Abstract: powder mixed EDM is
a way to improve the the EDM surface roughness and the processing efficiency of
advanced process methods in recent years, such as the phone shell, remote shell
mold cavity mold EDM finishing play an increasingly important role. In this paper, the cavity mold powder mixed EDM
machining applications technology to explore manufacturing companies to absorb
and digest the current state-of-the-art electrical discharge machining process
with the actual value of the mold.
Keywords: cavity mold; powder mixed EDM processing; process method
1 Introduction
The EDM technology widely used in the cavity mold manufacturing. At present, the rapid development of mold manufacturing technology has given a spark higher processing requirements. The surface roughness is an important technical indicators EDM, multi-cavity mold EDM implementation of uniform surface of Ra <0.4 um.
EDM finishing in the ordinary spark oil (not mixed powder), a large parasitic capacitance is formed when the machining area is larger, the workpiece and the electrode will produce the concentrated discharge phenomenon, the production efficiency is very low, the surface roughness is difficult achieve processing requirements, therefore, in the past, the complex cavity mold matt require surface can not achieve a uniform surface processing requirements Finishing mainly rely on manual polishing.
Powder mixed wire EDM It is based on the drawbacks of the above finishing the development of a technology. It has significant advantages are: high processing efficiency, the finishing time is greatly reduced, improving the efficiency of production mold; surface uniformity is good, a significant improvement in the finishing degree of uniformity of a large area, and to improve the mold surface quality; For large area of the processing, the same can reach surface roughness below Ra0.4um below, to meet the high demands of the mold manufacturer.
Powder mixed EDM technology has been commercialized, and some CNC EDM forming machine tools supporting application, favored by mold makers.
2 powder mixed EDM application technology of
Based on the application of the mixed powder processing practices of the the GF AgieCharmilles Blue Line SA CNC EDM, based on the actual processing experience, to explore the key technology of powder mixed EDM applications.
The 2.1 powder mixed EDM brief principle
EDM is the so-called powder mixed refers to the powder (such as silica fume), added in the working fluid throughout the EDM process in such a powder of the working fluid in certain concentration. Powder mixed EDM mixed with a certain proportion of the conductive or semi-conductive ultrafine powder due to the working fluid medium, the distances between electrodes of the discharge increase drastically reduced, so that the parasitic capacitance between the workpiece and the electrode, destructive parasitic capacitance discharge no longer occurs, easy to form the spark discharge, the discharge gap becomes larger than conventional EDM, can effectively prevent the concentrated discharge occurs, the discharge uniformly generated in the machining surface, the corresponding discharge pits uniformly distributed in the processing surface, the formation of large shallow discharge pits. Overlapping discoid pitted surface, than the ordinary discharge surface to be smooth, reduces irregular reflection of light and easy to form a flash of the mirror.
The 2.2 powder mixed EDM machine requirements
To successfully implement the powder mixed EDM, CNC EDM requirements.
1) Because the working fluid in the added powder, first requires the EDM machine having a device to prevent powder precipitated. SA CNC EDM of the GF AgieCharmilles Blue Line products installed around the workbench in working sump circle pipe, the pipe evenly distributed holes; same tank, install a circle with a hole in the pipeline; using high-power oil pump high-power pump work, the working fluid is ejected from the pipe holes, powder mixed working fluid is supplied to the working tank, while the liquid in the sump of work constantly circulating to prevent powder precipitation, on the other hand, the oil pump is the same to the fuel tank the conduit supplying the powder mixed working fluid, the working fluid discharged from the pipe holes so that the liquid in the tank is constantly circulating, to prevent the powder precipitated.
2) to request the EDM machine having a mirror-finished circuit, i.e. requirements pulsed power supply of the machine tool having a minimum of a single pulse energy (nanosecond pulse width, low power) of the peak current, stable discharge can be performed in the small discharge energy processing.Some of the ordinary type EDM pulse power having a small single pulse energy, but it does not meet the sustained and stable discharge of the mirror-finished, by mixing powder technology to improve the stability of discharge, but still can not ensure a reliable predetermined processing effects . High-performance pulse power can not only improve the processing efficiency can also reduce electrode wear and surface roughness. The GF AgieCharmilles Blue Line SA CNC EDM the Agie energy pulse power ISOPULSE.
