Understanding Injection Molding

A mainstay in traditional manufacturing for nearly a century, Injection Molding was created in the mid-1800s and is one of the oldest high-volume manufacturing processes–relying on metal molds which are filled with molten liquid. Once cooled, the metal structures are ejected as solid parts. While the technique quickly evolved, Injection Molding hit its stride during the 1920s with automotive parts production and then during the 1940s as demand for economical plastic parts increased.

Manufacturers turn to Injection Molding when they need a high volume of accurate, identical parts–generally of 10,000 parts or more. Benefits include the ability to scale parts en masse, as well as keeping costs down after making all the molds. In comparison to traditional manufacturing like CNC Machining, the Injection Molding process results in less scrap and material waste. Because products are produced from one master pattern mold, every part that is produced will look the same. In a high-volume production environment that can be a major advantage, building brand consistency, quality, and product reliability.

Injection molding worldwide was estimated at USD 261.8 billion in 2021 and is anticipated to expand at a compounded annual growth rate (CAGR) of 4.8% from 2022 to 2030. According to Grand View Research, Injection Molding industry growth is set to be driven by the increasing demand for mass production of thousands of identical components at lower costs–coupled with design flexibility, and “precision from various end-user industries such as packaging, medical, and electronics.” 

Shapeways offers a variety of options for mass production with Injection Molding, whether project requirements call for thermoplastics, nylon materials, or metal. Typical applications include aerospace, automotive, consumer goods, and medical.

Delving into the 3D Printing Revolution

Relatively new in comparison to Injection Molding, 3D printing offers infinite possibilities for innovation and is revolutionary. 3D printing offers myriad features rounding out the choices for manufacturers like never before. 

Also referred to as additive manufacturing, the 3D printing process serves in striking contrast to traditional methods like Injection Molding. Created in the 1980s by engineer Chuck Hull, who would go on to form 3D Systems, the additive manufacturing process originated from his desire to accelerate product development. 3D printed parts can be made in a fraction of the time, allowing for rapid prototyping which was unheard of previously. Before the ability to iterate via 3D printing came along, engineers were forced to wait long periods of time–weeks or even months–before they received models back simply to begin the testing process. With the efficiency and quick turnaround time in 3D printing, anyone can now make a prototype, quickly establishing and implementing suggestions during the feedback phase.

3D printing became accessible and affordable to the mainstream public as patents obtained in the 1980s expired around 2014. The ramifications for manufacturing were obvious with expanded design freedom, rapid prototyping, and the ability to manufacture complex geometries. Now, the worldwide 3D printing industry is projected to grow from $18.33 billion in 2022 to $83.90 billion by 2029, at a CAGR of 24.3% in the forecast period from 2022 to 2029. 

3D printing materials like metal continue to trend upward and are projected to expand at a compound annual growth rate (CAGR) of 23.9% from 2022 to 2030. Metal 3D printing is one such market that has benefited significantly from the growing necessity of rapid prototyping and advanced manufacturing practices. Not only is a rise expected, according to companies like Grand View Research, but the ‘industry is poised to witness unprecedented growth.’ Unsurprisingly, the reason cited is continued growth in innovation. 

Specific verticals like aerospace 3D printing are also expected to grow from USD 2.75 billion in 2022 to USD 8.39 billion by 2027, at a CAGR of 25%–while automotive 3D printing is projected to grow from USD 2.9 billion in 2022 to USD 7.9 billion by 2027, at a CAGR of 21.7%. 

Making the Choice: Parts and Production Requirements

Aside from unit cost and order volume, additional considerations come into play when choosing between Injection Molding and 3D printing:

• Complexity of End-Use Parts – Whether an object has rounded or ultra-sharp edges, overall structure and complexity of geometry can help decide which manufacturing method is best. When thinking of ‘creative’ or organic shapes as complex, 3D printing wins. When considering tight engineering constraints and tolerances, injection molding is usually the best choice for manufacturing.
• Production Time – Production time is determined by the size of the production run, manufacturing capacity, and necessary turnaround times. The steps influencing production timelines include: sourcing a manufacturer, making molds, monitoring quality control, shipping and delivery. 
• Iteration & Change – As with all competitive products and services, the ability to iterate during development and maintain agility is key. For businesses at the beginning of product development, spending copious amounts of capital on a mold that cannot be changed will slow the innovation cycle. If the focus is on intense mass production without worry for customization, then injection molding will prove more fitting over 3D printing.

