Material for injection mold (plastic mold steel) is required to have sufficient strength, toughness, heat resistance, wear resistance, and good corrosion resistance, heat treatment hardness must be greater than 42-48HRC, cavity working surface needs to keep the surface roughness unchanged for a long time.Commonly used materials are 45, Tl0, TlOA, 9Mn2V, 3Cr2W8, etc.Therefore its electric discharge machining process basic rules are as follows.

(1) The manufacturing process of upper die and lower die

(1) Plane shape, each put 0.5 ~ LMM, shape margin according to the cavity complexity and determined.

(2) Planing two planes and releasing grinding allowance.

(3) line.

(4) EDM, the cavity is generally deeper than the original cavity 0.3-0.5 RRM, set aside the amount of grinding, so that the grinding machine to go to the upper mouth collapse Angle caused by the locksmith dressing and polishing.

(5) Turning, drilling, boring and milling all kinds of holes and surfaces with the edM cavity as the reference.

6. The locksmith repaired the alignment.

Heat treatment, quenched 46-53HRC.

8) the fitter assembly, calibration mold pressure sample.

High purity fine graphite, red copper and tungsten copper can be selected as electrode materials.

(2) The graphite of electrode manufacturing process should be pretreated before processing and soaked well in the oil. In this way, the graphite chips are not easy to fly in the air and the angular line and angular line are not easy to flake off during the mechanical processing.

Graphite and copper electrodes are generally machined (turning, milling, planing, grinding, etc., CNC machine tools are used when necessary), and finally shaped by fitters.Copper tunji can also be used wire cutting processing.

For the cavity with simple shape, most of them adopt single electrode forming process, that is, one electrode is used to enlarge the gap with translational motion, so as to achieve the purpose of repairing the cavity.A single electrode may be a single electrode or a Mosaic electrode, depending on the electrode machining process.

For large and medium size molds and moulds with complex cavities, multi-electrode machining can be used. Each gun pole can be single block or Mosaic, depending on the specific situation.

(3) EdM cavity die (upper die or lower die) is generally processed the shape first, and then the cavity after EDM is taken as the reference to process other types of holes, so for the EDM operator, it is more convenient to find the correct positioning.But it is not always so, some molds involve many factors, the last process is edM, which has higher requirements for edM positioning, clamping, processing and so on.

In the mold processing to use edM is very much, because the speed of EDM is slower, so in the mold processing can be used in the cutting processing to try to use the cutting processing to process, the cutting processing can not be where the edM machine to process.

Edm generally goes through the following three processes:

(1) Rough machining of mold parts to be processed.

(2) Electrode processing.

(3) Electric discharge machining.

From the edM forming process specifications can be seen, the cost of EDM is higher, the speed is slower, but often the product strange shape, irregular, these shapes are milling, turning, wire cutting and so on can not be completely processed, have to be processed by EDM.This is also the current cause of high mold price of one of the reasons.