3) the EDM machine has a rich application functionality. Flexible preparation processing program, with translation space powder mixed EDM requirements (see below for more details).
Visible, choose a reliable powder mixed CNC EDM is a prerequisite for successful powder mixed EDM machining.
2.3 powder mixed EDM machining process
Carried powder mixed EDM process analysis, to determine whether the cavity suitable powder mixed EDM. Powder mixed EDM processing for a large area of high-quality finish. For the vast majority of the cavity mold, such as mobile phone shell mold, remote control shell mold powder mixed EDM can be used as the final machining of the cavity surface. Even high speed milling of the three-dimensional curved surface, due to the obtained non-continuous smooth surface and therefore still need to use EDM finishing was carried out, to give a smooth machined surface. Clear angle requirements for micro-cavity, mixed powder processing due to the presence of powder in the working fluid in the discharge gap large and difficult to achieve some fine pieces, such as IC die size requirements of precision, the mixed powder processing is clearly inappropriate.
Carried powder mixed EDM, the cavity must undergo pre-milling processing, and leaving an appropriate allowance. EDM is a process from roughing to finishing process. Replaced by a multi-electrode process methods, complete with two different sizes of the electrode of the amount of scaling to a cavity of the roughing and finishing. First using the roughing electrode, in conditions that guarantee a certain processing quality (dimensional accuracy and shape accuracy, position accuracy, surface roughness), the use of a large discharge energy erosion lot of metal, in order to shorten the processing time and improve the processing efficiency. (Cavity roughing required processing in the state of the non-powder mixed otherwise roughing erosion down coarse particles of the material and the powder is mixed, affect the machining effect); then finishing electrodes powder mixed EDM meet the requirements of the machining accuracy and surface quality.
To strictly control the powder mixed EDM roughing size. If roughing reserved processing volume is too small, then the mixed powder processing will not be able to fully repair on the impact surface effects; too if roughing processing capacity reserved, then the mixed powder processing will be difficult to remove excess material , resulting in very slow processing speed, fatigue electrode. Recommend roughing cavity surface reached VDI25 (Ra1.8um) level and underside reserved 0.07mm, side unilateral reserved 0.08mm.
Mixed powder EDM process, often highly stable discharge state can be maintained, and generally does not produce coke formation, and therefore in the process should be minimal downtime, especially not in the workpiece surface of the powder layer will remain clean out, so as not to interfere with the normal discharge process.
Powder mixed EDM requires good control of all aspects of, in pursuit of the success rate of primary processing, improper details of the deal to produce subtle defects will lead to repeated trimming often spend multiple of time.
2.4 powder mixed EDM working liquid and powder
Electric discharge working fluid in the process plays a deionization and cooling, to exclude the role of the product of the electric corrosion. For the EDM finishing with the working fluid, low viscosity requirements, to ensure that the slag between the electrodes has a good cleaning performance; oxidation resistance and thermal stability of the working fluid is also very critical, and to determine the service life of the oil. The GF AgieCharmilles Blue Line SA CNC EDM mixed powder processing recommends equipped with a spark oil TOTAL EDM 3 (Total of France, viscosity at 20 ° C: 6.7 mm2 / s (cST), a flash point of OC:> 135 ° C).
Powder mixed EDM working solution powder, silicon powder, aluminum powder, magnesium powder, graphite powder, several basic According to many domestic and foreign mixing powder processing technology reported. SA20 powder used AgieCharmilles Group study dedicated powder mixed solution and its main components for the graphite particles, the approximate length is less than 8um, the concentration requirements for the powder is added 2g / L. Every replacement powder mixed fluid needs to be filtered, clean spark oil to filter out the debris in the process and the failure of the powder then add the powder mixed solution. The mixed powder solution requires the best replacement after processing 350 or 400 hours. Black mud powder mixed precipitation processing will work inside the slot, and experience has shown that the mud sparks oil again mixed, because it would seriously affect the processing performance.
