3D Printing Vs. Injection Molding: An Overview
We know that 3D printing and injection molding are different. Still, if you are relatively unlearned regarding these two manufacturing methods, you probably do not know how or why the two are different. Fortunately, we’re here to provide a brief overview of each of these two methods and how they function differently from one another.
First, let’s take a look at 3D printing.
3D Printing: What is it?
3D printing is a manufacturing process that produces objects by constructing them layer by layer, from the bottom up. Its founding is largely attributed to Chuck Hull, co-founder of 3D Systems, the world’s first 3D printing company. This manufacturing process is known as an additive process, as the process requires added material to construct the object.
This added material is always in the form of a filament and is typically comprised of thermoplastics, nylon, and polycarbonates. These materials are perfect 3D printer filaments because they are flexible, durable, and easy to print. These materials also blend well with less malleable forms like metal, stone, and wood.
3D Printing: How Does it Work?
3D printing generally requires one of the materials listed above, a slicing software to upload and edit the model you wish to print, and, of course, a 3D printer. A slicing software, or slicer, allows you to upload and manipulate a 3D model, designate specific print settings for that model, and then notify your 3D printer when it is time to print.
The printing stage requires filaments made from flexible, durable materials like those listed above. The filaments are fed into the printer, melted, and then excreted from the printer, forming your three-dimensional digital model as a physical three-dimensional object.
The process typically takes several hours to complete but, depending on the model’s size, could take longer. The largest solid 3D-printed object took roughly 30 hours to print.
Many 3D printers and slicers also allow you to stop the print in the middle of its process and make further changes to the 3D model.
Injection Molding: What is it?
Injection molding is a manufacturing process that produces objects by heating and injecting a malleable material into a metal mold that shapes the material into the desired object. Although injection molding is not technically additive manufacturing, the process should not be confused with subtractive manufacturing, which manually cuts the material into a desired object.
Unlike 3D printing, there are two distinct but equally vital materials required for injection molding; a mold and a melting material. Molds are typically made from aluminum, hardened steel, or a copper alloy that can withstand high heat levels. Melting materials typically consist of a range of plastic polymers, but some metal alloys will work.
Injection Molding: How Does it Work?
Injection molding inextricably requires a mold and a melting material, but the process also requires an injection molding machine to administer the injections. This injection molding machine consists of a hopper, barrel, heater, and nozzle.
First, the melting material is fed into the hopper. It is then heated within the barrel and then excreted from the nozzle into a mold cavity. Once inside the mold, the material will harden into the shape built into the mold.
The injection molding process is far more rapid than 3D printing, producing each object somewhere between several seconds to several minutes. However, the brunt of the time commitment comes from building the mold used for the process.
Building a mold can take anywhere between a few weeks to a few months. However, once you have a mold, you can repeat the injection molding process with that mold many times as you desire.
3D Printing: Pros and Cons
Now that we have a general idea of what 3D printing and injection molding are, you may be wondering about the merits and demerits of each manufacturing process. The next two sections will detail each manufacturing process’s advantages and disadvantages, which will be measured in a final section, designating which process is the best option for you.
To assess a wide range of pros and cons associated with each manufacturing process, we will separate these pros and cons into five subsections; cost/materials, speed, quality, customizability, and size.
Let’s take a look at the pros and cons associated with 3D printing before we dig into anything else.
3D Printing’s Cost/Materials: Pros and Cons
A crucial facet of any manufacturing process is its upfront material costs and recurring maintenance and resupplying costs.
To start, let’s take a look at the pros associated with 3D printing’s costs and materials.
- Relatively Low Upfront Costs: Although the upfront costs associated with 3D printing may not sound inexpensive, they definitely will sound inexpensive when compared to the upfront costs of injection molding. A 3D printer can cost as little as $200, although the industrial models can cost upwards of $100,000.
Additionally, slicing software is generally open-source, which makes them available for free. Most thermoplastic filament types cost around $15 to $20 per kilogram, and other suitable materials like nylon and polycarbonates are around the same price. Ultimately, you could potentially get started in 3D printing for under $300.
