Common roughness defects produce analysis
1, cutter mark roughness analysis
Knife mark roughness defects are generally reflected in the increase in cutting feed, mainly due to the cutting process, due to the shape of the tool so that the metal processing surface part of the metal is not removed, residual in the processing surface, called knife mark.
2, scale phenomenon
Generally in the cutting speed is low, and the use of high-speed steel or carbide tools for cutting plastic metal materials, easy to appear on the surface of the scale-like cracks and burrs, this phenomenon is called scale phenomenon.Generally in broaching, inserting, hobbing and other machining processes are prone to this situation. When in the low speed, small front angle tool cutting plastic materials, will form the situation of extrusion chip, which causes the knife and chip between the force generated by the role of the knife and the periodic changes, which makes the metal accumulation, processing surface fracture and scale phenomenon.
3、Scratch and pull hair
Scratch and hair pulling in the roughness defect category is also relatively common, gear processing in the gnawing tooth phenomenon, grinding and so on, are scratched and hair pulling representative phenomenon. And we can according to the traces of scratches and hair pulling, their causes for analysis, in order to develop good measures to exclude.
4, knife flower uneven
For the phenomenon of uneven knife flower, the main reason still lies in the machine tool, the main performance is the metal surface of the cutting tool cutting traces are not uniform.
5, high-frequency vibration pattern
In the metal processing process, the entire process system will be followed by vibration, machine tools, tools, workpieces will have a great impact on the surface roughness of metal parts. One of the low-frequency vibration of the process system generally produces corrugation on the surface of the workpiece, while the process system of high-frequency vibration produced by the vibration pattern is the category of roughness.
Process system vibration mainly includes forced vibration and self-excited vibration. Forced vibration is due to the role of periodic external forces and vibration. Self-excited vibration is the system movement of its own vibration excitation, the most common self-excited vibration is cutting self-oscillation.
Analysis of common roughness defects elimination
1, cutter mark exclusion analysis
First of all, when cutting, you should choose a smaller feed within the allowable range, but the feed can not be too small, otherwise it also affects the roughness of the cut. Secondly, when sharpening the tool, to increase the tip radius within the allowable range, the roughness will have a certain benefit.
2, scale spurs phenomenon excluded from the analysis
First of all, we should control the cutting speed. Scaling phenomenon is to some extent due to the cutting speed, beyond or below a specific speed range, will produce scaling phenomenon. Second is the cutting thickness, to minimize the cutting thickness, cutting thickness increases, for the pressure between the chip and the front of the tool will be more and more big, if the formation of extrusion chip or unit chip, will make the scale phenomenon appear more frequently and serious. In addition, the use of better quality cutting fluid can also effectively inhibit the production of scale phenomenon. Reasonable choice of tool angle is also an effective way to eliminate scale phenomenon. Finally, the cutting processability of the workpiece material to continue to improve, for example, in some cases, the material can be heated before cutting, so that the phenomenon of scale phenomenon will also reduce the generation.
3, scratches and hair pulling to exclude analysis
Scratch and pull hair if the distribution of traces is more regular, generally because the machine tool problems, machine tools, such as spindle box, skateboard box, feed box and other traditional systems in the shaft bending, gear gear bad or damaged, will appear regular scratch and pull hair phenomenon, so we must regularly check the machine tool, often for maintenance. If the distribution of scratches and pulling traces is irregular, then it may have a relationship with the chips, tools, cutting fluid. For example, in the deep hole machining process, poor chip removal will cause scratches on the inner surface. Workpiece surface hair pulling, generally in the grinding process due to abrasive particles, abrasive chips off, may also be the grinding wheel is not suitable, cutting fluid is not clean, so choose the right grinding wheel and clean cutting fluid.
4, knife flower unevenness exclusion analysis
knife flower unevenness has a variety of reasons, but common, for example, in grinding cylindrical, the surface of the part will appear spiral linear traces. This is due to the straightness of the grinding wheel busbar error caused by the larger, which requires us to choose the grinding wheel and maintenance regularly do a good job. In addition, for example, the machine table or tool holder creep, will also cause uneven tool walking, so the maintenance of the machine, maintenance must be done to maximize the prevention and avoidance.
5, high-frequency vibration pattern elimination analysis
Eliminate high-frequency vibration pattern of the main method is to find the source of vibration, eliminate vibration, or vibration to the allowable range.
For example: due to the vibration caused by rotational imbalance of parts, machine tool transmission system caused by vibration, etc., all belong to the forced vibration, can be found through the vibration source, adjustment and repair of the machine tool, generally can rule out the impact of vibration, vibration pattern will also disappear. If the cutting vibration, this movement exists in the entire cutting process, it is necessary to machine tools, tools, workpieces, the entire process system together to adjust, such as changing the cutting dosage, a reasonable choice of geometric parameters of the tool, a reasonable clamping tool and the workpiece, adjust the machine gap, improve the vibration resistance of the machine tool and so on.
Through the study and analysis of common roughness defects in lathe machining, find out the factors affecting surface roughness in cutting, and find out the corresponding measures and elimination methods, on the one hand, can be prevented before processing, on the other hand, in the event of problems can be timely and accurate to find the cause of the problem, and timely to be solved, for the purpose of improving product quality, and to promote the interchangeability of the production of a practical significance.
