Advantages of Rapid Tooling and Low-Volume Molding

Advantages of Rapid Tooling and Low-Volume Molding

Introduction

Plastic injection molding is a ubiquitous manufacturing process used across countless industries to produce millions of plastic parts every day. However, the high cost of injection molds traditionally made mass production volumes necessary to justify the investment.

Recent advances in mold manufacturing methods now enable low-volume production to be viable and affordable. New rapid tooling techniques facilitate faster and cheaper mold-making for short runs. Companies can leverage these technologies for limited production of new products for market testing before high-volume tooling commitment.

This article will examine the advantages of creating tooling for low-volume injection molding. We’ll review rapid tooling methods and how they now make short-run production economical.

Overcoming Traditional Mold-Making Barriers

Injection molds require high-precision machining to yield flawless molded parts consistently. A typical steel or aluminum mold takes weeks or months to fabricate and requires extensive CNC milling, grinding, EDM, and polishing. Just the material cost can be $5,000 to $50,000. And complete tooling with design, machining, and engineering support often reaches $100,000 to $300,000.

This level of time and cost traditionally only made sense for very high production volumes of millions of parts to spread out the initial investment. As a result, companies would often outsource early-stage product prototyping because dies weren’t feasible.

New Technologies Changing the Game

Advancements in additive manufacturing and CNC machining now enable rapid tooling methods that reduce the time from weeks to days while requiring a fraction of traditional costs. Some technologies facilitating faster, low-cost tooling include:

• CNC Machining Soft Tooling – Aluminum mold bases are rapidly machined using advanced CAM programming and toolpaths. Soft aluminum won’t last as long as steel but enables quick turnaround and modifications.
• 3D Printing Metal Tools – DMLS printers build complex metal tooling containing conformal cooling channels in days versus weeks for traditional methods.
• Laser Sintering for Metal Inserts – Laser sintering rapidly produces durable metal mold inserts for short-run production. The laser fuses fine metallic powders to shape mold details.
• Silicone Molding – Liquid silicone rubber poured and cured in 3D printed molds creates flexible, reusable molds for tens or hundreds of parts.
• CNC Machined Graphite Electrodes – Graphite copies of parts made in hours enable fast EDM of mold details into tool steel production molds.

These rapid tooling techniques facilitate the affordable production of hundreds to thousands of parts. Lead times of 1-4 weeks and costs of $5,000-$15,000 enable companies to validate products and conduct market testing before investing in high-volume tooling.

Benefits of Low-Volume Tooling

Here are some of the key advantages possible with rapid tooling for shorter-run injection molding:

Test Marketing and Validation

• Get functional parts in customers’ hands for feedback on design, fit, and features.
• Gain real market data including pricing tolerance, demand, and targeted demographics before high-volume production.

Refine Product Engineering

• Assess parts’ performance under real-world conditions during testing and piloting.
• Identify potential design improvements early like wall thickness, ribbing, material grades, etc.
• Verify production methods and tooling functions to optimize high-volume molds.

Reduce Risk

• Avoid large investments in big steel production tooling before market confirmation.
• Change designs faster and at lower cost during pilot phases.
• Ensure quality standards are achievable before scaling to mass production.

Bridge Prototyping

• Maintain momentum from 3D printed prototypes to end-use parts.
• Make more accurate pilot parts with proper production-grade resins vs. prototyping materials.
• Enable limited testing of assemblies and final products before full production.

Flexibility and Customization

• Make quick tooling adjustments and tweaks for design iterations.
• Produce multiple variations and customizable or personalized parts cost-effectively in small batches.

On-Demand Manufacturing

• Respond rapidly to orders and market demand instead of stockpiling finished goods inventory.
• Handle fluctuating volume requirements cost-effectively.
• Produce replacement and service parts without tying up production tooling.

Accelerated Time to Market

• Launch products commercially faster without delays related to big tooling lead times and costs.
• Seize opportunities and compete against the extended development cycles of competitors.
• Recoup investment quicker by starting revenue months sooner than waiting on mass production molds.

Rapid Tooling Technology Details

To understand how these technologies enable fast and economical mold-making, let’s look at some of the rapid tooling techniques in more detail.

CNC Machined Aluminum Molds
Computer numerical control (CNC) machining can rapidly fabricate mold bases and cores from aluminum instead of steel. This soft tooling allows lead times of just 1-2 weeks and costs around $5,000-$10,000. The soft aluminum won’t last as long as hardened steel but enables many pilot parts. Agile CNC programming like 5-axis interpolation optimizes machining time. The aluminum blocks can also be modified easily. Small features are added using replaceable machined inserts to save time. While meant for short runs, some clever strategies can harden select mold surfaces and extend aluminum tool life substantially.

