Hey everyone, we have an older Mits FA20 wire EDM here that's having some major wire breakage issues. Were hoping to find suggestions on what might be wrong, or for suggestions on a competent repair center that could help us troubleshoot and or repair the machine.
I could write pages on how much trouble we have had with this machine over the last few years, but ill try to keep it as short as possible and relating to the current breakage issue, but even that will be long, so thank you to anyone that cares to read through it all.
About 2 months ago I had a piece of roughly 1.5” thick 420 stainless on the machine for a cut. It was a multi cavity cut, all straight, .060” drilled start holes, good flushing, normal settings I have used hundreds of times ect. For whatever reason the machine decided it wanted to bust the wire the moment it made its first spark on the rough cut. It would do this at least 10 to 20+ times until eventually it would take off and finish the rest of that rough cut with 0 problems. Once it finished the skim would run perfectly fine. It would repeat this process of wire break's for every new rough cut it moved to no matter what I tried to do with the machine.
What I did try was 4-5 different spools of wire (all the same brand but from multiple batches and previous half empty spools that ran perfectly for me). I tried flushing at all levels, full open, or various levels of restriction. I cleaned every part of of the wire transport system, guides, rollers, + complete upper / lower heads. I checked the diamond guides ensuring the cross drilled coolant holes were open and that the ID's were not worn and tried all of our power feeders in different combinations, I went through that entire cleaning/checking process at least 3 times for every component.
I checked pre tensions/main tensions with our meter, checked all ground connections, and eventually I started working with the E pack settings more. Our machine has never ran consistently with PM mode off, so by default its always on Varying (except for skims of course), I tried it at every level down to the minimum, as well as working with PM in the Off state, and manually adjusting settings down to extreme low levels. I even went as far as to try and use .010” Epack settings while using our .012” wire. I never in the past had to use the “startup” Epacks, except rarely on very tall open cuts, and even then varying usually worked just fine. However in this case I did try the start up Esettings as well, and had the same breakage results.
After everything above, and after about 6 chats with Mits tech we were finding absolutely nothing was working, the machine was still breaking the wire the instant it sparked on its rough cut. So I removed the part and transferred it to our Char290 in the room next door, and tried two pieces of scrap on the Mit's that were roughly the same thickness but different materials (303 and cold roll steel we commonly cut here). Same result on both of those.
Mits came to the conclusion that it must be our lower power cables since they had never been replaced. So about a week later our tech was able to see us. We did a couple checks on the machine (tension ect) and decided to try a test cut so he could see the problem. Funny thing is, the machine took right off and cut it just fine. Since we already had the new power cables shipped to us we decided to cut the wrapping on the old ones back and found that they were pretty badly corroded at the machine head. Our thought was maybe the machine had sat dry for a week and was able to run the test cut, and that if they stayed submerged long enough they must be causing the problems we had. So as a result we decided to have the tech replace them, which also included a new set of ground cables.
We had also decided to order and replace every single roller bearing in the wire transport system. New rubber / ceramic rollers, and main puller rollers on the back of the machine were all replaced, as well as all of the pinch / one way rollers for the AT unit. Then after all the work was done, the VG comp was wiped, ran and zeroed in from scratch.
Since then I cut about 250 hours worth of aluminium on the machine around 5-6” tall roughly with 0 problems. Last week I get a new multi cavity plate setup. 1.25” thick cold roll, flat, good flushing, .090” start holes, all straight cuts, and guess what. Yep, wires breaking non stop again.
I didn’t bother with all the previous things I tried except I double checked the Epack settings in the machine all matched the book, and I did experiment with our power feeders. A very interesting thing I found was that if a power feeder was present in the lower head it would bust the wire, but if I had one in only the upper head it would cut perfectly fine, just at 1/3 speed. So obviously there seems to be something way out of balance in the power getting to the heads.
So now were looking at the power supply thinking it might be one of the resistors, but until we get a more accurate meter here later today we wont know that for sure. With a cheap meter we did find they were all fairly close to what they should be, but Mit's tells us they need to be within 1% of the rating. I'm kind of believing at this point its going to be something else though.
So I'm curious if anyone else out there has had issues like this with a machine, what did you find the problem was? Or if you have dealt with a good CNC repair center who would you recommend? We are in the NE Ohio region, so some place nearby here would of course be preferred.
