The WIT water-injection technology or water-injection moulding is a method of fluid-assisted injection moulding. It is suitable for the production of functionally complex, highly integrated plastic components with hollow-core construction, large diameters and long channels. M.TEC simulates water injection technology in order to design both the component and the mould.
Simulation using Moldex3D
M.TEC uses the Moldex3D simulation software to simulate the water-injection moulding process. With the professional support of SimpaTec Simulation & Technology Consulting GmbH from Würselen, Moldex3D is an excellent simulation tool for M.TEC in the development of WIT components.
Advantages of water injection technology
Special advantages of water injection technology for the production of plastic components:
Component construction and functionality
- Long hollow body constructions with large diameter possible
- Particularly torsionally stiff/bending-resistant plastic components possible
- Smooth, closed surfaces even inside the component (ideal for media lines)
- Fewer weld lines, no meld lines
- Large wall thicknesses possible and at the same time few/no sink marks
- Controlled low wall thickness in turn allows material savings
- Particularly precise hollow body cross-sections can be realized using PIT projectile injection technology
Production and efficiency
- Practically no material scrap (mass return process: plastic melt is fed back directly into the plasticizing unit)
- High cooling effect through heat capacity absorption of water, which also acts inside the component; cycle time is significantly reduced
- Further extreme cooling effect possible through permanent flow through the hollowed-out component until demolding with the help of special system control technology from PME fluidtec
Comparison to gas injection technology GIT
- Often higher stiffness-to-weight ratio of the component
- Mostly larger material savings
- No costs or licence fees for industrial gases
- More uniform shrinkage
Component designs suitable for WIT
Component designs suitable for production using internal water pressure technology basically have a hollow body - a prerequisite for the channeling of the water used and its drainage after the cooling phase. The hollow body can be functional.
Media-carrying components
Examples of components with functional hollow bodies are fluid-carrying or media-carrying lines (media lines, plastic media lines). As a rule, they can be produced efficiently using water injection technology. The smooth, closed surface inside the component is well suited for media lines made of polymeric materials (e.g. water lines, air lines, oil lines, fuel lines, etc.).
Ergonomic components
Plastic components with ergonomic functions are also frequently produced by WIT, as weld lines can be avoided in internal water pressure injection molding. For example, plastic handles and carrying handles made of plastic require a seamless, haptically pleasant surface.
Structural components
If the component design is suitable for the use of internal pressure injection molding, structural components are also produced using water injection technology.
Further suitable for production by water injection molding:
- Components in which cores are to be replaced by a cavity
- Components with integrated thick-walled areas
- Rod-shaped plastic components
- Injection molded parts with large wall thicknesses, partial stiffeners and ribbed constructions
- Structural components with long glass fiber reinforcement
Components manufactured using the WIT process
Examples of components and subcomponents manufactured by means of water injection technology:
Automotive
- Car door, tailgate
- Car roof, roof rails
- Cross beams
- Air conditioning ducts, air conditioning components
- Lamp holders
- Cooling water pipe
- Pedals
- Car seat, armrests
Other typical WIT components
- Handles / Carrying handles
- Brackets
Restrictions of WIT procedure
The basic prerequisite for the use of water injection technology is an externally thick-walled component and a hollow body construction. In addition, the following possible restrictions apply:
- Water drainage by gravity required (position in the mold)
- Hole at injection point; reworking by sealing may be necessary, possible risk of leakage
- Investment in additional plant technology may be necessary
- With externally angular component constructions, more mass remains in the corner areas, which leads to higher material consumption. Therefore, it is recommended to round off the external contours (as far as this is technically possible).