What are the major Rapid prototyping techniques? (2020 Latest guide)

Evolution Rapid prototyping

Prototypes are used to quickly validate the design of a new product during the development phase in order to reduce the time to market. The impact of rapid prototyping is greatest in the first few weeks of design when changes cost very little.

How rapid prototyping works?

Traditionally, industrial prototypes were made using a technique known as injection. This is a prototyping method also known as injection molding and which originated in 1872 in the United States. The principle of plastic injection consists of softening plastic granules, which are then injected into a mold using a rotating endless screw.

The final part is obtained by removing the material from the mold after it has cooled. Synonymous with industrialization, this method makes it possible to manufacture identical objects in very large quantities.

3D printing works on a very different principle that begins with creating a digital model using design software. These data called G-Code and contained in a 3D file, provide the 3D printer with the information necessary to deposit the material along the XY and Z axes to arrive at the final object.

Among the 7 standardized additive manufacturing processes, we find stereolithography SLA which is one of the oldest techniques and the founder of this technology. This method, also called SLA, falls into the category of so-called liquid 3D printing materials.

No more expensive tools and molds. We can clearly see here that additive manufacturing therefore, makes it possible to obtain parts quickly and at a lower cost.

This allows the development phases of a new product to be validated as quickly as possible as part of an industrialization project.

Rapid prototyping brings together a set of techniques whose purpose is to quickly manufacture, using 3D representations from computer-aided design (CAD) software, a scale 1 model of a physical part or 'an assembly of parts.

what are the main rapid prototyping techniques?

The main rapid prototyping techniques are injection molding for good surface finish, CNC machining subtractive manufacturing, and 3D printing (additive manufacturing).

Injection molding

The injection molding , also called plastic injection parts. In this process a molted material is injected into a mold. Steel is used most often. The geometry of the mold is generally defined by means of a file resulting from the CAD.

Among the many materials compatible with this process, in the context of rapid prototyping, thermoplastic and thermosetting polymers are those essentially used. Likewise, for this type of application, the molds is rather made of aluminum to limit costs and delays. It is a popular process for rapid prototyping, which has a number of advantages, including:

Quantity: the cost price of prototypes is inversely correlated with quantity

A very good surface condition

The dimensions of the rapid proto: small or large, there are few limits to the dimensions of the prototyping process.

CNC machining

CNC machining is the abbreviation of Computer Numerical Control. It is a process of manufacturing parts by material subtraction (usually chip removal, turning or milling) with machine tools controlled by a digital computer. CNC machining can be done on both metals and plastics. The machine tool will accept various file formats from CAD or computer-aided manufacturing (CAM).

The operating costs are relatively low, but the economies of scale are small. Unlike plastic injection, this technique is not recommended for medium and large series, but is more suitable for a series of ten pieces.

Here are some advantages of this technique for rapid prototyping process:

• High accuracy
• Suitable for metallic or plastic materials
• Excellent surface condition of the parts
• Relatively low production costs
• Production versatility.

3d printing

3D printing, or additive manufacturing, appeared at the end of the 1980s. It refers to a set of techniques that consist in depositing material, layer after layer, to form a three-dimensional object. The construction of the object is done from a CAD file or a 3D file.

One of the advantages of this technique is the manufacture of complex parts that cannot be achieved by more traditional prototyping techniques, in particular hollow parts or with internal lattices. This prototyping method has the following advantages, among others:

• Great freedom of authorized forms
• Precision
• Speed
• Great latitude in the design phase, because manufacturing constraints are less.

This rapid prototyping technique is particularly suitable for production in very small quantities (a few pieces). It is the most versatile of the three, it is also the easiest and fastest to implement, to such an extent that online 3d printing services have developed.

Rapid prototyping Technology

layer-by-layer deposition modeling of thermoplastics FDM allows you to quickly and inexpensively produce fully functional samples of products and production tooling from a wide range of materials.

Inkjet printing with PolyJet photopolymers produces highly realistic color along with deposition modeling and multi-material products and tooling

Selective laser alloying of metals LBM / SLM is often used for high-precision prototypes of final products with complex geometry from metal-powder compositions of small fractions

Deposition of a gas-powder jet by means of a directed energy action DED / LMD is used for quick product surface finish, as well as for manufacturing products from scratch from metal-powder compositions

Wire fused deposition / cladding by 3DMP arc welding - the most affordable and productive solution for the fused deposition rapid production of final high-load metal parts and good surface finish.

The objectives

Making an error-free model is the major task of rapid prototyping in a given time scale. Similarly, it doesn’t cost much and the tools involvement on different stages is also minimum.

