1.Why wire is easy to break while cutting first start to cut(not during cutting)?
Reasons cause wire broken of wire cut EDM machines:
(1) Feed is not stable, when first start to cut, feed speed is too fast or electrical current is too big;
(2) While cutting, there is no working liquid flush out;
(3) The wire on wire drum is not even, some place is too loose, while some place is too tighe, it will cause vibration of wire seriously;
(4) Guide or bearing are worn out, or there is jump in axial direction of guide, these situation will cause vibration;
(5) Guide at rear of wire frame haven’t been adjust properly, the position of guide is not proper to cause overlap of wire;
(6) There is burr, oxide layer or sharp edge on the surface of workpiece.
Method to solve above problems:
(1) For first beginning of cutting, use small part and lower speed, and adjust to proper situation according to actual thickness, material of workpiece.
(2) Check and make sure working liquid flush out fluently;
(3) Tighten the wire, adjust height of wire frame to make it close to workpeice to reduce vibration of wire(if it is necessary, adjust position of guide, make sure wire in the groove of guide);
(4) If there is no problem of wire tension, and nothing change after change position of guide, it is better to change new guide or bearing, it is advised to change guide every 3-6 months);
(5) Check if wire tension control system is OK;
(6) Remove burr, oxide layer and sharp edge, etc.2.Why wire is broken during cutting?
Reason s will cause wire broken during cutting.
(1) Wire broken when wire drum change direction, for this case, wire is broken near two ends of wire drum, high impulse power haven’t been cut off when wire drum change direction, this situation will happen, high impulse power will burn wire to break;
(2) Material of workpiece should be even and been heat treated properly, if not been well heat treated, workpiece will deform and sometimes will break, and affect cutting efficiency and accuracy;
(3) Use proper electrical parameters, too large power will burn wire;
(4) Use working liquid improperly, too diluted or too dirty, and very less working liquid flushing;
(5) Contact of wire and power feed contact is not good, or power feed contact had already been curved, which will make wire stuck, to make wire can’t feed fluently.
(6) Bad quality molybdenum wire or expired wire, which is fragile to break.
Method to solve above problems:
(1) Check the problem of electrics which will cause no high impulse cut off while wire drum change direction;
(2) Material of workpiece needs to be even and properly heat treated.
(3) Choose proper electrical parameters according to different material and thickness of workpiece;
(4) Keep working liquid clean and mix working solution with water properly;
(5) Adjust position of power feed contact, power feed contact will wear out during cutting, it needs to position of wire where touch wire, or change power feed contact;
(6) Change good quality molybdenum wire, for cutting large thickness workpiece, use bigger diameter molybdenum wire, for example diameter 0.25mm.3.Other situation of wire broken
(1) Guide wheel doesn’t rotate or can’t rotate easily, friction between molybdenum wire and guide wheel and cause broken of wire. Adjust guide wheel, after change new guide wheel, there is already some damage of wire and will cause wire broken later on, when tighten wire, must use professional wire tighten wheel, don’t use any improper tools.
(2) Molybdenum wire brake when it is approaching the end of cutting, suck king phenomenon is usually caused by deformation of workpiece and brake wire, and before wire broken, short circuit happens. Mostly, it is suggested to use correct cutting path and material to reduce affection of deformation of workpiece
(3) When cutting finished, job falling down and crash wire to brake, so magnet could be used to hold workpiece before falling down;
(4) Wire brake while feed without cutting, check if wire is properly in the groove of guide wheel, check if there is overlap of wire on wire drum, check if wire drum turning correctly, check if there is curved mark of power feed contact.4.Why cutting accuracy is worse than regular level?
(1) Wire guide jump or shuttle badly out of acceptable range, measure error of wire guide jump and shuttle, (axial error 0.005mm, radial error 0.002mm). if large than this range, it needs to adjust or replace guide wheel and bearing;
(2) For slide ball screw and nut set, it should adjust to remove gap between screw an nut;
(3) Gap between gears, it needs to adjust position of stepper motor and spring to remove staggered teeth of gears;
(4) There is step loss of stepper motor, check if 24V power supply is OK.
(5) Deformation error caused by heat deformation of material.5.Surface finish is not good within usual range
(1) Wire guide wheel is not completely fixed, jump or shuttle badly, or up and down guide not in the same vertical level, adjust guide wheel to proper situation;
(2) There is metal chip in nozzle of cooling system, clean it;
(3) Axial gap of working table and wire drum between screw haven’t been properly adjusted, adjust them;
(4) Jump of wire drum is not good to cause vibration of wire, check jump accuracy of wire drum(less than 0.2mm);
(5) Improper parameters, use lower power to get better surface finish;
(6) High impulse and high impulse power is not appropriate to actual cutting ability, chose proper power;
(7) Working liquid is not proper or getting dirty, change new working liquidl
(8) Tension of wire is not ever or too loose to cause vibration of wire, tighten molybdenum wire.
