Let me explain to you how many processes exist in the processing of precision mechanical parts

Let me explain to you how many processes exist in the processing of precision mechanical parts

The mold is composed of multiple components.

The processing quality of precision machinery parts directly affects the quality of the mold, and the final quality of the parts is guaranteed by the processing of precision machinery parts.

Therefore, it is very important to control the machining of precision mechanical parts.

In most mold manufacturers in China, the methods used in the processing stage of precision mechanical parts are generally grinding, electrical machining and fitter machining.

At this stage, we should control many technical parameters, such as part deformation, internal stress, shape tolerance, and dimensional accuracy.

In the specific production practice, the operation is difficult, but there are still many effective experiences and methods worth reference.

The processing of mold parts can be roughly divided into three categories according to the appearance and shape of the parts: plate, special-shaped parts and shaft.

Its common process flow is roughly: rough processing-heat treatment (quenching, quality adjustment) -fine grinding-electric processing-fitter (surface treatment) -assembly processing.

The heat treatment process of parts needs not only to control the hardness of the parts, but also to control the internal stress to ensure the stability of the size during the parts.

Different materials have different treatment methods.

With the development of mold industry in recent years, in addition to the use of material type, also use more materials Cr 12,40 Cr, Cr12MoV, in addition to the carbide, for some high strength, stress convex concave mold, can choose new material powder alloy steel, such as V10, ASP 23, etc., this material has high thermal stability and good organization state.

For Cr12MoV for material parts, after rough machining quenching.

After quenching, the workpiece has a large retention stress, which easily leads to the cracking of precision mechanical parts in machining or work.

After quenching, tempering should be heated to eliminate the quenching stress.

The quenching temperature is controlled at 900-1020℃, and then cooled to 200-220℃ air cooling, quickly furnace 220℃ tempering, this method is called hardening process, can obtain higher strength and wear resistance, have better effect to wear as the main form of failure mold.

In some workpieces with many angles and complex shapes, the tempering is not enough to eliminate the quenching stress.

Precision mechanical parts should be stress annealed or repeated timely treatment before processing, in order to fully release the stress.

For V10, APS 23 powder alloy steel parts, because they can withstand high temperature tempering, quenching secondary hardening process, 1050-1080℃ quenching, and then 490-520℃ high temperature tempering can obtain high impact toughness and stability, is very suitable for the collapse blade as the main failure form of mold.

Powder alloy steel has high cost, but good performance, is forming a wide application trend.

There are three main types of grinding machine tools: plane grinder, internal and external circular grinder and tool grinder.

When processing and grinding the precision mechanical parts, the grinding deformation and grinding crack production should be strictly controlled.

Even very small cracks are exposed to subsequent processing and use.

Therefore, the precision grinding knife should be small, not large, the coolant should be sufficient, the size tolerance in 0.01mm as far as possible to grinding the internal parts.

It can be seen from the calculation that when the temperature difference of 300mm is 3℃, the material changes about 10.8 μ m, and 10.8=1.233 (deformation of 1.2 μ m / ℃ per 100mm). The influence of this factor should fully consider the processing process of each precision mechanical parts.

It is very important to choose the right grinding wheel during fine grinding.

According to the mold steel of high vanadium high molybdenum, choose GD single crystal corundum wheel is more suitable, when processing hard alloy, high quenching hardness material, priority using organic adhesive diamond wheel, organic adhesive wheel, grinding piece rough Ra = 0.2 μ m, in recent years, with the application of new materials, CBN grinding wheel, namely, cubic in the CNC grinding, coordinate grinding machine, CNC precision mechanical parts processing effect is better than other types of grinding wheel.

During the grinding process, attention should be paid to timely repairing the grinding wheel in order to maintain the sharpness of the grinding wheel.

When the grinding wheel passivate, it will slide and squeeze on the work surface, resulting in burns on the work surface and reducing the strength.

Most of the plate parts processing using flat grinder processing, in the processing process often encountered long and thin plate parts, difficult to process.

