Composite Terms

MIL’S, the designer and builder of vacuum-related systems has put all its know-how to work to develop a range of units and accessories designed to meet the specific needs of the composites industry. We have the widest range of vacuum units on the market to tackle processes such as infusion, vacuum moulding and R.T.M light (resin transfer moulding).

Whether you choose a mobile or fixed solution, our range helps you to produce the most complex parts whether you are working in the car industry, sanitary accessories, and aeronautics or water sports.

The production of indoor furniture for boats often requires vacuum lamination. The theoretical forces of 1 bar vacuum (maximum vacuum) exerts a pressure of 10 tonnes/m2.This force is applied using a stretch plastic film which assumes the shape of the mould and compresses the various layers.

R.T.M LIGHT

Polyester is used for its excellent mechanical properties and its resistance to corrosion. The R.T.M Light process consists of producing a composite part in a wooden or polyester mould. The Glass fibre is positioned in the mould.

The maximum vacuum ensures that the mould closes perfectly. The resin is then injected into the periphery using a machine at low pressure (1 to 2 bar) and under a controlled vacuum applied to the centre of the mould to ensure resin flow. Our COMPOSITVAC unit has been designed to perform this specific process. Its two vacuum levels are controlled by the operator to ensure accurate polymerization times and speeds for the different resins. The process is used to produce small to medium series of parts at low cost.  The vacuum technique reduces production time by 40% compared with standard contact bonding. The use of a closed mould means that a vacuum unit with an active carbon filter fitted to its discharges can evacuate any styrene vapour, ensuring that workshops comply with the new European regulations on volatile organic compounds (VOC) The current admissible rate of VOCs is 215g/m³ and is already lower in other European countries. This solution can also be implemented using a centralized system. In this solution an INDUSVAC unit is installed supplying maximum vacuum to the entire workshop. Each workstation is fitted with its own independent receiver controlled by a high-precision vacuum gauge to regulate the vacuum required for the resin to impregnate. The advantage of this concept is that each workstation can operate at the vacuum level appropriate to the part it is producing without the other workstations being affected.

THE VACUUM INFUSION PROCESS USES 2 LEVELS OF VACUUM

The vacuum infusion process uses 2 levels of vacuum, a maximum level to apply the plastic film to the parts to be bonded, and a second level to draw the resin from the pails and make it flow uniformly over the entire surface to be bonded. This tried and tested technique makes it possible to produce half the deck of a 30m boat in a single operation. The user sets the precise degree of vacuum required which is controlled by a motorized valve. The motorized valve opens and closes in line with consumption, ensuring that the resin impregnates regularly.

“HIGH TECH” INDUSTRY

The lightness and strength of carbon fibre have made it a highly prized material, ideal for manufacturing advanced high technology parts. It is used to make parts such as chassis, ailerons and spoilers for formula 1 cars, tennis racquets, racing-car silencers, aircraft parts and racing skis.

These parts are treated at 140^oC in an autoclave where the vacuum assists the compacting of successive layers.  The heat gradually frees the prepreg and the vacuum ensures its uniform distribution. In this configuration the vacuum unit is provided with 2 pumps because, given the cost of the parts being produced, the presence of a stand-by pump is essential,

P.E.T TECHNOLOGY: INNOVATIONS IN THE VACUUM SECTOR

Our new COMPOSITVAC unit uses the latest polyethylene (PET) technology receivers. In order to make the RTM light process as accessible as possible; this process matches the budget of the smallest business. Again the user can adjust the two vacuum levels.

EXPERTS IN VACUUM TECHNOLOGY FOR RAPID PROTOTYPING

Before launching serial production, manufacturers often need a few prototypes of a quality similar to that of the definitive parts. However, they do not want to invest in expensive equipment to produce these prototypes. And this is where the “rapid prototyping” system comes in. The part is first designed using CAD/CAM 3D Software which uses lasers to control the creation of a cavity block in liquid resin: this technique is known as stereolithography. Using this cavity, the company can produce the part in silicone, resin or hot wax using a vacuum casting machine.

Girovac has designed a universal machine to meet these ever-increasing needs, The advantage of this type of system is that it can mix 2 components under vacuum in order to eliminate air bubbles and give absolute uniformity. The mix can then be transferred under vacuum into the mould. The latest machine MIL’s have designed is a vacuum kneader that enables a 20 to 50 kg resin or silicone pot to be degassed to manufacture large parts. The raw materials can be kneaded in the pots the manufacturers supply them in, thereby eliminating a series of handling operations and the risks involved in repeated weighing. Certain automobile parts require 300 kg of silicone to make a single prototype part.

Our long experience and know how in the vacuum technology sector have enabled us to produce degassing chambers that can withstand the enormous mechanical stresses involved in vacuum technology.