Every year, humans produce and use countless plastic products in various shapes, sizes, and complexities. Plastic is highly adaptable, allowing you to utilize different manufacturing methods to make the final product. Injection molding and CNC machining are two of the most popular plastic production options.
While the processes have the same end product, they operate under different principles that determine their pros and cons, uses, and efficiency. However, deciding between the two for your next project can be tricky without our expert help at Crescent Industries.
Luckily, this guide to CNC machining vs. injection molding will help you determine the best fit for your needs. We’ll cover the different aspects of these processes and provide extensive insight into their industrial uses.
What Is CNC Machining?
Computer Numerical Control is a manufacturing process that uses pre-programmed computers to precisely cut material from a solid workpiece, creating complex final parts. This subtractive method can produce components with intricate designs and implement tight tolerances on flexible materials like:
- Plastics
- Metals
- Composites
The process starts with the design phase. Here, the designer relies on Computer-Aided Design (CAD) software to create technical drawings and models using a computer instead of a drawing board. The main types include:
- 2D CAD
- 3D CAD
- Freeform CAD
The machinist later translates the CAD design into a geometric code or G-code. This CNC language controls the machine’s numerous parts and tool movement. With the design ready and translated, the manufacturer can gather the necessary materials and tools.
The CNC machine executes the G-code to cut and shape the workpiece as intended. Afterward, the product undergoes final touches and evaluations to determine quality and market readiness.
What Is Injection Molding?
This manufacturing process involves pushing molten resin into a mold that shapes the final product. The molding process depends on an injection unit to heat and inject the material into the custom-designed cavity.
There’s also a clamping unit that holds the mold tightly shut during the injection process. The molten material cools to solidify into the desired shape and then finally undergoes ejection. The process offers an efficient and economical alternative for high-volume production of identical items.
Key Differences Between CNC Machining and Injection Molding
Depending on various factors, injection molding and CNC machining have different limitations and abilities. Some of these key factors include:
Cost
The upfront costs of both production methods vary significantly:
- Injection Molding, for instance, has a higher initial cost associated with designing and creating the molds. This cost rises when products with more complex geometries are needed. Luckily, once the mold is complete, the price per part reduces, making the process cost-efficient for moderate to high-volume production.
- Meanwhile, CNC Machining has a lower upfront cost for setting up the machine, tooling, and materials. It is more cost-efficient for low-volume projects. You can also cost-effectively tweak the G-code as needed to meet any spec changes that arise over time. However, the long-term higher operation costs make it less sought after for moderate to high-volume production runs.
Design Flexibility
Your project’s design complexity and flexibility are critical factors when deciding between CNC machining and plastic injection molding.
- Injection Molding, has a limited design flexibility once the mold is complete. Effecting any design changes can be time consuming and costly. However, it is an effective process for developing complex shapes with intricate surface details and internal cavities.
- CNC Machining, on the other hand, provides excellent product design flexibility. The machinists can quickly effect design changes by modifying the CAD file and computer program without interrupting production. As a result, you can produce highly intricate designs with varying depths and details that can be tricky to achieve with injection molding.
Lead Times
A manufacturing method’s lead time determines the process’s efficiency and turnaround time.
- Injection molding has a longer lead time as it can take several weeks to create. This duration varies depending on the part complexity. Afterward, the manufacturing speed significantly increases with production cycles ranging between a few seconds and several minutes per part.
- CNC Machining has much shorter lead times, lasting fewer weeks. The tooling setup in CNC machining is less time-consuming than mold creation. However, CNC production cycles are much slower, lasting several minutes to hours to machine individual pieces properly. The longer production cycle contributes to higher operational costs, especially for parts that need fine detailing.
Use Cases for CNC Machining
CNC machining is a versatile manufacturing approach compatible with various materials. Some of its uses apply to:
- The aerospace sector relies on CNC machining to produce metal aircraft parts with the highest level of precision. This accuracy is essential for safely using critical components like landing gear parts, fuel access panels, engine mounts, and fuel flow parts.
- The automotive sector benefits from using CNC machines for rapid prototyping and production. Extruded metal pieces can be machined into cylinder blocks, axles, valves, and gearboxes. CNC machining can manufacture plastic vehicle components like gas gauges and dashboard panels.
- The oil and gas sector has tight tolerances achievable through CNC machining. You can leverage this production process to machine corrosion-resistant metals and create intricate components like:
- Pins,
- Cylinders
- Pistons
- Valves
- Rods
Use Cases for Injection Molding
As a trailblazing Original Equipment Manufacturer, we at Crescent Industries utilize injection molding to produce plastic parts for various industries. These sectors include:
- Medical and Pharmaceutical. Plastic products in this field must meet strict health and safety standards. Luckily, with our over 50 years of experience in medical injection molding, you’re assured of reliable and durable medical-grade parts. We are experts in manufacturing Class I, II, and III injection-molded medical components like:
- Labware equipment
- Imaging components
- Diagnostic disposables
- Emergency medical devices
- Patient care and monitoring appliances
- Regenerative medical devices
- Orthopedic instruments
- Military and Defense. The military sector relies on technology and products that can withstand the harshest conditions on earth. Crescent Industries, an ITAR manufacturer, can deliver these military components, guaranteeing uniformity, functionality, and durability. The molded parts include:
- Handheld comms
- Guidance systems
- Decoys
- Weaponry
- Munitions
Recent Advancements in Manufacturing
The manufacturing sector constantly evolves to maintain competitiveness and overcome today’s challenges. These innovations help enhance customer satisfaction while mitigating continued supply chain disruptions, labor shortages, and fluctuating demand. Some of the emerging manufacturing trends include:
- Industry 4.0 and Automation improves production efficiency by enabling remote equipment monitoring, operation, and servicing. This enhanced real-time operation ensures flexibility, safety, and access.
- Sustainability practices are becoming more popular with growing environmental and social concerns amongst manufacturers. We’ve implemented several initiatives at Crescent Industries to lower our environmental impact, conserve energy, and reduce waste. They include:
- Recycling scrap plastic
- Sourcing materials from sustainable suppliers
- Utilizing energy-efficient lighting
Partner With an Expert for Your Custom Plastic Components of Devices
When comparing CNC plastic machining vs injection molding, each manufacturing process has pros, cons, and uses. Your decision depends on your project’s needs, such as part quantity, complexity, material, and cost.
With an expert custom plastic manufacturer like Crescent Industries, you can choose the right process. Contact us today to schedule your next project.