1 piping technical requirements
In electrical installations for home use, it is not allowed to directly lay plastic insulated wires in the cement or lime powder layer for dark line laying. Because the insulation layer of the wire embedded in the cement or lime powder layer is easily damaged, a large area of ​​leakage is caused and the personal safety is endangered. Home-installed electrical wiring should use rigid fire-retardant PVC wire and pipe.
2. Pipe diameter selection
The diameter of the wire protection tube is selected on the basis that the total cross-sectional area of ​​the wire (including the insulating layer) in the tube should not exceed 40% of the cross-sectional area of ​​the tube.
3. Pipeline tools and processes
1) Pipeline tools
The piping tools and equipment that should be prepared include wire cutters, electricians, (wall paper) J), pipe benders, shears, hand hammers, flame retardant cold-bending wire trough tubes, wires, line cards, and wire tubes, Wax casing, ladder and so on.
2) Process flow
(1) Processing pipe bends. Prefabricated pipe bends can be cold-rolled and hot-rolled. Fire-retardant wire-pipes are laid out in accordance with the following requirements for environmental temperature: The laying, installation and bending of flame-retardant wire and pipe fittings are to be specified in the raw materials. Allow to proceed at ambient temperature, its temperature should not be lower than -15 °C.
(2) cloth tube.
A special shear 59 is also suitable for wire cutting, but it can also be sawn with a hacksaw. The shear wire j7 provided by the PVC wire and pipe factory can cut 16- to 40-nm-thick tubes. When cutting the tube with scissors, first open the handle, put the tube into the mouth of J9, then grasp the handle, lock the 59th ratchet; release the handle and hold it tight until the tube is cut off. Use a special cutter 59 to cut the tube. The nozzle is smooth. If cutting with a hacksaw, the nozzles should be polished and the next process performed. Small pipe diameters can be used with pipe cutters. Large pipe diameters can be broken with hacksaws. Fractures should be flattened and milled. When the length of the straight section exceeds 15m or the turn exceeds 3, the bottom box must be added.
(3) Fixed. After the tube is finished, use a line card to fix it.
(4) Joints. Tube and tube, tube and box (box) connection.
The purpose of the wire tube and the bottom box is to fix the wire tube and the bottom box connector. The purpose of the wire tube is not easy to cause misplacement during threading, and also avoid damage to the wire insulation layer.
(5) Organize. The nozzles and pipe joints of the wire conduit should be sealed. The net distance from the surface of the conduit should not be less than 15mm. After the wire tube and the box are connected, the box should be positive and firm.
4. Protection of PVC conduits
After the construction of the wire conduits laid on the ground, the wooden sides shall be placed on the sides of the PVC conduits or sloped with cement mortar to prevent the PVC conduits from being walked over due to walking back and forth during construction of the workers.
The first process of Investment Casting production is the manufacture of investment mold, investment mold is used to form the cavity in the refractory shell model, so in order to obtain the casting with high dimensional accuracy and surface finish, the investment mold itself should have high dimensional accuracy and surface finish. In addition, the performance of the melt itself should also make the subsequent shell making process as simple as possible. In order to obtain the above high quality requirements of the investment die, in addition to good pressure (pressing the investment die), but also must choose the appropriate mold material (referred to as the mold) and reasonable mold making process.
The advantage of the investment casting method is that it can cast complex castings of various alloys, especially high temperature alloy castings. For example, the blade of jet engine, its streamlined outer profile and cooling inner cavity, with machining process almost impossible to form. Investment casting process can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual blade lines after machining.
The biggest advantage of investment casting is that because investment casting has a very high dimensional accuracy and surface finish, so it can reduce the machining work, just leave a little machining allowance in the parts requiring higher parts, and even some castings only leave grinding and polishing allowance, without mechanical processing can be used. It can be seen that the investment casting method can greatly save machine tools, processing time and metal raw materials.
silica soil casting parts, Precise dimension
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