Blades of a fan perform the major action and hence they must be manufactured with utmost precise. The manufacturing process involves various steps such as casting, welding, hardening etc.
Resin infusion technology
The main principle of infusion is to suck a resin into reinforced fibers using vacuum. The vacuum decreases the pressure at one end of the fabric, allowing atmospheric pressure to force resin through fibers. The distance and speed by which we can infuse a fabric will be dependent on
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- Resin viscosity
- Low viscosity allows the resin to travel more distance in the resin stack at given pressure gradient and it will create less drag in the induced stacks. This reduces the number of injection points needed on a large component and increases ease of infusion process.
- Permeability
- The permeability of a fabric is dependent on three factors, such as fiber diameter, fiber sizing and fabric type.
- The permeability is the ease of flow of a metallic or plastic material when it is in liquid form.
- Pressure gradient
- The pressure required to infuse resin stack is dependent on the atmospheric pressure and the performance of the vacuum pump.
- As the resin infuses into the fabric stack, the drag on the resin front begins to increase. The amount of drag is directly proportional to the volume of infused fabric stack and its permeability. So, when a given quantity of fabric stack is infused, the drag will be equal to the original pressure gradient, and the infusion will halt.
- Resin viscosity
- Infusion process
- The infusion carried by several steps which are to be performed by different equipments in the system. The parts are
- Resin feed station
- Sectional vacuum line
- Resin feed line
- Resin flow front
- Vacuum pots to collect resin
- The infusion carried by several steps which are to be performed by different equipments in the system. The parts are
- Process
- When the vacuum bag is fully pressurized and bridges are closed, the component is ready to be infused. If the resin is mixed manually, this is now coupled with a short rest time to allow the majority of air added at mixing to arrive at surface.
- The speed of the resin is controlled by valves on the inlet pipes. The speed of the resin is high at the beginning of infusion and this leads to extra lag on infusion creating dry spots which can exhaust the resin supply before batches are mixed.
- When process is running in controlled manner, more resin is mixed before opening the next set of valves. The set of valves open when the entire resin front has passed the feed line at bottom and top of laminated stack. This causes increase in speed of resin flow and increases pressure gradient by removing quantity of fabric in drag. The process is repeated until the entire component is infused with resin.
- This process has potential unpredictability for every component mainly in resin flow and susceptibility of system to failure generally caused by vacuum integrity.
Fan blades must be of precise design. So they must be manufactured with special process in order to have better efficiency.