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1 Introduction
WEDM widely used and important in the plastic mold , precision multi-position progressive die production process , to ensure good dimensional accuracy obtained directly affect assembly precision molds , precision parts and molds using life , etc. As high precision workpiece , so that if any one o'clock in the process negligence , it will cause the workpiece scrapped , but also to mold manufacturing costs and processing cycle negative 1 Introduction
WEDM widely used and important in the plastic mold , precision multi-position progressive die production process , to ensure good dimensional accuracy obtained directly affect assembly precision molds , precision parts and molds using life and so on. As high precision workpiece , so that if any one o'clock in the process negligence , it will cause the workpiece scrapped , but also to mold manufacturing costs and a negative impact on the processing cycle .
Engaged in wire cutting EDM machine programming and operation of the process, combined with years of practice, for the processing of deformation problems that arise and the difficulties encountered , summed up the points craft processing method and processing operation of the program
Two punch process
Punch in the mold plays an important role in its design shape and dimensional accuracy and have a direct impact on the hardness of the mold punching quality , the service life and precision stamping . In the actual production process , since the workpiece blank and the deformation of the internal residual stress generated by the discharge thermal stress and deformation , wear and should be processed first hole closed wire cutting, as far as possible to avoid the open -cut and deformed. If the limited size of the workpiece blank form can not be closed cutting blanks for the square , the programming should pay attention to choose a good cutting path ( or cutting direction ) .
Cutting path should be conducive to ensure that the workpiece during machining always clamp ( clamping bracket ) remain in the same coordinate system , to avoid the impact of stress and deformation . Clamps fixed on the left , gourd-shaped punch from the left , counterclockwise for cutting, cutting line basis throughout the blanks being divided into two parts . Since the connection blanks left and right sides of the material more smaller , moving away from the rough on the right with the fixture , unable to resist the internal residual stress and deformation of the workpiece also will be deformed. If the clockwise cutting , the workpiece stay in the left side of the blank , near the clamping position, the majority of the workpiece during the cutting process and the holder are held in the same coordinate system , good rigidity , to avoid stress and deformation . Under normal circumstances , the workpiece should be reasonable cutting path separating the clamping parts arranged in a cutting section of the cutting end of the program the total , about the suspended point (Bridge) to remain in position near the end of the blank holder .
The following analysis focuses on tooth carbide cutting punch Process . Under normal circumstances, the punch shape rules, wire cutting often connecting portion will be reserved ( pause point , namely that the workpiece at the 1st cut of rough and rough after complete separation is not set aside under the short cut trajectory ) remain in the flat position, the most precise cutting is completed, the connecting portion set aside only once for cutting , grinding later by the fitter formation , thus reducing LSWEDM punch in the processing costs.
Carbide punch and the shape of the strip material of high hardness , etc. , resulting in slow processing speed , and is easily deformed , particularly in the case of irregular shape , the connecting portion reserved grinding great deal of difficulty to the fitter . Therefore LSWEDM processing stages of the process can be appropriately adjusted so that dimension accuracy requirements , eliminating the fitter assembly point before the suspension grinding processes.
Since carbide high hardness, cutting thickness , leading to slow processing speed , torsional deformation serious , most of the connecting part contouring and reserved ( pause point ) processing were taken four times a cutting mode and the two parts of the cutting parameters and offset volume (Offset) are the same. First cuts the wire electrode offset to increase 0.5-0.8mm, so that the workpiece is completely fully release the stress and torsional deformation of the back three times to have enough margin for precise cutting processing , so that the final size of the workpiece can be guaranteed.
Specific process is as follows:
( A ) in advance in the appropriate position on the blank punch or EDM machining good Φ1.0-Φ1.5mm wear silk Kong , wear silk punch hole centers and the introduction of cutting contour line between the length of the line segment l select 5-10mm .
( 2 ) punch rough contour line width should be at least ensure that the edge of the blank thickness of 1/ 5 .
( 3 ) set aside for subsequent cutting the connecting portion ( pause point ) should be chosen close to the center of gravity of the workpiece blank portion , the width select 3-4mm.
( 4 ) to compensate for the torsional deformation of the majority of the residual strain amount remaining in the first rough cut stage 1 , the offset increases to 0.5-0.8mm. Subsequent three times using fine cut way, since the cutting margin is small, the amount of deformation is also smaller .
( 5 ) The majority of shape 4 cutting is completed, the workpiece with the compressed air , and then the blank face alcohol solution washed, dried , and then use an adhesive or a liquid adhesive quickly ( usually 502 drying glue ) will be polished by grinding the metal foil thickness of about 1.5mm in the rough on the cement , and then four times the original amount of the offset portion of the cutting of the workpiece reserved connection ( Note: Do not put plastic under the tap or drop into water droplets reserved to the connecting portion of the workpiece so as to avoid non-conductive and can not be processed ) .
