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FP2 Z axis rocking

muffins

Plastic
Joined
Feb 15, 2022
Hello guys.

I have just noticed a problem with my FP2. When I move the X axis from one side to the other the Z axis shifts by 0.03mm on the DRO.

I moved it around and put my weight on it to see if it would change and it does not. Does anyone know how I can start troubleshooting this?

The power feed is working fine, I suppose I can try drive the table from end to end without using the power feed and see if the result is the same.

* I edited the title of the thread to Z axis rocking instead of creep, as it was determined below that this is the problem.
 
Last edited:

rimcanyon

Diamond
Joined
Sep 28, 2002
Location
Salinas, CA USA
Do you have a sensitive level, e.g. .0002" in 10"? That would be the first thing I would bring out to diagnose the problem. How long has it been since the gibs were adjusted?
 

muffins

Plastic
Joined
Feb 15, 2022
I don't have a level. But perhaps I can borrow one. As for the gibs I have not adjusted anything since I got it in December and other than that I don't know.

I tried moving it without the power feed and got the same result. Gonna check through the manual now.
 

thanvg

Hot Rolled
Joined
Mar 3, 2015
You'd have to check whether it's rocking or creep.
Rocking would be dependent of the direction of X move. If you move your table along X all the way to one end you'd have a certain displacement on Z scale, if you move it all the way towards the other end you'd have, roughly, the opposite displacement on Z.
Creep could easily be proven if you put two dial indicators one near each Z box way. They should read the same value if the whole saddle moved down.
Combined root causes will give mixed results but you can isolate them with a couple of indicators!

BR,
Thanos
 

muffins

Plastic
Joined
Feb 15, 2022
Okay so I put indicators on each side of the ways for the Z axis and it is definitely rocking! One side goes up and the other goes down.

I've looked in the operators manual and the parts catalog with the exploded diagrams. It's not so clear how to go about adjusting the gibs, it doesn't seem covered in the manual at all. What proceedure do I need to follow to adjust them correctly?
 

thanvg

Hot Rolled
Joined
Mar 3, 2015
The general approach, I guess, is tighten the gib till it binds and then ease it off slowly until you have nice and free movement.
If your Z is rocking (hopefully only due to gibs needing adjustment) I bet your X should require some attention as well. Two gibs there
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Need to tell us which gen FP2 you have...the way the gib works is different for different generation FP2's....

Test the "rock" at various height of the "Z" axis....In general the upper 1/3 of the "Z" axis is where you will find the greatest wear on the box ways ("Z" axis).
I would take at least 3 readings (Upper 1/3, middle and lower 1/3 ) on the vertical.
On good machine i would expect to see about .0005"-.0015" of shift in position on the slide at each extreme position of the "X" slide (max weight shift)

To do the test, use a good magnetic base and a quality .0001" reading indicator. Position the vertical slide at the test height (vertical) with the "X" slide centered.
Clamp the mag bear on the face of the box way just above the vertical slide. position the indicator to read against the top of the vertical slide at its far outside edge (either side will do, generally i use the operators side for convenience) Set the indicator to "Zero" being sure that it has travel in both directions.

Run the table to the right or left to its max...Power feed is fine won't change the reading.
Note the shift in indicator reading. Move the "X" to the opposite end of travel and note the indicator reading.....

Test in at least 3 different heights along the vertical, note the position that gives the lowest shift on the indicator..that will be the guide for setting
the gib. You must have some clearance at the tightest point ,of binding will occur.

On first gen FP2's the gib that adjusts the rock is on the inside face of the operators side box way. Adjustment is from below.
The gib is held by a captive screw (straight slotted head) that will tighten the clearance when screwed in.....
The adjusting screw is held from drifting by a locking screw that intersects the adjuster from the side. (check your parts manual)

Make a small change, move the "Z" slide up and down some and check your "rock"
Its possible to have some wear in the slides and gib to where the screw will bottom out....If it goes hard, stop adjusting,your are at teh adjustment limit...If more adjustment is needed further measures will be needed.

On the later (square head) machines the gib is controlled by shims . Removing shims from between the retaining plate and the machine casting will tighten the gib clearance...Generally there are shims in the stack of varing thickness allowing better control of the amount that the adjustment provides.

Be sure that the DRO scale is running true and that the table gibs (X) are also adjusted .....Again this is dependent on the generation of the machine....

Good luck.
Cheers Ross
 

thanvg

Hot Rolled
Joined
Mar 3, 2015
...

On the later (square head) machines the gib is controlled by shims . Removing shims from between the retaining plate and the machine casting will tighten the gib clearance...Generally there are shims in the stack of varing thickness allowing better control of the amount that the adjustment provides.

...
Hi Ross,
out of curiosity, I understand how this can by with the retaining plates that hold the Z carriage from falling towards the front of the machine, but for the gib? Is there a retaining plate to control left-to-right as well? No tapered gib then?

thanks,
Thanos
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Ok so my term was a bit vague....
On the late manual and FP-NC's there are tapered gibs for the "X" axis slide, the "Y" axis slide, and the side of the "Z" axis.
This side tapered gib is made with a steel piece bolted to one end of the gib. The piece sits at a right angle to the long axis of the gib, and secured by bolts tapped into the end of the gib.
That piece is fitted offest to the gib center line (overhanging one side) and has hole through it .
There is a a stud tapped into the casting where the gib fits.....that stud passes through the hole in the offset steel piece.
The position of the steel part relative to the casting is controlled by shims (washers) on the stud that fit between the base casting and the offset part...All is secured via a nut on top of the offset part.

