Cnc Machining, both manual and automatic programming, involves process analysis of pre-programmed machined parts, process planning, selection of appropriate tools, and determination of cutting volumes. Programming also needs to address some process issues (tool configuration points, processing routes, etc.). Therefore, the process of NC programming is a very important task. The main purpose of this paper is to describe the processing process for metal disc parts. It mainly includes blank selection, reference selection, processing sequence, clamping method, surface treatment, parameter selection, and process route.
1. General process of CNC machining process design
- (1) Select a cnc machine tool suitable for machining parts and determine the content of the process.
- (2) Analyze the drawings of machined parts, clarify the machining contents and technical requirements, determine the machining plan, and develop the CNC machining route. Dividing processes, arranging processing sequences, connecting non-CNC machining processes, etc. Design CNC machining processes such as process partitioning, tool selection, jig positioning and installation, cutting volume determination, and cutter route determination. Due to the variety of parts and the contours and shapes of parts, the materials and sizes of blanks are not the same.
Therefore, the process design of CNC machining determines the efficiency of use of CNC machine tools, the machining quality of parts, the number of tools, and the economic efficiency. Attempts should be made to ensure machines that minimize intensive machining steps, shortest routes, and auxiliary machining times.
2. Analysis of processing technology for disc parts
(1) Selection of processing materials.
Disc parts made mainly of steel, cast iron, stainless steel, aluminum, brass, bronze, etc. Hot rolled or cold drawn rods are typically used for small diameter discs. Various materials may opt for solid casting. If the opening is large, you can use a pre-hole. For mass production, optional cold extrusion and other advanced blank manufacturing processes can not only increase productivity but also save material.
(2) Selection of processing criteria.
Depending on the characteristics of the part, standard overlap and benchmarking principles should be met as much as possible. The criteria for selection are usually the end face, the inner hole, and the outer circle. Planes are commonly used as datums when end faces are used as datums for disk parts. If the disc part is based on an inner hole, the end face is generally assisted by the end face. The method of referencing the outer circle is basically the same as the reference selection using the inner hole.
(3) Process placement
Typical disc parts usually consist of end faces, holes, and outer surfaces (some of which include stepped holes), and disc parts are characterized by radial dimensions that are greater than axial dimensions. .. Look for disc type parts factory Candín, quality assurance. Disc parts have surface roughness requirements as well as dimensional requirements. This usually includes requirements for radial runout, rounded runout, and verticality. Round runouts and end face round runs are important considerations when developing the processing process for disc parts. After termination, the outer circles, holes, and end faces must be terminated in one clamping process to avoid the second clamp. For parts that need to be clamped multiple times, the holes are first machined, then the outer circle or end face is machined through the holes.
(4) Selection and use of fixtures.
A general purpose 3-jaw chuck is used to clamp workpieces on small disc parts. 4 Jaw chucks or faceplates are suitable for clamping medium and large disc parts. For tangential accuracy, it is usually processed by clamping with a mandrel or face plate. If the disc component’s positioning reference is a machined hole, the mandrel method is used to clamp the component to ensure coaxiality between the outer circular axis and the hole axis. There are also many types of mandrel. Cylindrical hole or cylindrical mandrel for positioning or small taper mandrel. In addition, the corresponding cones and thread mandrel are used for special holes such as tapered holes and screw holes. The cylindrical mandrel centers the outer cylindrical surface and presses on the end faces to secure the part. A clearance fit is used between the mandrel and the part hole.
Spindles may be machined into smaller tapered vertebral bodies to improve spindle positioning accuracy. There are also common fixture discs for large disc sleeve parts. The disc is mounted on a large disc on the lathe spindle. Generally suitable for workpieces with irregular shapes, but cannot be used when clamping general chucks. When using discs to secure workpieces, you need to balance them. If it is not balanced, centrifugal force will be generated, which will eventually cause vibration and cause wear and tear of the spindle bearing.
(5) Processing of the finished surface of disc parts
The rotating surface of disc parts is roughened by turning. For finishing, machining methods such as finish turning, finish finishing, and finish grinding should be selected with further consideration of materials, machining requirements, and power output. Corresponding machining methods, milling, EDM, etc. can be used for the non-rotating surface of disc parts.
(6) Determination of disconnection parameters.
When a programmer chooses a cutting amount, it is necessary to carefully consider various factors that affect cutting, select the cutting conditions correctly, and determine the cutting amount reasonably. This effectively improves processing quality and efficiency. The factors that affect the disconnection conditions are as follows.
- > Rigidity of machines, tools, and workpieces.
- > Cutting speed, cutting depth, cutting feed rate.
- > Workpiece accuracy and surface roughness;
- > Maximum tool life and productivity;
- > Cutting fluid type, cooling method;
- > Heat treatment hardness of work material.
- > Number of workpieces.
- > Machine life.
Of the above factors, the feed rate, cutting speed, and cutting depth are the main factors. We mainly analyze the following points.
A.Selection of feed rate
Each rotation of the work and the distance that the tool moves in the moving direction is called the feed amount, and the unit is mm / r. Theoretically, it is the maximum feed amount during rough cutting. Feed rate is limited by several sizes of factors: machine tool, shank, blade, jig strength and stiffness. Finishing is mainly limited by machining accuracy and surface roughness, and feed rate is selected in combination with workpiece material, tool tip radius and cutting speed.
B.Selection of cutting speed
The linear velocity of the main motion is called the cutting velocity and its unit is III / s or III / min. In actual production, cutting speeds are usually chosen based on experience, and generally lower cutting speeds are chosen for roughing. For turning, choose a higher cutting speed. In addition, comprehensive consideration of material machining characteristics, tool cutting performance, working conditions, and other factors must be taken into account to reasonably determine the optimum cutting speed. Cutting speed is related to machine speed and there is a calculation conversion formula.
n = 1000v / dII
Equation Where d is the diameter of the workpiece and the selected velocity n must be within the rotational speed of the lathe. Appropriate processing parameters are selected by experience or the above formula.
(7) Formulate a processing route.
The biggest difference between disc parts and shaft parts is the mounting method during machining. Due to the various functional requirements of the part, the machining method may be completely different from that of the shaft part. Typical Disc Parts We typically use the following machining techniques: Blank Blank Removal Stress Treatment Preparation Rough Surface Rough Surface Semi-finishing and Non-Rotating Plane Finish Deburring, Heat Treatment (Quenching, Tempering) Etc.)) Completed surface inspection.
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