Powder mixed liquid concentration greater impact on the machined surface effect. The concentration of the solution of the mixed powder is not enough, within a short period of time can not meet the requirements of surface effects, reducing the processing efficiency. Occasion requires mirror surface finishing, it will lead to the effect of surface gloss is poor due to the mixed powder concentration is not enough; When the concentration of the mixed powder is excessively large, the cavity of the sharp edge corners will be damaged, reducing the machining accuracy. Between the electrode and the workpiece due to the presence of more powder, the powder will produce the bypass cause the flow of short-circuit serious when the workpiece surface scars.
Powder mixed EDM process, working sump tank liquid in circulation, and is not recommended to use the red liquid processing, in particular, can not use a strong red liquid, otherwise it will cause uneven flow field in the discharge process, affect the uniformity of the surface effect.
2.5 mixed powder EDM parameter configuration
Powder mixed EDM parameter configuration including: electric gage, such as current, pulse width, pulse gap; value of the discharge gap and set aside the amount of electricity per file gage.
Powder mixed EDM must ensure that each file electric Criteria for discharge to stabilize, the final gage can meet the requirements of surface effects. A plurality of gage sequentially reducing the current, pulse width sequentially reduced, then matching the corresponding pulse gap servo gap. Usually VDI18 level (Ra0.8um) Criteria The following the negative processing parameters (electrode negative). Stall regulating the discharge energy gradually decreases, and the to gradually repair of light to meet the requirements of the surface roughness. Worth mentioning is that the powder mixed EDM can generate a high processing efficiency, compared with the ordinary working fluid greater the discharge energy can be used to achieve the same surface roughness. Further, in the powder mixed EDM have a fairly good discharge stability, the discharge time to be set longer, carrying knives height shorter set such purpose is to maintain a stable electric erosion process, with a small energy conventional processing choice is different. [1]
Powder mixed EDM requires precise calculation of the electric gage the value of the discharge gap with the reserved amount. The smaller material reservation will affect the surface roughness of the processing, not only cause Revised. The optimal processing condition is the first condition After processing, subsequent processing only the wiper first surface formed by the processing conditions irregularities without knock down the new material. However, the actual processing, taking into account the constraints discharge status by the ever-changing, and therefore have to consider the safety of the reserved amount. The size of the margin can be determined according to the actual discharge condition, regarding the area is larger, the processing status is relatively good, may be appropriate to reduce the material margin, in order to improve the processing speed.
Advanced CNC EDM electric gage configuration generally intelligent. The machine has many sets of processing parameters, are the best combination of parameters through a lot of process experiments, according to the processing requirements to retrieve the processing conditions, such as input processing area and processing the shape of the electrode taper the electrode size scaling amount, shaking, and machined surface roughness value, the machine will be able to configure the optimal electric gage, it will process of processing multiple processing conditions in paragraph, paragraph by paragraph, the ability to reduce electrical erosion, smart set gage reserved. The electric gage generally chosen in such a smart way to meet the processing requirements, simple operation, but usually an automated way so as to ensure that the processing quality, processing efficiency will be lower. Actual production should be based on the repeated processing continue to accumulate experience, to optimize the process.
2.6 powder mixed EDM translational function
Powder mixed EDM of the cavity mold, required to achieve the requirements of dimensional accuracy, and additionally required the surface of the bottom and side of the same effect, which requires the CNC machine must have CNC translational functions. EDM machine tools with CNC translational function, it is relatively easy to control for dimensional accuracy. But to ensure the uniform surface of the bottom and the side effect, it requires the machine has to meet the requirements of the flat movable function. Powder mixed EDM process requires each gage the level of momentum with depth is to gradually increase the depth and level of momentum also will increase the bottom side in the synchronized axis linkage processing. Horizontally movable manner, while the timing of processing functions can be realized, that is, can specify the processing time of each gage, the bottom surface and the side surface of the surface obtained consistent results within a specified processing time. SA CNC EDM of the GF AgieCharmilles Blue Line products in powder mixed EDM space translation round selection. This horizontally movable manner in the finishing of the small energy, significantly improves the stability of the processing side and the bottom surface of the same effect can be realized. Some translational function in the powder mixed EDM NA, SA circular machine servo translational action is performed by the translational depth to complete electrical per file the Criteria must first processing run again a circumferential flat trajectory, obviously such a horizontally movable manner in the cavity mold powder mixed machining finishing stages are not suitable.