Metal 3D Printing
Additive manufacturing of metal parts has progressed enormously in recent years for production applications. Printers like DMLS (Direct Metal Laser Sintering) allow complex metal mold components to be 3D printed to near final dimensions in just days instead of waiting weeks for traditional machining. While not as strong as wrought metals, the layered 3D printing process results in decent strength for limited molding cycles. DMLS also facilitates very complex internal geometries so conformal cooling channels can be built into the tool. This lowers part costs and improves quality. The rapid printing of tooling inserts offers affordable short-run production.

Laser Sintered Metal Inserts
Similar to DMLS processes, laser sintering can fuse fine metallic powders into solid metal tooling components for low-volume molding. CAD models are digitally sliced and the laser scans each layer shape, sintering the powders together. A variety of metals are available with good longevity including maraging steels, stainless steels, tool steels, cobalt chrome, and more. The technology is advancing rapidly with higher-density parts. While not as dense as machined steel, laser-sintered tooling achieves hundreds of molding cycles. And it’s far faster and cheaper than machined inserts. Typical lead times are 1-3 weeks at 40% lower costs than traditional machining.

Silicone Rubber Molds
For truly low volumes of tens or hundreds of parts, molds can be 3D printed from standard resins and then used to create reusable silicone rubber molds via room-temperature injection molding. The silicone tooling can produce urethane, epoxy, or polyester resin parts. Silicone molds offer a very fast turnaround in days and handle around 25-100 cycles before wearing out. The flexible and pliable silicone allows easy part ejection. While part accuracy is not as high as steel molds, silicone tooling offers an ultra-affordable solution for concept models and early testing needs.

Graphite Electrodes for EDM
Shaped graphite electrodes can be machined rapidly from graphite blocks using CNC mills. The precisely machined electrodes then facilitate fast EDM of mold details like cores and cavities into standard mold bases. Graphite’s low hardness speeds electrode machining. Its high conductivity also increases the material removal rate during the EDM process. Reusing existing mold bases and plates reduces cost. Only the fine contour details require graphite electrode EDM. This hybrid approach takes advantage of existing tools while optimizing process speed. Graphite electrodes bring quick turn EDM for pilot production.

Optimizing Rapid Tooling Performance

While designed for short runs, there are ways to optimize performance and life of rapid tooling to maximize value:

• Strategically harden key mold surfaces like cavities through heat treating or surface coatings.
• Add pre-hardened tool steel inserts in high-wear areas.
• Utilize high-strength alloys and post-processing like H13 tool steel to add durability.
• Design streamlined cooling channels to prevent hot spots and fatigue.
• Simulate molding performance digitally to troubleshoot issues before cutting any metal.
• Perform proper mold surface finishing pre-texturing to enable demolding while minimizing ejector pin marks.

Combining these tactics with quality assurance checks ensures reliable production from rapid tooling.

Success Stories

Many companies are already using rapid tooling techniques to enable short-run injection molding economically. Here are a few examples across industries:

• A medical startup needed a few hundred nylon surgical handle prototypes for hospital testing before full-scale production. Silicone molds produced the parts 65% cheaper than machined tools.
• An automotive company 3D printed complex core inserts to injection mold prototype polypropylene truck interior parts for ergonomic studies and test fitting. This saved 5 weeks of machining.
• A consumer goods company laser sintered stainless steel mold cavities to injection mold a few thousand polycarbonate containers for initial store pilot testing in select regions.
• A plastic tray manufacturer CNC machined an aluminum mold to produce 1,000 new trays for samples and early marketing. This confirmed demand before investing $350,000 in final hardened steel tooling.
• An electric toothbrush startup iteratively modified and added features to low-volume molds based on user feedback before finalizing the design for mass production.

The Future of Rapid Tooling

As technology and quality continue advancing, rapid tooling systems will provide even more economical, timely, and flexible solutions to produce injection molded parts without high-volume requirements. Automation and optimization will also reduce labor time and simplify the process for more accessible adoption.

Expect expanded applications for limited-run packaging, personalized consumer goods, replacement parts on demand, regulated industries like medical, and continuous upgrades of electronics and Internet of Things products. Rapid tooling will see increasing deployment for cost-effective concept validation, market testing, custom orders, and bridging prototyping with production.

Conclusion

Rapid tooling technologies like CNC machined soft molds, 3D metal printing, laser sintering, silicone molding, and graphite EDM electrodes now facilitate fast and economical injection molding of limited volumes. This allows companies to test markets, refine designs, reduce risk, customize products, and accelerate time to revenue. While designed for hundreds to thousands of parts, clever strategies can also extend tool life. As rapid tooling quality improves, expect wider adoption across industries to optimize new product introduction and align production with actual demand.