Why do engineers still adhere to the rapid injecti

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Why do engineers still adhere to the rapid injection molding process?

most people think that 3D printing leads to too little oil pressure, which is a good substitute for injection molding that requires mold opening. Is this really the case? At present, 3D printing has brought great impact to the manufacturing industry. Those hand pieces that once cost hundreds of dollars and took several weeks can now be designed in the morning, printed at night and delivered to customers the next morning

some companies are already using 3D printing technology to manufacture injection molds. It is no longer necessary to spend months waiting for the manufacturing of molds that can be used for production, or a large amount of money invested in modifying molds due to downstream design changes, or uncertainties at the production level. Whether it is mold verification or small batch production of injection molded parts, it can quickly 3D print molds. If there is a problem with the mold or the design needs to be modified, print another one and repeat the verification or production

3d printing

there are some reasons for these views. The plastic 3D printing injection mold is a bit like the plastic shed in our backyard. It is cheaper than the metal shed. The plastic shed is built quickly and performs well under low load. But if there is too much snow, they will break into a house of debris

3d printing mold has its own place, and some enterprises have been successful in the application of 3D printing mold. Supporters say 3D printing molds are 90% faster and 70% cheaper than traditional mold processing methods. This may be true in some cases, but it is important to understand the advantages/disadvantages of metal molds over 3D printed plastic molds

3d printing

real mold, real fast

rapid manufacturing company protolabs has begun to produce rapid mold injection parts since 1999. The molds it provides can be used to manufacture parts made of engineering plastics, metals, liquid silica gel (LSR) and other materials. The mold is mainly machined from aluminum (in some cases, steel) materials, which can process several to 1000 parts, and the delivery time is days

its industrial 3D printing services include light curing (SLA), selective laser sintering (SLS) and direct metal laser sintering (DMLS). Printable materials include thermoplastic materials like polypropylene and ABS, industrial grade nylon and metals (such as stainless steel, aluminum alloy and titanium alloy) that should be used in the experimental machine according to the requirements of the manual

since there is such a large range of processing capacity, why not directly print the mold, but machine the mold

mold manufacturers should be vigilant

protolabs engineers have been considering printing molds, but after 16 years of rapid tooling business, some reasons still force them to adhere to the reliable rapid injection molding process:

01 surface quality

3D printing processing parts layer by layer, which will lead to the step effect on the product surface. There are similar problems with directly printed molds, which need machining or sandblasting in the later stage to eliminate these small, toothed edges. In addition, holes smaller than 1mm must be drilled, larger holes need to be reamed or drilled, and thread features need to be tapped or milled. These secondary processes greatly weaken the speed advantage of 3D printing molds

02 size factor

if you want to design a skateboard or plastic toolbox, 3D printing mold may be no problem. The size of parts is limited to 10 cubic inches (164 cubic centimeters), which is roughly the size of grapefruit. And although the accuracy of current additive equipment is very high, it is still unable to compare with machining centers and EDM equipment. The cavity precision of the latter is usually up to 0.003 inch (0.076mm), and the part volume is up to 59 cubic inches, which is roughly 6 times the volume of 3D printing parts

03 high temperature environment

in order to ensure good material flow performance, the injection mold needs to be heated to a very high temperature. Aluminum mold and steel mold usually experience 500F (260 ℃) or even higher temperature environment, especially in the processing of high-temperature plastic, cleaning the dust and sundries in the electrical box, such as PEEK and Pei (ULTEM) materials. It is easy to produce thousands of parts with these metal molds, and they can also be used as transition molds before the final mass production molds come out. Mold materials made by SLA or similar 3D printing process are generally photosensitive or thermosetting resins, which are cured by ultraviolet light or laser. Although these plastic molds are relatively hard, they are destroyed very quickly under the thermal cycle of injection molding. In fact, 3D printing molds usually fail within 100 times of use in mild environments. High temperature plastics such as polyethylene and or styrene. For glass filled polycarbonate and high temperature resistant plastic, even only a few parts can be produced

04 comparison cost

one of the original reasons for using 3D printing molds is their low cost. The production level machining mold cost is generally $20000 or more, which means that the printing mold with $1000 is similar. However, this analogy is not fair. The evaluation of print mold Chen usually only considers material consumption, and does not consider labor, assembly and installation, spray system and hardware. For example, protolabsd's aluminum mold costs $1500 and can be used for production. If more parts need to be produced? With 3D printing molds, you need to reprint and assemble machines to test new molds every time you produce a product. On the other hand, regardless of the plastic used, aluminum molds are usually in good service when producing 10000 parts

05 product design

the principle and practice of traditional injection mold manufacturing has a history of more than a century, and the industry has studied it thoroughly. 3D printing mold is very new. For example, the draft angle must be greater than or equal to 5 degrees to meet the requirements of most aluminum molds. Plastic mold injection plastic parts are facing challenges, and the number and installation position of plastic mold thimbles need extra care

the friction and wear testing machine industry is depressed for various reasons

in terms of increasing the wall thickness of the mold cavity and reducing the pressure, plastic molds (especially high injection temperature) are more flexible to some extent. The gate design is also different, and tunnel and dot gates should be avoided. The direct gate, sector gate and wing gate should be increased to 3 times the normal size

the flow direction of polymer in the printing die should be consistent with the 3D printing line to avoid high filling caused by viscosity and low pressure. The cooling system can improve the service life of the mold to a certain extent, but it will not significantly reduce the cycle times of the printing mold, because the heat dissipation capacity of the plastic mold is not as good as that of the aluminum mold or the steel mold


although rapid aluminum mold has many advantages, 3D printing mold will still play an important role in some cases. For manufacturers who have 3D printers and have enough time to explore how print molds work on injection molding machines, maybe they think they should print molds directly

of course, the mold designer must understand how to make functional molds, and the redesign and production of molds will cost a lot of money. Relevant technicians and equipment are also necessary - mechanical workers for mold sand blasting, thimble installation, injection molding machine operators, etc., because the settings of these parameters are very different from traditional molds

but wait -- why not use DMLS? Why not print the metal mold directly? DMLS uses lasers and precision optical devices to "paint" parts layer by layer on the fine metal powder bed. The completely dense commercial products produced by DMLS are widely used in the fields of aviation and medicine. Some people predict that in the future, aluminum and mold steel molds may be printed directly, which can provide ultra efficient conformal cooling channels, which will greatly reduce the injection time and prolong the service life of molds. To some extent, DMLS direct printing molds is slow and expensive, and is usually only used for very small and complex molds, or processing mold inserts that are difficult to manufacture by traditional machining methods

reliable measurement

in general, protolabs believes that it is best to use DMLS, SLA or other 3D printing processes to do what they are good at: printing parts rather than molds. However, if the following conditions are met, 3D printing injection mold will be a reliable alternative

1) for small batch and relatively simple parts, the product needs a relatively large draft angle

2) the tool and mold design team should be familiar with the design principles of 3D printing mold

3) have personnel and equipment for processing and assembling plastic molds

final design considerations. If you need the mold to be used for a long time, once the 3D printing mold has verified the rationality of the design, the next step is to use more permanent materials to make the mold, such as aluminum or stainless steel, because plastic molds are mainly used for small batch production. Because the design of 3D printing mold is different from that of traditional mold, a certain number of mold redesign and testing should be considered in the project time and budget

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