The hottest new molding technology of composite ma

2022-08-16
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New composite molding technology and new mold material

nickel steel alloy invar has always been the preferred mold material for large quantities of composite parts in the past, because its durability and coefficient of thermal expansion (CTE) are indeed similar to those of reinforced plastics used for parts molding. However, with the increasing size of composite parts, the overweight of metal molds has brought new challenges to processing plants. Therefore, many manufacturers turn to composite tools to reduce weight and avoid higher nickel steel processing costs

Bob Lacovara, former technical director of the American Association of composite manufacturers (ACMA), said that more and more molds began to be manufactured with epoxy resin and carbon fiber, especially in occasions with high requirements for size and mold stability

"epoxy resin is slightly more durable than polyester resin, and they have high thermal stability. Therefore, epoxy resin is a good choice in applications requiring high temperature curing." Lacovara said. He was recently selected as an ACMA standout

abandon the model

"I think the latest and greatest innovation is the NC machining of direct molds, which eliminates the steps of manufacturing models in the process of mold production." He said, "because the materials used in the model have some limitations, and the surface quality requirements of components are also a problem."

"the next step is to develop a technology that can obtain A-level surface, so as to greatly reduce the processing cost and time." Lacovara said. Lacovara heads a consulting firm called convergent composites

mollicam, a mold manufacturer in Florida, USA, uses a five axis CNC (computer numerical control) machining center to produce models, prototypes and molds for the composite industry, which can process direct molds for temporary and limited production molds. The factory has four CNC machine tools for the production of molds, hulls and other composite parts

one of the direct mold projects comes from the watercraft manufacturer wellcraft marine

"if the customer wants to test a new hull design, he needs a mold to produce a part to actually drive in the water." Jeremy Mollica, President of mollicam, said, "if the part works well, they plan to use the mold to produce another part and convert it into a glass fiber master mold. Then they will make a production mold."

"direct molds are based on the needs of customers. We often process direct molds, especially disposable parts. We have participated in many projects in theme parks and the boat industry. Art works and sculptures are usually disposable projects." He said

mold materials are determined according to the materials used by customers to manufacture parts

"if it is a one-time project and the surface quality requirements are not very high, we will directly process it into foam, and then apply a layer of sealant on the surface." Mollica explained, "if we only produce one part, but have high requirements for surface quality, we will process the size of foam a little smaller, then attach a layer of glass, and then spray a layer of Engineering putty on the glass laminate. We will make the final surface a little higher, and then process it to make it lower."

"when manufacturing moulds for a large number of 20 or more parts, it is best to produce a model first." Mollica said, "with the model, we can produce a sufficiently strong mold. If the mold needs to enter the autoclave and be heated frequently, we need to machine the model to make the mold meet the high temperature requirements."

CNC machining based on computer data is very accurate. The machinable composite die plates and plates used in the production of master molds come from different manufacturers. These products range from polyurethane foam, synthetic epoxy resin to carbon foam. After these materials are bonded together, they are processed into a specific mold shape, then sealed to prevent the penetration of laminated resin, and coated with bismaleimide or epoxy laminate before machining

Janicki industries, a leading American composite mold manufacturer located in Washington state, has developed one of the world's largest CNC grooving machines. The maximum shell size of the machine can reach 30.5 × six × 2.4 meters

in the process of preparing traditional molds, mollicam uses a five axis CNC grooving machine to process a hull model

the mold is made according to this model

Mollicam factory is using five axis CNC grooving machine to process direct molds for the hull

large Aerospace molds

Northrop Grumman aerospace system manufacturing and Development Engineer Bob vale said that the fuselage structure continues to increase the amount of composite materials, and also becomes larger and more complex. Last year, at the society of manufacturing engineers (SME) composite mold conference held in San Diego, California, he mentioned that Northrop has long regarded bismaleimide (BMI) as the best composite material for mold processing, and has continued to succeed in aircraft manufacturers' projects

northrop has designed and manufactured more than 600 BMI molds. Vale said that usually, these molds, which weigh only 40% of nickel steel molds, go through more than 700 high-pressure heating cycles at a temperature of 150 ℃ and a pressure of 100 psi. One of the difficulties in using composite materials to manufacture Aerospace molds and lay mandrels is to meet strict material requirements

these specific requirements include: being able to withstand at least 500 cycles; The glass transition temperature is above 204 ℃ to meet the curing temperature requirement of 176 ℃ under the condition of high production rate. These molds must also be cost-effective, UV resistant, wear-resistant, and resistant to environmental aging factors while maintaining high dimensional integrity and stability

the maximum shell size of this advanced super large CNC grooving machine developed and used by Janicki Industrial Company is 30.5 × six × 2.4 meters

formashape is one of the largest suppliers of composite materials and components in North America.