2.7 powder mixed EDM electrode
Powder mixed EDM electrode material, surface roughness, scaling size, accuracy.
Powder mixed EDM requires the use of high purity copper as the electrode material (such as Japan Sambo), processing performance is very good, and less prone to arc discharge or the transition arc discharge can obtain uniform machined surface. Graphite electrode in the the ordinary working fluid (no mixing powder) finishing in poor performance, but in the processing of the mixed powder, the powder is added to the working fluid, finishing discharge gap is large, field-proven, graphite electrode powder mixed electric EDM spark processing can also be achieved. Worthy of note is that the powder mixed EDM mirror processing, cavity claim must be strict requirements on the quality of the electrode material on affected otherwise processing effect, such as the use of the copper electrode material purity is not enough will lead to the processing of the mirror The effect of the surface may be local defects, uneven undesirable phenomena.
The EDM process is to copy the shape of the electrode to the workpiece up. Therefore, the electrode surface roughness to some extent determines the machined workpiece surface roughness, mirror finish with the electrode must be intensive polishing (at least after 1000 # sandpaper fine polishing), in order to achieve high-quality finish The EDM surface quality.
Determine the size of the EDM of the size of the first tranche of canonical energy libration amplitude scaling dimensions of the electrode process indicators that directly affect the processing speed, profiling accuracy. General finishing powder mixed EDM electrode size scaling amount taken unilateral 0.07 ~ 0.15 mm, processing area hours desirability of smaller, high profiling accuracy requirements desirable smaller.
With thick powder mixed EDM finishing electrode, which requires better consistency of the electrode manufacturing precision, replacement electrodes repeated clamping, higher positioning accuracy. High-speed milling can be used to manufacture electrodes, use the method of measuring the positioning of the reference ball, quick fixture positioning system repeatability of positioning and other advanced technology to meet the high requirements.
2.8 mixed powder EDM workpiece material
Powder mixed EDM machining results will produce different due to different workpiece material. The surface of different materials in the processing of grain surface level (VDI18 the surface / Ra0.8um) effects are not obvious, but due to the different characteristics of the workpiece material in the processing - mirror (VDI7 level surface / Ra0.2um of) access to the surface The effect of a greater difference. Some materials to get a good mirror effect, such as common mirror finish material: S136, SKD61, NAK80 steel imports; Some materials can not achieve the mirror effect, such as to the SKD11 (to equivalent of Cr12MoV). Mirror finish effect of the workpiece material impact that the following circumstances: a silicon-containing ingredients are conducive to better mirror effect; containing large particle size of coarse raw the carbide or coarse crystal particle additives adverse mirror processing, generating microcracks ; the sulfur containing fast-cut components of processing mirror to produce a surface stripes; material rolling direction the billet manufacturing process factors on the processing mirror to produce a surface stripes; metallic inclusions, bubbles, oxides and other factors in the formation of the eye of a needle and holes; The high hardness of the steel of the workpiece, and EDM mirror effect. General requirements for the mirror-finished workpiece material heat treatment hardened to HRC> 50. [2]
2.9 powder mixed EDM efficiency control
Efficient finishing powder mixed EDM control depends on several aspects: VDI22 more stronger regulations quasi processing efficiency is mainly determined by the amount set aside in the stall gage if the reserved amount is appropriate, with a certain ability to ablation , processing efficiency is relatively high electrical gage; VDI22 and below the more weakly electrically gage, each electrical electrical erosion gage weak ability, the processing when the size of the change is already small, substantially only play the role of the wiper, if strict accordance with the size specified in the execution of machining, the process takes a very long time. After the fact, as long as the processing requirements of surface roughness can end processing, timing CNC EDM machining function can be used to control the processing efficiency. According to the the EDM area to set the required light repair time.
3 Conclusion
With the increasing demands of the the mold industry manufacturing technology, powder mixed EDM will be the complexity of a large area of the cavity mold manufacturing technology. Powder mixed EDM study to provide reference for the promotion of technology for this application.
