Machine hang during tool change

[javajesus]

I am hoping someone here can help me with a problem I am having with my Sharp 2412 mill with FANUC Oi-Mate controller. There is no rhyme or reason to this problem and no pattern that I can find. Here is what happens. During normal program exec, the machine will hang during tool change. The TxM6 is called, the spindle goes to tool change height and orients then....nothing. Just sits there with the green light blinking and the control displays M6. I can push the RESET button, switch to EDIT and go back up a few lines to the new tool and start the program from there. It might work normally for a few tools, or hang on the next change. Sometimes, it will run totally normally. Pushing the CYCLE START button during the hang does nothing. I have made sure that M01 is not active on the panel. The problem seems to be getting worse. I am not afraid to dig into the guts and check whatever I need to. Anyone have any ideas?

[spock]

I have a very similiar problem, as yet unresolved.

Lets say I am running on 25% rapid, and have a tool change in the program. The machine will change tools, then take off at 100% rapid. It will execute the program until the next toolchange, but will hang up on m6 in the toolchange macro exactly as you describe. If it takes off with the wrong rapid rate, it hangs up EVERY single time.

I personally think it has something to do with being cold. I know that sounds crazy, but the only time mine does it is when it is fall or winter, and I didnt run the heat at night. Start machine up, it hangs up for about an hour then quits, and runs fine. I think is a bad connection somewhere, and when the control doesnt get both signals (in the ladder) it defaults to 100% rapid but cant tool cahnge because of the missing signal.

You said yours is getting worse, is it getting colder in your shop?

My dealer has looked at it twice, he added some more dwell time to the toolchange, might have helped some. It went several months without doing it, then 2 weeks ago, started again. I cant get my dealer to return any phone calls. I have an independant repairman coming Monday, if we figure it out I will definitly let you know.

[Mickey_D]

Mine used to hang randomly on tool changes (about 1 in 50) and more so when the machine was cold. I would hit the start button and it would continue like nothing was wrong. I turned up the the low side on my compressor so supply pressure would not fall below 100psi and adjusted the regulator on the back of the machine to the high side of the green zone. Knock on wood, it seems to have fixed it. Also, check your supply lines to make sure you are not restricting it through funky plumbing.

[javajesus]

Spock, you have described the EXACT same condition I have. I used to run on 25% rapid and after a tool change it would take off at 100% and then hang on the next change. I can say that I don't think temp has anything to do with it. It has run in a shop that was cold (55 degrees) and now in a shop that is around 70. It even did it in the summer. My machine will hang all day long. I originally thought that it might be electrical noise from my sharp lathe. The problem got worse after we installed that, but it still does it even if the lathe is not running. It is very frustrating and a huge waste of time.

[javajesus]

Mickey D,

I have had that problem as well, where the machine would just stop, mine usually in the middle of a cut. Push the start button and all would be cool again. I think my compressor might be a little low on the low side. I also know that my regulator on the back of the machine is set to about the middle of the yellow. I adjusted it up awhile ago and did not see any difference so put it back where it was. I will try those 2 changes together and see what happens. Spock, can you tell me what your compressor / regulator settings are? Maybe we might be on to something. I did read another post that talked about limit switches in the spindle gear box. Maybe the controller is not getting a signal it needs. I am not too familiar with that stuff and have no idea what the "Ladder" is.

[neilw20]

I've had similar problems on an rather large OKK CNC with a Bosch Controller.
Part of a cycle to say change a tool operates various mechanisms in sequence.
Cycle starts first part of sequence. Waits for a limit switch to say that part of cycle is complete.
Next step commanded, wait for next limit switch.
Each sequence starts moving something.
That sequence is usually completed by hitting some limit.
Eg Tool picker at location ready to pickup a tool.
If any of the limit switches are not sensed correctly, or at all then the cycle waits, hence the green light just waiting.
Also some parts of sequences may be progressed based on timers instead of limit switches. If a time is set to short, or something does not move fast enough to get to it's next spot, because it's gummed up that can do it too.

Easiest thing with limit switches is putting a 0.1uF Capacitor across the switch, so you get the capacitor supplies extra wetting current to keep the contacts clean. This is usually a safe fix, if no capacitor is across a switch.
If it causes some operational grief, then just remove it.

When the machine is 'stuck' try thumping around the areas where the limit switch(es) are/is and you may identify it. Careful of unexpected movement if the machine normally moves FAST.

Every case I have had on an aging machine has been tardy limit switches.
Clean plunger mechanisms and get rid of gummy old lubricant.

May appear temperature related, because lubricants get more sluggish at low temperatures.

Also look at connector plugs. Make sure all pins have positive pressure.

Search and destroy....... It will fix it. Don't blame software. It is just doing it's job. If it worked yesterday, it ain't broke.

[spock]

I am 100% sure it aint software, it is mechanical.

My air compressor runs between 140 and 170 on pressure.

My regulator on machine is set to .65 Mpa, near the top of the yellow.

The idea that there is some grease on a switch, getting cold and stiff, and not allowing it to move freely makes sense to me. Then, the switch cant send it's signal, in the ladder schematics in controler it defaults to 100%, machines until the next toolchange, then hangs up waiting for signal.

[javajesus]

I agree Spock. It does make sense that it could be a limit switch. Do you have the same machine? A sharp sv2412? Anyways, I will be running it today and I am sure it will hang. I will try Neil20's suggestion of banging around where limit switches are and see if that might be it. I think before that, I will take a good look at the Z axis limit switch that I can see. Lets work together on this one and see what we can find out ?

[PBMW]

I had that issue on the loaner machine I had for a couple of months. Charlton Lu told me to add a bit of dwell fro the limot switched in the tool change macro. That cured it na dI also did the same for my machine. I have not had any issues. I do keep the pmachine pretty clean though. Limit switched being what they are...

[spock]

I have a sv24-12 super mini with OI-MC control.

Adding dwell was what the dealer service did, and it seems to have helped alot, but didnt cure it for mine.

I keep my machine very clean, but I think when repairman gets here on Monday I will have him go thru switches with contact cleaner or something, check for anything loose, etc. Thing is, my machine did this when brand new, no chips or dried sticky coolant or anything!
I will let you know if we find anything out.

[javajesus]

Well another day of machine frustration. Did some bangin around with a rubber mallet. No luck. Checked what limit switches I could find. Not sure where they all are. How would I add more dwell in the tool change macro? I am pretty handy with computer stuff so if I knew what value to change I will give it a try. Also here is something I noticed. When the machine hangs, I can rotate the spindle freely. I know from experience that when I do an M19, the spindle is locked in its oriented position. Could the issue be here? Spock, let me know what the repairman says. Thanks.

[PBMW]

I'll send you my tool change macro in the morning if you send me an email...