- Minimal Storage Space Required: Not only will 3D printing save you money, but it will also save you space. The materials necessary to execute 3D printing are fairly small and easy to store. A 3D printer is small enough to fit snugly on desk space, and thermoplastic filaments can easily be stored in a quaint drawer or cupboard.
Now, let’s take a look at the cons associated with 3D printing’s costs and materials.
- Consistent Resupply: Because 3D printing is an additive process, it requires a constant supply of material to add to the manufacturing process. Thermoplastic filaments are not necessarily expensive, but it can be a hassle to resupply constantly. Most filaments come in 1-kilogram spools, which is enough filament to build roughly 103 chess pieces.
3D Printing’s Speed: Pros and Cons
Another facet of any manufacturing process that greatly determines that process’s efficacy is the rate at which it can produce.
First, let’s take a look at the pros associated with 3D printing’s speed.
- Quick to Start: It takes very little time to go from dreaming about three-dimensional printing objects to turning that dream into a reality. Once you have the necessary materials, a 3D printer, filaments, and slicing software, you could print out your first 3D object within the day.
Additionally, it should not take longer than a day to collect these materials. You can purchase a 3D printer online or at various retail stores centered around 3D printing. 3D printer filaments are even easier to find. Just go to the nearest Office Depot or fabrics store. Slicing software is available to download instantly, and the installation process is relatively short.
Now, let’s take a look at the cons associated with 3D printing’s speed.
- Slow Processing Time: In quite the contrast to its start-up time, 3D printing’s actual manufacturing process is lengthy and occasionally tedious. The 3D printing process can take anywhere between 30 minutes and multiple days, depending on your model’s size and complexity.
Although, as a beginner, you will likely not be printing any objects that take multiple days to process. However, you will likely find yourself spending hours waiting for your models to be completed. For reference, a miniature action figure at about 28mm layer height takes just under an hour to print.
3D Printing’s Quality: Pros and Cons
A manufacturer’s production is typically judged in two regards, quantity and quality. As we detailed the production rate in the preceding section, this section will be dedicated to the quality of production.
Now we’ll get into the pros associated with 3D printing’s quality of production.
- More Complex Designs: A 3D printer’s ability to add layers on top of each other allows for more complex designs. 3D printers come with a tool called an extruder, which can print nuanced and intricate details into your 3D print. For reference, 3D printers have been replicated as complex objects as dental products, prosthetics, and even ancient fossils.
And now we can take a look at the other side, the cons associated with 3D printing’s quality of production.
- Rough Around the Edges: A downside to 3D printing’s layer-by-layer production method is the ridged surface it creates on your finished product. For one, this leaves your objects looking rudimentary and unpolished.
However, this can become an even greater concern if you use this object to function as a moving part, amongst other parts. The ridges on your printed 3D object may prevent it from working in cohesion with other moving parts.
Any of the rough around the edges parts can be resolved by smoothing out the ridges using sandpaper, but this only adds another step to the process. To maintain the objects presentability, start at a coarse sandpaper grain and gradually move to finer grains. Then, polish the exterior using spray paint or a fine paintbrush.
3D Printing’s Customizability: Pros and Cons
An aspect of manufacturing that often flies under the radar is the room for customization and experimentation within the process.
To start, we’ll examine the pros associated with 3D printing’s customizability.
- Countless Design Possibilities: The excitement around 3D printing is largely in its boundless capabilities, limited only by one’s imagination. 3D printing has already been used to create miniature human organs, spacecraft parts, and even a meal with plates and utensils included.
With intuitive slicing software like Ultimaker’s Cura available for free, it isn’t even that hard to construct your quirkier fantasies. You may not be creating miniature human organs right out of the gate, but plenty of intricate designs are possible for even novice printers to construct.
- Make Changes During the Process: Not only are there countless design possibilities prior to construction, but you can even make changes to your print during the printing process. 3D printers generally allow you to pause in the middle of the process, and you can use your slicing software to make any modifications you’d like to try out.