We are working with Mit's on this issue as well, but there track record with helping us out over the last few years has been extremely poor and were really looking to get some second opinions.
I could write pages on how much trouble we have had with this machine over the last few years, but ill try to keep it as short as possible and relating to the current breakage issue, but even that will be long, so thank you to anyone that cares to read through it all.
About 2 months ago I had a piece of roughly 1.5” thick 420 stainless on the machine for a cut. It was a multi cavity cut, all straight, .060” drilled start holes, good flushing, normal settings I have used hundreds of times ect. For whatever reason the machine decided it wanted to bust the wire the moment it made its first spark on the rough cut. It would do this at least 10 to 20+ times until eventually it would take off and finish the rest of that rough cut with 0 problems. Once it finished the skim would run perfectly fine. It would repeat this process of wire break's for every new rough cut it moved to no matter what I tried to do with the machine.
What I did try was 4-5 different spools of wire (all the same brand but from multiple batches and previous half empty spools that ran perfectly for me). I tried flushing at all levels, full open, or various levels of restriction. I cleaned every part of of the wire transport system, guides, rollers, + complete upper / lower heads. I checked the diamond guides ensuring the cross drilled coolant holes were open and that the ID's were not worn and tried all of our power feeders in different combinations, I went through that entire cleaning/checking process at least 3 times for every component.
I checked pre tensions/main tensions with our meter, checked all ground connections, and eventually I started working with the E pack settings more. Our machine has never ran consistently with PM mode off, so by default its always on Varying (except for skims of course), I tried it at every level down to the minimum, as well as working with PM in the Off state, and manually adjusting settings down to extreme low levels. I even went as far as to try and use .010” Epack settings while using our .012” wire. I never in the past had to use the “startup” Epacks, except rarely on very tall open cuts, and even then varying usually worked just fine. However in this case I did try the start up Esettings as well, and had the same breakage results.
After everything above, and after about 6 chats with Mits tech we were finding absolutely nothing was working, the machine was still breaking the wire the instant it sparked on its rough cut. So I removed the part and transferred it to our Char290 in the room next door, and tried two pieces of scrap on the Mit's that were roughly the same thickness but different materials (303 and cold roll steel we commonly cut here). Same result on both of those.
Mits came to the conclusion that it must be our lower power cables since they had never been replaced. So about a week later our tech was able to see us. We did a couple checks on the machine (tension ect) and decided to try a test cut so he could see the problem. Funny thing is, the machine took right off and cut it just fine. Since we already had the new power cables shipped to us we decided to cut the wrapping on the old ones back and found that they were pretty badly corroded at the machine head. Our thought was maybe the machine had sat dry for a week and was able to run the test cut, and that if they stayed submerged long enough they must be causing the problems we had. So as a result we decided to have the tech replace them, which also included a new set of ground cables.
We had also decided to order and replace every single roller bearing in the wire transport system. New rubber / ceramic rollers, and main puller rollers on the back of the machine were all replaced, as well as all of the pinch / one way rollers for the AT unit. Then after all the work was done, the VG comp was wiped, ran and zeroed in from scratch.
Since then I cut about 250 hours worth of aluminium on the machine around 5-6” tall roughly with 0 problems. Last week I get a new multi cavity plate setup. 1.25” thick cold roll, flat, good flushing, .090” start holes, all straight cuts, and guess what. Yep, wires breaking non stop again.
I didn’t bother with all the previous things I tried except I double checked the Epack settings in the machine all matched the book, and I did experiment with our power feeders. A very interesting thing I found was that if a power feeder was present in the lower head it would bust the wire, but if I had one in only the upper head it would cut perfectly fine, just at 1/3 speed. So obviously there seems to be something way out of balance in the power getting to the heads.
So now were looking at the power supply thinking it might be one of the resistors, but until we get a more accurate meter here later today we wont know that for sure. With a cheap meter we did find they were all fairly close to what they should be, but Mit's tells us they need to be within 1% of the rating. I'm kind of believing at this point its going to be something else though.
So I'm curious if anyone else out there has had issues like this with a machine, what did you find the problem was? Or if you have dealt with a good CNC repair center who would you recommend? We are in the NE Ohio region, so some place nearby here would of course be preferred.
We are working with Mit's on this issue as well, but there track record with helping us out over the last few years has been extremely poor and were really looking to get some second opinions.