Keywords: cavity mold; powder mixed EDM processing; process method
1 Introduction
The EDM technology widely used in the cavity mold manufacturing. At present, the rapid development of mold manufacturing technology has given a spark higher processing requirements. The surface roughness is an important technical indicators EDM, multi-cavity mold EDM implementation of uniform surface of Ra <0.4 um.
EDM finishing in the ordinary spark oil (not mixed powder), a large parasitic capacitance is formed when the machining area is larger, the workpiece and the electrode will produce the concentrated discharge phenomenon, the production efficiency is very low, the surface roughness is difficult achieve processing requirements, therefore, in the past, the complex cavity mold matt require surface can not achieve a uniform surface processing requirements Finishing mainly rely on manual polishing.
Powder mixed wire EDM It is based on the drawbacks of the above finishing the development of a technology. It has significant advantages are: high processing efficiency, the finishing time is greatly reduced, improving the efficiency of production mold; surface uniformity is good, a significant improvement in the finishing degree of uniformity of a large area, and to improve the mold surface quality; For large area of the processing, the same can reach surface roughness below Ra0.4um below, to meet the high demands of the mold manufacturer.
Powder mixed EDM technology has been commercialized, and some CNC EDM forming machine tools supporting application, favored by mold makers.
2 powder mixed EDM application technology of
Based on the application of the mixed powder processing practices of the the GF AgieCharmilles Blue Line SA CNC EDM, based on the actual processing experience, to explore the key technology of powder mixed EDM applications.
The 2.1 powder mixed EDM brief principle
EDM is the so-called powder mixed refers to the powder (such as silica fume), added in the working fluid throughout the EDM process in such a powder of the working fluid in certain concentration. Powder mixed EDM mixed with a certain proportion of the conductive or semi-conductive ultrafine powder due to the working fluid medium, the distances between electrodes of the discharge increase drastically reduced, so that the parasitic capacitance between the workpiece and the electrode, destructive parasitic capacitance discharge no longer occurs, easy to form the spark discharge, the discharge gap becomes larger than conventional EDM, can effectively prevent the concentrated discharge occurs, the discharge uniformly generated in the machining surface, the corresponding discharge pits uniformly distributed in the processing surface, the formation of large shallow discharge pits. Overlapping discoid pitted surface, than the ordinary discharge surface to be smooth, reduces irregular reflection of light and easy to form a flash of the mirror.
The 2.2 powder mixed EDM machine requirements
To successfully implement the powder mixed EDM, CNC EDM requirements.
1) Because the working fluid in the added powder, first requires the EDM machine having a device to prevent powder precipitated. SA CNC EDM of the GF AgieCharmilles Blue Line products installed around the workbench in working sump circle pipe, the pipe evenly distributed holes; same tank, install a circle with a hole in the pipeline; using high-power oil pump high-power pump work, the working fluid is ejected from the pipe holes, powder mixed working fluid is supplied to the working tank, while the liquid in the sump of work constantly circulating to prevent powder precipitation, on the other hand, the oil pump is the same to the fuel tank the conduit supplying the powder mixed working fluid, the working fluid discharged from the pipe holes so that the liquid in the tank is constantly circulating, to prevent the powder precipitated.
2) to request the EDM machine having a mirror-finished circuit, i.e. requirements pulsed power supply of the machine tool having a minimum of a single pulse energy (nanosecond pulse width, low power) of the peak current, stable discharge can be performed in the small discharge energy processing.Some of the ordinary type EDM pulse power having a small single pulse energy, but it does not meet the sustained and stable discharge of the mirror-finished, by mixing powder technology to improve the stability of discharge, but still can not ensure a reliable predetermined processing effects . High-performance pulse power can not only improve the processing efficiency can also reduce electrode wear and surface roughness. The GF AgieCharmilles Blue Line SA CNC EDM the Agie energy pulse power ISOPULSE.
3) the EDM machine has a rich application functionality. Flexible preparation processing program, with translation space powder mixed EDM requirements (see below for more details).
