Fitted with a Harrison-GE Fanuc 21 i control.

This is the model that has a full functional Fanuc control (not the Alpha code only version).

Having a problem running the machine. Turned it on yesterday after it had set idle for some time and i get the following error:

Alarm: 300 APC Alarm: Z Axis need ZRN

Now reading the Fanuc manual i see that this is a problem with the absolute encoder needing to be reset to its reference position.

Would guess that the batteries on the axis have gone flat and the position of the Z was lost.

Checked and the servo drives show ready and linked….

Batteries show 5 volts on both axis drives , but this was after being powered up for some time so i guess some recharge had happened.

Also the position of the Z axis does not look wrong….Position is about what i would expect.

This machine has (to the best of my knowledge) no home hard switches or reference marks.

Read the section in the Fanuc manual about resetting a reference on an absloute encoder and it makes no sense.

Hoping some one here can give me a step by step process for this machine.

Ive only ever delt with absolute encoders on robots before. But I assume its not a heck of a lot different with a machine tool. All the robots I have worked on have had either a couple V or I marks stamped into the casting to set home position. From there it is as easy as being in a service mode to set the new position, basically whatever the encoder reads is now entered in the home position which becomes your new home/zero.

So you have found the place in the manual that talks about this eh? This is real helpfull – as you will want to know how the turret is to be guaged and then the value of it at that point.

Should read something like Place the turret X distance from spindle face.

This may require you to pull the chuck off. ???

At that position – the manual should then tell you what value to place into the Z axis position during the process.

Without those two pcs of info – you will have a trial and error routine. You would find this in a Harrison manual, not Fanuc.

We can guide you through the rest of it if you can find that info.

No such info in the Harrison manual that i can find.

Their book is pretty basic. Deals mostly with the use of the

Not sure it matters but this is a flat bed machine with a tool post, no turret.

Thanks for the info, now i guess i know what i am looking for.

I was thinking the batteries are lithium, so no recharging going on if so. I had the same issue when I bought it, except in my case it was because the batteries were dead as doornails. The tech at Clausing/Harrison told me how to reset the encoders…. was easy, but cant remember now the exact proceedure…hopefully the same tech still works there…

When this happened to me on my Okuma with fanuc 21i control it was a very simple procedure. First I changed the batteries, then I jogged the machine to the approximate home position, this was easy as there are little metal tags that line up. Then in home mode I just hit each axis in turn and the machine found its own home. I believe the encoders do have a reference position in them and as long as you are close it will find that position on its own.

If that doesnt work then there is a way to do it using gage blocks and a dial indicator. But you would need someone who has done this to explain how.

You should be able to do as Charles says, if you dont have tags then you need to know the distance from home position to your spindle face. Jog it to where your home position is and then press the zero return button. If the end result is off by anything other than a multiple of your z axis ball screw lead than something other than you battery is wrong, or someone did a grid shift sometime in there. Regardless, once you have done this your Zero is set and it will return to that position every time. If you want to re-home that axis you can set 1815 -APZ (on the z axis line) to 0 and then redo the proceedure. If you know how much it is off (aka not an even mulitiple of your ball screw pitch) you can set 1815 APZ and APC to zero then move the prescribed distance to where you want the home to be, then set them both back to 1 and restart the control. Your home will now be set to where it sits. This will not effect the incremental position of you reference home positions from the true home position.

I just went through all of this the other day on one of our mills as the heidenhain scale started losing its mind… I ended up disabling the scale and had to re-establish the Y-Axis Home position. In my case I knew the distance from home position to the top of a pallet. Granted I cant get it perfect but .0005 is good enough for us. When I get the scale fixed I will have to set it again, at that point I will make sure the ambient air temps arent out of control causing my column to grow excessively.

Procedure for absolute encoders on Fanuc 15/18/21 (IIRC)

Press Settings hard key and settings soft key

Change Parameter Write to (1) – Ignore the stupid alarm

Press System hard key, Press Param soft key

Type in 1815 and press Osrh (search) soft key

Cursor over to the bit APZ for the Z axis

Change the bit to the opposite (I can never remember whether its a 1 or 0)

Cycle power – (wait 15 seconds between off – on)

When it comes up, it will have the stupid parameter write alarm and will have the Z axis need ZRN alarm also.

Type 1240 and press Osrh soft key.

This should list the reference positions for X & Z, if not page down through 1251 and see if any values are set.

This would be the physical reference position from the spindle face.

