To help you look more thoroughly at what goes into the final cost of injection molding plastic, this guide is meant to help you make informed decisions, keep your costs in check, and receive the best value for your plastic manufacturing project.
What Is Injection Molding?
Injection molding is a manufacturing process where material that is molten or viscous is injected into a mold cavity. Once cooled, the mold opens, and the part is removed. While injection molding is used in multiple types of manufacturing, it is predominantly used in high-volume production like automotive, medical, electronics, consumer goods, and packaging.
Typical materials provided in injection molding include:
- ABS (Acrylonitrile Butadiene Styrene)
- Acrylic (PMMA)
- Polycarbonate
- Polypropylene
- Nylon
- Polystyrene
Regardless if you need translucent acrylic housings for electronics, or durable polycarbonate components, injection molding covers a range of materials available for your project, depending on your application's requirements.
The Main Factors That Affect Costs of Injection Molding
The total cost of injection molding will depend on a great number of factors—all determined per project. The following is a list of the primary cost items:
Cost of mold (tooling cost) - The biggest initial investment when it comes to injection molding is the price of the mold.
Cost of Mold
If you've never developed a mold before, it is vital to understand the importance of the mold when it comes to custom fabrication projects. Molds are typically designed to exact specifications.
Mold Costs can be developed for (3) basic types of molds:
- Prototype mold: $1,000 – $5,000
- Aluminum mold (low-volume): $5,000 – $15,000
- Steel mold (high-volume): $15,000 – $100,000+
Cost related to a mold can come from several issues:
- Material (e.g., aluminum vs. steel)
- Complexity (e.g., undercuts, inserts, tight tolerances)
- Number of cavities (e.g., multi-cavity molds reduce the cost per part)
- Surface finish (e.g., polished, textured finish)
If you are developing a project with a plastic manufacturer in Las Vegas, or any other major market for custom plastic fabrication, consider using local tooling services. Local tool shops can often get you a tool quicker, and can usually offer a more responsive service; and in some scenarios, this service can be worth the additional costs.
Cost of Materials
When it comes to resins and materials, it is important to understand that the type and amount of plastic resin will have a huge impact on the total cost. The type and grade of material part is based on a few considerations, including the part's function, required strength, finish, and aesthetic appearance.
Commonly used plastic materials with price (per lb):
- Polypropylene (PP): $0.80 – $1.20 per lb.
- ABS: $1.30 – $2.00 per lb.
- Acrylic (PMMA): $2.00 – $3.50 per lb.
- Polycarbonate (PC): $2.50 – $4.00 per lb.
- Nylon: $2.00 – $5.00+
Cost for specialty additives, UV protection, flame retardants, or color matching will increase the overall cost of resin. Purchasing resin in larger quantities will decrease resin costs on a per pound basis; larger material orders become less impactful with larger runs for production.
Cost of Production (Per Part Cost)
This is the easy part....ironically, the part cost is where injection molding starts to shine. Once you have drawn up the mold, you have also drawn up your per part cost, and the per part cost can quickly become very low - typically at high volumes. Typical Per-Unit Costs:
- Low volume (1,000-10,000 units): $1.00 – $5.00 per unit
- Mid volume (10,000-100,000 units): $0.50 – $1.50 per unit
- High volume (100,000+ units): $0.10 – $0.50 per unit
The cost per unit is determined by several factors, including:
- Cycle time (the shorter the cycle, the more units produced/hour)
- Part size and complexity
- Degree of automation
- Material waste and sprue design
Custom fabrication services can help you to limit scrap, cycle time, and in turn, limit your cost by optimizing part shape for you and placement of gates.
Secondary Services
The cost of post-molding operations will depend on the specifics of your project, but is likely to add to your overall cost. These operations may include:
- Trimming or deflashing
- Painting or pad printing
- Laser etching
- Ultrasonic welding
- Assembly and packaging
As an example, if you're producing branded acrylic products, a dictionary of potential services may be laser engraving. These finishing services usually cost $0.10-$1.00 per unit, dependent on complexity and size ordered.
Labor and Overhead Costs
In addition to part cost, labor will vary according to the location of the manufacture of the plastic parts. A Plastic Manufacturer in Las Vegas may have a higher labor overhead cost than an overseas supplier, though it may present you with better quality assurance, communication, and turnaround times.
- Overhead costs may include:
- Machine maintenance
- Energy usage
- Facility costs
- Quality assurance and inspection
Partnering with a reputable domestic partner often provides better visibility on pricing and fewer aspects of risk and hidden cost.
Injection Molding Projects: Cost Saving Tips
When you are building prototypes or moving into mass production, there are ways to achieve cost savings in your total injection molding costs:
1. Designing for Manufacturing (DFM)
Reducing undercuts, maintaining wall thickness variance, and limiting undue complexity can both mitigate mold and cycle time cost.
2. Using Family Molds
If you manufacture multiple similar parts, a family mold (one mold per part) can save both money and time.
3. Minimizing Material Usage
Engaging your supplier to pick the cheapest plastic that meets the requirements of your part, and avoiding overengineering it, is key.
4. Increasing Quantity of Order
Material costs are aggressive, and any time you can take per mold cost and divide it into more parts, you can save yourself serious money per part.
Working With a Local Plastic Manufacturer
A plastic manufacturer near you, in Las Vegas or elsewhere, can offer quicker prototyping, better communications, cheaper freight.
An Example of Cost
Say you need to design and manufacture 10,000 acrylic cosmetic containers shelf-ready.
- Mold: 20,000 (multi-cavity steel mold)
- Material: 3,000 (acrylic at $3.00/lb).
- Production at 0.75 per unit: 7500.
- Finishing and Assembly: 1500
- Total project cost: $32,000.
- Effective cost per unit, $3.20.
Increased volume, say you order 100,000. Your effective cost per unit can be as low as $1.50.
Is Injection Molding Worth the Cost?
YES, if your volume is high enough. The tooling investment can be the highest cost of injection molding, but the speed, low per-unit cost, and excellent quality make injection molding ideal for:
- Mass production
- Scaling production of a product
- Consistency in the performance of plastic parts
- Complicated or custom-fabricated plastic parts or sections
Otherwise, for low volume, or when the product chemistries or designs rapidly fluctuate, as in the case of 3D printing and CNC machining, injection molding may not be beneficial.
Final Thoughts
Being clued in about the real cost of injection molding plastic is imperative to project estimating and budgeting. From going through the costs of mold, to the sourcing of materials, to price per part, there are plenty of levers to go and control for you. Be it a custom fabrication, a new product, or you're working with a plastic manufacturer in Las Vegas, having a clear idea of where your money goes allows you to set attainable return on investment.
If you are putting together your next project, getting to know a plastic manufacturing specialist can help navigate through the practical and trivial decisions you need to make. Injection molding can be great quality at good prices and produced at scale if developed correctly.