Dialog Error 08 - Error in position control, X axis

My fp2NC D2 stopped mid-program with error 08. The manual describes the fault as an error in X axis position control and lists several possible causes. I restarted the machine, re-zeroed and re-ran the same program, no problems encountered. Any ideas what the most likely causes are? I haven't serviced the X-axis scale, perhaps that is the most likely cause? This is the second time this fault has occurred in the last three months or so.

One of the causes listed is fault in drive amplifier, drift error. I always see some movement away from program zero as the machine warms up, and need to re-zero, maybe every couple of hours, is that possibly related?

-Dave

Clean the Tach...adjust tach and offset at the axis card...
Resetting the position display on power up is normal, but faulting out on position moves is not.

Dirty scale or poorly aligned lamp will give the letter "V" following the position display, cause the machine to E-stop and require cold shut down and re-power to get the machine to work again.
Cheers Ross

AlfaGTA said:

Clean the Tach...adjust tach and offset at the axis card...
Resetting the position display on power up is normal, but faulting out on position moves is not.

Dirty scale or poorly aligned lamp will give the letter "V" following the position display, cause the machine to E-stop and require cold shut down and re-power to get the machine to work again.
Cheers Ross

Click to expand...

Thanks Ross. I found lots of information about cleaning and adjusting the tach in this thread: http://www.practicalmachinist.com/vb/deckel-maho-aciera-abene-mills/fp2nc-y-axis-unstable-279855/
and will give it a try.

-Dave

Cleaning the tach was easy. I was a bit worried removing the brush carrier, due to the magnetism and cautions raised by Don in other threads, but it was only off a short time. Lots of black residue came off the commutator. Its back in service and no errors seen so far. Ross thanks for posting the details in the other threads, it was a big help.

-Dave

After two years I am seeing the E08 errors again if I leave the machine powered down for a day or two. I will try cleaning the tach again, but the manual says the cause could be scales, gib adjustment, and a few other things. I read Ross' post about adjusting servo gain, so that is something else to check. The E08 error occurs after switching from mode 1 to any other mode, but not always immediately. Sometimes all the servos start, then 5-10 seconds later the error occurs. Right now it happens as soon as the machine is switched from mode1 to mode 2, and the X axis jerks when the servo starts, ending up about .1" from the start position before throwing the error. I am not getting the v next to the X axis display, so does that eliminate the X axis scale from being the cause of this problem? If the machine warms up for an hour or two the problem will usually go away.

I need to clean that scale and install new wipers anyway - it is the only scale I haven't serviced (due to the difficulty of removal).

Another issue I am seeing is that the Z-axis handwheel switch (that tells the control when the axis handwheel has been pulled in manual mode) is balky. i.e. after putting the Z-axis handwheel back in CNC mode from manual, the display continues to show manual for Z, and no amount of engaging/disengaging/rotating clears it. However if I wait a few minutes it clears. Where is that switch located, and are the contacts cleanable or is there any adjustment?

Dave- don't think your problem is the scale, though it is possible.
Have noticed one of my FP4NCs gets really cranky if the main power is turned off, and runs better when mainpower is left on and the machine gets used regularly.
Could try isolating the X axis as the problem-with the main power OFF, pull the Bosch servo driver board for the X axis ONLY. Then turn the power on and see if problem persists. You can swap Bosch cards for diagnostic purposes but they are optimized for particular axis.

There's a possibility your DAC on the NRP board is going bad, only fix for that is replacement. There are a couple different variants to that part, it is obsolete and hard to find. Forum member miburk has made replacements.

Can't remember where the Z axis switch is, it's probably right behind the handwheel under the side cover. Should be able to remove the round handwheel, take the big green cover off and see it. Might just need a good cleaning with plastic safe contact cleaner.

Steve is correct! Interlock switch for the "Z" axis hand wheel lies behind the large operators side cover...Remove the "Z" and "Y" axis hand wheels and the panel Allens and it will be found where the "Z" axis cross shaft
enters the casting,...
Switch is fitted inside a cast aluminum housing
Never have had any issues with these switches...don't think they are serviceable....Sounds like yours is sticky and slow to return via its spring once the trip cam on the hand wheel has been moved away....
The cover housing has a plunger that is separate from the switch actuator....likely there is where your problem lies....
Cheers Ross

Thanks Steve and Ross. I am using the machine right now so it will be a few days until I get a chance to look at the Bosch cards and adjust gain, etc. I just ordered a set of casters (Bassick Low Profile Swivel Caster - 1/2" Threaded Stem) to install on the electric cabinet at the same time, since I have a hard time accessing the side with the servo cards. I will leave the machine running, and don't expect to see any problems. I noticed when I opened the electric cabinet this morning that it was quite warm inside, probably 100 degrees. Is that normal, or should a fan be running at a certain temp.