When Injection Molding and 3D Printing Intersect–and When They Diverge

Shapeways customers continue to enjoy numerous 3D printing materials, along with diverse technologies. Drone technology customers Quantum-Systems and Kespry save thousands by prototyping with Shapeways, and using the same 3D printing materials for end-use manufacturing. 

Customers like 67 Designs have partnered with Shapeways over the years and are deeply committed to the value of 3D printing. Designing and manufacturing luxury accessories for vehicles like offroading SUVs, 67 Designs has prototyped and 3D printed their parts with Nylon 12 [Versatile Plastic] and Selective Laser Sintering (SLS) technology. For 67 Designs, a serious belief in and dedication to 3D printing technology meant sticking with use of the technology despite more conventional ideology which could have pointed toward a return to traditional manufacturing like Injection Molding.

About Shapeways

Enjoy the benefits of this advanced technology and a wide range of materials from Shapeways for 3D printing your creations with accuracy, complex detail, and no minimum or limits in terms of mass customization or single part orders. Shapeways has worked with over 1 million customers in 160 countries to 3D print over 21 million parts! Read about case studies, find out more about Shapeways additive manufacturing solutions, and get instant quotes here.

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So you’re launching a physical product. Maybe it’s just a simple object, maybe it’s a hardware product with integrated electronics, or maybe it has mechanical functionality. You’ve built one (or probably many) prototypes, you’ve launched a successful crowdfunding campaign in order to manufacture your first batch, and now you need to do just that.

This is the point at which many entrepreneurs run into trouble – how do you scale from 1 to 1,000 units? Or 10,000? Maybe even 100,000 if you’re lucky. There are many factors to consider when scaling your manufacturing, but one of obvious concern is the method with which you’ll create the physical components for your product.

So how does someone go about choosing the right method that will scale along with his or her business? Here we’ll explore the pros and cons of two popular types of plastic part manufacturing: injection molding and 3D printing.

Background

When focusing on plastic components and products, there are traditionally few manufacturing methods available, the oldest and most common being injection molding. While injection molding has dominated the manufacturing landscape for decades, new techniques, such as 3D printing, have begun to gain traction by offering an alternative at costs competitive with injection molding for low-volume runs.

Unfortunately, there is no single manufacturing method that is perfect for every part and situation. As you’re thinking about creating a new product or scaling up the production of an existing one, it’s critical that you take special care to understand the advantages and disadvantages associated with both methods.

Injection Molding

Injection molding is one of the oldest high-volume manufacturing processes, wherein a molten material (such as a thermoplastic) is injected into a metal mold. Once injected, the thermoplastic takes on the mold cavity’s shape, is cooled, and is ejected as a solid part.

Injection molding is typically used for producing high volumes of the same object. For instance, if you’re looking to manufacture 100,000 pairs of identical plastic sunglasses, injection molding would be a great way to go about doing that.

The method does have its pitfalls, however. First, there is a large upfront investment involved in making a mold. Molds can be reused to make hundreds of thousands, if not millions of parts, but can cost anywhere from a few thousand dollars to over $100,000. As a result, there is an inflexibility that comes with needing to create a new mold for every new or modified part. That said, injection molding is a complex but powerful process that has been the go-to solution in the plastic part manufacturing market for years.

3D Printing

3D printing, or additive manufacturing, is a 30-year-old technology that has picked up a lot of steam in recent years. Unique to 3D printing is the process of adding material together to create the end part. This is opposed to cutting material away, like in milling, or reshaping it, like in injection molding.