Due to the processing process, under the action of magnetic adsorption, workpiece deformation, close to the surface of the workbench, remove the workpiece, the workpiece will produce recovery deformation, thickness measurement, but the parallelism cannot meet the requirements, the solution can use magnetic grinding method, grinding pad under the workpiece, block death, processing knife, light knife, after processing, do not need to pad, direct adsorption processing, can improve the grinding effect, meet the requirements of parallel processing.

shaft parts have rotating surface and are widely used in inner and outer round grinder and tool grinder.

During machining, the head frame and the top are equivalent to the bus bar.

If there is a beating problem, the processed workpiece will also produce this problem, affecting the quality of the parts.

Therefore, the head frame and top should be done before processing.

When grinding the inner hole, the coolant should be fully poured into the grinding contact position to promote the smooth discharge of grinding.

When processing thin-wall shaft parts, it is best to use the clamping process table, the clamping force should not be too large, otherwise the inner triangle deformation is easy to produce around the workpiece.

Modern mold factory can not lack of electric processing, electric processing can process a variety of special-shaped, high hardness parts, divided into wire cutting and electric spark.

The slow wire cutting accuracy is ± 0.003mm and the roughness Ra 0.2 μ m.

At the beginning of processing, first check the condition of the machine tool, check the deionization of water, water temperature, the verticality of the line, tension and other factors, to ensure a good processing state.

Wire cutting processing is to remove the whole material, destroy the original stress balance of the workpiece, easy to cause stress concentration, especially at the corner, so when R <0.2 (especially the sharp corner), improvement suggestions should be put forward to the design department.

The principle of vector translation can be used for the treatment of stress concentration in the processing process, precision machinery parts have a margin of about 1mm before processing, pre-shape, and then heat treatment, so that the processing stress is released before the processing of precision machinery parts, to ensure thermal stability.

When processing the convex mold, the cutting position of the filament and the choice of the path should be carefully considered.

Using perforated silk processing, the best effect.

High precision wire cutting processing, usually cut four times, can ensure the quality of the parts.

When processing the cone concave mold, according to the fast and efficient position, the first rough machining straight edge, the second cone processing, and then precision mechanical parts machining straight edge, no need for X section vertical machining to precision mechanical parts, only precision mechanical parts machining edge straight edge, saving time and cost.

Electrospark processing should be made electrodes, electrodes can be divided into coarse, fine.

Precision mechanical parts processing electrodes need good shape compliance, the best use CNC machine processing.

Purple copper electrode is mainly used for general steel processing.

Cu-W alloy electrode has good comprehensive performance, especially in the processing process, its consumption is significantly less than copper.

Combined with enough cleaning solution, it is very suitable for processing material processing and cross-section shape of complex precision mechanical parts processing.

When making electrodes, the calculation of the gap and the number of electrodes.

When large area or heavy electrode processing, the workpiece and electrode clamp should be firm to ensure sufficient strength to prevent the processing loose.

In the process of deep step processing, attention should be paid to the arc discharge caused by electrode loss and poor drainage.

The knife marks and grinding marks left on the surface of the parts in the processing process are the place of stress concentration and the source of crack expansion.

Therefore, after processing, it is necessary to strengthen the surface of the parts and polish them through the fitter to deal with the hidden dangers of processing.

Some edges, sharp corners and holes of the workpiece are blunt, R generally speaking, the electroprocessing surface will produce about 6-10 μ m deterioration hardening layer color is gray white, hardening layer crisp, with residual stress.

The hardening layer should be fully eliminated before use.

The method is to polish the surface, polishing to remove the hardening layer.

In the process of grinding and electrical processing, the workpiece will have a certain magnetization, weak magnetic force, it is easy to absorb some small things.

Therefore, before assembly, the workpiece should be demagnetized and the surface should be cleaned with ethyl acetate.

In the assembly process, first refer to the assembly drawings, find all parts, and then list the equipment order between the parts, list the matters needing attention, and then begin to assemble the mold, assembly generally first install the guide guide, and then install the mold and concave mold, and then the assembly gap, especially the concave mold gap, assembly mold test, write the overall situation report.

For the problems found, we can use the reverse thinking method, that is, from the back process to the front process, from the precision mechanical parts to the rough machining, check one by one, until we find out the key and solve the problem.

Practice has proved that good precision mechanical parts processing process control can effectively reduce the poor and scrap of parts, effectively improve the one-time success rate and service life of the mold.

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