this mold is specially manufactured for light RTM process

Larry Carver, President of Carver composite mold company in Lynnwood, Massachusetts, said that the trend of aircraft manufacturers to increase the use of composite materials has promoted the development of BMI and other advanced materials, opening up a new path for composite mold. At the SME composite mold conference, Carver said that the original intention of Northrop's attempt to adopt epoxy composite mold was to meet the thermal expansion coefficient requirements of carbon fiber components in f/a 18 a/b hornet fighter

carver said that today, Northrup uses about 59% of carbon fiber materials in its Super Hornet. He proposed a material concept with carbon foam as the core material and bmi/carbon fiber as the skin to manufacture composite molds for large composite components. He believes that BMI, carbon fiber and carbon foam are very suitable for manufacturing large laying mandrels. In the manufacturing of composite skin, automatic laying and manual laying of fibers can be carried out

bmi based material

hexcel's hextool M61 is produced by hexply M61 BMI resin, which is very suitable for high temperature and high pressure processing. It contains an irregular unidirectional carbon fiber prepreg layer. Hextool can be used as a multi-layer quasi isotropic hand paste material and processed to tight tolerances with CNC machine tools. This material is very suitable for the high-pressure curing process at ℃. It can be repaired, has stable size, and can maintain a complete vacuum. It has no effect even after more than 500 curing cycles

hextool molds are lighter and more energy-saving than those made of steel or nickel steel, and have tighter tolerances than standard composite materials, so they are more cost-effective. The company also provides an epoxy resin based mold hextool M81, which is composed of quasi isotropic prepreg felt, which is thicker than the standard composite mold. The mold prepreg is first cured at 120 ℃ for 6 hours, and then cured at 204 ℃ for 2 hours. It is specially used to produce 120 ℃ cured parts

duratool 450 bmi/carbon fiber mold prepreg of Cytec engineering materials company is a high-performance mold system, which can work continuously at 190 ℃ and carry out short cycle at 204 ℃. After the initial high-pressure curing process, the die laminate is separately post cured after demoulding. Practice has proved that the prepreg will not age after more than 100 high-pressure cycles at 190 ℃. Other mold prepregs provided by Cytec also include cyform 7620, a medium temperature curing epoxy system that can bring maximum adhesion and long service life to large and difficult to lay molds

Advanced Composites Group (ACG) recently launched two BMI substrate systems, HTM 556 and HTM mold prepreg, providing excellent processability and high temperature resistance for the structural mold and component market. It is said that these two materials have higher strength and no micro cracks, which can improve the vacuum integrity and prolong the service life of the mold. Htm 556 can be used continuously at 200 ℃, while HTM can withstand the thermal cycle of 250 ℃

a composite mold made of cfoam carbon foam from touchstone research lab for lightweight composite racing seats

raku-tool series epoxy and polyester boards of Rampf tooling company can be made into molds with good dimensional stability and high temperature resistance

the company also has LTM series of low-temperature curing epoxy based prepregs, which can be post cured and use low-cost low-temperature master molds to produce high-temperature resistant lightweight composite molds. Another product of ACG dform deformable composite mold prepreg is said to be a labor-saving prepreg technology, which not only has the consistency of short fiber molding materials, but also has the directional characteristics of high-performance long fiber composites

amber composite company provides HX series low temperature epoxy mold prepreg. For example, hx42 has a 5-day out of warehouse life, and the terminal service temperature reaches 200 ℃. Another product of this series, hx90n, uses nano modified epoxy resin, which has better surface smoothness and mold surface quality. It is said that the prepreg not only has minimal thermal expansion (lower% than other materials), but also has excellent surface quality and high end use temperature

Machined plates

grafoam carbon foam of graftech international can be successfully used as a core material in the manufacture of composite molds. The foam is made of isotropic carbon, which has CTE similar to carbon fiber composites and very high temperature resistance. ACG grafoam fpa-20 carbon foam mold system developed by ACG and graftech has the characteristics of high compressive strength, light weight and stable size, so it is unnecessary to use master mold. Plates used to manufacture large structures are available in a variety of sizes and densities

cb1100 ceramic mold plate provided by ACG has high temperature resistance and low coefficient of thermal expansion. It is said that it can produce very accurate and stable molds. This ceramic plate can be compatible with ACG's LTM epoxy mold prepreg and HTM BMI mold prepreg. After being bonded together, it is processed into the core of the mold, and then the carbon fiber skin is laminated, without the use of a master mold. Since the skin is fully supported by the ceramic core, there is no need for another supporting structure; Moreover, ceramic materials will not absorb water, so there is no need for drying or ventilation process

touchstone research laboratory's cfoam is a structural material made of coal, using its proprietary low-cost high-pressure process, which can be used in many applications, including composite molds. The material can be made into a variety of structural forms, showing a variety of surfaces, from thin sheets to approximate three-dimensional parts, and can be made according to the size of components and

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