Switch to JOG mode and move the axis to the correct physical position.

Cursor over to the APZ bit you changed earlier

Set the parameter write enable back to 0 to get rid of the STUPID alarm.

mechanically locate table where it needs to be using test bar, gage blocks, dial indicators, etc.

control alarms to cycle power ( make damn sure your batts are already replaced/ issue fixed while the power is on or you are doing all axes)

I dont recall if I have to do it twice like Tony says for the i series…. but its similar.

The batteries are generally a 3-4 d cell battery pack on the electrical cabinet door – maintains encoder power so it never has to home until the batts die ( supposed to be an alarm for that too)

The catch is how to locate the z slide to tell it where home is. The only good thing about not knowing is you can decide for yourself and keep notes so yuo keep doing it the same way, but things like soft limits and diagrams in the harrison book for machine coordinates home will also help.

mechanically locate table where it needs to be using test bar, gage blocks, dial indicators, etc.

control alarms to cycle power ( make damn sure your batts are already replaced/ issue fixed while the power is on or you are doing all axes)

I dont recall if I have to do it twice like Tony says for the i series…. but its similar.

The batteries are generally a 3-4 d cell battery pack on the electrical cabinet door – maintains encoder power so it never has to home until the batts die ( supposed to be an alarm for that too)

The catch is how to locate the z slide to tell it where home is. The only good thing about not knowing is you can decide for yourself and keep notes so yuo keep doing it the same way, but things like soft limits and diagrams in the harrison book for machine coordinates home will also help.

BIG HINT – check all your tool offsets and work offsets before you run a single thing after you reset home

…and yes – you will need to cycle the power twice.

Will run the through this tonight, and hopefully i will be up and running.

This is a late response to the thread, but this is the procedure for a Fanuc 160i control, particularly on an Amada LC-1212 laser. It may be helpful for other machines:

Amada LC-1212 B-Axis Zero / Homing Reference Procedure

The B-axis is equipped with a memory so that normally it is not needed to reference in

the morning during normal power up. After a battery change, or any other event that

causes the reference to be lost you will need to follow this procedure in the Fanuc 160i or other similar controls.

If B has overtraveled in the + direction and stopped at ~0.830 on the readout, removal of the ballscrew cover on the laser head may be necessary and the servo shaft being turned backwards using a small blade screwdriver in the provide slot on the end of the ballscrew. Typically turning it while watching the on-screen DRO until its ~0.250 less than the overtraveled value and backed off its limit / hard stop.

4. Set Parameter Write Enable to 1 then [INPUT] key (Alarm will flash. Ignore or press [CANCEL] and [RESET] if desired)

12. After boot, go to Reference / Zero / Homing mode

13. Hold the B+ button then pressing and holding the adjacent Enable button. Watch the numbers on the Position readout screen. When the numbers and B servo accelerate, release the button. The B light will illuminate

21. After boot, go to Reference / Zero / Homing mode

22. Home the B-axis, typically in the negative direction, and in similar manner to 13 above

29. Set Parameter Write Enable to 0 then [INPUT] key

Can anyone chime in on the correct procedure for a 10M control to clear the OT032 Need ZRM (ABS PCDR) error? I had to remove the encoder cable to do some other repairs. Cant seem to even jog the Z axis with this alarm active- is that normal? Getting a 2nd following error message when I try to jog. The drive ready light is lit on the axis drive so Im assuming Im not doing something to make it happy. Dan

Well, on an 18i, you would go to param 1815 and shut off the 1 in the right hand column – of the two columns of 1s – of the axis that is at fault obviously…

Then you need to position your slide at some pre-determined position, and enter the value that is in the param register a few params later.

Before we git too involved, better see if you have 1815 and if what I said so far makes any sence, then we can figger the rest out later.

Ox- thanks for the reply- my 1815 parameter, according to the manual only assigns values to the two right hand bits- bit 0 is RESx (digital or analog encoder) and bit 1 is OPTx (designates optical scale (1) OR NOT (0)). There is a line for each axis and bits 4 and 5 are high for x and y where as only bit 5 is high for Z. BUT, the Fanuc manual has no assignments for these, so ???

Actually I think I have another issue in that I cant jog the Z axis at all without getting either an additional excess following error or V ready off fault when I try to jog or MPG the z, so I have to get that figured out as well. Fanuc is closed for the holidays so I have to wait on this. The amplifier is a rebuilt I just received and the motor just came out of the shop with a clean bill of health so Im scratching my head at this point. This is an AC servo on a Mori MVJR. Dan

……Actually I think I have another issue in that I cant jog the Z axis at all without getting either an additional excess following error or V ready off fault when I try to jog or MPG the z, so I have to get that figured out as well.

