FP4NC Axis Overhaul (Large)
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  1. #1
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    Well time has come to do some needed heavy repairs on my trusty FP4NC.
    Here is my tale: For some time now i have been having some trouble with my machine. The symptom is that from time to time i get positioning errors on the "Z" axis. The trouble is that the slide "sticks" when going down, the axis servo adds more power to make the move and the slide moves and overshoots posioion and then recovers. You can see the effect by placing a dial indicator on the machine and indicate the position of the vertical slide. Make a "-Z" move with the electronic handwheel and all is fine. Make a "+Z" move and the slide junps too far down and comes back.

    I have done the ovious stuff: replaced the "Z: axis thrust bearing on the screw and had the ball screw rebuilt. These repairs helped but did not cure the trouble.

    I have spent some time adjusting the axis gib and that has has sone effect but not enough.

    Coarse measurments indicated that the ways were worn on the inside faces (that is where the table "rock" is controlled). There was also some gauling visible on the surface of the inside way opposite the gib. (that is the surface that is iron on iron)
    I made the decision to repair the slide and fit Turcite to give a good sliding surface.

    First step: remove the work table, the "X" slide and the vertical slide.
    I am having a professional do the scraping as this is a bit more than i want to tackle.

















    If you look carefully you can see the gaulling on teh vertical way surface. This was not visiable when the machine was assembeled.....

    More later as at the momnent the machine is lying on its side to facilitate the way scraping.
    Cheers Ross

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    Ross,
    I wonder if that galling is an achilles heel of these mills. I'm afraid my FP2NC has some, too. I don't know yet if it causes vertical axis motion problems. I sure hope not. It looks like a bugger of a job to take apart sufficiently to access the problem. Do you have a crane? Who are you having do the scraping?
    Rich

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    I've seen something similar before. It's Probably NOT the same thing but I remember reading about an adjustment on the Z axis that keeps it from falling (overshooting on the NC). Over-adjusted it might cause this.
    I think it was somewhere in the handwheel side of things.
    I've got a ton of things on my mind right now and it was quite some time ago that I browsed past that tidbit, but I think I do remember an adjustable counter to the moving mass of the Z table headed towards earth.
    Just thought I'd mention it.

    Sean

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    Russ,
    since this is probably the first time this machine has been rebuilt, why not scrape/grind the dovetail the minimum needed to remove the galling, and fit it back together without turcite? Otherwise you will have to remove 75 thousandths for the thinnest turcite, or 150 thousandths if you want turcite on both slides...

    Are Deckel dovetails hardened?

    With all the extra lubrication cycles you run, don't you think the galling must have a specific cause (blocked oil port, chips, prior owner's neglect, ...)?

    Also, I have reservations about the idea of using turcite for an uneven load, like you get with a vertical dovetail (due to the cantilever). It is plastic, plastic creeps, ... For an even load, like horizontal ways on a lathe or mill, that is not an issue.

    -Dave

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    I've seen many FP3 and FP4 with such damaged z-ways. May be it's a coincidence, but I've ever seen such worn out ways on an FP1 (may be the square ways are more prone to collect chips than the FP1 dovetail ?)

    Mine also shows a noticeable amount of wear in that area, with the same marks of scrapped iron.

    I think the z bellow is the really most important on these machines, although it's not the one you see the more often.

    Do you have an idea of the final cost of the scrapping operation for the sole z axis ?

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    Interesting pictures.
    Was it hard to disassemble? Its pretty ungainly stuff right? I mean just the x axis got to be like 600 pounds.
    In the second picture from the bottom one can see 8 black circles on the ways. What are these for? Clamps? I wondered about black circular stains on my z axis ways. Probably caused by these circles when the machine sat for a long time.

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    The circles are the lubrication channels on the ways.
    Nice to see what makes them work. There must be some 3rd body wear on the z slides to cause this problem, like dust or chips getting interposed in the ways.
    Steve

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    OK some answers to the questions. First i don't think this is the first time the machine has been this far apart. In the picture of the way surface note the dark stripe towards the bottom of the photo. This is a groove that has been filled with some type of epoxy to repair similar damage ealier in the machines life. Don Sentner has a name for this material, apparently it is not uncommon on these machines.

