding technology. However, creating hollow parts like tubes requires alternative methods that differ from traditional techniques used for solid injection molded components.
In this complete guide, as a professional plastic injection molding manufacturer, I will share everything you need to know about injection molding hollow tubes and parts, including specialized techniques like gas-assisted injection molding, insert molding, and more. I’ll also cover key considerations when designing injection molds for tubes to help you determine if this process aligns with your production needs.
An Overview of Injection Molding Hollow Parts
Traditional injection molding works by injecting molten plastic into a mold cavity, allowing it to cool and harden into solid plastic parts. However, directly forming hollow components like tubes is not possible using standard injection techniques.
Instead, innovative methods have been developed to produce hollow injection molded components:
Gas-Assisted Injection Molding
Gas-assisted injection molding injects pressurized gas (usually nitrogen) into the molten plastic inside the mold cavity. This gas applies outward pressure as the plastic cools, resulting in an internal hollow channel once the gas is vented.
This technique allows for injection molding larger, lighter hollow components while using less material.
Insert Molding
Insert molding involves first manufacturing solid mandrels or inserts that are embedded into the mold cavity. After injecting plastic into the cavity, the mandrel ends up positioned inside the cooled part, creating a hollow inner channel once removed after molding.
Insert molding enables precise control over the shape and size of the interior hollow section.
Core-back Injection Blow Molding
This hybrid approach combines injection molding a preform and blow molding it into a hollow final shape. The preform is injection molded with an internal void around a core, then transferred to a blow molding station where compressed air expands the preform into its final hollow tube configuration.
This two-step method facilitates molding intricate hollow geometries to tight tolerances.
Now that you understand the primary injection molding techniques used for hollow parts, let’s explore key considerations for manufacturing hollow plastic tubes.
Critical Factors When Injection Molding Hollow Tubes
Successfully injection molding hollow plastic components like tubes requires careful planning and mold design. Below are vital elements to factor into your injection molding process.
Selecting Suitable Plastics
The right plastic material with melt flow properties suited for hollow part injection is paramount. Thermoplastics like polyethylene, polypropylene, PVC, and PET are commonly used. Glass-filled polymers can provide enhanced tube strength.
Mold Design Complexities
Mold tools must facilitate gas injection channels, room for inserts, sliding cores, and efficient cooling systems to produce hollow tubes. This substantially increases mold fabrication and validation complexity.
Tight Process Control
Closely monitoring and controlling injection pressures, temperatures, cycle times, clamping forces, and more is mandatory to prevent tube wall deformation, warpage, or defects. Automated process control is recommended.
Secondary Operations
Post-molding operations like hole drilling, tube forming, flaring, or attachment manufacturing might be required to produce functional hollow plastic tubes. Factor any needed secondary processes into production planning.
Comparing Injection Molding Hollow Parts to Alternatives
Now that you grasp the basics of injection molding hollow components using specialty techniques, how does it compare to other plastic tube manufacturing methods?
Vs. Extrusion
Extruding plastic tubes is simpler and cheaper than injection molding, especially for high volume, low complexity tubes. However, injection molding facilitates superior tolerance control and design flexibility. Insert molding also enables incorporating functional features into the tubes.
Vs. Blow Molding
Like injection molding, blow molding inflates heated plastic into hollow molded cavities. However, injection molding permits substantially thicker, stronger tube walls thanks to higher available pressures. This allows injection molding applications requiring enhanced performance.
Frequently Asked Questions About Injection Molding Hollow Tubes
Below I answer some common questions engineers have when evaluating injection molding for hollow plastic components:
Can You Injection Mold Hollow Parts?
Yes, injection molding can produce hollow plastic components using secondary techniques like gas assist, blow molding, and insert molding covered earlier. These approaches form interior voids within solid plastic matrices.
What Plastics Work Best for Injection Molding Tubes?
Polyolefins like polyethylene and polypropylene are well-suited for injection molding hollow tubes thanks to excellent melt flow and stability. Amorphous resins like PET are also easily molded into hollow channels. Talk to your material partner about best plastic grades.
How Thick of Tube Walls Can You Injection Mold?
Injection molding facilitates fabricating plastic tubes with substantially thicker walls vs. extrusion or blow molding, ranging over 1 inch thick in some cases. Maximum wall thickness depends on factors like material, molding pressure, and machining equipment.
Can You Injection Mold Long Tubes?
Yes, long hollow plastic tubes exceeding multiple feet can absolutely be injection molded assuming sufficient molding machinery shot capacity. Mandrels must also be designed to facilitate demolding long hollow tubes after plastic injection.
Key Takeaways About Injection Molding Hollow Tubular Components
Injection molding technology can produce void-containing plastic components by:
- Using gas injection to internally pressurize molten plastic outwards during molding
- Inserting temporary mandrels that form interior voids once extracted post-molding
- Combining injection molding preforms and blow molding to achieve final hollow part shape
Critical considerations include plastic material selection, increased mold complexity, tight process monitoring, and secondary operations.
Compared to alternatives like extrusion or blow molding, injection molding tubes boasts superior dimensional consistency, thicker walls, and expanded geometric freedom.
Ready to discuss injection molding high-quality hollow plastic tubing for your application? Reach out now to connect with an engineering thermoplastics expert.
