Need Help!- Fanuc 16iMA-mc lost home position when Power OFF

[cnc_mould]

Hi everybody!

Anyone pls help me in my machine trouble.

-We just buy used 3 axes milling machine with Fanuc 16i-MA controller, after install mc, alarm 300 (APC alarm) X, Y, Z needed to reference return (at first Power ON) (although we never disconnect motor or encoder). I try to manual ref return and completed with X and Z. But Y axis homing always end with alarm 90 ref return incomplete (machine use abs encoder and linear scale for all axes, X and Y used a common Amplifier). I turn of then on machine, and try to homing several time, also the same thing happen. I also try to do some others things as:

To clear alarm 90 and complete ref return process:
1: move Y far from home position, increase homing speed, the same alarm 90
2: change pare #1815 bit 5 from 1 to 0, power off then on, change back bit 5 to 1. power off, then ON and perform Y homing, alarm 90 again.
3: move Y axis far from home position, change para #1815 bit 5 from 1 to 0, bit 4 from 0 to 1. Power Off then On, change para 1320 limit 1+, set for Y axis value is 99999999. Perform homing, alarm 90 again
4: Exchange X and Y encoder, the same thing happen for Y axes. X axis homing OK
5: Check DEC LS signal is normal. And alarm 90 always appears immediately after DEC signal went OFF, and moving stop at distance ~2mm from home position (I see on the machine coordinate)
6: Adjust DEC LS hard position, can not complete homing with alarm 90
7: Disconnect motor from ball-screw, rotate motor only 1/2 turn, then reconnect motor. the same thing happened while homing
8: I try to manual set home position. Move Y axis to where it should be home position, change Para #1815 bit 5 from 1 to 0, bit 4 from 0 to 1, then change back bit 5 from 0 to 1, Power OFF and ON again with holding P+CAN when NC control start up.
No alarm coming, i can perform homing completely

But I got another trouble.

Every times, When I power OFF machine, then POWER ON, when NC control is ready, machine lost the home position and it auto reset machine coordinate for Y axis to 0 and take the position where it stop when power OFF as new home position without any alarm. I must manual ref return, this process is success. but i check the home actual position is wrong, it is minus ~0.8 mm from last home position which I set, and not stable.
This trouble make me headache and I hope somebody has ideas to troubleshooting.

Thanks!

[fanucman]

ok so..

make parameter 1850 (grid shift) a 0 for y axis and do reference return.
check the scale feedback with scope
check the battery for y axis scale
check the feedback cable for breaks

[cnc_mould]

Thank you, Fanucman
I already change # 1850 to 0 but nothing is difference,
also interchange scale between X and Y axis. it seem the scale feedback
signal is normal
now, I look up for parameter which helpful to turn off scale, anyway i'll try and see how

[MysticMonkey]

If your machine is changing from power off to power on

I would suspect either the battery or the encoder

if there is no ABS alarm active I would suspect the encoder or battery wires in the cable.

you have a linear scale so this complicates it a bit but I still believe the encoder is at fault.

Try swapping the encoders (move the machine to home position first)
on power on set 1815.4 from 0 to 1 power off and on and see if the error has swapped axis.

[cnc_mould]

Hello my friends,
Firstly, I wish to thanks both of you

It's exactly as fanucman suggestion, this related to scale, I tried to turn of scale then I can let machine homing normally. after that I clean scale (inside is dirty) and turn it on. finally I can get machine ready status.

Thank you^n

[frigoteknika]

HELLO CNC MOLD

these is happen if you disconnected the cable from the servo,or the encoder is fealty.

you are making mistake ,wen you turn the machine on you hawe alarm 300 yes.

go to parameter 1815 then you will sy the the 1815 5 is 1 and the 1815 4 is 0

dont change the 1815 5 1 power off,move axis manually ,start the machine and go to 1815 4 put in 1 then power off and power on again

these will help