Idler maintenance
The idler and idler bearings are the key parts of the wire cutting machine. Good precision, good finish and high efficiency all depend on a pair of balanced, light and precise idlers.
The maintenance of the guide wheel and bearing should start from the installation. It is required that the tools used and the assembly environment should be clean, and the working position of the bearing should not be brought into the dirt. Eliminate all over-tight installation, knocking and strong press-fitting are not allowed in the whole process. The deformation caused by this installation will completely destroy the original accuracy of the guide wheel and bearing.
Special attention should be paid to the guide pulley in use. When the bearing rotation is not flexible enough or there is foreign matter blocking the guide pulley, the wire will be dried in the V-shaped groove and the shape accuracy of the V-shaped groove will be lost instantly. The working environment of the bearing cannot enter the sewage, and the sewage containing impurities can grind the bearing very quickly. What’s more worth noting is that the bearing and the guide wheel are never allowed to flow through the current. If the high frequency power supply is used as the channel, the instantaneous corrosion will be very serious. Dirty water, especially for cutting aluminum, should be replaced in time.
Machine tools that have been running for dozens of hours
Be sure to wipe down the roots of the idler pulley and bearing housing to remove any clogged sludge. And drop in a small amount of oil, let the wire run at full speed for a few minutes, so that the dropped oil and dirt are thrown out together, and then drop in the oil, and so on for several times. A consistent guide wheel with reasonable assembly, proper use and effective maintenance should usually be used for 2~3 years, and a pair of bearings should also be used for more than half a year.
It should be noted that the quality of the bearings purchased on the market is very worrying. The radial runout and axial clearance of the inner and outer rings and the wear resistance of the beads and ballistics are not credible enough. Although its packaging and markings are invisible, be careful. Choose to use with caution.
Unilateral loose silk
The speed of the wire drum is inconsistent in the forward and reverse rotation, which is closely related to the wire feeding method. According to the experimental results, we can see that the molybdenum wire is not loosened to a certain extent and will not affect the cutting effect. The problem of loose silk is completely eliminated, but the speed of the silk drum is inconsistent with the forward and reverse rotation, but it is not completely eliminated
In short, in the future: if the above situation occurs on a certain machine tool, we must first check whether the water spray can completely envelop the molybdenum wire, so that the coolant can fully enter the cutting gap to form an effective discharge and arc extinguishing process, and check the upper and lower wires. The rigidity of the frame, especially whether the screws are effectively fixed, in addition, it is necessary to pay attention to whether the contact surface of the wire frame and the scraping surface of the column after the wire frame pressing plate are in effective contact. If there is no guide wheel hole, the inclination will increase.
resistance
The rotation of the guide wheel must be flexible. The height of the conductive block is preferably slightly higher than the bus bar of the guide wheel. When installing the molybdenum wire, the force of the molybdenum wire should be grasped. The minimum and effective contact with the guide wheel and the conductive block is appropriate. Measure the circular runout of the bobbin <0.02mm, and identify whether the bobbin fluctuates when it moves in a straight line
Method: Disconnect the screw rod and push the wire drum. Use a dial gauge to measure the side bus bar and the upper bus bar of the drum. It has a significant impact on the cutting effect. If the lead screw is improperly installed, it will cause inconsistent resistance during operation, resulting in obvious displacement of the molybdenum wire.
How to improve the finish in the wire cutting process, the wire cutting finish is composed of two elements, one is the size of the pit removed by a single discharge, and its RZ is usually between 0.05μ ~ 1.5μ, which is a Minor.
The second is the convex and concave stripes caused by the commutation. Its RZ is usually between 1μ ~ 50μ, and it is possible to be as large as 0.1MM or more, which is the most important factor for the finish of the wire cutting. At the same time, it is accompanied by black and white stripes of reversal, giving people a very strong visual impact.
Control of the pit size due to a single discharge is relatively easy, simply by reducing the energy of a single pulse. It’s just that the energy of a single pulse is so small that the thick workpiece cannot be cut, or even a non-sparking state with only short circuit and no discharge.
This is similar to fine gauge in EDM, resulting in unstable machining with extremely low efficiency and poor chip evacuation. What’s more, the RZ caused by the discharge pits and the RZ caused by the commutation stripes are not in the same order of magnitude, so it is the most important to control the RZ accompanying the commutation stripes.
Idler and bearing accuracy
The constancy of tension when going up and down and other reasons result in inconsistent movement trajectories of the wire going up and down. This mechanical factor is the main reason for the convexity and concavity of the commutation.
Taking the following measures will improve the finish to a certain extent
1. Appropriately reduce the pulse width and peak current, that is, reduce the size of the corrosion pit.
2. The guide pulley and bearing maintain good precision and smooth operation, reduce wire shaking and wire jumping, and keep the wire movement trajectory to a minimum.
3. The wire maintains proper tension, and adjusts the guide wheel and the feeding block, so that the tension in the working area remains unchanged when the wire goes up and down.
4. The wire should not be too tight, and the water should not be too new. The new water is definitely beneficial to the cutting efficiency, but the cutting finish is not the best.
5. Add a splint to the upper and lower sides of the workpiece that is too thin, so that the reversing stripes are buffered within the range of the splint.
6. It is also extremely important for the XY movement to be stable and accurate, with good follow-up fidelity and non-blocking crawling.
7. Maintain stable and loose frequency conversion tracking.
8. Re-cut or multiple cuts with an appropriate amount of cutting, sweep the cutting surface once when the cutting amount is small, and adjust the size accurately.
Both the precision and the finish will have beneficial effects. Sweeping three times in a row will basically remove the reversing stripes. As long as the machine tool has high repeated positioning accuracy, and the appropriate allowance is used for progressive processing, the finish of the cutting surface will be improved by one or two points. Level, the effect is similar to the slow wire cutting machine, and it does not take too much time, which is one of the advantages of the fast wire cutting machine.
9. For thicker workpieces, short wires can be used appropriately, and the reversing feed at one time is less than half the wire diameter, which also conceals the reversing stripes. Of course it’s just a cover up
Post time: Aug-12-2022
