1, CNC CNC lathe processing preliminary steps. First determine the process requirements of the parts, the batch of processed workpieces, the formulation of CNC lathe should have the function of making good preparations for the reasonable selection of the prerequisites for the CNC lathe to meet the typical parts of the process requirements of the typical parts of the process requirements are mainly the structural dimensions of the parts, machining range and accuracy requirements.
2, according to the precision requirements, i.e., the workpiece dimensional accuracy, positioning accuracy and surface roughness requirements to select the control accuracy of the CNC lathe. Selected according to the reliability, reliability is to improve product quality and productivity.
3, the reliability of CNC machine tools refers to the machine tool to perform its functions under the specified conditions, a long time of stable operation without failure. That is, the average failure-free time is long, even if the failure, a short time to recover, back into use. Select a machine tool that has a reasonable structure, is well manufactured, and has been mass-produced. In general, the more users, the higher the reliability of the CNC system.
4, CNC CNC lathe processing materials are: 304, 316 stainless steel, carbon steel, copper, aluminum, alloy, plastic, POM and so on. However, the car of different materials need to use different quality of products, in order to ensure the accuracy of each product requirements.
The lathe cutting process, in the processed surface of a variety of phenomena, some are very obvious, but also in the magnifying glass to be observed, which is more common are the following:
1, hardening
Tools in the cutting process, due to the workpiece by the tool, chips and other high temperature and pressure of the impact of the workpiece has been machined surface hardness has increased, known as hardening. Known as work hardening, the main factor is the cutting edge of the tool rounding.
2, residual area:
In the lathe turning cylindrical, the cutting layer remains in the machined surface area is not excised called residual area. Usually the size of the height of the residual area to measure the degree of non-glossy, by the past processing experience can be concluded to reduce the feed, reduce the tool's primary and secondary deflection, increase the tip of the arc radius, can make the height of the residual area is reduced. In fact, in the residual area is also superimposed on many other factors caused by the surface of the processed surface of the phenomenon of impurity, resulting in the actual height of the residue than the calculated value to be larger.
3, the accumulation of chips tumor:
The accumulation of chips tumor that the tip of the building. In the process of machining, because the workpiece material is squeezed, so the chip on the front of the tool to generate a lot of pressure, and friction to generate a lot of cutting heat. In this high temperature and pressure, the part of the chip in contact with the front face of the tool due to the influence of friction, the flow rate is relatively slow, the formation of stagnant layer. When the friction once greater than the bonding force between the internal lattice of the material, some of the material in the stagnant layer will be adhered to the cutting tool near the tip of the front surface of the tool, the formation of chip tumors.
The cutting process produces a chipoma, its protruding chips adhere to the tip of the tool, thereby replacing the cutting edge of the cutting into the workpiece, so that the machined surface of different depths, intermittent grooves; when the chipoma off, part of the chipoma fragments bonded to the machined surface to form a prominent small burr.
4, scale:
Scale is really processed on the surface to produce fish scale-like burrs. Appearance of this phenomenon so that the surface roughness decreased significantly.
The cause of scale has four stages:
The first stage is to wipe the stage: the former cutter surface outflow of swarf will be lubricating film wiped, the lubricating film was destroyed.
The second stage is the guide crack stage: there is a large extrusion pressure and friction between the front tool surface and the chips, the chips are temporarily bonded to the front tool surface, and instead of the front tool surface pushes and squeezes the cutting layer, so that the chips and the machining surface to produce the guide crack.
The third stage is the lamination stage: the front face continues to push the cutting layer, the accumulation of cutting layer more and more, the cutting force increases to a certain extent so that the chip overcomes the bond between the front face and continue to flow.
The fourth stage is to scrape into the stage: the knife edge scraped, the part of the guide cracks remain in the processed surface into the scale spines.
5, vibration:
Tools, workpieces, machine components or system rigidity is insufficient to produce a periodic beating called vibration, especially when the depth of cut is large or chip tumors continue to produce the disappearance of the cause. Longitudinal or transverse ripples appear on the surface of the workpiece, is a significant reduction in surface finish.
