Selecting the accurate manufacturing process can either make or mar your project. Imagine you’re an engineer, working on a new product for your customer. You may need to test various prototypes before advancing/commencing mass production. Do you select injection molding because of its durability and precision, or do you move to urethane casting, as it offers flexibility and speed? It all comes down to your budget, time duration, and order quantity.
However, if you are required to produce several 1000 parts, injection molding is the clear-cut option. Molding is built for high-scale manufacturing and cost economical benefits at large scale. But, if your requirement of production is a few 100s, or you want to test a few prototypes, then urethane casting is an optimal option.
Overall, both techniques have their strengths in their operations. A keen understanding of such strengths and limitations will assist you in making the right selection for the desired output. Let’s break it down:
What Is Injection Molding?
Injection molding is a widely used manufacturing process typically used to produce high-volume, precision parts. It injects molten material, usually thermoplastic polymers, into a highly engineered mold under high pressure.
Professionals prefer this option in industries like automotive, electronics, and consumer goods where you can create 1000s of identical parts. Moreover, It is also efficient, and precise, and can create intricate geometries which makes it ideal for mass production.
Operation Breakdown
The molding is started by creating a mold, often made from steel or aluminum. Features such as cavities and channels for material flow are built into the mold so that it is designed to match the final part’s shape. Thermoplastic material is heated to the point of melting and forced into the mold under high pressure once the mold is ready. The material is then melted cooled and solidified inside the mold. The mold is then cooled and the part is ejected from the mold when opened.
Materials Used
ABS, Polycarbonate, Nylon, and Polypropylene are fundamentally used thermoplastics used in injection molding. These are durable heat-resistant, and high-performance materials used for diverse applications. Generally, the part’s intended function and environmental exposure determine the material.
Key Advantages
- High production efficiency
- With tooling in place, it becomes feasible to produce parts in fast succession, thus reducing per-unit costs in large volumes.
- Injection molding also provides good precision and repeatability for complex geometries and intricate details.
Limitations
- Creating molds from metal is expensive and it is a high initial investment, as the initial tooling cost is high.
- The process takes longer lead times, sometimes from weeks to months, to set the molds.
- For small batch production or prototypes, injection molding is not economical because of high setup costs.
What Is Urethane Casting?
Urethane Casting is a low-volume production and prototyping process used for low volume production. Unlike injection molding, the parts are made from a silicone mold which is created from a master pattern. Since it is cheaper and faster, it is a better process for smaller production runs or when quick iterations are required. Designers use them in parts that require flexibility or special mechanical properties, which cannot easily be met with thermoplastics.
Operation Breakdown
The process starts with the master pattern creation (the prototype or model that represents the final part). A silicone mold is made from this master pattern. After the mold is ready, polyurethane resin is poured into it. The resin is then cured to become the desired shape. When the part is cured, it is removed from the mold, and the process is completed.
Materials Used
Urethane Casting uses common polyurethane resins. They can duplicate the properties of various thermoplastics and are flexible enough to make parts with desired qualities, such as flexibility or rigidity, in the formulation.
Key Advantages
- Urethane Casting is one of the cheapest methods of production for low-volume production.
- Since silicone molds are relatively inexpensive to make, the initial tooling cost is much lower than injection molding.
- Urethane Casting is ideal for prototypes or small batch parts where high volume is not needed. The process is also faster than injection molding which makes it an appropriate process when speed is critical.
Limitations
- Due to the shorter lifespan of silicone molds, which tend to last only 20–25 uses, it is not ideal for large-scale production.
- Urethane cast parts are not as precise as injection molding
- Parts requiring tight tolerances are not as suitable as urethane-cast parts.
Injection Molding Vs Urethane Casting: A Detailed Comparison:
Are you unsure if choosing between injection molding vs urethane casting? You can consider cost, turnaround, material properties, and production volume. Let’s compare each process in detail.
Table 1: Injection Molding Vs Urethane Casting: Comparison Summary
| Feature | Injection Molding | Urethane Casting |
| Initial VS Per unit cost | High capital due to metal molds | Low initial amount, because of silicon-based mold |
| Speed & Production Time | Mold making takes several weeks to months | Molds ready in 5-10 days |
| Material Properties & Durability | High durable. Suitable for thermoplastics like ABS, Polycarbonate, and Nylon | Less durable. Uses thermoset polyurethanes. |
| Surface Finish & Accuracy | High tolerance within ± 0.05 mm | Comparatively less tolerance values i.e., ±0.1-0.3 mm |
| Production Volume | Ideal for mass production of (10000+ units) | Ideal for less volume items (Several hundred) |
| Design Flexibility & Materials | Limited flexibility and machining/repairing are costly and time-consuming. | Highly flexible, best for prototyping. |
Initial vs. Per Unit Cost Analysis
Since injection molding employs metal-made molds, and comes at a higher expense. But it becomes economical in high volume production (usually above 10,000 units). Once the tooling is established, the per-unit cost drops dramatically. Urethane Casting uses silicone molds which are cheaper to make and hence tooling costs are lower. Nevertheless, the per unit cost for urethane casting is more expensive than injection molding and is suitable for low-volume production (10–500 units).
Speed & Production Time
Tooling setup in injection molding takes 4–12 weeks. The cycle time for each part is 30 to 60 seconds after which it is efficient for large production runs. If the need is for faster prototypes, urethane casting can offer molds in 5-10 days, and the casting cycle time will be 30 to 60 minutes/part. In addition, urethane casting has a faster lead time and is appropriate for prototyping and small runs.
