Mits FX2 - Frequent Wire Breaks

[weblogictech]

Hi Forum Members,

I have one used Mits FX2 Wire EDM.. I am facing two typical problems.. First if frequent wire breakage.. another is cutting speed. I am new to wire edm.

1) Frequent Wire Breakage..
The wire breaks very frequently.. sometimes near the workpiece, sometimes in wire collection pipe and sometime just at the end of the wire collection pipe. What I have noticed is that when in adaptive control, the speed increases from 1-2 FC directly to 8-9 FC and the wire breaks immediately. Sometime just when the cutting starts, the wire breaks. I have no idea what the problem is.. There is no local mits support in India. I have changed even different wires from different manufacturers.. But the problem is same.. Some part of the wire drive mechanism are missing.. Like the wire chopper and the Aspirator for cutter unit. We are collecting the burned wire in the large plastic container. AWT is not installed. Is it required to give Air Supply even if we are not using AWT.. There is one limit switch at the end of the wire collection unit.. It is broken.. What is the purpose of that limit switch.. Is there any setting in the system to limit the maximum FC in adaptive control?
2) Cutting Speed.
The cutting speed is very poor. The specification of the machine is 250Sq. MM per min. but the maximum speed that we get is 30% of the original specs. Also irrespective of the thickness of the material.. be it 5mm or 50mm.. the actual FC averages to below 2.5. We are doing regular maintenance of cleaning the upper and lower units.
3) Also when we start the machine.. We get L/R out of control error.

Thank you for your time and support in advance.

Regards,


Rizwan Bhola

[roysol]

I have a Mits FX10K, so some of what I tell you may not be directly comparable.

The maximum cutting speed is based on ideal cutting conditions, burning high quality d-2 tool steel. If you are cutting poor quality low carbon steel, you will get erratic cutting, slower speeds, and frequent wire breaks. Materials other than steel have different cutting speeds. Optimum speed also requires perfect flush. The workpiece must have parallell top and bottom surfaces, and be fixtured the correct distance from the flush cup, and the upper head positioned the correct distance. Poor flush will typically result in a loss of speed of 50%.

Another common problem is worn carbide contacts. If you are not feeding the power to the wire properly, it never makes it to the workpiece. Likewise, corroded or broken ground cables can have the same effect. Since you are not using the wire chopper, be sure the spent wire is not touching anything on it's way into the collection bin and causing a short circut.

The L/R error is liquid resistivity, which trells me you have a problem with your resin system. If you conductivity is too high, or too low, it will result in lost speed, inconsistent cutting and overburn, and possibly wire breaks. Start by making sure your sensor is cloean and functioning properly. Then check that your resin is still good, and finally that the seloinoid valves that control flow through the resin system are working.

Check the pinch rollers to see if they have a groove in them, and that the tension is set correctly for the diameter wire you are using. If there are grooves in the rollers, the wire can slip, which decreases the effective wire speed and causes wire breaks.

In your program you should be setting an "F" value for your target cutting speed, generally about half of your actual cutting speed. This acts to limit how much the adaptive control can increase the feed rate. The information for "FC", and "FA", should be in your manual of technology settings.

When cutting from an outside edge, or a large diameter start hole, you have to reduce power settings untill you are far enough into the cut to get good flush. There are settings in your technology book called "start-up", and you should be using those for entry cuts.

There's more to it than that, but you've got quita a struggle ahead of you to try and figure out what you're doing, without any experince or support.

Cheers!

Roy Solomon

[weblogictech]

Could it also be due to wire tension and pretension. Can you explain what is WT - Wire Tension and PT - Pretension?