    As to the material thickness, Dave the thinnest Turcite is .015" and that is what i am using. I opted for the Turcite to give better sliding friction reduction and hopefully prevent this trouble in the future. I talked with a number of rebuilders and the problem of material compression was believed to be neglicable with the thin section material i am using....hope they are correct.
    By removing .015" from the inside way surface we get rid of all the scoring and gauling but unfortnatuly not the epoxy.

    The scraper guy has done all this by hand in one day so far. (used a grinder to rough it out i had to go into the other room could not watch, and power scraper) We applied the Turcite to the saddle yesterday and today i suspect it will be ready for fitting and alignment.

    As to disassembly, i did it myself. I have a "LIGHT" duty crane that can reach the machine. The crane is shop built and only intended to aide the removal/instullation of tooling and accessories. It is stout enough to remove the universal table from the "X" slide.

    The "X" axis table i removed using a hydraulic lift table ...sort of a die cart we have here. I plsced teh cart at the end of the table and took the weight. Moved the cart with table to the operators side. Supported the free end of the table with the shop crane, moved the cart toward the machine and took another bite. Several moves in this mode allowed me to get the weight on the cart.
    The vertical slide i removed with the crane.

    To lay the machine down, the scraper brought a portable gantry and chain hoists....bit scary but all went well. Now i have puddles of oil everywhere..can't keep up with the dripping. I did remove the lube resivour,adn drained the catch basin for the used way oil and drained the sump of the hydraulic pump, but totally forgot about the gearbox on the "Y" ram...jsut did not get it drained and with teh machine lying horizontal, there is plenty of oil oozing out. Of course ther is the ages of trapped oil under the coloum that has found its way out... :mad:

    As to the scraper, i am using a local guy. He is an old world guy orignally from Poland. Has a machinery rebuilding sservice operating out of Sunnyvale. For any locals the company name is:
    MK Machine Tool. His name is Marek Kosiorek.
    Nice guy, a little hard to understand because he has only been here for the last 20 years, but seems very good with the scraper! He has done some decoratieve work for us scraping the blocks and crankcases of Bugatties. (they were factory flaked as a finishing technique)

    Merek has also done some machine scraping for Jim Dour of MegaCycle Cams in rebuilding his cam grinding machines. Dour is quite demanding and the job that Merek did for him worked out well.
    Cheers Ross

    On edit: The gauling trouble i believe is the result of lac of lube. When i first got the machine i was much less vigilant with the lube cycles and no one told me of the potential danger lurking there, so........Now a wiser and more careing user i pay attention to the lube and have made it a priority, but the damage is already there. What you have to understand is that when running a long program , say 3-D proifiling the lube will not happen even if it is programmed until the machine makes a rapid move...no lube in a normal contouring move(g01). This is to mantain the accuracy and prevent the slides from "floating" and changeing the "Z" depth. It should also be noted here that i have a small amount of similar slide dammage to the bottom sliding surface of the table..also a flat way. We will be repairing this area as well.
    Also it should be noted that Merek was somewhat surprised at how soft the iron was in the iron on iron verticaal slide areas. Don Sentner told me that this area was hardened, but the scraper says it scrapes easily......Mine is a very early FP4NC,(3015) so possibly this was improved in later machines.

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    As a related note: Someone here in the forum posted that he is operating his machine with electrical cabinet door open to cut down the fan noise.
    I just read in the D2 troubleshooting manual that this will prevent the autolube function from operating. Its good to be aware of this.

  10. #10
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    OK... I have mixed feelings here. I haven't read all the posts but I struck with the feeling of sorrow that you have to go through this, married with a feeling of relief that you are. Huh? Well, put bluntly, your posts, Ross, are always so much fun to read, contain really well done photographs, etc. I always learn a lot out of them. So I will be following this one with a great deal of interest. [img]smile.gif[/img] (obviously a tongue-in-cheek comment here...)

