In moulding process, production and discharge processing of copper electrode is an important part of it. Quality of copper electrode and difference of processing technology directly affect external effect of product.

1. What is copper electrode? Copper electrode is also called electrode. Most of electrodes are processed with red copper since its’ good conductivity and easy processing, heat generated by electrode itself is small and loss is relatively low during EDM. Therefore, in coastal areas, electrode of EDM is called copper electrode. It means to use copper to "discharge" workpiece (mold). According to needs of processing, it is also divided into rough electrode and finish electrode.
2. What is electrode design? That is, mold designer converts a product drawing into a mold design drawing, determines processing method according to shape of product. Only when shape of mold is designed, can we know where it needs to be machined, milled, planed, ground, drilled and discharged to desired shape; when EDM is to be used, an electrode (copper) can be processed at this time. Electrode is equivalent to a forming knife in milling process. Shape of knife is opposite of tool shape. Electrode design means it is divided into several parts according to difficulty of processing shape of product. That is, shape of product in the part where you want to perform EDM is processed by copper, and then electric discharge machining is performed on spark machine.
Specific process: product drawing - mold drawing - copper electrode - mold - products.
In order to facilitate electrical discharge machining, according to needs of processing, shape or structural part of product is divided into several parts, process of forming copper electrode processing drawing is “Electrode Design”.

 

1. Before writing knife path, after finish three-dimensional picture, move center of graphic to origin of coordinate, move the highest point to Z=0, add shrinkage rate, then process it. Spark position of copper electrode can process negative reserve. Before machining, check whether clamping direction of workpiece is same as direction of graphic in computer, whether positioning in mold is correct, whether fixture interferes with processing, whether direction of front and rear molds match. Also check tools you are using are complete, benchmarks in calibration table, and so on.
2, Determination of spark position, general finish electrode reserved amount of 0.05 ~ 0.15, rough electrode 0.2 ~ 0.5, specific size of spark can be determined by mold maker.
Is there any dead ends that can't be processed with copper electrode, and it is necessary to design one more. Machining path of processing copper is generally: large knife (flat knife) for rough - small knife (flat knife) clear angle; light knife with ball cutter for finish machining. CAM/rough is generally more common with a flat knife without a ball cutter. After large knife, use a small knife for rough, then large ball cutter and small ball knife for finish machining. For some small corners, use a small knife to process dead angle that big knife can not pass. Ignore range of small knife to create too many empty process.
Copper electrode, especially finish electrode, is precision requirement. Tolerance is generally 0.005~0.02, and step is 0.05~0.3. When for rough, it is necessary to leave position of ball, that is, Rough shape of copper electrode should be processed to a thicker knife radius. Copper electrode also needs to be processed in middle position, calibration standard, and it should be corrected during spark discharge. Copper electrode processed on three sides (up, down, left, and right) must have three reference faces. Copper material is easy to process. Speed of cutter can be faster. When for rough, machining allowance is 0.2~0.5, depending on the size of workpiece.
3, Problem of rough process of front mold: First, copper diagram is rotated 180 degrees in front view or side view to become front mold drawing, of course, add shut-off, PL surface. Where original body is to be left in mold, do not use mirror method to turn copper drawing into a front mold drawing, sometimes it is wrong (when copper figure X direction is asymmetrical).
There are two difficulties in processing of front mold: Material of front mold is relatively hard, so it cannot be easily soldered.
Principle of using knife for rough machining of front mold is similar to that of copper electrode. Large knife for rough → small knife for rough → large knife for finish machining → small knife for finish machining. Front mold should use large knife as much as possible, small knife are easy to tremor. For finish machining, use a round nose knife since it is large enough and powerful. When front mold has a parting surface, it usually encounters a problem. When for finish machining, parting surface should be accurate due to punching machine, cavity should have a machining allowance of 0.2~0.5 (for EDM).
This makes it possible to correct surface of mold cavity to positive direction by 0.2 to 0.5, and set machining allowance to 0 when writing tool path. When front mold is for rough or finish machining, range of cutter is usually limited. Remember that range you set is range of tool center, not range of tool boundary, not range to which knife is machined, but a tool radius. Common method of cutting front mold is curved groove and parallel finish machining. When front mold is processed, shut-off is generally processed to a quasi-number, kiss-off can be left with a quantity of 0.1 to match mold.

