If you are a professional CNC machining lathe person, it is not difficult to understand the dimensions and professional symbols on the drawings of precision metal parts machining, but if you are initially exposed to the CNC machining industry, or you need to develop a project, The dazzling drawings may make you very big. If you can’t understand the drawings, it is difficult to guarantee the efficiency and effect of many things. Today we will learn how to understand the drawings of precision metal parts processing:
1. Dimensions of common structures
Dimensions of common holes (blind holes, threaded holes, countersunk holes, countersunk holes); dimensions of chamfers.
Blind hole
Threaded hole
Counterbore
Spot facing
Chamfer
2. Machining structure on CNC machining parts
Undercuts and wheel overruns
During the machining of CNC machining parts, in order to facilitate the withdrawal of the tool and ensure that the contact surfaces of the relevant parts are close during assembly, the undercut groove or the grinding wheel overrun groove should be pre-machined at the step of the machined surface.
The size of the undercut when turning the outer circle can generally be marked in the form of “groove width × diameter” or “groove width × groove depth”. Grinding wheel overrun grooves when grinding external circles or grinding external circles and faces.
Drilling structure
The blind hole drilled with a drill has a taper angle of 120° at the bottom, and the drilling depth refers to the depth of the cylindrical part, excluding the taper. At the transition of the stepped drilling, there is also a cone with a cone angle of 120°, its drawing method and dimensioning method.
When drilling with a drill bit, the axis of the drill bit is required to be as perpendicular to the end face of the drilled hole as possible to ensure accurate drilling and prevent the drill bit from breaking. Correct construction of three drilled end faces.
Bosses and pits
The contact surfaces of CNC machined parts with other parts are generally CNC machined. In order to reduce the processing area and ensure good contact between the surfaces of CNC machined parts, bosses and pits are often designed on castings. Bolted support surface bosses or support surface pits; in order to reduce the CNC machining area, a groove structure is made.
3. Common CNC machining parts structure
Axle bushing parts
Such CNC machining parts generally include shafts, bushings and other parts. When expressing a view, as long as a basic view is drawn and appropriate cross-sectional drawings and dimensioning are added, its main shape features and local structures can be expressed. . In order to facilitate the viewing of drawings during CNC machining, the axis is generally projected horizontally, and it is best to choose the position where the axis is the vertical line.
When dimensioning the CNC machining parts of the bushing, its axis is often used as the radial dimension reference. From this, note the Ф14 and Ф11 shown in the figure (see A-A section) and so on. In this way, the design requirements and the process benchmarks during CNC machining are unified (when the shaft parts are CNC machined on the lathe, both ends are pressed against the center hole of the shaft with a thimble). The datum in the length direction is often selected from important end faces, contact surfaces (shoulders) or machined surfaces.
As shown in the figure, the right shoulder with a surface roughness of Ra6.3 is selected as the main dimension reference in the length direction, so dimensions such as 13, 28, 1.5 and 26.5 are injected; then the right shaft end is used as the length direction The auxiliary base of , thus marking the total length of the shaft 96.
Disc cover parts
The basic shape of this type of parts is a flat disc, generally there are CNC machining parts such as end caps, valve covers, gears, etc. Their main structures are generally rotary bodies, usually with flanges of various shapes, evenly distributed. Local structures such as round holes and ribs. When selecting a view, generally select the sectional view of the symmetry plane or the axis of rotation as the main view, and at the same time, it is necessary to add other appropriate views (such as left view, right view or top view) to express the shape and uniform structure of the part. A left view has been added as shown to represent the square flange with rounded corners and four evenly spaced through holes.
When dimensioning the CNC machined parts of the disc cover, the axis passing through the shaft hole is usually selected as the radial dimension reference, and the main dimension reference in the length direction is often selected as the important end face.