[alfaguilar]

I have an acroloc machining center, that sudenly did not want to home, I do the Zero return but it always overtravels on X, Y and Z, I have checked the limit switches but they seem to be ok, when it hits the middle switch it does not slow down, any help will be appreciated.

[Al_The_Man]

Have you checked power on the switches?
Sounds like you have lost the power to all somewhere.
Al.

[mfgbydesign]

First thing I usually check is the inputs. Don't remember exactly how to do it on that control, but there is a page you can bring up that shows the I/O. Toggle the switch manually and see if you get a bit to change zero to one. If no input its a switch circuit. If input is working you need to check the ladder logic to see what other condition is not being met.

[Al_The_Man]

First thing I usually check is the inputs. If input is working you need to check the ladder logic to see what other condition is not being met.

Good idea, the status is on the diagnostic page, if you have the schematic of the inputs it will tell you the bit number to check.
Unfortunately the ladder does not display on the 6.
Al.

[Dan Fritz]

Sounds like the control can't see the ZRN (Zero Return) input. If you jog or rapid toward the limit switches, it will just overtravel like you describe. If you turn on the ZRN input, it's supposed to slow down when it hits the zero-return switch cam, then drop off the cam, then find the "1 pulse per rev." signal on the pulse coder.

You didn't mention what model CNC this is. Some controls use encoder feedback with battery backup, so the "zero" point is never supposed to be lost. Older controls must manually zero-return every time you power up, or they won't know where machine zero is.

Acroloc used several different Fanuc models, starting with the 3000C and system 6M. Those had resolver feedback with no battery backup. Let us know what control you have and we can give you the diagnostic bit for that ZRN signal. If the panel switch for ZRN is not seen by the control, that would explain your problem.

[alfaguilar]

Thank you very much for your prompt response.
I will discribe more what I have done.
Originally The machine would go over the limit switch and make a noise like something being forced (it even crashed against the hard stopper making a big noise while running a program), then it would alarm, I had to turn off the whole machine then it could recover from that, I looked at the limit switches and I found out there was an open wire, I resoldered it to the switch then it did overtravel but the limit switch would work stoping the movement.

So, my situation right now is that the machine does not slow down when pressing the decel switch (it seems that the decel switch is not there) then overtravels, when making the zero return on all 3 axis.

I have checked the " Pressing P and CAN keys while boots up" and makes no difference I have also pushed the decel switch down and check diagnostic #32 bit 5 for X axis , #33 bit 5 for Y axis and #34 bit 5 for Z axis and they all change from 1 to 0 when the switch is pressed.

Before all this I was playing with parameters 24 25 and 26 to make the RS232 comunication, I did make that to work but now I dont know if I messed up another parameter related with the zero return because I only realized this after downloading my program, once I was ready to test the program machine gave me the alarm 010, for any program we try to run it gives this alarm, then we figured out the machine needed to be home, so here we go with this problem.
My controller only goes up to parameter 166, some other posts talk about parameter 1815 bit 5 I guess but this machine does not have it.
I am running out of ideas, any help I will appreciate it

[alfaguilar]

Yes I did not say what control it has.

Here is what the machine has.
On the CRT screen appears Sistem 6m 991 VER. 2
On the control panel it says GN series

[Dan Fritz]

You have an early model Fanuc 6M (sometimes called the "6M-A") with resolver feedback.

Press the DGNOS key and page up to show diagnostic 101. This is an 8-bit register where you can see the status of some input signals. The bit on the FAR LEFT is for the ZRN input. When you rotate the operator's panel mode switch to the "Zero return" position, that bit should change from "0" to "1". If it does not, there may be a problem with the panel switch, or you may have a bad input for the ZRN input on the I/O board.

Hope this helps.

[alfaguilar]

Dan thank you very much,
I will check that tomorrow.
I am new with this, sorry to ask you but where is the I/O card located? aslo I don't have any documentation for this control, where could I get something, that would help me troubleshoot the Zrn switch signal.

[alfaguilar]

I checked the signal on the DGNOS key to show diagnostic 101.
The bit on the FAR LEFT "Zero return" position, changes from "0" to "1".
so that means the signal from the zero return switch goes to where it is supposed, the signal from the decel switch goes to were it is supposed to.
what else do I need to check?
is there any parameter that that could be causing this?
Thanks in advance

[mfgbydesign]

I do not have an answer for you but suggest now that DNC is working backup your parameters. There should also be a paper copy in the control that shows factory original settings. You could compare to see what's changed.

[alfaguilar]

how do I make a back up?