Three concave deformation analysis template processing
Before cutting line , the template has been carried out cold , thermal processing , has produced a larger internal residual stress , and the residual stress is a relatively balanced stress system , remove large waste line cutting , the stress along with the destruction of the balance released. Thus , the template cutting line , with the role of the original and the internal stress generated by spark discharge processing heat stress, would produce non-directional , irregular deformation, so that the back of the cutting uneven thickness of cut , impact the machining quality and precision.
In such cases , relatively high demand for precision template , usually four times a cutting. 1st cutting of all types of waste hole cut , remove the waste , and then by the machine 's automatic shift , automatic threading function , complete the first two times, 3rd , 4th cutting . a cutting 1st , take scrap → b Cutting 1st , take scrap → c cutting the 1st , take scrap → ...... → n cutting the 1st , take scrap → a → b cut 2nd cut 2nd → ...... → n → a second cutter cuts the 3rd → ...... → n → a third cutter cuts the 4th → ...... → n cutting section 4, processing is completed.
This cut in such manner that for each type of hole machining sufficient time after the release of internal stress , can each type of hole machining sequence difference in the result of the mutual influence of trace to minimize the deformation , to better ensure the template processing size accuracy. However, this processing time is too long , a large consumption of the machine wearing parts , increasing the manufacturing cost of the template . Further processing of the machine itself with the extension of time and temperature fluctuations will produce creep Thus, according to the actual measurement and comparison templates permit precision , can be taken 1st unified processing waste unchanged, while the back of the 3rd and 4th cut together ( i.e. a cutting section 2 times, does not shift , do not cut wire followed by cutting the first three or four times → b → c ...... → n), or eliminating 4th cut while doing three cuts . After cutting through this measure , geometric dimensions basically meet the requirements. 4 times and three times each time the cutting allowance , machining accuracy, surface roughness reference values in Table 1 and Table 2 . Preliminary estimates about, type the shift between the holes , wear silk , cut wire , Sheung Shui, water and other calculated according 1min . With this cutting method , processing a hole with 100 -type templates , each will save about 9h machining time , cutting four times a total savings of about 30h, so the use of expensive WEDM speaking, both to improve the efficiency of production , consumption and reduce costs , and therefore reduce the manufacturing cost of the template .
4 small corner concave shaped hole template processing technology
As the selection of the cutting wire diameter larger shaped hole cut out of the corner radius is also greater. When the template shaped hole is very small corner radius requirements ( eg R0.07-R0.10mm), you must switch to filaments ( eg Φ0.10mm). But relatively thick filament , the filament processing speed is slow, and expensive ( mostly to be imported silk ) . If you have used the entire filament -shaped hole machining , it will extend the processing time, resulting in waste. After careful comparison and analysis , take the first right corner radius increases, with a thick wire cutting holes meet size requirements of all types , and then replace the filaments shaped hole uniform mowed all corners reach the required size.
Here are moments concave tooth template ( inner corner radius R0.07mm) of the wire cutting process .
( A ) first with Φ0.20mm rod working template shaped hole cut to the required size , the inner corner part of the processing to R0.15mm.
( 2 ) demagnetization , shut down.
( 3 ) Replace Φ0.10mm filaments. The cutting wire conveyor belt moves unused locations. If the belt three locations have been used and nip filaments ineffective, then the replacement of the conveyor belt .
( 4 ) Re- alignment center. Cone with two diamond cutting wire guide insert ( the guide insert is AGIE company WEDM special ) point support allows cutting wire under partial points are precisely positioned so that the cutting wire is guided accurately . When cutting a wire diameter of Φ0.20mm when looking at the exact center point b , when the cutting wire diameter of Φ0.10mm when looking for a spot in the center , | ab | = | bo | - | ao | = 0.1 〖 KF ( 2 〗 〖 KF) -0.05 〗 〖 KF ( 2 〗 〖 KF) 〗 = 0.0707mm. So to re-find replacement Φ0.10mm filament center of the coordinate values of the center should coordinate with the original value of the difference of about 0.0707mm.
( 5 ) modify graphic fillet radius , re- programming, avoiding other shaped hole contour, the radius of the corner -shaped hole trimmed to R0.07mm.
Over five shaped hole die , fixing plate , stripper plate processing order
Multi -shaped hole die , the fixed plate , taking into account the respective stripper plate -shaped hole in the process of processing by the residual stress and thermal deformation of the impact generated in trace , so in the actual production using the same type of hole machining methods in order to ensure its type consistency deformed hole , thus ensuring the die , the fixed plate , stripper plate hole concentricity .
6 Conclusion
WEDM machining high precision, strong function, but the high processing costs , to give full play to the role of the machine , to create a good economic benefits, the workpiece must be a reasonable process analysis and technical performance analysis , to fully understand the structure of the machine performance and proficiency in machine operation skills , rational use of water parameters and electrical parameters, to reduce processing of broken wire condition , in practice, constantly sum up experience , so as to maximize the machine 's potential to improve production efficiency.