This guide provides a breakdown of the major differences that exist between custom fabrication and injection molding. This will enable businesses, engineers, and designers to assess the best process for their project requirements.
What is Custom Plastic Fabrication?
Custom plastic fabrication is a wide range of processes that can turn plastic material into parts or products. Custom fabrication does not typically use premade molds; standard and accepted methods include:
- CNC machining
- Laser cutting
- Laser etching and engraving
- Thermoforming
- Plastic welding
- Bending and bonding
- 3D printing
These processes work best in low to medium volume manufacture or when very bespoke pieces are required.
What is Injection Molding?
Injection molding is a high-speed process involving molten plastic injected into a steel or aluminum mold at high pressures. The molten polymer is cooled down and solidifies into its final shape. Injection molding is one of the most popular methods of plastic production, as it is inexpensive and efficient for high-volume production of duplicate parts while honoring tolerance requirements.
Common plastics in Injection Molding:
- Acrylic (PMMA)
- ABS (Acrylonitrile Butadiene Styrene)
- Polypropylene
- Polycarbonate
- Nylon
Key Differences at a Glance
| Feature | Custom Plastic Fabrication | Injection Molding |
| Production Volume | Low to Medium | Medium to High |
| Tooling Cost | Low to Moderate | High (initial) |
| Turnaround Time | Fast | Longer (due to mold creation) |
| Design Flexibility | Very High | High (within mold limitations) |
| Material Variety | Broad | Broad |
| Ideal Use | Prototypes, small batches, and unique parts | Mass production, high consistency |
When to Choose Custom Fabrication?
Custom fabrication is the correct choice when your project needs:
Unique, or One-off Designs
When you are creating a custom display, enclosure, or prototype, custom plastic fabrication will allow you to change your design while you work on it. This is especially helpful for startups and engineers who are still figuring out their product concept!
Short Turnaround
Fabricated parts in plastic can take days to construct instead of weeks. Additionally, because you use laser cutting or 3D printing and do not need to create molds in advance, the prep time is shorter.
Lower upfront investment.
Injection molding is somewhat expensive, especially for the mold. Generally, the molds cost in the range of $5,000-$100,000. Conversely, because custom fabrication does not require the same amount of tooling, it is an excellent option for short runs and/or one-time use.
A variety of materials and thicknesses.
In general, custom fabrication is able to offer more variety. You can have a broader range of material thicknesses, and custom plastic fabrication techniques include using different plastic types, including acrylic, polycarbonate, PVC, and PETG. Additionally, the finishing techniques (special finishes and coatings) are often much more customizable. Local Prototyping and Fabrication Services
If you are working with a plastic manufacturer in Las Vegas or other local services, working with a custom fabrication shop that is geographically close provides more control over your production, quality control, and schedule.
When Should You Choose Injection Molding?
Injection molding is a good fit when your project is going to be:
High Volume
Once you build the mold, injection molding can produce tens of thousands of identical parts faster and more consistently than any other process. It is an investment for the long run with great cost savings to come if done in volume.
Tight Tolerances/High Precision
Injection molding offers tighter and higher precision part dimensions due to sophisticated mold designs and standardized processing parameters. It is important to have dimensional accuracy for automotive, medical, and consumer electronics.
Durability/Complex Geometries
Injection molding can create complex multi-piece components to a degree that may be difficult or impossible to do with a normal fabrication process.
Recyclability & Repeatability
Most injection molded plastics, like acrylic, ABS, and polypropylene, are recyclable. Injection molding also allows for a much more repeatable process with less variability from one batch to the next.
Surface Finishing & Branding
Want your parts to be glossy, matte, or textured? Want your logo etched into the surface of the part? Molds can be made to imprint, which can cut down on steps after production.
Industry Applications: A Comparison
Realizing how each method applies to each method can help solidify your decision.
Retail and Point of Purchase Displays
- Best Method: Custom Fabrication
- Why: Shapes, Branding, and Low Volume
- Material: Laser Cut Acrylic or PETG
Automotive Parts
- Best Method: Injection Molding
- Why: High Volume, Durable Components with Defined Tolerances
- Material: ABS, Nylon, or Polypropylene
Medical Devices
- Best Method: Injection Molding
- Why: Consistent, Hygiene requirements, and FDA approved.
- Material: Medical Grade Plastics
Prototypes and Concept Models
- Best Method: Custom Fabrication or 3D Printing
- Why: Fast Iterations, Low-Cost Alternatives
- Material: Acrylic, PLA, or ABS
Architectural Signage
- Best Method: Custom Fabrication
- Why: Need for Custom Design, LED Integration, and Engraving.
- Material: Acrylic or Polycarbonate
Cost Comparison - Custom Fabrication vs Injection Molding
| Factor | Custom Fabrication | Injection Molding |
| Upfront Cost | Low | High (due to mold) |
| Per-Unit Cost (Low Volume) | Higher | Not cost-effective |
| Per-Unit Cost (High Volume) | Moderate to High | Very Low |
| Maintenance | Low | Moderate (mold upkeep) |
Eco-Friendly and Waste
It is now time to think about sustainability with a growing number of manufacturers, and it is time to understand how those processes can add waste to the environment.
- Custom Fabrication: will create very little waste, provided you are only producing small quantities and their cut-off pieces can be used again.
- Injection Molding: Will create much less waste per product, giving you a large production series if an excess of parts are produced by defective designed molds, which create a lot of pile us of unnecessary production, including jigs and fixtures.
Plastic manufacturers are now producing acrylic that is recycled as well as usable bio-based polymer to lessen your ecological footprint.
Choose a Process with Your Requirement
Consider:
- I need 10 or I need 10,000.
- Is speed as important as cost, or a combination?
- Is complex detail important, or flexibility to design?
- What is my tooling and molds budget?
If you are experimenting, a low volume or artwork, custom fabrication is your only choice. If you are ready to move forward to an established product that you want to clamp down on and stick it in your assembly line consistently, it is time to have the conversation for injection molding.
Partnering with A Plastic Manufacturer
If you are looking for custom plastic fabrication services, or injection molding capabilities, you need to find a plastic manufacturer that understands your goals, materials and markets - with experience in ideal materials.
When looking for partners, consider:
- Do they have in-house design or engineering design capabilities?
- Do they manage a prototype and full production?
- Do they offer materials like acrylic, polycarbonate, or ABS?
Are they centrally located to you (plastic manufacturer in Las Vegas) - to ensure they are capable of providing highly integrated communication, with quick response times, and shipping.
Final Thoughts
Custom plastic fabrication and injection molding can assist you in modern plastic manufacturing. The difference comes down to the makeup of the product you will be creating or enjoying, the value of timing, the importance of your budget, and the value of volume.
Choosing early on in your project the correct process will save time and money, and give your product a better chance of succeeding in the marketplace. Consider maybe doing a prototype with custom fabrication and then converting your manufacturing option to injection molding for mass production.
Whether you are creating custom acrylic displays, engineering plastic housings, or creating components that last, by understanding these processes and how they will affect your finished product, you are one step closer to making your anticipated idea a reality.