A custom raised an interesting question: “I’m looking to create a product similar to the plastic assembly models often included as freebies in kids’ snacks. However, I only plan to produce a few hundred units per design. ”
they have three question for prodcution:
- Q1: Is injection molding the only viable production method?
- Q2: Is custom mold manufacturing essential?
- Q3: Are there cost-effective alternatives that avoid mold expenses?
This is a fascinating topic, and I’m sure many professionals have faced similar challenges. Even general electronic design and manufacturing companies often deal with comparable issues.
Given current industrial standards, obtaining affordable small-batch samples remains a challenge, which is why the reliance on manufacturers for molds or samples is so widespread.
If you’re curious, searching for “small-batch plastic production” online will likely yield many manufacturers. However, don’t lose hope—with technological advancements, cost-effective small-batch production may soon become a reality.
Here are some methods I’ve come across for creating prototypes or samples.
Of course, if there are other techniques, I’d greatly appreciate insights from experts. After all, individual knowledge is limited, and collective wisdom helps us broaden our horizons.
Rapid Prototyping - CNC Machining
CNC (Computer Numerical Control) machining is a highly precise and versatile rapid prototyping method for creating plastic parts. It involves the use of computer-controlled machines to remove material from a solid block of plastic, shaping it into the desired geometry based on a 3D CAD model.
This process is ideal for producing prototypes with tight tolerances, complex features, and excellent surface finishes.
Unlike additive manufacturing methods, CNC machining is a subtractive process, making it particularly suitable for materials that are difficult to 3D print or for parts requiring high strength and durability.
It is recommended to limit production to 100 pieces or fewer to maintain consistent quality.
Rapid Prototyping -3D Printing
The 3D design file is transmitted to an SLA (Stereolithography Apparatus) rapid prototyping system, where a laser scans liquid epoxy resin. The resin undergoes controlled exposure, triggering a photothermal reaction that solidifies it. By adjusting the laser scanning speed and curing depth, the system can produce highly complex shapes or intricate mechanical models in a single, seamless process.
Rapid prototyping technology utilizes 3D CAD data to build physical prototypes layer by layer using a rapid prototyping machine.
Rapid Prototyping (RP) encompasses a variety of techniques, with SLA being one of the earliest commercially adopted methods. Other technologies include LOM (Laminated Object Manufacturing), SLS (Selective Laser Sintering), FDM (Fused Deposition Modeling), and more. Notably, 3D printing technology also falls under the umbrella of RP.
One of the key advantages of RP is that it eliminates the need for molds, enabling the production of individual parts. The time required to create a prototype can range from a few hours to one or two days, depending on its size, complexity, and level of detail.
Vacuum Casting
This process involves creating a precise silicone mold from a master prototype. Plastic material is then injected into the mold using vacuum casting equipment, followed by controlled temperature curing to produce plastic parts with various material properties.
By repeating this process, multiple replicas of the prototype can be efficiently produced. Due to its low cost and short lead time, vacuum casting offers an ideal balance of speed, quality, and quantity, making it highly economical.
However, controlling the precision of the replicated parts can be challenging. Typically, a single silicone mold can only produce around 25 parts, and the quality tends to degrade significantly after the 20th casting.
It is recommended to limit production to 500 pieces or fewer to maintain consistent quality.
Laser Cutting
Laser cutting is a fast and efficient rapid prototyping method for creating plastic parts. It utilizes a high-powered laser beam to precisely cut or engrave flat sheets of plastic material based on a digital design. This process is ideal for producing 2D or layered 3D components with intricate shapes, fine details, and smooth edges.
Laser cutting is particularly suitable for materials such as acrylic, polycarbonate, PET, and ABS, offering high accuracy and repeatability. It is widely used for prototyping applications that require quick turnaround times, such as creating enclosures, panels, or decorative elements.
This process does not require molds and produces one part at a time. The production time for a single sample can range from a few hours to 1–2 days, depending on its size, complexity, and level of detail.
Injection Molding Services
For mass-produced plastic products, injection molding remains the most cost-effective method, which is why it’s so widely used in the industry. However, dedicated molds are typically reserved for large-scale production runs in the millions to offset the initial mold development costs.
The cost of a mold is influenced by the hardness of the steel used. For example, molds made from softer materials like aluminum or copper alloys (as opposed to standard steel) are cheaper but have a shorter lifespan. Similarly, softer plastic materials are less abrasive on the mold but result in less durable products.
To reduce mold costs, designs should aim for simplicity, ideally requiring only upper and lower molds. Additional features like sliders or lifters increase complexity and cost.
Standard steel molds typically have a lifespan of 500,000 to 1,000,000 cycles, depending on the steel grade and mold complexity.
Key Considerations for Cost Reduction
#1. Design Optimization:
Simplify designs to reduce material usage and production complexity.
Avoid unnecessary features like undercuts, thin walls, or intricate details that increase costs.
Use standard geometries and dimensions to minimize customization.
#2. Material Selection:
Choose cost-effective materials that meet your functional requirements.
Consider recycled or off-the-shelf materials to reduce costs.
Avoid exotic or specialty plastics unless absolutely necessary.
#3. Batch Size:
Match the production method to your batch size. For example, 3D printing or vacuum casting is ideal for small batches, while injection molding is better for large volumes.
Plan production runs to maximize efficiency and minimize waste.
#4. Supplier Collaboration:
Work closely with manufacturers to identify cost-saving opportunities.
Leverage their expertise to optimize designs and production processes.
Request quotes from multiple suppliers to compare costs and services.
#5. Prototyping Iterations:
Use rapid prototyping methods like 3D printing or CNC machining to test and refine designs before committing to expensive molds or large production runs.
Iterate quickly to identify and address design flaws early in the process.
Case Study: Small-Batch Production of Kids’ Snack Toys
Let’s revisit the original question: How to produce a few hundred units of plastic assembly models for kids’ snacks without incurring high mold costs?
Recommended Approach:
Prototype with 3D Printing:
Use SLA or FDM 3D printing to create initial prototypes. This allows for quick design iterations and testing.
Ensure the design is optimized for functionality and manufacturability.
Small-Batch Production with Vacuum Casting:
Once the design is finalized, use vacuum casting to produce 200–500 units.
Create multiple silicone molds to meet the production volume while maintaining quality.
Cost Analysis:
Compare the total cost of vacuum casting (including mold and material costs) with other methods like 3D printing or CNC machining.
Ensure the chosen method aligns with your budget and quality requirements.