It is thus possible, during the product development process :

• Detect any design problems as early as possible, without major consequences on the final product cost,
• Test alternative solutions (technological choices for the part, processes used for its manufacture, etc.),
• Quickly validate the industrial feasibility of the part and optimize the shapes and cost of future tools required for its mass production, and therefore minimize the risk of modifications during industrialization,
• Refine the operational characteristics of the final product development (mechanical, aerodynamic, aesthetic, ergonomic, etc.) through full-scale tests on a physical rapid prototyper,
• Have a support object, and thus avoid arbitration of possible conflicts or the parallel manufacturing process elements inherent in each business (obtaining the raw material, machining, metrology, assembly, packaging, etc.) .

Rapid tooling (rapid tooling or consumable tooling)

Pre-production cannot be carried out by rapid prototyping machines for reasons of time and cost. The tooling thus produced is made using several technologies recognized by their specificity, such as for example metal powder sintering inserts, turning spindles, the parting line by electroerosion,

Rapid manufacturing

These would be new machines that would use the principle of manufacturing products layer by layer, therefore without special tools, but very quickly for small and medium series. These products would have good mechanical, chemical, and other characteristics without being linked to the conventional production method.

What are some other names for rapid prototyping?

The different types of prototypes

Virtual proto (or virtual model)

• Digital model (CAD model): Texture, realistic rendering.
• Numerous simulations (kinematics-mechanical behavior, ...).
• The virtual prototype is the basis of the rapid prototype (creation of STL file ).

Shape proto (appearance, design)

• Required for shape validation.
• Communication support (geometry, design, aesthetics).
• Objective basis of exchange.

Functional proto (good material)

• Necessary for the validation of prototyping rapid product functions (size, kinematics, clipping, resistance to aggressive environment, ...).
• Close to the actual material of the product.

Industrialization (or technological) proto

• Used to validate the industrialization phase before mass product development.
• Prototype real material and close to the manufacturing process.
• Quantity of the pre-series from a few pieces to 1000 pieces.

Rapid prototyping machines:

• Stereolithography
• Stratoconception
• Powder sintering
• 3D printer

3d printing, some explanations

As a reminder:

There are different 3d printing technologies (called additive manufacturing in the industry ), selective laser sintering sls, laser fusion … and different materials, abs or pla wire…

What is selective laser sintering sls?

Selective Laser Sintering (SLS) technology is a method of additive manufacturing of products from metals and other fine powder materials, through selective laser sintering. The method allows you product development of any shape from metal using 3D models, prepared in advance in the CAD modeling system.

But the basic principle does not change, additive manufacturing consists of creating a part, from a material, layer by layer.

The professional 3D printer receives data (STL file) via a computer which makes it possible to control the entire manufacturing phase.

Traditionally, different technologies such as injection made it possible to manufacture rapid prototypes.

But this technology requires, first, to create a mold into which the material will be injected to make the prototypes.

There is also a rapid prototyping technology called vacuum casting.

With this technique, you need a model, which is usually printed in stereolithography to obtain a detailed part. A silicone molding is then formed around this part and once this mold has hardened, the part is removed. All that remains is to pour resin inside the mold using a vacuum casting machine, cook the resin, open the mold and finally take out the finished part.

What are the objectives?

The feasibility of a product from an industrial project is a major issue.

These parts can be optimized using a digital method called "topological optimization".

After analysis of the calculation results, the geometry of the part is then modified and then re-tested.

In general, this optimization consists in "removing" the material to optimize their design according to one or more functional constraint (s) (mechanical strength, weight reduction, etc.).

The main objective of this prototyping rapid process is therefore to test ideas in a very short time.

It is the solution for testing functional prototypes and printing parts in small series.

What are the advantages of rapid prototyping?

The advantages of "rapid proto typing" are numerous with real added value.

Here are a few, a non-exhaustive list:

• Speed

Indeed, in terms of deadlines, 3D printing makes this technique faster than older processes, which are heavier to implement.

This advantage is essential because it makes it possible to quickly detect any design problems in support structures.

These possible problems can be corrected with lower costs, and therefore finalize the development of a product for its future production.

• Cost

As we have just seen, additive manufacturing technology makes it possible to control the costs of rapid prototyping.

This low cost also makes it possible throughout the rapid prototyping, rapid tooling phase to test alternative solutions and other technological choices.

• Limited risks

These tests made possible by this technique to improve the mechanical characteristics of the model.

In fact, full-scale tests will make it possible to better test and therefore refine the characteristics of the product.