what is rapid prototyping？

Rapid prototyping (rp) is also known as rapid prototyping manufacturing (rpm).

Rapid prototyping was born in the late 1980s and is a high-tech manufacturing technology based on the material accumulation method. It is considered a major achievement in the manufacturing field in the past 20 years.

It integrates mechanical engineering, cad, reverse engineering technology, layered manufacturing technology, numerical control technology, material science, and laser technology. 

It can automatically, directly, quickly and accurately transform design ideas into prototypes with certain functions or directly manufactured parts , So as to provide a high-efficiency and low-cost realization method for parts prototyping and verification of new design ideas.

That is, rapid prototyping technology is to use three-dimensional cad data, through the rapid prototyping machine, layer by layer of materials are piled up into a solid prototype.

Whether you work independently or as a team member, fast action is the key. This is why rapid prototyping is advocated, a design process that includes ideation, prototyping, and testing. Can help designers quickly discover and verify their best ideas.

Basic principles of rapid prototyping

Rapid prototyping technology is a general term for product prototypes made with the principle of discrete layering. Its principle is: 

→ product three-dimensional CAD model 

→ layered discrete-process and pile up raw materials layer by layer according to the discrete plane geometric information 

→ generate a solid model.

This technology integrates computer technology, laser processing technology, and new material technology. 

It relies on CAD software to establish a three-dimensional solid model in the computer and divide it into a series of plane geometric information to control the scanning direction and speed of the laser beam. The raw materials are selectively processed layer by layer by means of bonding, sintering, polymerization, or chemical reaction, so as to quickly build a solid model of the product.

Advantages of rapid prototyping

Rapid prototyping technology breaks through the traditional part processing mode of "blank→cutting→finished product", creating a precedent for making parts without using tools, and is an unprecedented thin-layer superimposed processing method. Compared with traditional cutting methods, rapid prototyping has the following advantages:

(1) Free-form surfaces and more complex parts can be quickly manufactured, such as grooves, shoulders and hollow parts in the parts, which greatly reduces the development cost and development cycle of new products.

(2) It belongs to non-contact machining, which does not require tools and fixtures necessary for machine tool cutting, and has no tool wear and cutting force influence.

(3) No vibration, noise and cutting waste.

(4) Fully automated production at night can be realized.

(5) The processing efficiency is high, and the product solid model and mold can be produced quickly.

Introduction to the rapid prototyping model

A.The rapid prototyping model requires the rapid construction of a runnable software prototype in order to understand and clarify problems, so that developers and users can reach a consensus, and finally develop customer-satisfied software products based on the determined customer needs.

B.The rapid prototyping model allows preliminary rather than complete analysis and definition of software requirements in the requirements analysis stage, and quickly design and develop a prototype of the software system, which shows users all or part of the functions and performance of the software to be developed.

C.The user tests and evaluates the prototype, and gives specific suggestions for improvement to enrich and refine the software requirements. Developers modify and improve the software accordingly, until the user is satisfied and approved, complete the software implementation, testing, and maintenance.

Advantages of rapid prototyping model:

• The advantages of the model are reduce development risks caused by unclear software requirements.

shortcoming: 

• The selected development technology and tools may not be in line with the mainstream development;

• Rapidly established system structure coupled with continuous modification may lead to low product quality;

It can be seen from the above description. The rapid prototyping method is a commonly used method when the requirements are not clear.

Brief description of the rapid prototyping model

Prototype refers to the original model that simulates a certain product, which is often used in other industries. The prototype in software development is an early runnable version of the software, which reflects the important characteristics of the final system.

Rapid prototyping model is also called prototype model, which is another form of the incremental model; it constructs a prototype before developing the real system, and gradually completes the development of the entire system on the basis of the prototype. 

The first step of the rapid prototyping model is to build a rapid prototype to realize the interaction between the customer or future user and the system. The user or customer evaluates the prototype and further refines the needs of the software to be developed. 

By gradually adjusting the prototype to meet the customer's requirements, the developer can determine what the customer's real needs are; the second step is to develop a software product that the customer is satisfied with based on the first step.

Where the rapid prototyping method is used?

Use rapid prototyping to make a master mold, and cast wax, silicone rubber, epoxy resin, polyurethane and other soft materials to form a soft mold. For example, the mixed material of metal and epoxy resin is colloidal at room temperature and can be poured and cured at room temperature, so it is particularly suitable for replicating molds. 

The service life of the injection mold made of this synthetic material can reach 50-5000 pieces. When using room temperature curing silicone rubber to make injection molds, the life span is generally only 10-25 pieces. When vulcanized silicone rubber molds are used for low melting point casting, the mold life is generally 200-500 pieces.

Using rapid prototyping to make master molds or soft molds combined with traditional processes such as investment casting, ceramic precision casting, electroforming, cold spraying, etc., can be made into hard molds, which can produce plastic or metal parts in batches. Hard molds usually have good machining performance, can be partly cut to obtain higher precision, and can be embedded in inserts, cooling components, and burning channels.

(1) The silicone mold uses the prototype as the original part, and is poured with vulcanized silicone rubber to directly manufacture the silicone rubber mold, and because the silicone rubber has an inverted draft angle and a part with a deep groove, the production can be completed and the casting can be completed. Take it out directly, which is unique compared to other molds.

