System supplier and complete solutions
When Ljungby Komposit was established during 2009 we took over the necessary production equipment from Polytec Composites.
One example is our robotic water cutting equipment with a work area of 3500 x 2000 mm. It is specially adapted for parts with a large surface area, such as larger injected body parts (VARI, RTM) or volume products in SMC.
Another example is a hydraulic press with a press force of 1400 tonnes with a table size of 2500 x 2150 mm and an opening of 1900 mm. Everything to achieve cost effective production.
Our long industrial experience has provided us with a broad contact network, which has been further extended during recent years in order to strengthen our role as system supplier of complete solutions.
Efficient processes with great flexibility
The manufacture of parts, components and products via different composite solutions is an area that is rapidly growing today.
Despite this, the level of knowledge is relatively low in general, perhaps due to industrial and design engineering traditions, but also because composite is another way of thinking and solving problems.
There are many different types of fibre, many different plastics, different curing methods, different forming technologies, different ways of producing tools, etc.
In every situation it is important to evaluate, calculate and choose the combination of material and method depending on the objective. And there are often many unexpected approaches for solving or circumventing specific problems.
This is one of Ljungby Komposit’s absolute strengths.
Vacuum Assisted Resin Injection (VARI)
The method, also named RTM Light, means that dry fibres are laid up in a tool (mould) which is then closed. Mould halves that are produced in composite material are used in this method.
The matrix (resin) is injected into the fibre-filled cavity using a pump, which simultaneously mixes the two components of the thermosetting plastic. At the same time the air in the cavity is evacuated using a vacuum pump in order to provide optimal distribution of the resin inside the shell.
The advantage of VARI is that tool cost can be kept down considerably compared with stable mould halves in metal.
Usually the gelcoat is sprayed on the tool surfaces (the front and sometimes also the rear) before the fibres are laid up in the tool. By using coloured gelcoat it is possible to replace painting. The gelcoat can be mixed in any colour.
Resin Transfer Molding (RTM)
RTM is equivalent to VARI in terms of the process, but instead of composite moulds, solid tool halves in metal are used. This provides better control of material thickness and measuring accuracy. Another advantage is that the metal tool can be tempered. By these means the cycle time can also be reduced.
Sheet Mold Compound (SMC)
This means that pre-impregnated fibreglass, so-called prepreg, usually with polyester, is supplied ready on rollers for application in production. The material is cut in accordance with a specified pattern and is then pressed between heated steel tools under high pressure.
SMC pressing is a very stable process, where it is easy to monitor/log each cycle if required. The process results in a surface that is easy to paint and shape stability is good. Other fibres can be used, but then under the denomination of “hot pressing”.
Glas Mat Termoplastic (GMT )
Metoden innebär att förtillverkade plattor med glasfiber och oftast polypropylen värms upp i en ugn, placeras i tempererade metallverktyg och pressas ut under högt tryck och hög slutningshastighet.
Processen är snabb och cykeltider mellan 25 till 60 sekunder är vanligt. Processen kräver hög volym för att bli lönsam.
This method involves panels that are prefabricated in fibreglass, and usually polypropylene, being heated in an oven, placed in tempered metal tools and pressed out under high pressure and high closing speed.
The process is fast and cycle times between 25 to 60 seconds are common. The process requires high volumes to be profitable.
Hand lay-up is primarily suitable for short series and prototypes. It is an open process with low tool investments.