CNC Machining · 2021年5月7日

Detailed explanation of CNC machining equipment and process knowledge, worth collecting

01 CNC machining equipment
1. Ordinary lathe: Lathe is mainly used for processing shafts, discs, sleeves and other workpieces with rotating surfaces. It is the most widely used type of machine tool in mechanical manufacturing. (Achievable accuracy of 0.01mm)
2. Ordinary milling machine: It can process planes, grooves, various curved surfaces, gears, etc., and can process more complex profiles. (Achievable accuracy of 0.05mm)
3. Grinding machine: The grinder is a machine tool that grinds the surface of the workpiece. Most of the grinders use high-speed rotating grinding wheels for grinding, a few use other abrasives such as oilstone, belts and free abrasives for processing, such as super-finishing machine tools, belt grinders, grinders and polishing machines. (It can achieve accuracy of 0.005mm, and small parts can achieve 0.002mm)
4. Fitter: Pliers work mainly includes filing, sawing, scribing, drilling, reaming, tapping and threading, scraping, grinding, straightening, bending and riveting.
5. CNC lathe: Mainly process batch products, high-precision parts, etc. (Achievable accuracy of 0.01mm)
6. CNC milling machine: mainly processing batch products, high-precision parts, complex parts, large workpieces, etc. (Achievable accuracy of 0.01mm)
7. Wire cutting: The electrode used for the slow wire is brass wire, and the middle wire is molybdenum wire. The slow-moving wire has high processing precision and good surface finish. Process some fine holes, fine grooves, etc. (Slow wire can achieve an accuracy of 0.003mm, and medium wire can achieve an accuracy of 0.02mm)
8. EDM machine: EDM can process materials and complex-shaped workpieces that are difficult to cut by ordinary cutting methods (such as groove corners, small holes, deformed holes, cemented carbide processing), and there is no cutting force during processing. Defects such as burrs and knife marks and grooves are produced. Not affected by the hardness of the material, and not affected by the heat treatment conditions. (Achievable accuracy 0.005mm)

02 process flow
The machining process specification is one of the process documents that specify the machining process and operation methods of parts. It is used to write a more reasonable process and operation method in a prescribed form into a process document under specific production conditions. Direct production.

The machining process of the parts is composed of many working procedures, and each working procedure can be divided into several installations, stations, working steps and cutting tools.

Which processes need to be included in a technological process is determined by the complexity of the structure of the processed parts, the requirements of processing accuracy, and the type of production.

Different production quantities have different processing techniques.

Process knowledge

1) Hole milling with precision less than 0.05 cannot be done, and CNC machining is required; if it is a through hole, it can also be cut by wire.
2) The fine hole (through hole) after quenching needs to be processed by wire cutting; the blind hole needs to be roughed before quenching and finished after quenching. The non-precision holes can be in place before quenching (the quenching allowance is 0.2 per side).
3) Slots with a width of less than 2MM need wire cutting, and 3-4mm grooves are very deep and need wire cutting.
4) The minimum allowance for rough machining of quenched parts is 0.4, and the allowance for rough machining of non-quenched parts is 0.2.
5) The thickness of the plating layer is generally 0.005—0.008, and the size before plating should be used during processing.
03 process man hours
The time quota is the time required to complete a process, which is an indicator of labor productivity. According to the time quota, the production operation plan can be arranged, the cost accounting can be carried out, the number of equipment and staffing can be determined, and the production area can be planned. Therefore, the time quota is an important part of the process regulations.

The time quota should be determined according to the production technical conditions of the enterprise, so that most workers can reach it through hard work, some advanced workers can exceed it, and a few workers can reach or approach the average advanced level through hard work.

With the continuous improvement of the production technology conditions of enterprises, the fixed time limit will be revised to maintain the average advanced level of the quota.

The time quota is usually determined by the combination of craftsmen and workers, through summing up past experience and referring to relevant technical data. Or it can be calculated based on the comparison and analysis of the time quota of the workpiece or process of similar products, or it can be determined after the measurement and analysis of the actual operating time.

Process man-hours = preparation man-hours + basic time

Preparation man-hours are the time spent by workers getting familiar with process documents, receiving blanks, installing fixtures, adjusting machine tools, and disassembling fixtures. Calculation method: Estimate based on experience.

The basic time is the time it takes to cut the metal.