Rapid prototyping

The Rapid Prototype model, also known as the R.P., refers to the first or first batch of samples before the plastic mold is cut in the new product development stage.

The production process of the Rapid Prototype model is mostly manual, so it is widely called the “hand model.”

The Rapid Prototype is the first step to verify the viability of the product. It is the most direct and effective way to find the product design defects to improve the defects until the model has no problems.

Small batch tests are often required to verify the assembly of the product in future mass production.

Rapid prototyping is a layer processing technology and a kind of synthesis technology of CAD and CAM.

Unlike traditional machining, it can produce complex shapes with micro characteristics of the workpiece and dramatically reduce design time and costs.

Rapid prototyping has the following important features:

•   It could create any complex 3D geometry entity. Due to the principle of discrete / stacking forming can simplify the very complex 3D manufacturing process to a 2d process. The more complex the part is, the more obvious it displays the superiority of RP technology. The RP technology is particularly suitable for complex cavity and complex surface manufacturing.
•   The renewed part design and processing can be quickly obtained by modifying or restructuring a CAD model for just a few hours, displaying the outstanding characteristics of rapid manufacturing.
•  Without any special fixture or tool, it could complete the complex manufacturing process for rapid tooling and prototype parts.
•  Rapid prototyping technology has realized the two advanced targets of mechanical engineering: 1.the integration of material extraction (gas, liquid solid) process and manufacturing process, 2. the integration of design (CAD) and manufacturing (CAM).
•  Combined with Reverse technology, CAD, network, virtual reality, it becomes a powerful tool for new product development.

Purpose:

1. Appearance: It is mainly used to test the feasibility, market research, and exhibition and judge the mass production process such as product size, color, material, cost evaluation.

2.Structure: It is mainly used to check the internal assembly structure of the product, material strength analysis, performance testing, cost evaluation, new product investment, etc., thus greatly reducing the risk of direct mold building.

3. Vacuum Casting: It is mainly used to test new products in small batches to improve the feasibility of mass production of new products and can be used for new product investment.

Therefore, rapid prototyping technology plays an increasingly important role in the manufacturing field and will impact this industry.

main application:

• Design and functional verification 

RP technology can quickly convert the CAD model into a real part, and this process can easily verify the rationality of the design idea and the product structure.

The Traditional method needs to complete a whole process from the drawing, process design, tooling to manufacturing with a long time and high cost.

Direct production without verification maybe invites a great loss for the initial design fault.

•  Verification for manufacturing, assembly, inspection, and market promotion

The design and manufacturing verification of automotive, satellite, and missile should adopt the RP method initially, which will greatly reduce the system design and manufacture difficulty.

For complex parts, The R.P. can be used to determine the optimum process of RP.

In addition, it is an effective communication way from design to manufacture, likes providing a few product samples for marketing promotion.

It has become a concurrent engineering and agile manufacturing technology approach.

• The direct production of small batch and special complicated parts

High strength engineering plastics can be directly and quickly used for plastic parts fabrication. And the complex metal parts could be directly made of rapid casting metal

• Rapid tooling manufacturing

RP prototype could be used for manufacturing various kinds of fast toolings, such as alloy mold, silicone mold, metal injection mold for the small-batch parts fabrication to replace the ready products.

Application areas:

• Communication products,
• Digital products,
• Household appliances,
• Medical equipment,
• Aviation
• Vehicles,
• Car audio,
• Instrumentation,
• Toys and gifts.

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Prototype Molds

In order to evaluate a newly developed shape, prototype molds are needed to make samples of the new product that can be observed visually and/or touched. The stress and wear on molded samples is much higher than on hand-made (machined or assembled) models. Additionally, a simulation may be less cost-effective (and more accurate) than a physical experiment. Injection molds can be made of mild steel, aluminum, or plastics (epoxy), as long as they are sufficiently strong and resistant to the high pressure and temperature of the injection process, since it is only necessary to mold the overall shape of the product, not the productivity of the mold.

In most cases, close tolerances are not required. The surface appearance (polish, engraving, flashing, etc.) is generally not an issue. The molded sample will just need a little longer to cool before it can be removed from the mold; therefore, cooling channels are not required. A mechanism for ejecting the film is also not required in many situations. You may not need much more than a few simple ejector pins, which are angled so that they can be manually pushed to eject the product at the parting line.

By using loose inserts in the mold, the product can be produced with features such as internal or external threads that can then be unscrewed by hand. You can also use loose inserts for odd shapes on product sides that would otherwise require side cores. The sidewalls could be machined with holes and simple openings after the molded piece has cooled. The above features can be removed from the prototype mold to simplify the stack and to reduce cost.

It may be feasible to mount the stacks in a common mold shoe if prototypes are frequently needed, thus reducing costs even further. For edge gating, a sprue and short runner system could be used, rather than a direct runner to the product. Once the gate has been cut manually, it will be reinstalled.

Experimental Mold

The purpose of this mold is different from a prototype mold: it’s intended for determining how the plastic will behave when it’s injected into a newly developed product. You can use some of the above-cited shortcuts to save money, but generally, a single-cavity molding would be closer to the original mold.

Gates need to be located in accordance with plans during production. You can use the mold to determine where and how to place the gates for a certain product. Molds must normally have the correct appearance. The flow of plastic is altered in thin walled products owing to finishes.

It is more important to maintain a stable mold temperature with some cooling as opposed to cooling efficiency in a production mold. For reducing the possibility of operator-caused variations in ejection (and cycle) times, it is recommended that manual product removal be replaced with an ejector mechanism instead.

Coupling of Prototype and Experimental Mold

Usually this applies to molds that are inexpensive to create but nevertheless will be manufactured in large numbers to test for market acceptance. In such cases, full automation of the mold is desired, but achieving maximum efficiency in molding is not necessary, for example through better cooling, a better runner system, etc., or by adding special finishes or engravings. Moreover, shrinkage conditions can be determined using such molds.