The quality of the finished parts directly affects the quality of the mold, and the final quality of the parts is guaranteed by finishing.
In most domestic mold manufacturing companies, the methods used in the finishing stage are generally grinding, electrical machining and fitter machining. At this stage, it is necessary to control many technical parameters such as part deformation, internal stress, shape tolerance and dimensional accuracy. In the specific production practice, the operation is more difficult, but there are still many effective empirical methods that are worth learning.
The machining of mold parts can be roughly divided into three categories according to the appearance and shape of the parts: plates, special-shaped parts and shafts. The common process is roughly: rough machining-heat treatment (quenching, quenching and tempering)- Fine grinding-electrical machining-fitter (surface treatment)-assembly machining.
1. Heat treatment of parts
In the heat treatment process of the parts, while obtaining the required hardness of the parts, it is also necessary to control the internal stress to ensure the dimensional stability of the parts during machining. Different materials have different treatment methods. With the development of the mold industry in recent years, the types of materials used have increased. In addition to Cr12, 40Cr, Cr12MoV, and cemented carbide, for some convex and concave molds with high working strength and severe stress, new materials powder alloy steel can be used. , Such as V10, ASP23, etc., this kind of material has high thermal stability and good organization state.
For parts made of Cr12MoV, quenching is performed after rough machining. After quenching, the workpiece has a large residual stress, which is likely to cause cracks during finishing or work. After quenching, the parts should be tempered while hot to eliminate quenching stress. The quenching temperature is controlled at 900-1020℃, then cooled to 200-220℃, air-cooled, and then quickly returned to the furnace for tempering at 220℃. This method is called a primary hardening process, which can obtain higher strength and wear resistance. The mold that is the main failure mode works better. In the production, some workpieces with many corners and complex shapes are encountered. Tempering is not enough to eliminate the quenching stress. Stress relief annealing or multiple aging treatments are required before finishing to fully release the stress.
For V10, APS23 and other powder alloy steel parts, because they can withstand high temperature tempering, the secondary hardening process can be used during quenching, quenching at 1050-1080℃, and then tempering at 490-520℃ for many times. With high impact toughness and stability, it is very suitable for molds with chipping as the main failure mode. The cost of powder alloy steel is relatively high, but its performance is good, and it is forming a trend of widespread use.
2. Grinding of parts
There are three main types of machine tools used in grinding: surface grinders, internal and external cylindrical grinders, and tool abrasives. During finishing grinding, grinding deformation and grinding cracks should be strictly controlled. Even very small cracks will be exposed in the subsequent machining and use. Therefore, the feed of the fine grinding should be small, not large, the coolant should be sufficient, and the parts with the size tolerance within 0.01mm should be ground as much as possible at a constant temperature. From the calculation, it can be seen that for a 300mm long steel, when the temperature difference is 3℃, the material will have a change of about 10.8μm, 10.8=1.2×3×3 (1.2μm/℃ per 100mm deformation), and each finishing process needs to fully consider this The influence of one factor.
It is very important to choose an appropriate grinding wheel during fine grinding. For the high vanadium and high molybdenum condition of the mold steel, it is more suitable to use GD single crystal corundum grinding wheel. When machining hard alloys and materials with high quenching hardness, organic bonding is preferred. The self-grinding properties of diamond grinding wheels and organic binder grinding wheels are good, and the roughness of the ground workpiece can reach Ra=0.2μm. In recent years, with the application of new materials, CBN grinding wheels, namely cubic boron nitride grinding wheels, have shown Very good machining effect, finishing on CNC form grinding, coordinate grinder, CNC internal and external cylindrical grinder, the effect is better than other types of grinding wheels. During the grinding process, attention should be paid to dressing the grinding wheel in time to keep the grinding wheel sharp. When the grinding wheel is passivated, it will rub and squeeze on the surface of the workpiece, causing burns on the surface of the workpiece and reducing its strength.
Most of the machining of plate parts are processed by surface grinders. In the machining, a long and thin sheet part is often encountered, and the machining of such parts is difficult. Because during machining, under the action of magnetic force, the workpiece deforms and sticks to the surface of the worktable. When the workpiece is removed, the workpiece will return to deformation. The thickness measurement is consistent, but the parallelism cannot meet the requirements. Solution Magnetic isolation grinding method can be used. Contour blocks are used to pad under the workpiece during grinding. Blocks on all sides are used to resist the death. During machining, small feeds and multiple smooth knives can be used. , This can improve the grinding effect and meet the requirements of parallelism.
Shaft parts have revolving surfaces, and internal and external cylindrical grinders and tool grinders are widely used for machining. During the machining, the headstock and the top are equivalent to the bus bar. If there is a runout problem, the processed workpiece will also have this problem, which will affect the quality of the parts. Therefore, the headstock and the top must be inspected before machining. When grinding the inner hole, the coolant should be poured to the grinding contact position to facilitate the smooth discharge of the grinding. For machining thin-walled shaft parts, it is best to use a clamping technology table, and the clamping force should not be too large, otherwise it is easy to produce "inner triangle" deformation on the circumference of the workpiece.