[mfgbydesign]

Perhaps someone with more recent experience can post, it's been 10+ years since I stood in front of this control.
I think you place in "edit" mode, set up DNC to recieve, then P9999 "punch"
Did you find any schematics, parameter lists, or ladder diagrams in the control cabinet?
*** darn can't spell this morning. Also can't change title in edit. Paramerters?***

[alfaguilar]

Thanks for your reply,
I have not found any documentation, I would really appreciate if I could find the parameter so I can compare it

[mfgbydesign]

The parameters are (part of) what tells the control the type of machine. To compare parameters you will need to find a machine pretty much EXACTLY like the one you have. Try to find any documentation you can and in the meantime start tracing wires, cleaning & testing switches, and anything else you can think of. Keep eliminating potential problems and the cause will eventually become evident.

[Dan Fritz]

Check to be sure the limit swiches are working also. There should be one switch on each axis that is operated by a cam. As you approach the travel limit, it turns on, then after an inch or so of additional motion, it turns off again. Shortly after the switch drops off the cam, you should hit the actual overtravel switch.

These signals can be seen on the diagnostic screen, which will confirm whether or not the CNC can see them. Press the DGNOS key to display the diagnostics screen, page up to diagnostic 032, then have someone manually actuate the switches on the X axis while you watch the display. 032 bit 5 (the 6th bit from the right) should change from "1" to "0" when you press the X zero-return switch. 032, bit 0 (the bit on the far right) should change when you press the +X overtravel switch, and 032 bit 1 (the second bit from the right) should change when you press the -X overtravel switch. Same bits in diagnostic 033 is for the Y axis, and 034 is for the Z axis.

If the CNC can see these signals OK, and your control is in ZRN mode, then moving the axis in the direction of the zero return should cause it to decellerate from rapid to a "creeping" speed when it hits the zero return switch. This speed is set by parameter 114. Also the DIRECTION of zero-return can be plus (+) or minus (-). If the direction is set wrong, then you'll have a problem also. The zero return direction for each axis is set with parameter 012. The right-most 4 bits are for the direction (bit 0 = X, bit 1 = Y, bit 2 = Z) a "1" in these parameter bits means minus (-) and a "0" means plus (+). Bits 4, 5, 6, and 7 of parameter 012 should all be zeros for the normal "Grid system" of zero return. In VERY RARE cases, a magnetic proximity switch is used with an inductosyn scale, and these parameters are set to "1". Let me know if that's the case because that's a whole 'nuther ball game.

Also, older Acrolocs had a small "gearbox" mounted near the servo motor. Inside that box, you have a worm gear driving a ring, which actuates some small limit switches. look for a broken coupling on the worm gear, or maybe smashed wires between the box and it's cover plate.

[alfaguilar]

Dan, I checke everything you mentioned, and nothing seems to be different
Parameter 12 is 00000001
Parameter 114 is 0200
I have attached a file with pictures for you to take alook, I put is the contol panel, just for you to have an idea of what we are talking about, a picture of the X axis where the switches are located.
I also put in a picture of a relay board, before all this started the machine was crashed into the hard stop, then it turned off, I could not turn it on anymore, then I played with the relays of the machine, the very low one on the right I unplugged nad plugged again then the machine worked, I wonder if the relay is damged, or not making good contact I have taken out and reseated, but makes no difference, I am prepairing a list of parameters for you ta take look, I need to double check it with the machine, I dont want to put something wrong.

[alfaguilar]

I have attached 2 files that show parameter and settings also the x axis limit switches maybe that helps for you to understand more the situation

[Dan Fritz]

Your option parameters are not right. The options are set with parameters 000 through 005. Parameters 300 through 305 are also used for options on the 6M-B (you have an "A").

I'm paying special attention to parameter 000, which is shown on your photo of the "Parameter 01" page. The bit on the far LEFT (bit 7) is for the "zero return A" option, and the bit next to it (bit 6) is for the "zero return B" option. Both of these options were "standard" features when General Numeric sold this control to Bayer Industries. You also show that bit 5 (3rd from left) is set to "0", which is the inch-metric option. You may not notice this because Acrolocs had inch ballscrews anyway, but if you ever want to program in metric, the G21 command would likely throw an alarm (alarm #10 - illegal G-code). All GN sold controls had this option as standard.

Try to find a listing of what parameter 000 should be set to (from the factory). I'll bet that it should be : 11100111. If you have any paperwork inside the CNC control cabinet, you may find what we used to call "the onionskin". It's a print out on very thin paper, which has the parameters as set from the Fanuc factory. It should show the option parameters as they were ordered from Fanuc by GN.

[alfaguilar]

Dan
I changed the parameter 0000 and the machine did home in all 3 axis
You mentioned about alarm #10 (ilegal G code) that is the alarm we were getting before, then we thougt it was the zero home failing that was giving this problem, the drawing we converted the G code from on solidworks was in metric dimentions, it still might give us the same alarm, does it mean we will have to convert it to inches?
what does it mean "zero return A" and "zero return B" ?