Also, I have been using the horizontal arbor, so when I returned to using the vertical head and re-trammed the machine I decided to see what the machine geometry looked like, since that should tell me if the gibs are in need of adjustment. I lightly stoned the table and found that the high spots were along the edges of the T-slots. After knocking those down, I checked table height at 9 points, using a centricator with a 1x2x6 granite parallel laid flat in the Y direction to average out the readings. I first tried X = 6" and X = -6", both generated over limit errors (which I found surprising because the operator's manual says the max. travel is 12" in X). It is actually 300mm or 11.81".

From the operator's perspective, the points are A(-5.5,-4) B(-5.5,0) C(-5.5,4) D(0,-4) E(0,0) F(0,4) G(5.5,-4) H(5.5,0) I(5.5,4)
Table heights measured using 1" thick granite parallel: A:.0008" B:.0006" C:.0009" D:.0002" E:0.0" F:.0004" G".0007" H: .0004" I: .0006"

So it looks like the table rocks a bit, maybe .0004" to .0005" in 5.5" of travel, or .0009" to .0011" in 300mm (11.81") of travel. Is that correctable by tightening the Z gib? I probably should try measuring at different heights, but I don't have the right tooling to extend the centricator (it has an integral sk40 shank), so it would probably be limited to quill travel.

-Dave

There are two elements to the "Z" axis gib.
First off there is the tapered and Turcite lined gib that runs vertically along the inside edge of the operators side box way. This gib controls the "rock" or "tilt/shift" of the table as it moves from side to side and
the weight shifts.....
To check this gib setting, i fit a tenths indicator so that it is reading the top surface of the vertical slide (where the plate that covers the top vertical way cover) Indicator is positioned to read at the outside edge of that surface and
held via magnetic base to the face of the box way...
Set the indicator to zero with the table centered...then move full right and full left on the "X" and read the movement on the indicator.....
This test should be run in at least three positions along the height of the "Z" travel ....one almost to the top of travel,(4-5" from the top limit) one at mid travel and one at almost the bottom....
There are likely differences and i would expect to see the most at the top where most work is generally done. (most wear)
Adjustment must account for this difference...can't make the gib tight in the middle if the top will bind.

Movement should run somewhere at .010-.015mm (.0004-.0006")


The second gib adjustment for the "Z" are the two plate gibs that capture the back side of the vertical slide....These are changed by grinding the steel and/or scraping the Turcite bearing face....
These gibs will affect the "Droop" of the fable as it attempts to lean forward from its weight......These gibs i adjust by grinding the steel surface where they make up to the back face of the vertical slide to tighten the contact to
the sliding surface (Turcite) ,. Then i scrape to get a good consistent pattern on the Turcite, and continue scraping flat to get light contact....Not sure this is the preferred method, but its how i have done this....
Cheers Ross

on my machine the plunger on the micro for the z stuck
in the closed position.This would cause the z axis to creep down.
Pulled it off the machine,warmed the plunger area with a
very small propane torch flame to "melt" the old oil that
had collected there.washed out the rest of the oil with some solvent,blew dry and reinstalled.worked fine.

AlfaGTA said:

There are two elements to the "Z" axis gib.
First off there is the tapered and Turcite lined gib that runs vertically along the inside edge of the operators side box way. This gib controls the "rock" or "tilt/shift" of the table as it moves from side to side and
the weight shifts.....
To check this gib setting, i fit a tenths indicator so that it is reading the top surface of the vertical slide (where the plate that covers the top vertical way cover) Indicator is positioned to read at the outside edge of that surface and
held via magnetic base to the face of the box way...
Set the indicator to zero with the table centered...then move full right and full left on the "X" and read the movement on the indicator.....
This test should be run in at least three positions along the height of the "Z" travel ....one almost to the top of travel,(4-5" from the top limit) one at mid travel and one at almost the bottom....
There are likely differences and i would expect to see the most at the top where most work is generally done. (most wear)
Adjustment must account for this difference...can't make the gib tight in the middle if the top will bind.

Movement should run somewhere at .010-.015mm (.0004-.0006")

Click to expand...

Ross, that makes sense. Table tilt could also be caused by wear or gib play in the X axis, so your test will remove that factor. I checked for wear in the Z slide plate gibs by measuring table height using the centricator with the Y slide fully open and fully retracted, and with the table externally supported from the front and with the table supported only by the Z slide and screw. I did not see any difference.