Don't have my parts book here to show a drawing of the gib, but here is a shot of the gib being fitted with "turcite" and the bolt hole for the top plate is visible on the large end of the gib.....


Cheers Ross
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
OK so this might make my explanation a bit more clear......

full


Its the way the gibs are controlled in the FP-NC's but its the same on the late square head manual machines.

Cheers Ross
 

thanvg

Hot Rolled
Joined
Mar 3, 2015
OK so this might make my explanation a bit more clear......



Its the way the gibs are controlled in the FP-NC's but its the same on the late square head manual machines.

Cheers Ross

Hey Ross,

thanks for the elaboration, I got it. I like this design, I guess the goal was to eliminate the dreaded fit of a conventional gib adjusting bolt to the gib slot and all that comes with this design.

I bet that half of the squarehead deckels out there have loose gibs: I'd expect their users being too lazy to start playing with shims.... :)

Thanks for pointing out yet another improvement of the later models, I was completely unaware of this. I'd assume your 5-Tslot FP3 has such a configuration for X and Z but a conventional gib on Y, right?

BR,
Thanos
 

muffins

Plastic
Joined
Feb 15, 2022
Thanks for the help guys, it is much appreciated.

As an update, I have managed to access the gib adjustment and took the time to clean all the parts removed along the way. Unfortunately there is a new problem, the hex head screw fastened into the gib has a stripped hex socket. Not sure why they chose to use a short head cap instead of a normal one here.

1655798701944.png
Here is a pic of the gib adjustment, the adjusting shim is held captive by the plate fastened onto the gib. To swap out the shim I need to either move the whole gib to clear the stud or remove the stripped head screw.

How would I get the screw out in this situation?
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Don't need to remove that cap screw.....Unless you just wish to make things back fresh....Used the reduced height bolt because they wanted to keep the height down.
When the gib is new it sits taller than after years of wear and adjustments....

Run the slide up some then use a "rolling head" pry bar to lever up the gib plate while you lower the slide...the movement will ease the release of the gib.


Believe if you go full down on the slide once the gib is loose you can withdraw the entire gib.....then some vise grips on the bolt head will likely remove it.

There is a product, "Sock-it-out" that make extractor tools for just that sort of damage.....

Cheers Ross
 

muffins

Plastic
Joined
Feb 15, 2022
Thanks guys.

Prying out the gib was the way. Once it was loose it came out without issue.
20220622_072245.jpg
This is what the tapered gib looks like.

20220622_072304.jpg
It was caked in some brown gunk. I'm not sure the oil from the lubrication system is reaching it very well so that is the next thing to investigate.
20220622_072320.jpg
It has some wear near the top, it seems like the bottom section has flake marks. This was after cleaning up all the gunk from the holes and surfaces.
20220622_072339.jpg
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Wear generally happens at the ends of the gib.This is due to the pressure applied by the weight shift or the moving elements....
This is why when re-scraping a gib you generally relieve the center 1/3 by taking an additional pass of two in the middle to force the ends of the
gib to do the work.
Betting if you place that gib on a surface plate with the wear face down, it will spin like a helicopter blade rotating on the high spot in the middle of the gib.
I don't use soluble oil on any of my machines (with the exception of my cylindrical grinder)
I use a light cutting oil even on my CNC mills....Not as good at removing heat and a bit more difficult to clean up, but kinder to the machine. No rust or brown gunk on any in my shop!

If that were my mill , i would take a cut on the gib face and clad with "Turcite" or :Rulon" and scrape for good contact with the ways.
Turcite will allow a bit tighter adjustment and ease the friction of moving the slide.
Stuff is kind of fun to work with. Scrapes easily (draw scraping is recommended) and it will provide an opportunity to restore the gib to max available adjustment.


Cheers Ross
 
Joined
Jan 15, 2005
Location
The Netherlands
Turcite it too thick Thinnest is 0.75mm And wear is mostly less as half of that So you have to machine the gib
Also 0.75mm is not thick enough for oilgrooves
So you end up with a lott of egdes where the turcite can peel off
I would prefere a shim behind the gib
Do not glue that shim on That will not keep the shim flat Better is a sharp bend at the thinner side
Scrape to fit and releave in the middle

Peter
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Don't know where you get your Turcite, but over here it comes as thin as .015"....That is like .4mm by my math...needs about .004" for the glue.
And sure you would tale a cut on the gib. (rough)..makes a good clean surface for the glue to adhere to.....Also straightens any wear on the face of the gib.
The advantage to Turcite is the reduced friction it provides plus the relative ease of scraping.
Oh and i don't see any oil grooving in the original gib...but lengthwise grooving that does not break out of the sides of the gib are not prone to peal off....Just has to be applied with care to a good clean surface and use of "fresh" glue.
Cheers Ross
 

AlfaGTA

Diamond
Joined
Dec 13, 2002
Location
Benicia California USA
Might want to have a look at this posting about redoing a "Z" axis gib....
Sorry about the photos...no longer fully visible , but think you can get the ides....


Here are a couple of photos of the repair.....


Cheers Ross
 








 
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