Visible, choose a reliable powder mixed CNC EDM is a prerequisite for successful powder mixed EDM machining.
2.3 powder mixed EDM machining process
Carried powder mixed EDM process analysis, to determine whether the cavity suitable powder mixed EDM. Powder mixed EDM processing for a large area of high-quality finish. For the vast majority of the cavity mold, such as mobile phone shell mold, remote control shell mold powder mixed EDM can be used as the final machining of the cavity surface. Even high speed milling of the three-dimensional curved surface, due to the obtained non-continuous smooth surface and therefore still need to use EDM finishing was carried out, to give a smooth machined surface. Clear angle requirements for micro-cavity, mixed powder processing due to the presence of powder in the working fluid in the discharge gap large and difficult to achieve some fine pieces, such as IC die size requirements of precision, the mixed powder processing is clearly inappropriate.
Carried powder mixed EDM, the cavity must undergo pre-milling processing, and leaving an appropriate allowance. EDM is a process from roughing to finishing process. Replaced by a multi-electrode process methods, complete with two different sizes of the electrode of the amount of scaling to a cavity of the roughing and finishing. First using the roughing electrode, in conditions that guarantee a certain processing quality (dimensional accuracy and shape accuracy, position accuracy, surface roughness), the use of a large discharge energy erosion lot of metal, in order to shorten the processing time and improve the processing efficiency. (Cavity roughing required processing in the state of the non-powder mixed otherwise roughing erosion down coarse particles of the material and the powder is mixed, affect the machining effect); then finishing electrodes powder mixed EDM meet the requirements of the machining accuracy and surface quality.
To strictly control the powder mixed EDM roughing size. If roughing reserved processing volume is too small, then the mixed powder processing will not be able to fully repair on the impact surface effects; too if roughing processing capacity reserved, then the mixed powder processing will be difficult to remove excess material , resulting in very slow processing speed, fatigue electrode. Recommend roughing cavity surface reached VDI25 (Ra1.8um) level and underside reserved 0.07mm, side unilateral reserved 0.08mm.
Mixed powder EDM process, often highly stable discharge state can be maintained, and generally does not produce coke formation, and therefore in the process should be minimal downtime, especially not in the workpiece surface of the powder layer will remain clean out, so as not to interfere with the normal discharge process.
Powder mixed EDM requires good control of all aspects of, in pursuit of the success rate of primary processing, improper details of the deal to produce subtle defects will lead to repeated trimming often spend multiple of time.
2.4 powder mixed EDM working liquid and powder
Electric discharge working fluid in the process plays a deionization and cooling, to exclude the role of the product of the electric corrosion. For the EDM finishing with the working fluid, low viscosity requirements, to ensure that the slag between the electrodes has a good cleaning performance; oxidation resistance and thermal stability of the working fluid is also very critical, and to determine the service life of the oil. The GF AgieCharmilles Blue Line SA CNC EDM mixed powder processing recommends equipped with a spark oil TOTAL EDM 3 (Total of France, viscosity at 20 ° C: 6.7 mm2 / s (cST), a flash point of OC:> 135 ° C).
Powder mixed EDM working solution powder, silicon powder, aluminum powder, magnesium powder, graphite powder, several basic According to many domestic and foreign mixing powder processing technology reported. SA20 powder used AgieCharmilles Group study dedicated powder mixed solution and its main components for the graphite particles, the approximate length is less than 8um, the concentration requirements for the powder is added 2g / L. Every replacement powder mixed fluid needs to be filtered, clean spark oil to filter out the debris in the process and the failure of the powder then add the powder mixed solution. The mixed powder solution requires the best replacement after processing 350 or 400 hours. Black mud powder mixed precipitation processing will work inside the slot, and experience has shown that the mud sparks oil again mixed, because it would seriously affect the processing performance.
Powder mixed liquid concentration greater impact on the machined surface effect. The concentration of the solution of the mixed powder is not enough, within a short period of time can not meet the requirements of surface effects, reducing the processing efficiency. Occasion requires mirror surface finishing, it will lead to the effect of surface gloss is poor due to the mixed powder concentration is not enough; When the concentration of the mixed powder is excessively large, the cavity of the sharp edge corners will be damaged, reducing the machining accuracy. Between the electrode and the workpiece due to the presence of more powder, the powder will produce the bypass cause the flow of short-circuit serious when the workpiece surface scars.
