Epoxy impregnation: Cannon provides four winning tools!
The recent introduction of new Cannon technologies for the manufacture of Epoxy-based composites found an overwhelming response from the market. In addition to a significant number of low-pressure dispensing machines sold for the impregnation of the giant blades used for the eolic generators industry, Cannon have introduced three different impregnation systems based on high-pressure technology. A whole range of solutions is now available to respond to different needs and processes. Cannon supplies today the widest set of tools, including dispensing and mixing devices, preformers, presses, moulds, manipulators, ovens and controls.
Exactly two years ago, at Jec 2010 in Paris, Cannon launched their new high-speed RTM technology for Carbon-reinforced composites based on Epoxy resins. The new process, called ESTRIM (Epoxy Structural Reaction Injection Moulding) was making possible the industrial use of new, fast reacting Epoxy formulations developed to comply with the high productivity required by the automotive industry for their rising number of structural composite parts. Based on a series of integrated products - Carbon reinforcement handling systems, dedicated preformers, high-pressure dosing unit for Epoxies, multi- component mixing heads with different distribution methods, polymerisation presses and relevant handling systems of preforms and moulded parts – the ESTRIM process immediately received a positive response from the industry.
The possibility to cut almost by ten the curing time of a large moulded part – going from a traditional 30 minutes cycle of conventional RTM down to 3 minutes with ESTRIM – appealed OEMs and Tier 1 companies.
All the major players in the field of automotive composite parts visited during the past 18 months the Cannon R&D laboratory in Italy, either to run moulding tests with their own raw materials and moulds or to discuss directly the supply of equipment for their composite research and production departments.
New Solutions Are Now Available
The intense exchange of experiences matured during these visits stimulated the development of new methods for distributing the liquid Epoxy resins in the Carbon preforms.
In addition to the ESTRIM RTM fast injection technology, Cannon have developed two alternative methods for the impregnation of these more or less flat mats, both to be applied in open mould prior to the closing of the press:
· ESTRIM SL (Spray Laydown) – the Epoxy formulation is sprayed directly over the reinforcement, covering each square centimetre of mould with extreme precision, applying the desired amount of liquid resin where it is required by the part's geometry. This technique allows for the use of viscous formulations, characterised by low flowability: being directly deposited in-situ the liquid does not need to flow through the fibers, avoiding any distribution problem. A certain degree of part's three-dimensio- nality can be approached without problems, since the head can be tilted on a fourth axis over the vertical sides of a mould during the spraying operation.
· ESTRIM LL (Liquid Laydown) – the Epoxy formulation is laid over the Carbon mat in “liquid ribbons” of varying width, typically from 40 to 120 mm, perfectly impregnating the reinforcement without the minimum possibility of air inclusions in the moulded part. This technique allows for the production of very large parts, wetting uniformly the huge, almost flat preforms that characterise parts such as roofs, engine hoods, fenders and doors. The reactivity of the systems being controllable on a part- to-part basis, this system allows for a comfortable laydown time even for the largest pieces. As in the SL alternative, the formulation does not need to flow through the mould, therefore guaranteeing the most homogeneous distribution of liquid resin in the Carbon reinforcement.
We should not forget the development of new alternatives for the traditional high-pressure injection in closed moulds, performed with the original ESTRIM technology. The experiences matured in the past in the field of short-stroke polymerisation presses have allowed for at least three more injection methods:
1. We can inject the resin with a variable output, commanding the operation by reading the internal pressure in the moulds with a series of pressure sensors. The signal is sent to the unit's computer, that defines the new output value to be applied and commands the dosing pumps accordingly. The press does not move during the injection.
2. We can apply the injection-compression method, by leaving the mould partially open during the injection (still guaranteeing the tightness of the cavity) and applying the final compression stroke at the end of it.
3. We can inject the resin and apply a low clamping force on the mould, which will tend to open during the liquid-filling phase: at the end of it we apply the full nominal clamping pressure and compress the mould and its content.
Worldwide recognition ESTRIM SL, a new
Spray Laydown impregnation system, provides a calibrated distri- bution of Epoxies over Carbon preforms
Up to date, seven different contracts for these Epoxy-dedicated technologies have been signed with major manufacturers of parts and Raw Material Suppliers, in Europe and Japan, in the past 18 months.
The new E-System: an industrial success
The Cannon high-pressure metering unit E-System brings a new dimension to the field of Epoxy resin processing. The benefits of high-pressure mixing technology have been appreciated for many years. Highly accurate metering pumps give consistent outputs and mixing pressures to produce high quality mouldings. The progress occurred both in the mechanical and electronic fields during the last years, ensures that the E-System metering unit improves the efficiency and bring the main processing parameters under closer control.