Material Properties & Durability
Injection molding employs thermoplastic materials like ABS, Polycarbonate, and Nylon for fabricating unique design features. These materials provide high strength, durability, heat resistance, and chemical impact. On the other hand, urethane casting utilizes polyurethane resins. They are not as durable and possess lower heat resistance than injection-molded parts.
Surface Finish & Accuracy
Injection molding offers high precision with tolerances as tight as ±0.05 mm and with consistent high-quality finishes across large runs. On the other hand, the surface finish is also consistent and comes with glossy, matte, or textured finishes. However, Urethane Casting is less accurate (±0.1–0.3 mm) and may require further post-processing such as sanding or coating to achieve a better finish. Since cosmetics finish is not the priority, it is better suited for low-tolerance parts or prototypes.
Production Volume: Small vs. Large Runs
For large volume production (10,000+ parts) injection molding is best when the initial cost associated with the tooling is offset by the lower per unit cost at scale. In contrast, urethane casting is a good fit for low-volume production (10–500 parts) for rapid prototyping, small batch runs, or when tooling costs need to be minimized.
Design Flexibility & Modifications
The ease and low cost of changing silicone molds make urethane casting more flexible in design. It is a preferred choice for iterative design or prototyping. As opposed to injection molding, it is less adaptable to design changes after tooling is complete due to the cost and time required to make mold modifications.
Tooling & Mold Life
Metal molds are used in injection molding, which has a lifespan of 100,000+ cycles or more for high-volume production. Silicone molds are used in urethane casting and generally last 20–25 cycles, which makes them more suitable for short-term, low-volume applications.
Whether you are testing designs or scaling up your production, our professionals at PremiumParts can provide tailored solutions to scale up your production. Contact us today!
Real World Case Studies
Urethane casting for GoPro Outer Body
For its iterations of different camera series, GoPro, one of the top action camera manufacturing companies, used a polyurethane casting procedure.
Why Urethane Casting?
- It helped in iterating various complex designs with no high-cost tooling requirements.
- In a week, silicone molds were ready for prototyping to speed things up.
- Improved final item properties by utilization of polyurethane resins.
Outcome:
GoPro was able to iterate their camera designs, within weeks, in urethane casting, and minimize time to market by a large margin.
Injection Molding for LEGO Bricks
LEGO is one of the iconic toy manufacturing companies. It heavily relies on injection molding technology for the production of billions of plastic bricks per annum.
Why Injection Molding?
- It is helping to achieve high tolerance values for highly precise plastic brick-making.
- Large production with precise dimensions and quality.
- Used ABS-based plastics for precision and durability.
Outcome:
LEGO confirms scalability and durability by using injection molding to make more than 3600 bricks per minute with desired dimensions.
Key Reasons for Selecting the Best Manufacturing Option:
Here are the best tips for selecting the right manufacturing technique:
What are the Material Options?
If you are designing for functional parts that will be exposed to harsh conditions like like automotive components, and electronic housings, you must go for injection molding. It lets you use high-performance materials such as ABS or Nylon that resist heat, chemicals, and physical stress. However, if your project involves prototyping or parts in a small volume that will not be under much stress, urethane casting may be the better choice. For non-functional parts, where flexibility is more concerned than extreme durability, it is dominant.
What Lead Time and Setup are needed?
Injection molding is beneficial if you are dealing with large-scale production. When the tooling has been paid for, the per-unit cost is minimal, and it can be a wise choice for mass production. However, if your project is more about low-volume runs or rapid prototyping; for example, creating a prototype for testing, then Urethane Casting could be more beneficial. The upfront cost is low and it helps you test your designs without the hefty investment.
What are Expected Production Volume and Cost Efficiency
Urethane Casting is great when you have a situation where time is critical, such as if you need a prototype in a matter of days to meet a project deadline. In a few days, you can be ready with your molds. Injection molding is better for long-term high-volume production runs, especially if you are not in a rush.
How Much Modification Do You Need in Your Mold?
Urethane Casting, however, is more flexible if your project includes a lot of design iterations or if changes are expected to be frequent. For instance, if you are developing a new product and require to modify your prototype multiple times before finishing, this method is far less expensive and easy to change. Injection molding will be more efficient once the tooling is set, but less adaptable during the design phase if you’re working on a finalized design for a mass production run.
Summary
By understanding the differences between injection molding vs urethane casting, manufacturers can optimize production costs, increase efficiency, and meet certain project requirements. Large-scale production requires injection molding; it is precise, durable, and has lower per-unit costs at high volumes. However, Urethane Casting is more appropriate for small batch production and prototype needs with faster turnaround and flexibility. Both procedures have their benefits. Selecting the right one depends on your manufacturing requirements including material selection, cost, lead time, and production scale.
Order High Quality End-User Products From Premium Parts
At Premium Parts, we offer supreme quality molded parts as per customer requirements. Whether you need prototypes for rapid development or precision molded components, we offer seamless production solutions. Our advanced techniques confirm durability, accuracy, and cost-efficiency, no matter the production scale. From automotive to consumer items, we help our customers to provide flawless and precise products. If you are looking for high-performance and customized molded parts? Contact us to get manufacturing excellence.
FAQ’s
Q1: Which process is more cost-effective?
Urethane Casting is good for low-volume low-cost prototyping. While injection Molding is good for high-volume production.
Q2: Which procedure can make the product quickest?
Urethane Casting has a quick turnaround. Contrarily, injection molding has a longer setup and runs faster in mass production.
Q3: Which process gives more material strength?
High-strength thermoplastics allow for durable and high-performance parts in an injection molding process.
Q4: Which process should I choose for prototypes?
For functional prototypes, Urethane Casting is the best because of low tooling costs and quick production.
