Before any product hits retail shelves, it has to go through an extensive prototyping period. Many new inventions don’t get made at all unless there is a suitable prototype to function as a proof of concept. Look at the presentations from shows like Shark Tank, any presentation with a functioning prototype is much more compelling than even the best sales pitch without one. Of course, sometimes not even the inventor knows whether or not the prototype will need some minor adjustments. This is exactly why rapid prototyping exists: it allows those in the early stages of product development the opportunity to more finely tune their product, usually in order to secure new funding from elsewhere. Those are just a few of the most obvious reasons to consider rapid prototyping, many people use rapid prototyping technology at just about every step of their product creation process as it allows for very useful tweaks to be done long before thousands of any one item are ordered from the factory.

Let’s start with the basics and work our way to the more complex aspects of rapid prototyping, shall we? It is a very expansive industry, after all.

What Is Rapid Prototyping?

In simplest terms, rapid prototyping is a manufacturing technique in which full scale 3D replicas of a part or unit can be made. While some choose to only make a 2D model, experts at Prototech Asia (https://prototechasia.com/en) explain that when designing a new product that uses metal or plastic, it’s important to create a 3D design to make sure you will have a uniform prototype. Typically 3D printers are employed in this endeavor and it is mainly to check for any glaring issues with regards to how the part will move or function normally. Kinks are rapidly worked out during this phase, it serves mostly as quality control for the future, more advanced units. Many things from simple figures to electric cars were at one point at the rapid prototyping stage. Many new features on cars are also tested using rapid prototyping technology. There are many different ways to create a rapid prototype, all with their own pros and cons. Some methods allow for practically functional replications of a 3D model in common materials while some function solely to display the shape of an object. The only thing that really separates rapidly prototyped materials from conventionally created materials is that we are still refining how precisely our 3D printers can make a model.

Making a model that’s relatively the same size is one thing, but having to make thousands of models with dimension tolerances within an inch of each other is still something 3D printing has yet to master. Still, rapid prototyping plays an important part in modern product development, especially among novel industries like aerospace engineering and the medical industry.

Methods Used For 3D Rapid Prototyping

Now that we know what rapid prototyping is, we can get to the bottom of how we actually manage to pull it off:

Selective Laser Sintering (SLS)

With SLS technology, a laser is used to make several layers on a build plate coalesce into the desired shape. Complex geometries can be replicated accurately but sanding is required afterwards if a smooth finish is desired. Both plastic and metal prototypes are made with SLS, some eventually serving as a master cast/mold for replicating the product further. A model is melted together layer by layer that is very close to the model’s exact specifications. SLS is a very functional way to churn out prototypes, although durability with this method isn’t the greatest. Because of the strong laser used and lab setup required, SLS style printers are seldom seen inside of a personal home. Parts made with this kind of prototyping philosophy are functional, chemically resistant, very stiff, and self supporting.

If plastic is used, it is imperative that a coating be added to the model immediately as it will be porous otherwise. Total accuracy to desired tolerances is very good unless polycarbonate is used during the printing process.

Fused Deposition Modeling

Most people commonly associate 3D printing with this method. A spool of plastic filament is melted and then the structure is made layer by layer by squeezing the melted plastic into the shape designated by the user. Most people present during the printing process describe it as oddly satisfying to watch. It is considered a form of additive manufacturing since each layer is “added” one by one.FDM is noted for how inexpensive and easy to use it is. Since the color of the plastic can be customized, many choose FDM for a prototype that doesn’t have to be supremely functional but accurately represent how the protect is expected to look in its finished state. These types of models are most often employed by hobbyist builders, good FDM printers are starting to show up at department stores across the nation, so there is evidence to suggest home prototyping is on the rise. The benefits of FDM in rapid prototyping would be how quickly and easily slightly different models could be created to test what design is ultimately the most effective.

Stereolithography (SLA)

One of the earliest forms of 3D printer, SLA printing is ingenious in how it works. A bath of a substance sensitive to light is solidified from the inside out by using UV light to control what shape is being made. This form of rapid prototyping makes for smooth models with some durability to them quickly and easily. SLA printed materials are often used for later vacuum casting, but it still holds strong as a common rapid prototyping method. One common source of SLA made materials are medical models that can be created from the data on a CT scan or MRI. In the world of rapid prototyping, SLA remains popular for being able to make even the most irregularly shaped prototypes very early on in their development.