There are many benefits inherent to this process, such as the ability to produce completely custom parts with virtually no upfront cost. With 3D printing, rather than needing a new mold for every new part, all you need is a new digital file. Additionally, 3D printing is capable of producing shapes that are impossible, or very uneconomical, to produce with any other manufacturing method.

Like injection molding, 3D printing also has its downsides. Today, many 3D printing processes are expensive, slow, and may produce parts that are not up to industry quality or material standards.

So, what process should you use to manufacture your parts – 3D printing or injection molding? When considering both methods, deciding between the two can become rather complicated and case-specific.

Considering Unit Cost & Order Volume

As previously mentioned, the prerequisite to injection molding any part is creating the mold itself. Mold costs vary greatly, but the cheapest ones typically start at around $5,000. Once you have a mold, the cost to make each unit is very little considering it really only includes the plastic used (which is very cheap), and perhaps a tiny bit of labor. This means that the upfront cost of making a mold gets amortized over your production run; with each additional unit you produce, the unit cost decreases since the initial mold cost is being spread across another unit.

3D printing is a different animal. Because 3D printing is a digital manufacturing technology, there is virtually no upfront cost to making a new part. At the end of the day, 3D printed part costs can be attributed mainly to material cost, manufacturing time, and labor. All of these are more expensive for 3D printers than for injection molding, but again, without an upfront mold cost the barrier to entry is a lot lower.

So, looking purely at unit costs, which method is more economical? There is always a point at which injection molding becomes more price competitive than 3D printing. Today, this point is usually somewhere between 1 and 10,000 units for parts that could be made to satisfaction with either method.

The figure below shows the relative unit cost for runs of the same theoretical injection molded and 3D printed part, plotted logarithmically. This model assumes a mold cost of $10,000 with each injection molded unit adding $0.20 of material cost. It assumes the 3D printed unit cost for the same part to be $20/unit for any run volume.

This logarithmic graph shows the theoretical unit cost for the same part manufactured separately with 3D printing and with injection molding. Using 3D printing, the unit cost remains at $20, regardless of the number of parts produced. Using injection molding, a $10,000 mold must be made prior to making the first unit. From there, each unit can be made for an additional $0.20, thus making the effective unit cost equal to $0.20 + $10,000/# of units produced. From the above graph, we can see that due to the upfront mold cost with injection molding, it only becomes the more cost effective production method if you are producing more than 500 units.

Other Considerations

Outside of unit cost and order volume, there are other considerations that come into play when choosing between injection molding and 3D printing:

Complexity – Whether an object is organically shaped or has ultra-sharp edges, its type and degree of complexity can help inform which manufacturing method you choose. Ultimately, you should choose the method best suited for making what you’ve designed. When thinking of “creative” or organic shapes as complexity, 3D printing wins. When thinking of hard engineering constraints and tolerances, injection molding [ed. note: most often] wins.

Production Time – Production time is typically determined by the manufacturer’s capacity and and the size of the production run. The many steps required to get something into production can factor into this timeline, from sourcing a manufacturer, to making a mold, to quality control, shipping and eventual delivery. You should always consider the manufacturer’s location, steps to getting to production, and guaranteed delivery time.

Iteration & Change – As with all competitive products and services, being able to iterate often and maintain agility is key to innovation. If you’re at the beginning of a long product development journey, spending a few thousand dollars on a mold that cannot be changed will most likely slow down your innovation cycle. However, if you’re at a point where your focus is scale and repeatability, then injection molding may prove to be more fitting than 3D printing.

Into the Future

As we look towards the future we’re seeing exciting developments within the realms of both 3D printing and injection molding. These advancements are making it easier and faster to get things made, and will hopefully lower the barrier so that more and more people can make the products they dream up.

Next time you find yourself on the journey to get something manufactured, consider the above factors and make the decision that will increase your chances of success in bringing a new product or part to life.

Looking to explore what 3D printing can do for your business? Get in touch with the Shapeways for Business team.

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