Marusen Craft Co., Ltd.
Marusencraft
Method
Molding Methods
Molding Methods and Products
Available from Marusen Craft
The performance of FRP depends greatly on the accuracy of the molding technology and the suitability of the process selected.
In particular, if impregnation, forming, curing, and other processes
are not properly controlled,
it is difficult to achieve the mechanical properties and dimensional accuracy specified in the design.
We primarily employ the molding methods described below,
focusing on understanding material behavior and optimizing process conditions at every stage.
This enables us to manufacture highly reliable FRP products that meet the required performance specifications.
HLU
Hand Lay-Up
Hand lay-up is a fundamental FRP molding technique and a highly flexible process suited to large products,
low-volume production, complex-shaped components, and one-off prototypes.
Although its use has declined with the spread of automated molding technologies,
its practical advantages are expected to sustain continued demand.
Japan has a national skills certification system for this process,
with successful candidates officially certified as Grade 1 or Grade 2 Hand Lay-Up Technicians.
We primarily handle large and complex FRP products
and can produce prototypes and molded parts using hand lay-up and RTM molds.
Our matrix resins include
unsaturated polyester, vinyl ester, epoxy, and phenolic resins,
while our reinforcement fibers include
glass, carbon, basalt, and alumina fibers,
allowing us to meet a wide variety of performance requirements.
Molds (HLU and RTM), large tanks, large L-shaped domes, containers, and railway vehicle components
Example Applications
RTM
Resin Transfer Molding
A preform is placed in a mold and the mold is clamped,
after which resin is injected under pressure to impregnate and cure the preform.
The following three material properties have a major influence on molding quality:
• Permeability: the ability of resin to penetrate uniformly through the fibers
• Drapeability: the ability of the reinforcement to conform closely to the mold geometry
• Compressibility: the ability to compact the fibers to the specified fiber volume fraction (VF)
Relatively thick products in particular
carry a risk of unimpregnated areas, or dry spots.
For this reason, post-molding quality verification
using non-destructive testing such as ultrasonic inspection or X-ray CT is recommended.
Medical device components, vehicle components, and electrical insulation components
Example Applications
LRTM
Light Resin Transfer Molding
A preform is placed in the mold and the mold is closed under vacuum pressure.
Resin is then injected while a separate vacuum circuit keeps the mold cavity under vacuum.
Because resin can be injected at low pressure, a flexible resin mold can be used for the upper mold.
Once mold-making expertise has been established,
LRTM can replace hand lay-up at lower cost,
improving both production efficiency and quality.
Machine covers, water-treatment components, railway vehicle components, and medical device components
Example Applications
VIM
MARCO Process
Commonly known as a resin draw-up molding process,
resin is injected from the bottom of a resin mold at low or positive pressure,
while vacuum is applied from above to impregnate and cure the preform.
We apply this technology
to the mass production of ring-shaped components using metal molds
and have extensive experience in this field.
Pressure-vessel components
Example Applications
VARTM
Vacuum-Assisted Resin Transfer Molding
Also known as resin infusion, this process generally involves
placing a dry preform or non-crimp fabric in the mold,
installing resin-feed lines, vacuum lines, and auxiliary materials,
then applying a nylon-film vacuum bag and infusing the resin.
This versatile process can be adapted in many ways and is categorized as an out-of-autoclave (OoA) process.
Building on extensive prototype and development experience, we have established proprietary expertise
covering a wide range of resins, from room-temperature-curing to high-temperature-curing systems.
We also manufacture molds and can integrally mold sandwich panels using honeycomb, ROHACELL®, urethane foam, balsa, and other core materials.
Wind-turbine components (blades, nacelles, and spinners), radomes, railway vehicle components, electrical insulation components, and sandwich panels (flat and curved)
* For mass production, reusable silicone vacuum bags eliminate disposable bagging waste, making this a more environmentally responsible molding method.
Example Applications
VB
Vacuum Bagging
In vacuum bagging, prepreg is normally laid up,
vacuum consumables are installed, the perimeter is sealed, and a nylon film or similar material is used to form the vacuum bag before curing in an oven or autoclave.
For sports-related components, we use
carbon-fiber (CF) and glass-fiber (GF) prepregs,
which are laid up and then oven-cured.
We can also apply a two-step process using an interleaved resin film
to manufacture honeycomb sandwich panels.
Sports equipment components, medical device components, and sandwich panels (flat and curved)
Example Applications
VACP
Vacuum-Assisted Cold Pressing
After a preform is placed in the mold,
resin is introduced and the mold is closed under vacuum pressure, causing the resin to flow through the preform in this closed-mold process.
The vacuum improves resin impregnation
and suppresses air entrapment for more consistent quality.
Drawing on extensive experience with this technology,
we efficiently produce high-quality molded parts even with complex geometries.
Machine covers and other components with relatively simple geometries
Example Applications