Drilled cooling channel

Figure 1. Schematic view of a design concept for CMC combustion chambers, based on joined segments (left and center). WHIPOX combustion chamber shingle with laser drilled cooling channels for rig testing (right).

The vent opening will pass through a boss in the baffle to the back or outside of the mold. In machined molds, care must be taken so that vents miss the drilled cooling channels. When core vents cannot be used because the slots mark on the blown part will show, small drilled holes can be used. The effect of the size of hole on the surface of the part is shown in Figure 26. 

Drilled cooling channels are used for steel and forged aluminum and for mold inserts. To achieve good cooling in the molds, it is important that the channels are as close to the surface as possible and closely spaced. In aluminum molds, greater distances than in steel are possible because the heat conductivity of aluminum is about five times higher than that of steel (Table 1.6). 

The efficiency of gas turbines is limited by the maximum allowable turbine inlet temperature (TIT). The TIT may be increased by cooling of the blades and vanes of the high pressure turbine. Cooling channels can be casted into the components or may be drilled afterwards. Non-conventional processes like EDM, ECD or Laser are used for drilling. Radiographic examination of the drilled components is part of the inspection procedure. Traditional X-Ray film technique has been used. The consumable costs, the waste disposal and the limited capacity of the two film units lead to the decision to investigate the alternative of Real-Time X-Ray. 

Drilling, Fig. 4 Twist drill with int nal cooling channels... 

The aspect of the position tolerance of the internal cooling channels that gains in importance especially in extra-long twist drills is taken up by a search strategy to find a robust position that is unsusceptible to deviations in order to reduce the risk of tool failure. Thus, all important properties of the twist drill are optimized with respect of certain restrictions. In the following the overall concept and one exemplarily fitness function are presented. 

In mold design, the core is (1) a channel in a mold for circulation of heat transfer media or (2) a part of a complex mold that molds undercut parts. In the latter case the cores are usually withdrawn to one side before the main sections of the mold open (also called a core pin). Cores are usually withdrawn before the main sections of the mold are opened. A core drill is a device for making cooling channels in the mold. 

Heat is removed from the plastic by conduction through the surfaces of the cavity and cores, and is absorbed by the mass of the cavity block, core, and entire frame of the mold. To facilitate this cooling, channels are drilled longitudinally... 

When a number of cooling channels are drilled parallel, they should be connected in parallel from the water supply and not in series. The outlets should be designed at least as large as the inlets. 

Preferably, aluminum castings are used with drilled or milled cooling channels. Care must be taken to clear the flash area to ensure that the fixture can close properly. The cavity dimensions must have reduced shrink allowances that is, the cavity of the fixture must be smaller than the blow cavity. 

For drilling depths above f = 10 D, as it is often the case in cooling channels, very sharp HSS drills (DIN 1869) must be used. To avoid jamming of the drill, it is advantageous that the drill tip is ground 0.1 to 0.3 mm off center for deep bore holes that are not subject to specific tolerances. The application of a cooling water emulsion, with increased concentrate proportion if possible, is advisable. 

This paper deals with the reduction in blow mould process time of a 1-litre motor oil bottle produced at a local manufacrnring company by considering the design of straight drilled conformal cooling channels, which can be easily created in metal moulds by conventional machining. 

Partitioned mold cooling occurs when a large-diameter hole is drilled into the mold (usually the core) and partitioned by a metal plate extending to near the bottom end of the channel. Water is introduced near the top of one side of the partition and removed from the other side. 

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