Powder mixed EDM process, working sump tank liquid in circulation, and is not recommended to use the red liquid processing, in particular, can not use a strong red liquid, otherwise it will cause uneven flow field in the discharge process, affect the uniformity of the surface effect.
2.5 mixed powder EDM parameter configuration
Powder mixed EDM parameter configuration including: electric gage, such as current, pulse width, pulse gap; value of the discharge gap and set aside the amount of electricity per file gage.
Powder mixed EDM must ensure that each file electric Criteria for discharge to stabilize, the final gage can meet the requirements of surface effects. A plurality of gage sequentially reducing the current, pulse width sequentially reduced, then matching the corresponding pulse gap servo gap. Usually VDI18 level (Ra0.8um) Criteria The following the negative processing parameters (electrode negative). Stall regulating the discharge energy gradually decreases, and the to gradually repair of light to meet the requirements of the surface roughness. Worth mentioning is that the powder mixed EDM can generate a high processing efficiency, compared with the ordinary working fluid greater the discharge energy can be used to achieve the same surface roughness. Further, in the powder mixed EDM have a fairly good discharge stability, the discharge time to be set longer, carrying knives height shorter set such purpose is to maintain a stable electric erosion process, with a small energy conventional processing choice is different. [1]
Powder mixed EDM requires precise calculation of the electric gage the value of the discharge gap with the reserved amount. The smaller material reservation will affect the surface roughness of the processing, not only cause Revised. The optimal processing condition is the first condition After processing, subsequent processing only the wiper first surface formed by the processing conditions irregularities without knock down the new material. However, the actual processing, taking into account the constraints discharge status by the ever-changing, and therefore have to consider the safety of the reserved amount. The size of the margin can be determined according to the actual discharge condition, regarding the area is larger, the processing status is relatively good, may be appropriate to reduce the material margin, in order to improve the processing speed.
Advanced CNC EDM electric gage configuration generally intelligent. The machine has many sets of processing parameters, are the best combination of parameters through a lot of process experiments, according to the processing requirements to retrieve the processing conditions, such as input processing area and processing the shape of the electrode taper the electrode size scaling amount, shaking, and machined surface roughness value, the machine will be able to configure the optimal electric gage, it will process of processing multiple processing conditions in paragraph, paragraph by paragraph, the ability to reduce electrical erosion, smart set gage reserved. The electric gage generally chosen in such a smart way to meet the processing requirements, simple operation, but usually an automated way so as to ensure that the processing quality, processing efficiency will be lower. Actual production should be based on the repeated processing continue to accumulate experience, to optimize the process.
2.6 powder mixed EDM translational function
Powder mixed EDM of the cavity mold, required to achieve the requirements of dimensional accuracy, and additionally required the surface of the bottom and side of the same effect, which requires the CNC machine must have CNC translational functions. EDM machine tools with CNC translational function, it is relatively easy to control for dimensional accuracy. But to ensure the uniform surface of the bottom and the side effect, it requires the machine has to meet the requirements of the flat movable function. Powder mixed EDM process requires each gage the level of momentum with depth is to gradually increase the depth and level of momentum also will increase the bottom side in the synchronized axis linkage processing. Horizontally movable manner, while the timing of processing functions can be realized, that is, can specify the processing time of each gage, the bottom surface and the side surface of the surface obtained consistent results within a specified processing time. SA CNC EDM of the GF AgieCharmilles Blue Line products in powder mixed EDM space translation round selection. This horizontally movable manner in the finishing of the small energy, significantly improves the stability of the processing side and the bottom surface of the same effect can be realized. Some translational function in the powder mixed EDM NA, SA circular machine servo translational action is performed by the translational depth to complete electrical per file the Criteria must first processing run again a circumferential flat trajectory, obviously such a horizontally movable manner in the cavity mold powder mixed machining finishing stages are not suitable.
2.7 powder mixed EDM electrode
Powder mixed EDM electrode material, surface roughness, scaling size, accuracy.