6, knife edge reproduction:
The knife edge is uneven, groove marks and other traces on the processed surface.
7, pulling hair
Pulling hair is in the turning process, the chip to the processed surface discharge, chip winding in the workpiece has been processed on the surface, so that has been processed on the surface, resulting in scratches, burrs and so on.
8, bright spot bright band
Because of the wear of the rear blade surface produces more intense friction and extrusion, in the processed surface to form a block or band of bright blocks. In addition, when the machine's movement accuracy is low, such as spindle runout, feed movement is not uniform, etc., will also make the workpiece surface quality.
Turning machining is a method of cutting the workpiece on a lathe using the workpiece to rotate relative to the tool. The cutting energy of turning is mainly provided by the workpiece rather than the tool. Turning is the most basic, the most common cutting methods, in production occupies a very important position. Turning is suitable for processing rotary surfaces, most of the workpiece with a rotary surface can be processed by turning methods, such as internal and external cylindrical surfaces, internal and external conical surfaces, end surfaces, grooves, threads, and rotary molding surfaces, etc., the tool used is mainly a turning tool.
The process of CNC lathe machining and ordinary lathe machining process is similar, but because the CNC lathe is a clamping, continuous automatic machining to complete all the turning process, and therefore should pay attention to the following aspects.
1, a reasonable choice of cutting volume: for high-efficiency metal cutting process, the material being machined, cutting tools, cutting conditions are three major elements. These determine the processing time, tool life and processing quality. Cost-effective processing is bound to be a reasonable choice of cutting conditions. The three elements of cutting conditions: cutting speed, feed and depth of cut directly cause tool damage. Along with the increase in cutting speed, the temperature of the tool tip rises and mechanical, chemical and thermal wear occurs. A 20% increase in cutting speed reduces tool life by 1/2.
The relationship between feed conditions and wear behind the tool arises on a very small scale. However, with high feed, the cutting temperature rises and the back wear is high. Smaller than the effect of cutting speed on the tool. Depth of cut on the tool, although not as large as the cutting speed and feed, but in the tiny depth of cut cutting, the material being cut to produce a hardened layer, the same will affect the life of the tool.
Users should select the cutting speed according to the material to be machined, hardness, cutting condition, material type, feed, depth of cut and so on. The most suitable machining conditions are selected on the basis of these factors. Regular and stable wear to achieve life is the ideal condition. However, in practice, the selection of tool life is related to tool wear, variation of machined dimensions, surface quality, cutting noise, and machining heat. When determining the machining conditions, it is necessary to study the actual situation. For difficult-to-machine materials such as stainless steel and heat-resistant alloys, you can use coolant or choose a rigid blade.
2, reasonable selection of tools:
(1) rough turning, to choose high strength, good durability of the tool, in order to meet the requirements of the rough turning of the large back draft, large feed.
(2) fine turning, to choose high precision, good durability of the tool, in order to ensure that the requirements of machining accuracy.
(3) In order to reduce the time of tool change and facilitate tool setting, machine tool and machine clamped inserts should be used as much as possible.
3, a reasonable choice of fixture:
(1) try to use the general fixture clamping workpiece, avoid the use of special fixtures;
(2) the parts positioning datum overlap, in order to reduce the positioning error.
4, to determine the machining route: machining route refers to the CNC machine tool machining process, the tool relative to the movement of the parts trajectory and direction.
(1) should be able to ensure that the machining accuracy and surface roughness requirements;
(2) should try to shorten the machining route, reduce the tool idle time.
5, the machining route and the link between the machining allowance: in the CNC lathe has not yet reached the popularization of the use of the conditions, generally should be too much allowance on the blank, especially containing forging, casting hard skin layer of the allowance is arranged in the ordinary lathe processing. If you must use CNC lathe processing, you need to pay attention to the flexible arrangement of the program.
6, fixture installation points: hydraulic chuck and hydraulic clamping cylinder connection is the realization of the tie rod, hydraulic chuck clamping points are as follows: first of all, use the hand to remove the hydraulic cylinder on the nut, remove the pull tube, and from the back end of the spindle, and then use the hand to remove the chuck fixing screws, you can remove the chuck.