3D printing was originally used for rapid prototyping, so experimentation is a fundamental component of the process. There is little cost for failure, so you are free to experiment with your object’s customization a little bit.
It is tough to pick out any negatives associated with 3D printing’s customizability as they are at the forefront compared to all other manufacturers in this regard. Therefore, there are no cons associated with 3D printing’s customizability.
3D Printing’s Size: Pros and Cons
Finally, the ability to create objects of varying sizes is an important component of any manufacturing process.
There is one major pro that 3D printing has in the ability to create objects of varying sizes department:
- Can Go Very Little: 3D printers are renowned for creating minuscule objects that maintain intricate designs. Many have printed objects no larger than several millimeters, and the German company Nanoscribe claims to have constructed an object as small as 500 nanometers.
Up next we take a peek at the cons associated with 3D printing’s ability to create objects of varying sizes.
- Cannot Go Very Big: Most 3D printers are limited in their build size due to the printing space’s size and the extruder arm’s limited reach. Industrial 3D printers can perform larger-scale constructions, but you would have to shell out somewhere between $10,000 and $100,000 to purchase an industrial 3D printer simply.
Injection Molding: Pros and Cons
As we have gone over the pros and cons of 3D printing’s costs, speed, quality, customizability, and size, we will now do the same with injection molding.
Injection Molding’s Costs/Materials: Pros and Cons
To start, let’s take a look at the pros associated with injection molding costs and materials.
- Minimal Material Waste: If there is one good thing to say for injection molding’s costs and materials, it is that the process results in minimal material waste. Unlike subtractive processes that cut off the spare parts of a material to form an object, injection molding only uses the necessary amount of material to form the object.
Now, let’s take a look at the cons associated with injection molding’s costs and materials.
- High Upfront Costs: Even the simplest injection molding machines cost between $1,000 to $5,000. The average injection molding machine costs around $12,000, so spending less than five figures is probably an unrealistic option. The upfront cost does not even take into consideration the melting material and mold material costs. Both of those can add up quickly and become a hefty expense on their own.
- High Recurring Costs: After purchasing your injection molding machine, you still have to worry about recurring melting material and mold material costs. Additionally, you will run through several prototypes before achieving your desired mold, which will run up these recurring costs even more.
Injection Molding’s Speed: Pros and Cons
First up, the positives of the built in speed of injection molding.
- Ability to Mass Produce: Once you have gone through several prototypes and found the mold or molds you would like to use, injection molding becomes an incredibly efficient process. The machines can produce anywhere from dozens to thousands of objects from a multitude of molds.
Additionally, injection molding machines are designed to process multiple molds at once. Therefore, if you have multiple designs you would like to print, you can mass produce all of them at the same time.
- Speed: Ultimately, the greatest pro associated with injection molding’s speed is simply its speed. As mentioned earlier in this article, injection molding machines can produce objects in mere seconds. The process rarely takes longer than several minutes, so with the machine’s ability to produce multiple objects, this can lead to massive production quantities.
There’s just one major drawback to the speed of injection molding.
- Lengthy Setup Process: Although injection molding is an expedient process once it’s inaction, setting up and perfecting the process can take a great deal of time. It can take months to create your own mold, and once you have completed it, you still need to troubleshoot it. It will probably take several prototypes before you finally nail that first mold.
Injection Molding’s Quality: Pros and Cons
The positives of injection molding definitely outweigh the negatives. But how, exactly? Let’s see.
- Strength: Injection molding creates objects of superior strength to most other comparable manufacturing processes. The process creates objects with only a single poured layer, devoid of any weak points.
Additionally, injection molding machines can handle denser materials like metal alloys and concrete that 3D printers would not be able to utilize.
- Smooth Surfaces: In contrast to 3D printed objects, injection-molded objects typically do not require extra steps to achieve smoothness. As the process creates objects with only a single poured layer, there are rarely any ridged edges or bumps along the surface. As long as the mold is precise and smooth, the object will follow suit.
There’s just one major con for injection molding’s quality, but it’s a big one. Let’s take a look.
