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Overview

- Features of each Forming method -

Injection	Melted resin is pushed into mold by high pressure then cooled and solidifies.	・Short forming cycle ・Enables high-volume production. ・Expensive facilities are necessary.
RIM	2 materials are mixed and poured into mold to provoke polymerization reaction then solidify.	・Forming pressure is low. ・Large/complicated shape can be formed. ・Mold is inexpensive. ・Suitable for low-volume production.
Blow	Tube-shaped material is put into mold then air is blowed to form.	・Bottle-shape is possible to form. ・Suitable for constant wall thickness.
Vacuum	Sheet-shaped material is heated and pushed onto the mold to form. The mold consists of only one side of male-femail pair.	・Forming pressure is less than atmosphere. ・Inexpensive and large product is possible. ・Facilities including mold are inexpensive. ・Suitable for constant wall thickness.
FRP	Glass fibers and resin are sticked onto a model to react at normal temperature then solidified.	・Large/complicated shape can be formed. ・Mold is inexpensive. ・No need of expensive facilities. ・Forming cycle is extreamly long.

What is RIM forming?

RIM is short for "Reaction Injection Molding", meaning a forming method where 2 materials which are low-molecular, low-viscosity and reactive are pushed into the space in the mold to react in high pressure resulting in producing high-molecular resin.

Features of RIM Forming

RIM has the following features compared to injection forming in thermoplastic forming technology.

Forming temperature is relatively low. (Material temp. is 20-50 degrees centigrade and mold temp. is 40-80.) Mold and press machine can be small as the pressure in the mold is low. (3 - 5Kg/cm2) As low-viscosity materials flow smoothly in mold, large and complicated shape can be formed. Products with bosses and ribs will have smaller and fewer sags. Easy to form thin and complicated shape because the materials are pushed into mold with pressure. As wide variety of materials can be used, it is easy to adjust the hardness of the products.

Comparison to Other Methods

Handling of RIM Materials

Genaral Handling	Handling at Proto Co., Ltd.
Polyol with long chains (bifunctional) Chain Extender (bifunctional) Catalyzer Foam Conditioner Foaming Agent Coloring Agent Isocyanate	Polyol with long chains (partially trifunctional) Chain Extender Cross-linker (trifunctional) Catalyzer Foam Conditioner Foaming Agent Coloring Agen Isocyanate

In order to give heat resistance, generally high functional material is used. However, the product apts to be hard and fragile.

Internal Structure of RIM material

Bifunctional Material	Bifunctional/Trifunctional Materials
Reacted with isocyanate, molecules extend linearly. The structure is flexible.	Putting trifunctional material into bifunctional, bridges are made between linear molecules. The product becoms rigid and heat resistant. However, the more bridges, the harder the product is.

Reaction Control

To improve heat resistance above-mentioned methods are to be considered. As there are long and short molecules, each reacts differently. In order to have constant reaction, material temperature should be controled properly, the materials should be mixed strongly and poured into the mold quickly. We have to be careful to the items below to get stable products.

compounding ratio material temperature mold temperature (constant temperature distribution) discharge pressure nozzle diameter gate structure (balancing with discharge rate)

Manufacturing Process

Paintless Process at PROTO Co., Ltd.

Adopting the paintless process, we have attained 30% cost down compared to conventional manufacturing method!

PROTO Co., Ltd.

1117 MUJINAZUKA, ORA-MACHI,   ORA-GUN, GUNMA 370-0613 JAPAN 　　■ TEL +81-276-60-5322 　　■ FAX +81-276-60-5323