    --Alan
    P.S. But I am still sorry you have to go through this. I know you'll get it all working well though. You've been through a lot with that 'ole FP4NC, and I suspect it is like your best friend.

  11. #11
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    Regarding the compression issue: it looks like the compression modulus of Turcite-B is around 1 MPa or 145 ksi. If you're willing to tolerate half a tenth (0.00005") of squish of the 0.015"-thick Turcite layer, it takes about 480 PSI compressive stress to do it. I think the pressure loading on this way area is a lot less than that, even under worse case conditions.

  12. #12
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    Alan:
    You are correct, this has been a big struggle both mentally and in laying up the machine long enough to do this work.
    Hope everything works out and the machine is happy when reassembeled...more to come i am sure.

    Rich:
    Thanks for the information...makes me feel better about my decision.

    My shop is a total site of devistation! there is a dead FP4NC lying on its side in the center of the work area leaking vital fluids. The electrical cabinet is totally disconnected with the conduit and connectors lying about in a heap. Looks like it has had its guts pulled out. The "X" axis servo motor is also lyiong in a heap on the floor. I left that connected to avoid the trouble of disconnecting the conduit and related wiring.

    Just finished the work on the table. Bottom way surface re-scraped and the flat face of the dovetail away flaked along with the non turcite top way....starting to look like macjhine parts again.
    Merek is finishing the vertical surface of coloum for flat and alignment. (parallel with the opposite way face)
    Cheers Ross

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    Actually from the way its written, and the pictures taken, I thought this was just a first-half-of-the-week side project for Ross. 50 percent driven by boredom and curiosity for new frontiers. And everything in the pictures is so clean and orderly and actually gives a spacious impression. I now have to clean my machines some more.

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    Wow. That brings back fond memories.

    So Marek has his own business now. He was working for John Servin in Santa Clara back in the early 90's.

    He did my Lodge and Shipley back then. Small world.

    Hope it all goes well for you Ross. I wish I were back down there. I'd love to stop by.

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    Sean,
    Your adjustment sounds like it can best be described as a means to dampen the sytem with friction. I'm surprised that they would do something like that... It seems like a better solution to this whole mess would have been to counter-weight the saddle assembly. Just thinking out loud here.

    --Alan

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    OOPS...mis post, sorry
    Cheers Ross

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    Sean,
    Your adjustment sounds like it can best be described as a means to dampen the sytem with friction. I'm surprised that they would do something like that... It seems like a better solution to this whole mess would have been to counter-weight the saddle assembly. Just thinking out loud here.
    Note i should have added that i do not think the problem was control related as the slide worked normally in the spots where i run the machine most. (read where the slide is most worn)

    Sean i would be interested in that information if you can find it.

  18. #18
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    OK more to look at.
    Martin: Now i have a real mess. Not bored now ,just worried







    Cheers Ross

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    Yikes! Your machine! It fell over!

    I do have to agree with Martin though. Your machine is so nice and clean, as is the shop. I swear that if you said this was Herr Singer working on an FP4NC I would not question you. (that is a compliment, by the way).

    I find it interesting that it appears as though the only damage to the ways is on the inside of the box way. Is there any immediate reason why that is the case? I'm curious to hear if DonS has any thoughts on that (although I know he is away on travel right now... he might not be following this thread).

    --Alan

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    Alan:
    That inside way surface is one that has iron/iron sliding action. Think on the larger machines this area becomes loaded as the table moves from side to side. (overhung loadings trying to rotate the vertical slide) Couple this with the fact that any and all vertical programmed moves are on this slide and the area is relatively small compaired to the table way, i think it becomes the weak point of the way design. Also because the surface is vertical (not in the shown photos however) the oil tends to fall out although the way wipers at the bottom of the slide do keep it in to some degree. Remember on a CNC Deckel any moves like a peck drill cycle and you have lots of vertical rapids, up and down. Put a universal table on that slide and now there is some mass to move. (Alan, best get rid of that universal table before you have this sort of trouble )

    Remember ,Mobil Vactra is not the product it used to be. Won't see it in any of my machines ..fair warning!
    Cheers Ross


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