The E-System machine is suitable for processing very high quantity of hardener and a smaller quantity of release agent in high pressure. As a matter of facts, precise metering of the low output is by means of a hydraulic plunger, driven by a dedicated hydraulic unit.
In particular, the release agent hydraulic cylinder is positioned as close as possible to the mixing head. The flow transducer installed between the dosing plunger and the mixing head allows the best metering by a closed loop system. Also base and hardener are metered in a closed loop system. Many advantages of the metering unit deserve to be highlighted: - Capacitive continuous level (for base and hardener materials) with four setting points: min/max alarm, start/stop filling. Accurate level controls are able to maintain a constant quantity of material in the tanks.
- Rust-proof treatment of the pumps - Stainless steel components for the hardener material
- Electrical cables and wires are fitted inside the machine frame, protecting them from dirt, allowing easy maintenance and giving a pleasant and tidy look to the machine.
- High-performances mixing heads, specifically developed for Epoxy resin; hardening treatment of the mixing head parts is done not only on the surface but also in the core.
- Each component can be calibrated directly at the mixing head, so calibration conditions and working conditions are the same.
- A special program “weekend cycle” is highly customizable, for controlling the sequences of the metering unit in order to avoid the component s stagnation when the machine is not in working cycle for long periods.
Precision is one of the main requirements for low output machines. Therefore the machine is provided with high-precision dosing pumps driven by closed loop motor (frequency inverter controlled).
Another important feature is the continuous recirculation of the chemicals near the mixing head. All these items together allow the
An important German manufacturer of composites parts, destined to the most prestigious car makers, purchased in 2011the first E-System dosing unit, with a LN 7/3 mixing head, and a vertical press, which is based on the 4-tie-bar design to give all- around access to the machine. The special short stroke design is selected to reduce the overall height, in order to install the equipment in the existing facilities at customers' site, without additional civil works. The moving platen is guided over the tie- bars by means of long guides for improved parallelism during its movement. The lower table is foreseen with the possibility to slide outside of the press center, to ease the loading-unloading tasks, maintenance and cleaning, as well as the mould change operations. These operations outside of the press working area are to the further benefit of the operator's safety.
A few weeks later one of the most important European producers of car interior plastic parts ordered a E-System machine with LN 7/3 mixing head, plus a dedicated, special pre- heating oven that guarantees at the same time a fast and well distributed supply of heat over the preform. This opportunity stems for Cannon from a number of positive experiences made in the 1990's by supplying dedicated ovens for GMT (Glass Mat Thermoplastic sheets in Polypropylene). The same heating concept – based on a mix of IR elements plus a forced circulation of air – was adapted to the new reinforcements and worked perfectly!
The Composites Developement Centre of a major Japanese car maker purchased an E-System machine with LN 7/3 mixing head and other special equipment for In Mould Coating, for a new development project for exterior body parts.
Two E-System machines with LN 7/3 mixing heads were ordered during 2011 by another major Japanese producer of car parts, one of which - a very large one! - will be developed jointly with a major German car manufacturer.
Momentive – formerly Exion, the world leading Raw Material Supplier for Epoxy formulations – after a set of positive trials in Cannon lab in Italy ordered a complete technology development line composed by one E-System dosing unit, one LN 7/3 head, two moulds, a vacuum-system and a clamping/polymerisation press for their German laboratory.
Another major European manufacturer of composites, supplying parts to the two most prestigious German car manufacturers, has granted to Cannon an important contract for a complete ESTRIM LL line, destined to produce a complex mix of composite parts that can reach the size of 1,200x800 mm. After the application of the liquid resin over its whole surface, the wet preform is handled into the press by a special frame and here it's laid over the very hot mould; the polymerisation occurs here at 130 °C, under pressure. At the end of the cycle the robot extracts the cured part and introduces a new wet preform to be pressed.
With the availability of proven industrial solutions for a vast range of needs, Cannon is today the ideal partner for complex – and also for simple – Epoxy processing projects for the composite industry. Once again, the concept of “One-Stop-Shop” for all the chain of equipment and tools can be the winning move for both parties!
ESTRIM LL, the new Epoxy Liquid Laydown impregnation system developed by Cannon for a very homogeneous distribution of liquids over Carbon preforms
Final touches to the new Cannon E-System, high-pressure metering unit to inject Epoxy resins on Carbon preforms
system to correctly maintain the set temperature within a close tolerance range.
The thermostatisation of the chemicals is a key point of the complete process. Cannon experience in managing these chemicals leads to use jacketed tanks, supplying temperature controlled oil by a thermoregulator (for resin and hardener). To maintain the required temperature heated pipes are used: coaxial pipes with internal chamber for the heated oil and traced flexible hoses, for the resin line.
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