Powder mixed EDM requires the use of high purity copper as the electrode material (such as Japan Sambo), processing performance is very good, and less prone to arc discharge or the transition arc discharge can obtain uniform machined surface. Graphite electrode in the the ordinary working fluid (no mixing powder) finishing in poor performance, but in the processing of the mixed powder, the powder is added to the working fluid, finishing discharge gap is large, field-proven, graphite electrode powder mixed electric EDM spark processing can also be achieved. Worthy of note is that the powder mixed EDM mirror processing, cavity claim must be strict requirements on the quality of the electrode material on affected otherwise processing effect, such as the use of the copper electrode material purity is not enough will lead to the processing of the mirror The effect of the surface may be local defects, uneven undesirable phenomena.
The EDM process is to copy the shape of the electrode to the workpiece up. Therefore, the electrode surface roughness to some extent determines the machined workpiece surface roughness, mirror finish with the electrode must be intensive polishing (at least after 1000 # sandpaper fine polishing), in order to achieve high-quality finish The EDM surface quality.
Determine the size of the EDM of the size of the first tranche of canonical energy libration amplitude scaling dimensions of the electrode process indicators that directly affect the processing speed, profiling accuracy. General finishing powder mixed EDM electrode size scaling amount taken unilateral 0.07 ~ 0.15 mm, processing area hours desirability of smaller, high profiling accuracy requirements desirable smaller.
With thick powder mixed EDM finishing electrode, which requires better consistency of the electrode manufacturing precision, replacement electrodes repeated clamping, higher positioning accuracy. High-speed milling can be used to manufacture electrodes, use the method of measuring the positioning of the reference ball, quick fixture positioning system repeatability of positioning and other advanced technology to meet the high requirements.
2.8 mixed powder EDM workpiece material
Powder mixed EDM machining results will produce different due to different workpiece material. The surface of different materials in the processing of grain surface level (VDI18 the surface / Ra0.8um) effects are not obvious, but due to the different characteristics of the workpiece material in the processing - mirror (VDI7 level surface / Ra0.2um of) access to the surface The effect of a greater difference. Some materials to get a good mirror effect, such as common mirror finish material: S136, SKD61, NAK80 steel imports; Some materials can not achieve the mirror effect, such as to the SKD11 (to equivalent of Cr12MoV). Mirror finish effect of the workpiece material impact that the following circumstances: a silicon-containing ingredients are conducive to better mirror effect; containing large particle size of coarse raw the carbide or coarse crystal particle additives adverse mirror processing, generating microcracks ; the sulfur containing fast-cut components of processing mirror to produce a surface stripes; material rolling direction the billet manufacturing process factors on the processing mirror to produce a surface stripes; metallic inclusions, bubbles, oxides and other factors in the formation of the eye of a needle and holes; The high hardness of the steel of the workpiece, and EDM mirror effect. General requirements for the mirror-finished workpiece material heat treatment hardened to HRC> 50. [2]
2.9 powder mixed EDM efficiency control
Efficient finishing powder mixed EDM control depends on several aspects: VDI22 more stronger regulations quasi processing efficiency is mainly determined by the amount set aside in the stall gage if the reserved amount is appropriate, with a certain ability to ablation , processing efficiency is relatively high electrical gage; VDI22 and below the more weakly electrically gage, each electrical electrical erosion gage weak ability, the processing when the size of the change is already small, substantially only play the role of the wiper, if strict accordance with the size specified in the execution of machining, the process takes a very long time. After the fact, as long as the processing requirements of surface roughness can end processing, timing CNC EDM machining function can be used to control the processing efficiency. According to the the EDM area to set the required light repair time.
3 Conclusion
With the increasing demands of the the mold industry manufacturing technology, powder mixed EDM will be the complexity of a large area of the cavity mold manufacturing technology. Powder mixed EDM study to provide reference for the promotion of technology for this application.
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Its good one to read and think about. Thanks a lot for providing valuable information. SINOMOULD is a leading Chinese mold manufacturing Company and a well known Mould Tooling industries in China for its quality injection Moulds, molded plastics, custom molds etc.
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