3. Electrical machining control
Modern mold factories cannot lack electric machining. Electric machining can process all kinds of special-shaped and high-hardness parts. It is divided into two types: wire cutting and electric spark.
The machining accuracy of slow-moving wire cutting can reach ±0.003mm, and the roughness is Ra0.2μm. When the machining starts, check the condition of the machine tool, check the deionization degree of the water, the water temperature, the perpendicularity of the silk, the tension and other factors to ensure a good machining state. Wire-cutting machining is to remove machining on a whole piece of material, it destroys the original stress balance of the workpiece, it is easy to cause stress concentration, especially at the corners, so when R<0.2 (especially sharp corners), you should The design department makes suggestions for improvement. The method to deal with stress concentration in machining can use the principle of vector translation. Before finishing, leave a margin of about 1mm, pre-process the rough shape, and then perform heat treatment to release the machining stress before finishing to ensure thermal stability.
When machining the punch, the cutting position of the wire and the selection of the path should be carefully considered. The best effect is achieved by perforating and threading. High-precision wire-cutting machining, usually the number of cutting passes is four, which can guarantee the quality of the parts. When machining taper dies, based on a fast and efficient standpoint, the first round of rough machining of straight edges, the second pass of taper machining, and then the finishing of straight edges, so that X-segment vertical finishing is not required, only Finishing the straight edge of the cutting edge section saves time and cost.
EDM first needs to make electrodes. Electrodes can be coarse and fine. The precision machining electrode requires good shape conformity, and it is best to be processed by CNC machine tools. In terms of electrode material selection, copper electrodes are mainly used for general steel machining. The Cu-W alloy electrode has good overall performance, especially the consumption during machining is obviously smaller than that of copper. With a sufficient amount of scouring fluid, it is very suitable for the machining of difficult-to-process materials and the finishing of parts with complex cross-sectional shapes. When making electrodes, it is necessary to calculate the amount of electrode gap and the number of electrodes. When machining large areas or heavy electrodes, the workpiece and electrode should be clamped firmly to ensure sufficient strength to prevent machining looseness. When performing deep step machining, pay attention to the wear of the electrode and the arc discharge caused by poor drainage.
4. Surface treatment and assembly
The tool marks and wear marks left on the surface of the part are the place where the stress is concentrated and the source of the crack propagation. Therefore, after the machining is completed, the surface of the part needs to be strengthened and polished by a fitter to deal with hidden machining hazards. Some edges, acute angles, and orifices of the workpiece are dulled and rounded. Generally, the electro-processed surface will produce a metamorphic hardened layer of about 6-10μm. The color is off-white, the hardened layer is brittle and contains residual stress. The hardened layer must be fully eliminated before use. The method is surface polishing and grinding to remove the hardened layer.
In the process of grinding and electrical machining, the workpiece will be magnetized to a certain extent, with weak magnetic force, and it is easy to attract some small things.
Therefore, before assembly, the workpiece should be demagnetized and the surface should be cleaned with ethyl acetate. During the assembly process, first refer to the assembly drawing, find the parts, and then list the equipment sequence between the parts, list the items that should be noted, and then proceed to assemble the mold.
The assembly generally first installs the guide pin and guide sleeve, and then installs the mold Frames and convex and concave molds, and then adjust the various gaps, especially the gap between the convex and concave molds.
After the assembly is completed, the mold inspection should be carried out and the overall situation report should be written. For the problems found, the reverse thinking method can be used, that is, from the back process to the previous process, from finishing to roughing, checking one by one until the crux is found and the problem is solved.
Keywords:finished parts
What is the difference between precision cnc machining and sheet metal machining...
The density of magnesium and magnesium alloys is low, only 1.74g/cm3, which is t...
The accuracy of CNC machining center mainly includes geometric accuracy, positio...
In our precision CNC hardware machining, the machining allowance is too small to...
CNC turning is mainly used to make round parts and is also the first choice for ...
Computer numerical control CNC milling is generally a metal fabrication process;...
Magnesium parts are easily oxidized by air after CNC milling, so how should anti...
Aluminum precision parts machining technology are the most widely used non-ferro...
CNC machining is a process method for machining parts on a CNC machine tool, and...
How to improve the efficiency and quality of CNC machining ? This is a commonpla...
What does 7:24 in CNC MACHINING BT handle mean? What are the standards of BT, NT...
Ordinary CNC machining generally refers to precision machining, CNC machining la...
Various casting methods including sand casting magnesium alloy, metal casting ma...
In our precision parts machining industry, the most commonly used machining meth...
There are many kinds of aluminum parts processed by CNC machine tools, among whi...