The process is: 

→ making a prototype, treating the surface of the prototype to make it have a good surface roughness

→ fixing the prototype and the mold frame, applying a release agent on the surface of the prototype 

→ placing the silicone rubber mixture in the vacuum device, Take out the air bubbles, pour the silicone rubber mixture to obtain a silicone rubber mold-silicone rubber curing 

→ cut the silicone rubber along the parting surface and take out the prototype to obtain the silicone rubber. If it is found that the mold has a few defects, it can be repaired with new silicone rubber.

(2) Resin composite mold This method is based on the composite of liquid epoxy resin and organic or inorganic materials as the matrix material, and a mold making method based on the prototype.The process is: 

→prototype production and surface treatment-design and production of mold frame 

→ selection and design of parting surface 

→ brush release agent (including parting surface) on the prototype surface 

→ brush gel coat resin.

The purpose is to prevent the mold surface from friction, collision, atmospheric aging and medium corrosion, so that the mold is safe and reliable in actual use. Casting the concave mold-when the concave mold is completed, it is inverted, and the prototype surface and parting surface are also required. 

Evenly apply the release agent and gel coat resin once the mold is separated, and the mold poured at room temperature will basically be cured and shaped in 1-2 days, that is, the mold can be divided, the prototype can be taken out, and the mold can be repaired.

Compared with metal resins with high heat resistance and high wear resistance, epoxy resins cured at room temperature often cannot meet the requirements. For this reason, epoxy resins cured at high temperatures must be used first.

This is bound to cause problems for prototypes made with photosensitive resin. Because it starts to soften at 70-80, a transition core is needed for this. Epoxy resin, gypsum, silicone rubber, polyurethane, etc. are commonly used as transition mold cores, and plaster and silicone rubber mold cores are more common.

This kind of epoxy resin mold manufacturing technology has the characteristics of simple process, high mold conductivity, high strength and unprocessed molding surface, and is suitable for plastic refraction molds, sheet drawing molds, blister films and polyurethane foam forming molds.

(3) The arc spray mold is based on the prototype. The molten metal is fully atomized and sprayed onto the surface of the sample mold at a certain speed to form the surface of the mold cavity. The backing is filled with composite materials, and aluminum-filled epoxy resin or silicon is used. The rubber support separates the shell from the prototype to obtain a precise mold, and adds a gating system and a cooling system, etc., together with the mold structure to form an injection mold.

It is characterized by simple process and short cycle; the cavity and surface fine patterns are formed at the same time; it eliminates the need for expensive and time-consuming processes such as drawing in traditional mold processing and heat treatment of CNC machining, and does not require machining; mold size accuracy is high, The cycle is shortened and the cost is saved.

(4) The process of chemically bonded ceramic pouring cavity mold: 

→ use rapid prototyping system to make a master mold

→ pouring soft materials such as silicone rubber, epoxy resin, polyurethane, etc. to form a soft mold

→ remove the master mold, in the soft mold Pouring chemically bonded ceramic (CBC, ceramic-based composite material. material) cavity 

→ curing the CBC cavity at 205 ℃ 

→ polishing the surface of the cavity 

→ adding a small batch production injection mold such as a pouring system and a cooling system. 

The life of this chemically bonded ceramic cavity is about 300 pieces.

(5) Use ceramic or plaster mold to cast injection molding steel or iron cavity. The process is: 

→ use rapid prototyping system to make master mold 

→ pour soft materials such as silicone rubber, epoxy resin, polyurethane to form soft mold 

→ remove master mold 

→ in Pouring ceramic or plaster molds in soft molds-pouring, steel or iron cavity-cavity surface polishing-processing pouring system and cooling system, etc. 

→ injection mold for mass production.

The advantage of ceramic mold casting is that the process equipment is simple, and the obtained mold has excellent reproducibility, small surface roughness and high dimensional accuracy. It is particularly suitable for small batch production of parts, integral forming manufacturing of complex-shaped parts, tool and die manufacturing, and forming of male processing materials.

(6) Investment casting method for manufacturing iron and steel molds

①Only the process of making a single piece of iron and steel cavity is: 

→ use the rapid prototyping system to make the master mold 

→ soak the master mold in the ceramic sand liquid to form the mold shell 

→ solidify the mold shell in the furnace and burn off the master mold 

→ pre-heat the master mold in the furnace Hot mold shell 

→ pouring steel or iron cavity in the mold shell 

→ polishing the surface of the cavity and adding the injection mold for mass production such as the casting system and the cooling system.

②The process of manufacturing multiple iron-steel cavities is: 

→ using rapid prototyping system to make master mold 

→ spraying with metal surface, or aluminum-based synthetic material, silicon rubber, epoxy resin, polyurethane casting method, forming a wax film forming mold 

→In the forming mold, cast the wax film with molten wax 

→ put the wax film in the ceramic sand liquid to form the mold shell 

→ solidify the mold shell in the furnace and melt the wax film 

→ preheat the mold shell in the furnace 

→ cast steel in the mold shell Or iron-shaped brain-the surface of the cavity is polished and added to the injection mold for mass production such as the gating system and the cooling system.

Its advantage is that it can use prototypes to manufacture parts with very complex shapes.

(7) The process of chemically bonded steel powder pouring cavity mold is: 

→ use rapid prototyping system to make paper master mold-pouring soft materials such as silicone rubber, epoxy resin, polyurethane, etc., to form soft mold 

→ separate from master mold 

→ in Pouring chemically bonded steel powder cavity in the soft mold, burning out the binder in the cavity, pouring steel powder 

→ cavity copper infiltration-cavity surface polishing 

→ adding pouring system and cooling system, etc. 

→ mass production injection mold.