In the machining industry, the surface roughness of mechanical parts is also a part of quality. How to control surface roughness in machining and what effect surface roughness has on part quality, let’s take a look at it
The machining requirements of surface roughness will be indicated on the machining drawing of mechanical parts. If the machining process fails to meet the requirements, the surface roughness of parts has a great impact on the mechanical assembly performance and service life, mainly in four aspects:
If the surface roughness of parts is not reached, the contact area will be reduced, the pressure per unit area will be increased, the contact deformation will be increased, the friction resistance will be increased, and the wear of parts will be accelerated;
The surface roughness affects the fitting properties. For the clearance fitting, the surface roughness is easy to wear, resulting in the rapid increase of the gap. For the interference fitting, the small convex peak can be flattened during assembly, the effective interference can be reduced, and the strength of the fitting parts can be reduced;
The surface of the parts is rough and low, and corrosive substances are easy to accumulate at the bottom of the surface, which is not easy to remove, resulting in surface corrosion;
When the part bears load, stress concentration is easy to occur at the concave bottom, resulting in cracks and part fracture.
In the machining process of mechanical parts, the parts with high requirements for surface roughness shall be finished with machining allowance. The above is about the influence of surface roughness in machining mechanical parts. Thank you for your attention!
During part processing, 45# steel blackening treatment has no effect on dimensional accuracy, because blackening is a common means of chemical surface treatment. The principle is to produce a layer of oxide film on the metal surface to isolate air and achieve the purpose of rust prevention. The size will not be deformed during surface treatment, so it will not affect the accuracy of parts.
In the process of machining, the parts with low appearance requirements need surface treatment process, and blackening treatment can be adopted. In the same industry of machining, 45# steel surface blackening is also called bluing. If the machining dimensions of precision mechanical parts have precision requirements, different surface treatment processes can be selected according to the purpose of part design. In the surface treatment process, 45# steel is treated with blackening, chromium plating, nickel plating and zinc plating. If the processing accuracy requirements on the production drawings are different, a reasonable surface treatment process is selected.
The above is to share 45# whether the blackening treatment of steel has an impact on the accuracy of parts. Thank you for your attention!
In the machining circuit, parts with high precision requirements are often encountered. Now let’s understand the analysis of positioning error in processing technology
In terms of machining process, the positioning error is divided into many cases. The following shall be paid attention to during operation:
Positioning error refers to the positioning error of a machining accuracy parameter in the machining process of machining a part. It is an integral part of the machining error of the machining accuracy parameter.
A process and positioning scheme can produce different positioning errors for several machining accuracy parameters of the process. Therefore, the positioning errors of these machining accuracy parameters shall be calculated respectively.
The premise of analyzing and calculating the positioning error is to use the fixture to clamp and process a batch of parts with the adjustment method to meet the processing requirements.
The positioning error calculated by analysis refers to the maximum positioning error range that may occur when processing a batch of workpieces. It is a limit value, not a specific value of the positioning error of a workpiece.
The most position change of the design basis for processing a batch of parts relative to the fixture tool adjustment basis is the reason for the positioning error, not necessarily the positioning error.
These points simply understand the analysis and calculation of positioning error. There are many reasons for the error affecting the size in the process of precision CNC machining parts and mechanical parts machining.
In NC machining, the selection of cutting tools is very important, but the common sense in this regard has not been introduced before, so it needs to be supplemented as soon as possible. So let’s introduce it in detail this time,
Selection criteria of NC tools
Generally speaking, the tool life is closely related to the cutting parameters, so the selection of tools is very important when formulating the cutting parameters. Tool life is usually divided into the highest and lowest. The former is related to the single piece man hour, while the latter is related to the process cost.
When considering the service life of cutting tools, it should be determined according to the degree of disorder of cutting tools and production cost. If it is a multi knife mechanical equipment with messy operation, it should be selected with high service life and good reliability.
CNC tool, which is a kind of tool, has higher requirements for tool than usual. It not only needs good rigidity, strength and precision, but also requires stable scale and good durability.
