中文The occurrence of carbon deposition in all EDM:
(1) It is easy to trigger carbon deposition in finishing, that is, in the processing occasion where the current condition is small. In rough machining, due to the large discharge energy, large spark gap and good chip removal effect, it can often achieve more stable processing, while finishing is the opposite, which is more prone to discharge instability and arc tendency.
(2) Large-area electrode processing and small electrode processing occasions. The former is more prone to concentrated discharge because of the large discharge area and uneven distribution of discharge energy, and the latter is more likely to cause arcing because the discharge area is too small and the local excessive discharge energy leads to arcing.
(3) Deep hole processing occasions. For deep blind hole machining, carbon deposits are more likely due to unfavorable chip evacuation conditions.
Methods and techniques to avoid carbon deposits:
The first step is to optimize the tool lifting parameters:
The tool lifting parameter is the basic parameter of processing, and the tool lifting action needs to be reasonably controlled. If the discharge time is too long and the lifting height is too low, it is easy to lead to carbon deposition in machining, and the lifting parameters in the finishing discharge conditions are more important. In deep hole machining, the discharge time and the height of the tool are very important, otherwise it will lead to carbon deposition and even immobility.
Reduced discharge time
Increase the height of the knife
Speed up knife lifting
The second step is to optimize the discharge parameters:
In the case of optimizing the lifting parameters, if the discharge is still unstable, the pulse gap should be increased, and the pulse width should be appropriately reduced according to the processing situation.
Increase the pulse gap
Reduced pulse width (significantly increases electrode losses)
In roughing, pay attention to the peak current not to be too large in the processing area.
Reduction of processing current (significantly reduces processing speed)
Other improvements:
The bottom surface retention and flat momentum in the finishing of the large electrode can not be too large, because under weak machining conditions, due to the poor chip removal of finishing machining, and the electrode is easy to fatigue in the case of a long time of finishing, if it is necessary to erode more processing amount, it is easy to lead to carbon deposition, and also greatly reduces the processing efficiency, and the allowance should be minimized in the case of meeting the surface roughness.
Secondly, flushing also has a big impact. Improper flushing method and flushing pressure make the electrocorrosive material unable to be discharged smoothly, and the discharge state is very unstable and causes arc discharge. The general flushing method is downward flushing, flushing towards the opening, pouring oil, etc. The flush pressure is controlled close to the critical pressure range of the process, and the spark oil used should be clean. If the machine has a high-speed tool lifting function, it is not recommended to add additional flushing to avoid the formation of uneven flushing pressure.
If the spark oil used does not meet the requirements, mainly because the viscosity is too high, then the chip removal performance in finishing is poor, and it is easy to have a slight discharge black spot and other undesirable phenomena.
If the processing state is found to be bad, whether there are too many electroerosion products in the processing part should be considered. Pause the machining, clean the electrode and workpiece (e.g. gently grinding with fine sandpaper) and then re-process. If there is already a carbon deposited surface, this step is very important, only the arc product is cleaned, can continue to process, otherwise it can not be processed at all.
During the whole processing process, the processing stability should be monitored at any time, and evaluated by looking at sparks, listening to sounds, observing currents, and voltmeters. Take corresponding measures in time for abnormal phenomena in processing.