 

4, Problem often encountered for black mould processing: back mold has original body or inlaid ke, Same as front mold, back mold use steel, material is hard, should be processed with a knife as much as possible, common cutting path is surface grooving Shape, parallel milling cutter. Principle of selection of the knife is big knife for rough → small knife for rough → large knife for finish machining → small knife for finish machining.
Back mold drawing is usually a copper figure to reduce material level add PL surface, shut-off, and original body left. If material is relatively uniform, you can leave material directly in processing information, but PL, shut-off, wearing surface can not be reduced. At this time, you can correct these surfaces in positive direction.
One problem that origin often encountered was that sharp angle can not be cleaned by ball knives. At this time, sharp slanting surface of curved knives could be used to process clear angles; if inserts, rear molds were divided into hide frame and core(maybe no right in English, let me know if improvement). For add “hide frame”, process a few more empty knives. Otherwise, frame will have a slope. Upper side is accurate and lower side is small. It is difficult to match mold. Especially for deeper frame, we must pay attention to this problem. Knife for finish michining frame should be new and large knife should be used. If core is too high, you can turn it over to process frame, assemble it into frame, and shape it. Sometimes there is a branch, be careful not to overcut. When using ball cutter, you must protect branch step.
5. Problems in processing of loose copper electrode: Sometimes there is difficulty in overall copper electrode processing, there is a dead angle that cannot be processed, or it is not easy to process. If required tool is too long or too small, you can consider dividing one more copper electrode, sometimes it needs a copper electrode for clear angle, this copper is not difficult to process, but it is necessary to find out partial number of EDM and proofreading benchmark.
6, Processing of copper electrode for slice position: This kind of copper electrode is easy to break when processing, new knife should be used and knife should be small, feeding can not be too large, length can be accurately determined during processing, but leave a large margin (such as 1.0mm) for thickness and then walk on both sides. Each time depth is h=0.2~1, depth of feed is not too much, and it is not necessary to process in one circle, but to divide it into two sides.
7. Direction of mold: Four guide holes of mold base are not completely symmetrical, and one is asymmetrical. Therefore, it should be clear when machining front and rear mold. Each template has a reference, front and rear molds after processing must be matched, especially for molds formed by original mold base.
Pay attention to direction when drawing. Direction of copper electrode and front view (top view) are same. Direction of core and hide frame is same as that of copper, and front mold is opposite.

 

Quality of copper electrode, especially quality of finish machining, directly affects external quality of product. Therefore, after completion of copper production. Be sure to review and then take to workpiece. For product engineers, this is part of job details and needs to be seen by mold factory. Inspection of copper electrode mainly pays attention to following points:
1. Copper electrode generally requires two groups of rough electrode and finish electrode. If it is not followed up, mold factory will only make one electrode in order to save costs, which is not good for product.
2. Is dismantling of copper electrode reasonable? For appearance of special requirements or difficult to process, it also needs to be divided into copper.
3. Compare with product drawing to check if there is something wrong with copper electrode?

 

4. Check if there are any defects such as trachoma or bruise on the surface of copper electrode. If necessary, remake copper electrode.

 

5. Pay attention to surface transition, whether it is very smooth, or good polishing.

 

6. Pay attention to places where curved surfaces intersect and places where some ridges clear corners. Is there any ridge line blurring and sag distortion due to polishing? Special attention: Whether transition position of fillet is smooth and round.

 

7. For places where copper electrode is defective, it is necessary to follow up with mold factory for repair or redo.