Usually the alarms saying excess following error are related to a mechanical drag on the axis.

IIRC, newer MVJRs did not have a counterweight for the Z and had a brake on the Z ballscrew to keep the head from falling when power is off. That type brake is spring actuated and electrically released. No power to the brake, a bad coil in the brake are possible causes.

Older MVJRs had a chain hung counterweight behind the column and did not have the brake. Ive seen them break a chain and hang crooked and bind. Ive seen the bearings in the sprockets go bad and cause a bind. There a Vee-grooved rollers that guide the counterweight so it does not swing and bang around. Ive seen the bearings in those go bad and cause the weight to get stuck.

Vancbiker- this one has a counter weight- pretty sure its all in good shape, but Ill check it out, but I have always made sure the chain and sprockets were lubed well. This all started with an sv003 excess current alarm on the Z axis at control power up, before anything moved. I would rattle the top card on the amplifier a little and the alarm would clear. Never did it alarm during actual operation. Service guy thought the motor was the culprit, as disconnecting the motor caused the alarm to go away. Had the motor baked and revarnished – problem with amp still there. Tried new rebuilt amp and now the current dilemma. I can move the head by grabbing the screw/belt and turning it by hand- does not seem to be dragging. Grr!! and thanks! Dan

Have you tried running the motor with a known good drive or a known good motor on the repaired drive? Call me a cynic, but Ive seen enough newly rebuilt/repaired components still be bad to make me want to always test with components that I personally know are good.

Its pretty rare IME, but an open transistor in the drive can behave like you describe.

With everything powered up can you turn the screw by hand? Do this very carefully and be sure to only try it if you can be 100% safe while testing. If you can move it, your servo drive is not sending power to the motor and you should get an alarm something like excess error stopped.

Excess following error results from the control sending a motion command to the drive and not getting enough encoder feedback pulses or seeing encoder feedback pulses with no movement commanded.

We meggered the motor and the cable together, the motor alone and the cable alone before the motor was sent out. I really dont think the motor needed anything, but the old drive did not fault with the motor or the motor/cable disconnected. The motor meggered as I recall 400 megs, but based on the drive not faulting we had the motor baked and reinsulated. Im gong to try your suggestion on seeing if the motor can be moved while powered up and also with the belt popped off- its easy to do. I have to check if the X or Y motor is the same- just hate to tear more stuff apart than necessary. One question on the new drive- I only found two jumbers S1 and S2 that I set the same as the old drive- are there more things that need to be set like the old drive, or are those it? Cant get phone support now due to the holidays so . . . Thanks so much for your help! Dan

You should also check continuity on the power cable. The megger check is to look for shorts. For the behavior you described you want to look for an open connection. Ill get down to my shop later today and take a look through some early AC servo info and see if stirs up any other ideas.

As far as swapping drives, it is pretty safe to mis-match sizes as long as you are just hand wheeling or slow jog.

Fabrication: CNC Laser, Waterjet, Plasma, Welding & Fab

Schaublin, Cazeneuve, Weiler, Graziano, Mori Seiki Lathes

Cincinnati Milacron, Kearney Trecker, VN, USA Heavy Iron

Machine Reconditioning, Scraping and Inspection

Tooling, Parts and Accessories For Sale or Wanted

Machinery Manual, Brochure and Photo Archives

With more than 10.6 million unique visitors over the last year, Practical Machinist is the most visited site for metalworking professionals. Practical Machinist is the easiest way to learn new techniques, get answers quickly and discuss common challenges with your peers. Register for the worlds largest manufacturing technology forum for free today to stay in the know.

Copyright 2019 vBulletin Solutions, Inc. All rights reserved.

This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. If you want to know more or withdraw your consent to all or some of the cookies, please refer to thecookie policy.

By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to the use of cookies.

The latest industry newsstraight to your inbox

Sign up for our eNewsletter now to stay in-the-know. Well bring you the most relevant peer-to-peer conversations happening in the trade and tips and tricks to help you get the job done.

I agree to receive emails from Practical Machinist containing industry news and updates from Practical Machinist and its sponsors. You may unsubscribe at any time.

This site is protected by reCAPTCHA and the GooglePrivacy PolicyandTerms of Serviceapply.