Selection of cutting tools for NC turning
NC turning tools usually include type turning tools, pointed turning tools and arc turning tools. When selecting, we should consider all the characteristics of NC machining, and also take into account the tool itself, so as to select the most appropriate tool.
Selection of cutting tools for NC Milling
The primary requirement for NC milling tools is that they have sufficient stiffness and can be used very well. Therefore, we should consider these in order to select the most appropriate.
This paper focuses on the processing technology of box parts from three aspects: the formulation of technical road, the selection of positioning datum and the processing of primary appearance, puts forward the leading hole finishing technology plan, and points out that the processing accuracy of the primary hole system of box parts has become the key to the processing technology of box parts.
[Key words] technical road planning; Selection of positioning datum; Box plane processing; Internal stress; Hole series processing box parts are typical parts of mechanical parts, such as lathe headstock, gear transmission box, gearbox, etc. they are one of the basic parts of the machine. They adhere to the accurate orientation of the shaft, bearing, sleeve and gear in the machine and components, and make them move harmoniously with each other according to the pre planned transmission connection to form a whole. The assembled box parts are installed on the machine with the planning datum plane of the box. Therefore, the processing quality of the box not only affects its installation accuracy and motion accuracy, but also has a decisive impact on the operation accuracy, service performance and service life of the machine.
1、 Planning of technical road
There are many surfaces of the box that require processing, such as lathe head box, gear transmission box, etc. in these processing surfaces, the plane processing accuracy is easier to ensure than the hole processing accuracy. Therefore, the processing accuracy of the spindle hole (primary hole) and the hole system processing accuracy in the box become key technical problems. Therefore, I prefer to pay attention to several points in the arrangement of the technical road.
(1) Machining sequence from face to hole
Machining the plane first not only cuts off the roughness and sand inclusion on the surface of the blank, but also makes it convenient to scribe and align when machining the holes scattered on the plane, and when the boring cutter starts boring, there will be no impact oscillation and damage to the cutter due to the roughness of the end face. Therefore, it is generally best to machining the plane first.
(2) The rough and finish machining shall be separated
The box structure is disordered, the accuracy of the main surface is high, and the cutting force during rough machining
The clamping force and cutting heat have a great impact on the machining accuracy. If finishing is carried out immediately after rough machining, the internal stress of workpiece deformation caused by various reasons after rough machining is not fully released, which cannot be eliminated in finishing machining, and then the box body deforms after unloading, affecting the final accuracy of the box body. I think in the process of rough machining, It is best to loosen the fixture repeatedly to release the internal stress as soon as possible, so as to ensure the processing quality of the box to a greater extent.
(3) Resolution of process convergence or laxity
The separation during the rough and finish machining of the box conforms to the principle of lax process. However, in order to reduce the number of machine tools and fixtures used and the number of box transfer and installation, the rough and finish machining can be relatively concentrated and placed on the same machine bed as far as possible during the medium and small batch production.
(4) Arrange appropriate heat treatment process
The casting box has disordered structure, uneven wall thickness, inconsistent cooling speed during forging, simple internal stress and hard appearance. Therefore, sandblasting and quenching and tempering personnel shall be reasonably arranged after forging.
In the machining industry, there is such a machining machine tool. The operation process is completely commanded by technicians with computer programming code. It belongs to precision machining equipment, which is often referred to as CNC machining. Today, let’s briefly understand the clamping methods in CNC machining parts
Before CNC machining parts, different clamping methods need to be selected for the size of parts. What kinds of clamping methods are there in the process of part processing? The first is to clamp the parts with the jaw, which is suitable for the processing of parts with small appearance and without exceeding the jaw range; Thirdly, it is directly fixed to the platform for processing. Generally, it is the processing of large and complex parts, because fixed on the platform can also improve the processing quality; Finally, the fixture is used to clamp parts for processing. For some batch parts or mass parts processing, the main advantage is accurate positioning processing and improve production and processing efficiency!
The above is the description of clamping methods in CNC machining parts.
