What is Plastic Prototyping? An Overview of the Process

Plastic prototyping refers to the process of creating a plastic model of a part or product design to test its functionality, aesthetics, ergonomics, and manufacturability before large-scale production. Prototyping is a critical step in product development as it allows design errors and flaws to be identified and corrected early on, saving companies significant time, money, and resource investments down the line.

The growing accessibility and cost-effectiveness of plastic prototyping technologies like CNC machining and 3D printing are making rapid iteration and design validation more viable than ever.

Why Prototype with Plastics?

Plastics offer some major advantages when it comes to prototyping compared to alternatives like metal machining. Plastic resins are inexpensive, easy to work with, and can replicate most product designs, geometries, and features.

Decisions around specific resin choices also provide flexibility in cost, strength, heat resistance, transparency, coloring, and more based on prototyping requirements. These combined qualities make plastics the ideal option for design, engineering and marketing teams looking to iterate quickly without breaking the bank.

Most importantly, modern manufacturing overwhelmingly relies on plastic and injection molding to produce end-use parts. Testing prototypes in the same or highly similar materials as final production is key for identifying issues around fit, strength, heat dissipation, and more before committing to tooling.

Custom Plastic Parts CNC Machining

A diverse range of processes exist nowadays for creating functional plastic prototypes. One of the most precise and versatile options is CNC machining. CNC (Computer Numerical Control) machining utilizes automated machine tools to carve, shape, and form parts from plastic blocks or rods known as stock material based on digitized designs.

Common techniques/machines used for plastic CNC prototyping:

• Milling: Uses rotary cutting tools to carve away material
• Turning: Spins stock against a stationary cutting tool to contour the edges
• Laser/Water-jet Cutting: Burns/pressure cuts shapes into flat sheet plastics
• CNC Router: Similar to a vertical mill optimized for plastics

CNC machining brings exceptional accuracy, repeatability and material options relative to alternatives. It also avoids the geometric, batch size and material limitations associated with injection molding that limit more iterative prototyping. Almost any plastic from soft plastics like polyethylene to higher performance engineering resins can be precision machined into fully functional Custom Plastic Parts CNC Machining prototypes with tight tolerances down to +/- 0.005 inches for testing in realistic conditions.

Beyond functional prototyping, CNC machined urethane foam molds can also be utilized as a stepping stone for validating designs at higher production intents with silicone molding and casting while more expensive metal injection molds are being developed.

3D Printing

Another rapid, additive option for plastic prototyping is 3D printing. 3D printing builds up parts layer-by-layer based on a digitized model – usually designed in CAD (computer-aided design) software and then converted to an STL file read by the printer. A range of techniques exist, including:

• Fused Deposition Modeling (FDM): Extrudes heated plastic filament
• Stereolithography (SLA): Photopolymerizes liquid resin with a laser
• Selective Laser Sintering (SLS): Laser-fuses powdered plastic

3D printing brings exceptional speed in directly realizing intricate CAD models as physical prototypes. While traditionally limited in terms of strength, accuracy, and surface finish, machines and material capabilities continue to advance. Visual models are often entirely sufficient for design evaluation stages before later relying on machining for functional testing units.

Rapid Tooling

For prototyping needs requiring higher production realism like large part batches, dimensional stability, and certain material properties, a range of rapid plastic injection molding tooling options exist. Producing steel injection molds remains slow and expensive. Rapid tooling sacrifices some mold longevity for quicker turnaround at lower costs by utilizing easier-to-machine materials like aluminum or entirely different mold types:

• Aluminum molds: Around 20% of the steel cost while providing 100+ part runs
• Silicone rubber molds: Flexible, reconfigurable, fast for resins/casting (urethane)
• Bridge/modular tooling: Mix of standard + custom mold components

While geometrically limited relative to final molded production parts, rapid tooling opens doors for simplified validation testing of 20-100+ samples simultaneously within days/weeks rather than months.

Prototyping Process Steps

While specific plastic prototyping techniques and sequences vary across industries and projects, the overall progression usually involves:

• Initial Concept Generation: Early sketches, CAD models, idea pitches
• Design Refinement: Optimization for aesthetics, function, ergonomics
• Prototyping: Realize the designed concept physically via a chosen process
• Evaluation Testing: Determine issues around form/function/quality
• Iterate/Feedback: Refine, re-prototype, re-test until satisfied
• Final Design: Lock-in optimized concept to progress development

Having a well-defined list of design requirements and success metrics is key here for objectively evaluating prototypes against expectations around dimensions, performance, durability, etc. That data then directs any critical design modifications between iterations before committing to production tooling for manufacturing.

Prototyping Best Practices

Following prototyping and testing best practices helps companies maximize learning while avoiding common, costly mistakes:

• Test in actual use conditions early and often
• Check interference fits/Clearances with real mating components
• Accelerate testing schedules to compress lead times
• Simulate dimensional variations to assess tolerances
• Validate strength/durability with installed fasteners
• Use production-representative thermoplastics when possible
• Confirm plastic resin/process achieves final surface qualities

Review manufacturability via DFM analysis

Getting well-made prototypes matching the final part design, geometry, materials, and process (molded vs machined) proves critical. Rushing through prototyping stages without those realistic validations inevitably leads to problems discovered too late downstream once production tooling is locked in and changes become very expensive. Investing sufficient resources upfront in engineering hours as well as budget for carefully crafted prototypes minimizes program delays and prevents companies from incurring major costs in reworking tooling.

Prototyping Trends

Many exciting advancements around plastics prototyping are emerging to quicken lead times and reduce expenses for companies:

Rapid + Affordable Tooling

With modular mold designs, aluminum mold blocks, and additive manufacturing of tooling, short-run injection molding continues to get faster and cheaper. Silicone rubber molds enable reconfigurable, sacrificial cavity tooling for dozens of casting cycles.

Improved 3D Printing Quality

Most major 3D printing methods are expanding choices for high-performance polymers beyond standard ABS/PLA prototypes, bringing exceptional surface finish, dimensional accuracy, material strengths, and heat resistance.

CNC Machining Efficiency

Emerging options like 5-axis control machines, robotic arms, and multi-axis cutting allow drastically improved machining rates for rapid, intricate plastic parts. Quick-turn CNC machining networks also continue spreading nationally to meet surging prototyping demand.

Accessibility Trends

Beyond material and process improvements, the internet has enabled highly convenient outsourcing for prototype needs. Various quality-focused rapid prototyping services offer instant quoting, interactive design reviews, and exceptionally fast turnaround for CNC-machined or 3D-printed plastic parts sent directly to your door. Leveraging such specialized prototype suppliers reduces in-house equipment demands and labor while bringing flexibility plus design expertise/support – getting prototypes into the developer’s hands literally overnight for assessment and modifications.

So, by combining expanding equipment capabilities, quality materials, and competitive suppliers, plastics will continue fueling prototyping efficiency. Both CNC machining and 3D printing processes enable remarkable design agility as more industries push the boundaries for plastic products by deploying prototypes at each iterative stage.