- User Error: Although this may be a pro for some people, a great deal of the injection molding process is left up to the manufacturer’s volition. Therefore, any slight err in constructing the mold can lead to lower quality products. That is why many go through several prototypes before achieving the desired mold.
Injection Molding’s Customizability: Pros and Cons
To start out, let’s take a look at the pros associated with injection molding’s customizability.
- Hand-Made: If there is anything positive to say about injection molding’s customizability, it is that the process is literally hands-on. You are constructing a physical mold, not designing it on software. This can be more intuitive for the less technologically inclined.
Now, let’s take a look at the cons associated with injection molding’s customizability.
- Design Limitations: An often-disregarded step in the injection molding process is removing the cooled material from the mold. This can be a tricky procedure that can occasionally lead to breaks if the mold is designed to delicately. This restricts the amount of intricacy and nuance you can add to your mold design.
- No Changes Made During Process: Unlike 3D printing, once you begin the injection molding process, you cannot stop. Additionally, if you have made a mistake along the way, you will likely not be able to rectify the mistake. Instead, you will have to start from scratch, as injection molding is a practice of trial and error.
Injection Molding’s Size: Pros and Cons
The ideal production size for injection molding is specific, let’s look at the pros first.
- Allows for Larger Sizes: Injection molding machines are less limited in scale than 3D printers in regard to larger sizes. Although not much less limited, injection molding machines typically allow for objects around 4 feet by 4 feet in size.
Now, let’s take a look at the cons associated with injection molding’s ability to create objects of varying sizes.
- Does Not Allow for Smaller Sizes: On the other hand, injection molding machines cannot create objects as small as the minuscule 3D printed creations mentioned earlier in the article. This is due to the potential breaks in removing the cooled object from the mold.
3D Printing Vs. Injection Molding: Final Verdict
Now that we have delved deeper into the pros and cons of each manufacturing process, it is time to stack them up against one another. In doing so, let’s use the five categories used in the pros and cons section; costs, speed, quality, customizability, and size.
With injection molding’s extremely high upfront costs and recurring costs, it would be hard not to choose 3D printing for this category. Even though $200 to $500 doesn’t necessarily sound inexpensive, relative to injection molding, it is practically free.
It is also important to keep in mind the ease of storing 3D printing supplies versus injection molding supplies. Injection molding necessitates a decent amount of open garage space, whereas a 3D printer could be placed on your average work desk.
Advantage: 3D Printing
3D printing is a lot quicker of a setup process, but the rate of production injection molding can handle tough to argue against. Doing what takes 3D printers hours to do in mere minutes, potentially with multiple objects at a time, is enough to set injection molding above its competitor.
Advantage: Injection Molding
3D printing does offer the potential for more complex designs, but we must take into account the surface roughness issues that are endemic to the process. Although injection molding can lead to more instances of user error, the strength and smoothness of its single layer mold are tough to beat.
Advantage: Injection Molding
Injection molding is rather limited when it comes to customizability and experimentation. Too fine or delicate details will likely lead to breaks, and the trial and error of starting from scratch with various molds can be tedious.
On the other hand, 3D printing allows for an incredible amount of customizability and experimentation. You are able to construct any design your imaginative mind can think of, and you can even stop the process of making edits as the model is being constructed.
Advantage: 3D Printing
3D printing has been a tool for a ton of neat, intricate designs. However, there are strict limitations to the bigger sizes a 3D printer can create. Ultimately, injection molding cannot create objects as small as 3D printers can, and 3D printers cannot create objects as large as injection molding machines can.
3D printing and injection molding are two incredibly unique methods for manufacturing objects. The experimentation and customizability present in 3D printing are perfect for those keen on pushing the boundaries on manufacturing. The quality and speed of injection molding are perfect for those who require mass production of a certain object or objects.
Ultimately, both manufacturing processes are excellent at achieving their own contrasting results. Although injection molding may be a little out of the average person’s price range, 3D printing is an excellent process to get familiar with as the manufacturing landscape enters a new revolution.