In the machining circuit, parts with high precision requirements are often encountered. Now let’s understand the analysis of positioning error in processing technology
In terms of machining process, the positioning error is divided into many cases. The following shall be paid attention to during operation:
Positioning error refers to the positioning error of a machining accuracy parameter in the machining process of machining a part. It is an integral part of the machining error of the machining accuracy parameter.
A process and positioning scheme can produce different positioning errors for several machining accuracy parameters of the process. Therefore, the positioning errors of these machining accuracy parameters shall be calculated respectively.
The premise of analyzing and calculating the positioning error is to use the fixture to clamp and process a batch of parts with the adjustment method to meet the processing requirements.
The positioning error calculated by analysis refers to the maximum positioning error range that may occur when processing a batch of workpieces. It is a limit value, not a specific value of the positioning error of a workpiece.
The most position change of the design basis for processing a batch of parts relative to the fixture tool adjustment basis is the reason for the positioning error, not necessarily the positioning error.
These points simply understand the analysis and calculation of positioning error. There are many reasons for the error affecting the size in the process of precision CNC machining parts and mechanical parts machining.
Nowadays, in the field of machining industry, ordinary machining equipment can not meet the quality requirements. Now CNC machining equipment replaces the traditional machine tool machining, mainly precision CNC machining and CNC lathe machining; Let’s learn about the characteristics of precision CNC machined parts:
Advantages of CNC machining center in precision machining process:
Precision CNC has high machining precision and high machining quality;
CNC machining can carry out multi coordinate linkage, and can process parts with complex shapes;
When precision CNC machining parts are changed, generally only the NC program needs to be changed, which can save the production preparation time;
Precision CNC machining itself has high precision and rigidity. It can choose favorable processing dosage and high productivity (generally 3 ~ 5 times that of ordinary machine tools);
CNC machine tools have a high degree of automation, which can reduce labor intensity;
CNC machining center mass production, easy to control product quality and save labor operation;
The above is about the characteristics of precision CNC machining. Thank you for your attention!
In the field of mechanical parts processing industry, “machining” refers to the process of changing the overall dimension or performance of the workpiece through a kind of mechanical equipment. Can precision machining be used? “Precision machining” belongs to the finishing process in machining. It is divided into cold machining and hot machining according to the temperature state of the machined workpiece. This is the difference between “machining” and “precision machining”!
What is the difference between machining and precision machining in the working process? Precision machining often refers to the processing of parts with special requirements, which should be matched with reasonable processing equipment, such as CNC processing, CNC lathe processing, precision grinder processing, etc; Machining refers to ordinary turning, milling, grinding and other equipment. It can also be said to be one of the differences between “machining” and “precision machining”.
The above is the difference between “machining” and “precision machining”. Thank you for your attention!
In the mechanical parts processing industry, the unreasonable processing technology of precision parts will directly affect the quality. How to ensure precision parts processing, reasonable processing technology is closely related. Let’s take a look at the solution to the tool receiving trace during the processing of aluminum CNC parts:
Finish machining and rough machining shall be separated, and an appropriate amount of finish machining allowance shall be reserved: in order to ensure that the appearance and size of the product meet the standard value, usually there will be a knife path on the part surface before finish machining, so the allowance after rough machining should be guaranteed to be between 0.05mm ~ 0.15mm.
Aluminum material is light and belongs to one of the easy cutting materials. Programming command cutting command, the dialog box will also change due to different programming software, but the cutting tolerance is an indispensable setting parameter in programming, and the size of the tolerance also directly affects the accuracy and appearance of the product.
In the cutting process, optimize the overlap of advance and retreat tools: after optimizing the program, although there will be overlapping traces at the advance and retreat tools, the embossing and tool receiving marks can be eliminated.
It can improve the size and appearance. Selective feed / retract: extend the feed / retract line so that neither feed nor retract will contact the workpiece, making the machining surface smoother.
Finally, check the accuracy of the machine tool, which needs regular maintenance. Using the platform bottom plate for a long time will damage and the machine tool platform will also produce errors.
The above are the solutions to the precision CNC machining process.