Aluminum and aluminum alloy cnc machining can be divided into rolling, extrusion...
CNC machining operation specification, mainly divided into 10 parts of CNC machi...
Many previous production and CNC machining methods and machining equipment have ...
CNC machining, also known as CNC machine tool machining, refers to the machining...
Aluminum alloy precision parts have high strength, good plasticity, excellent el...
Many people want to know what is the process of aluminum machining? In fact, the...
Nowadays, there are more and more, and the machining of precision parts is the s...
During the welding process of aluminum plate, if the atmosphere is in direct con...
There are generally two processes for mirror aluminum machining. One is to polis...
When looking for aluminum alloy precision parts machining plants, we need to cho...
Aluminum alloy machining technology is obtained by adding other metal elements t...
magnesium and aluminum Comparison In terms of technology, the current production...
CNC machining is still one of the cost-effective methods of on-demand production...
What are the Precision parts cnc machining skills characteristics of precision m...
Generally, the traditional Magnesium micro-arc oxidation film of magnesium alloy...
magnesium Micro-arc oxidation is a new technology for in-situ growth of ceramic ...
CPCI Rugged Chassis Shell is a customized chassis of our company. It has sturdin...
ATR chassis case machining was drafted by the American Avionics Technical Commit...
Aluminum alloy welding heat input is easy to quickly lose to the base metal, and...
Break through the technical difficulties of magnesium alloy machining,This techn...
The CNC machining process of magnesium alloy must be operated continuously, and ...
3D printing is a new type of rapid prototyping technology that integrates cuttin...
Compared with the equivalent material manufacturing process 3D printing has many...
Many people want to know what the aluminum profile machining process is like? In...
In the investment Precision casting production process, the reason for the burrs...
The structural parts with magnesium alloy as the base material are mainly used i...
Cutting fluids are generally divided into two types: oil-based and water-based. ...
The connection parts of the aluminum alloy body frame structure are formed by ca...
Aluminum forming The internal high pressure forming technology is a new type of ...
The solid shell protects the board, power supply and storage equipment, and can ...
Aluminum alloy is obtained by adding other metal elements to metal aluminum to o...
Aluminum shells are various shells made of aluminum alloys. It is highly flexibl...
Magnesium alloys are more and more widely used in modern society. Due to their u...
A lathe is a machine tool that mainly uses a turning tool to turn a rotating wor...
Usually five-axis linkage refers to the linear interpolation movement of any 5 c...
Four-axis: Generally, when the workpiece is not positioned in space, there are s...
Welding, also known as welding, is a manufacturing process and technology for jo...
For mechanical precision machining of gears and shaft parts, it is necessary to ...
CNC machining center is an automatic processing equipment developed by CNC milli...
Castings obtained by casting methods are called castings. So do you know what th...
Three-axis machining is processed by linear feed axes X, Y, and Z. Used for gene...
Precision workpiece roughness is in line with international standards (ISO), and...
There are many Parts machining technology, and the types of workpieces to be pro...
The role of the Precision parts Roving frame is to guide the yarn, and then guid...
Today I will talk about the general inspection and maintenance methods when the ...
In the near future, this project, known as the first unmanned CNC machining fact...
How will the tension in Ukraine affect China's manufacturing industry? This art...
Under the COVID-19 pandemic, China's manufacturing industry has resumed work on...
CNC machining quotations include material costs, machine depreciation costs, lab...
Because of the differences in aluminum materials, different machining processes,...
Chinese precision machining plants are high-end in many fields and in the world....
Aluminum alloy has better physical and mechanical properties than pure aluminum,...
Now every step of the mobile phone we hold in our hands is inseparable from prec...
Precision machining in China,China's machining industry, which is gradually grow...
Aluminum alloy forging production technology has developed by leaps and bounds, ...
In 2020, my country's total casting production has reached 51.95 million tons, ...
CNC machining can be said to be a more popular machining method at present. Comp...
CNC machining is a method of controlling machine tool movement and machining pro...
manufacturing machining 4.0 development was first proposed by Universal Robots o...
The United States has put forward the concept of smart manufacturing, which is g...
In recent years, the equipment manufacturing industry has achieved rapid develop...
In German manufacturing, there is a very interesting and crucial point: don't b...
The quality of the finished parts directly affects the quality of the mold, and ...
How are many things in daily life made from small springs to large cars? In fact...
Magnesium alloys have always attracted designers due to their low density. In th...
For a military case, it is very important to have a solid appearance, but when w...
Latest news
What is the difference between precision cnc machining a ...
The density of magnesium and magnesium alloys is low, on ...
The accuracy of CNC machining center mainly includes geo ...
In our precision CNC hardware machining, the machining a ...
Latest cases
The advanced equipment of the receiver housing can guara ...
The CPCI reinforced chassis is made of high-quality alum ...
Scan! Add WhatsAPP
Scan! Add WeChat