Binder Jetting

What’s kept 3D printing niche is that there isn’t an effective device that can make high volume orders possible and truly replace regular kinds of manufacturing. In binder jetting, a print bed covered in metal powder is sprayed with a special liquid that creates a single layer. This process is repeated until the entire model is made. Once it is finished in the printer, it needs to be cured to get off excess liquid and properly fuse the metal together. Since high fidelity metal parts can be created, this is perhaps one of the few rapid prototyping strategies that may one day be employed large scale for items we’d expect to buy in a store. Binder jetting is excellent for putting the rapid in rapid prototyping as models are made at great speed. The layers are read as cross sections of the 3D model. If you’re still confused at all about how binder jetting works, simply think of the name. Binder is thrown around via jets which ultimately culminates in the desired shapes being created. Also adored by the people who run the printers is that the structures made are self supporting during the entirety of their creation. Loose powder functions to support the model on a molecular level.

These printers don’t play around, they usually start in the $50,000 range, with some models selling for much more.

Laminated Object Manufacturing

With this particular technique, metal foil, paper, or plastic laminate sheets are laid down layer by layer and cut to specifications with a laser. As older layers are cut away the surface lowers in kind to accommodate the excess plastic. Once all of the layers have been applied, the prototype is ready. It is extremely inexpensive and products a good prototype to show the shape and size of the item, but not much of anything else. Finished models can be machined or further manipulated easily. Also, large parts can be made easily since there’s no need to control conditions to maintain chemical reactions. One of the few rapid prototyping methods that’s used exclusively for making these kinds of models, LOM will always be one of the cheapest and easily available options. Besides rapid prototyping itself, laminated object manufacturing is also employed during the marketing phase when a product is still a prototype to allow for promotional materials to be made. A high volume amount of models made in this way is much cheaper than having to recreate the models through normal methods.

Digital Light Processing

Similar to SLA, DLP prototypes are made using a bath of photosensitive material cured by specific wavelengths of UV light. A slight difference is that instead of lasers DLP only requires a projector light, this fact makes it a less costly unit overall. In fact, rudimentary digital light processing printers can be made by someone at home with enough dedication plus a little trial and error. DLP differs in that it requires curing after the fact, but it is more efficient with regards to the amount of photo resin used which makes it a much more cost effective method on a per unit basis. Also noteworthy is that DLP structures are not self supporting, so supports material has to be added to any DLP endeavor. DLP is excellent when precision prototypes are necessary that are very close to the desired dimensions in a replicable way. The prototypes are typically non-functional but represent very closely what the final product is expected to look like.

Selective Laser Melting (SLM)

For this process, the conditions of the printing bed must be kept very pristine and controlled. Metal powder is fully welded onto the build plate through the use of a laser and a specially calibrated chamber. Instead of melting parts strategically, it can be said that SLM techniques fully melt the material, this translates into more uniform and desirable end product. Besides being used in rapid prototyping, it is also an effective way to make small parts with complex geometries. Desirable materials such as titanium and stainless steel can be used in this process, especially those that require very precise machining. Excellent prototypes that are more or less completely functional are possible thanks to SLM. It is gaining steam among various industries as a great form of rapid prototyping since very specialized equipment can be made that will be able to proceed directly to the testing phase.

How Do People Choose?

Three main aspects come into rapid prototyping: price, adherence to tolerances, and speed. The “best” form of rapid prototyping, if it did exist, would be a method in which models of practically completed quality were able to be made cheaply and quickly, with supreme replicability of these attributes. Usually one of these aspects is more important than others to a particular creator so they’ll choose a method that suits their needs & budget best.

So there you have it, just about every way there is to turn a block of unfinished materials into a 1:1 replication of anything you can draw up in AutoCAD. As these methods become more and more sophisticated, there might be a point where they aren’t used for rapid prototyping, but instead for mass production. The 3D printer stands to revolutionize our ability to make & test new products on the fly. There are even firms that exist solely to make the designs of other people, so cost is rapidly declining as well. Soon we’ll be living in a world where every neighbor & friend you have might have designed something themselves & use it every single day thanks to 3D printing. It is interesting to note that 3D printers aren’t quite at the level that they can make, say, custom Lego blocks.

Our current printer technology can’t make bricks that reliably fit together as perfectly as conventionally made blocks to. One day though, I’m confident we’ll be able to make our own custom Lego parts at will. Of course I joke, but that is the end goal of most of these printing technologies: the ability to create just about anything at the drop of a hat. Instead of companies taking months to years to create better products, it could simply be a matter of a few rapid prototypes later instead of such a long, drawn out R&D process.
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