Agie Challenge Cut wire keeps breaking on trim cut, need your help finding the cause!

[8InchCaliper]

Hi folks, new to the forum, and thanks for reading my thread, I really need your expertise here as I've exhausted my resources.

I'm cutting a solid 17-4 stainless steel block (condition H1150) using Agie Wire EDM, the workpiece 2.5 inches tall, the profile is about 6 inches long.

I am using two cuts (1 main cut and 1 trim cut), main cut takes about 2 hours. I set the Z value at 4 inches to avoid hitting the strap clamps. The wire is the 10 thousandth FireWire. (https://electrodesinc.com/product-category/edm-wire/fire-wire/)

The wire breaks occasionally on the main cut, and A LOT on the trim cut (like 5 times), I couldn't figure out why, the break piece of wire is about 55.5 inches long, which is almost all the way to the wire shredder in the back.

I did the following:

1. Cleaned and rotated the upper and lower power feed to a new spot.
2. Put in brand new bearings for the bottom roller guide.
3. Cleaned the two rollers that pinch the wire in the back that is right beside the wire shredder.
4. Double-checked the technology and perimeters.
5. Switched from two cuts to one cut (which works fine).

At this point I really don't know what to do. Last time, the service person claimed the wire was "crunchy", but I thought the wire quality was ok.

Can you please give me some pointers on what might be the cause based on your experience?

Much appreciated!

 

[jdd]

If you have a tension meter you should check if it matches technology and there
are no significant changes in tension values. I work on Agievision machines and
have found on two occasions that wire breaks during skim cuts were a result of
a defective wire brake motor.

 

[8InchCaliper]

Thanks for the reply jdd! We do have a tension meter, I checked it today, it matches the FW (wire tension) perimeter, which was 17, so the wire brake motor seems fine.

I made a call to the service guy, he said the wire becomes slightly undersized during the trim cut, and the pinching rollers in the back don't put enough pressure on the wire, but I wonder then how come the main cut was fine?

Other than the wire brake motor issue, he said there could be two other reasons:

1. I need to increase the Wire Feed perimeter AW, increase it to at least 165 (in the metric system).
2. Change the pressure of pinching rollers in the back, put it on highest.

For the first suggestion, my main cut already has AW at 180, which works fine, I'll try another trim cut, and see where AW would be at.

I have reservations about the second suggestion, since it's already at the recommended level, also last time we played with that thing, all it did was giving this alarm "Wire Break, Wire Break signal was false", basically the wire was slipping or something.

 

[Jim7511]

Sounds like the pinch rollers are the issue probably loaded up with debris or worn too smooth.

 

[implmex]

Hi8InchCaliper:
It could be nothing more than a bad spool of wire.
I recently had one too... ran just fine until I got to about mid-spool and then it broke a gazillion times in succession.
I'd have to pull the upper wire guide and pick out all the bits of wire, and I must have done that 20 times.

It was my last spool so I grit my teeth and kept running it.
Now the spool is running fine again.
When I looked at a sample of the broken wire under the scope it was obviously fractured at a defect at both ends.
Looked like a fold got drawn into the wire when it was made.
It happens.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[8InchCaliper]

Hi8InchCaliper:
It could be nothing more than a bad spool of wire.
I recently had one too... ran just fine until I got to about mid-spool and then it broke a gazillion times in succession.
I'd have to pull the upper wire guide and pick out all the bits of wire, and I must have done that 20 times.

It was my last spool so I grit my teeth and kept running it.
Now the spool is running fine again.
When I looked at a sample of the broken wire under the scope it was obviously fractured at a defect at both ends.
Looked like a fold got drawn into the wire when it was made.
It happens.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Thanks for the input!

Today I did an experiment - I'm wiring two identical pockets on the same stainless block on different surface (now 1.5 inches tall). One pocket I used only 1 cut, the other I used two cuts. I set pinch rollers pressure at highest.

The first cut is fine for both pocket, for the 2nd one that does the trim cut, the wire would break roughly after cutting half of that profile at the same spot (I tried this 3 times on 3 blocks), after rethreading the wire, if I manually increased Wire Feed perimeter AW from 150 to 180, it would finish the cut with no problem, but if I did nothing, the wire would break again and again, immediately after each restart.

So I guess it's not the pressure on the pinching rollers, just the Wire Feed is too slow. The wire probably has poor quality too, AW needs to be adjusted to accommodate it. We used to have coated wires, but we cheaped out because the other costs $400 whereas this one maybe $200.

 

[plastikdreams]

Cheap wire is like cheap carbide endmills, it always ends up costing you in the end.

There are guys that use the machine and guys that know the machine, be the latter. I'm a mits guy so I can't really offer help to ya, but it seems like you got some good direction.

 

[8InchCaliper]

To give an update, poor wire quality was the cause. I switched from cheap FIRE wire to higher quality Hatachi wire, no more wire breaks on the trim cut.

For the cheap FIRE wire, to make it work, I need to increase the wire feed perimeter AW on the trim cut (it was not feeding fast enough). Thanks everyone!

 

[implmex]

Hi 8InchCaliper:
Yeah I've been using Firewire too, and I had zero problems until this one spool.
I bought another case recently and it's been fine.
Shit happens!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[plastikdreams]

If it's coated wire sometimes the coating can be too brittle and starts fracturing and making a mess...that's the chance you take for pushing the edge. I've only run uncoated wire but have heard the heartaches coated wire can cause, although I've also heard the huge gains as well. Always heard good things about cobra cut wire.

 

[SeikiCorp]

The majority of my work is INCO 718 and 17-4.
I was using Bedra HEAT wire for years. It does have a speed advantage, But the wire is very inconsistent batch to batch. Some batches were dark brown colored, some almost as light as plain brass. Sometimes it would flake off the coating and deposit it all over the feed rollers at the top of the machine and in the tank. Sometime it would rough cut ( high power ) but could not keep the spark going while on a trim cut ( low power ).

Starting this year, I switched to Bedra Gapstar wire (900).
It is still a dirty wire and deposits powder residue on the rollers and tension wheel, But it auto threads at 8" tall and is the same cost from my supplier. It does skim and polish passes without the spark blowing out and has a good size. It anneals fine in the threader and comes out mostly straight from the spool.

I have used about 25 spools so far ( .010 & .012 ) and it has not had any bad batches yet. The cutting speed is about 2% faster than the HEAT. But it cannot carry the same current that HEAT wire could. I could crank a .012 HEAT wire to carry 12 amps without breaking on 5" tall INCO 718. The Gapstar melts above 8 amps. I will know more by next year. So far it has been a good switch.

I am getting 2 spools of Bedra 'Blacspark-H' wire this month. I am cautious about any wire that is not made in Japan or Germany ( made in Vietnam I think ). But I am always looking for a faster wire...

 

[nlancaster]

Seikicorp,

My wire vendor just sent me a 3.5pound spool of Blacspark to try out. I will say it is alot faster than the SST Optima TA we have been using.

The OptimaTA is a Gamma-brass coated wire and was quicker than the Bedra CobraCut-A we had been using.

This Blacspark is 16% faster on the existing program I tested with the same settings as the CobraCut A and when I used the suggested settings which increased on time and lowered off time on my Sodick AG600L, it was 36% faster in the same program.

With similiar surface finish numbers, a little worse but not much.

 

[SeikiCorp]

My P10 test spool arrived yesterday.
I am going from Bedra Gapstar ( already a great wire ) to Blacspark on cutting 5" tall inco 718.
Should have time to test that today.

Did your spool have any Bedra marking on it? Mine says EDM FOUR 23. But not Bedra or the hardness number.