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    Default Okamoto help

    Hey there, first post...I have an Okamoto ACC1632DX grinder...nice machine. We purchased it new a few years ago, and we were a little slow, and decided that it would be beneficial to do some PM on the machine. We reached out to the Okamoto rep in our area, and they suggested the hydraulic oil to be changed, but prior to, draining approximately 5 gallons of oil, and adding 5 gallons of system cleaner. We did that, and rand the machine for the recommended amount of time. The Okamoto tech arrived and performed the suggested maintenance. Within a week, the machine stopped moving. Called Okamoto back in ($6500.00)...they cleaned the valve body, and got it working. Within a week, it has stopped again. Now they are claiming that we need a replacement valve body...I hope they are wrong. I have read elsewhere on this forum where other Okamoto owners add filters to the hydraulic system; is this advisable? Without having detailed knowledge or seeing the guts of this machine, is it possible to add an external oil tank with a filtration system? I did not mention that we grind silicon carbide based composites...pretty tough stuff. Thanks, Mark

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    The worst thing you can do is run a oil cleaner/solvent/thinner through a grinder without first removing the sludge layer at the bottom of the tank. The cleaner would tend to break up the grinding sludge at the bottom and force it back into circulation.

    The hydraulic oil sumps are sized for oil heat transfer to the surrounding area and to insure that the residence time of the grinding fines is sufficiently long that they settle to the bottom of the tank rather than recirculate through the pump and valves.

    The density of hydraulic fluid is roughly 0 .8 gm/cc
    water is 1.0 gm/cc
    iron is 7.8 gm/cc
    silicon carbide is 3.1 gm/cc
    Oil contamination by silicon carbide, aluminum or ceramics would stay afloat in the sump much longer than iron would.

    The best solution is to have adequate dust extraction near the wheel guard to minimize oil contamination. Flood coolant at the wheel exit will also help capture any grit that makes it past the vacuum pick up hood. The grit that does escape can end up in the way oil drains and eventually flow to the oil sump.

    The sump can be continuously filtered by attaching a hose to the sump drain port and connecting the external pump to a bag or cartridge filter. The oil is then returned to the sump through a spare port below the fill line to avoid dragging in oxygen and water vapor.

    There have been several earlier posts describing the details . The more elaborate systems have a 25 micron pre- filter followed by a 5 micron final filter. The filtration packages can be purchased ready made from Parker or other manufacturers.


    Have you verified that there is grit contamination by filtering a gallon of sump oil through a lab style paper filter or sending the oil sample out to a lab for analysis?

    Your original setup was adequate The grinder ran for years without a problem.

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    Robert,

    Thank you for the reply. No, we have not done an analysis on the oil to determine the composition of the particulate present. We followed the procedure for the oil change recommended by Okamoto, but it does make sense that the existing sludge would be disturbed and flushed thru the system. I don't understand how the oil would get contaminated; can you explain that? The ways of the machine are covered/enclosed, and I dont think that they are contaminated by the grinding process. We do use flood coolant for our grinding operations; again, using diamond wheels, and grinding SiC based materials. I have been grinding SiC, B4C and various other abrasive composites my entire 33 year career, and this is the very first time that I have ever know of the equipment failing due to the oil being contaminated by the work...I'm not saying that you are wrong or I doubt you.

    I have seen the previous posts regarding the additional oil filtration that others have added to their machines; I just was unsure if it was "custom" or a readily available kit "off the shelf"; thank you for the information regarding that.

    Mark

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    Post 2 has some good thoughts, for another perspective you can try pinging this guy:

    Okamoto service engineer- ask me anything

    [Oops, noticed that you already posted to that thread]

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    We have a 12-24DX that has been having x-axis traverse issues. After talking to service for a while, we were advised to take out the valve body, clean it, polish any scoring marks, and put it back together.

    I was told that valve body is very expensive and rarely gets replaced.

    I am in the process of putting the machine back together so I dont know if we fixed the issue or not, but may be worth a try before replacing parts. The removal and cleaning is a pretty straight forward process.

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    Put the machine back together and it is running like a dream.

    I would say you should pull the valve body out yourself and inspect it. There isnt really anything to fail within the valve body unless there is some sort of catastrophic failure.

    Have you done any testing to make sure the solenoid valves are working properly?

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    Quote Originally Posted by M. Roberts View Post
    Robert,

    I don't understand how the oil would get contaminated; can you explain that? The ways of the machine are covered/enclosed, and I dont think that they are contaminated by the grinding process.

    Mark
    There will be a cloud of dust in your grinding area unless you have a completely enclosed carriage with tight fitting seals The way covers do not provide protection from the dust. They do protect against splashed coolant or large grit.

    I had to remove a 1/2" layer of orange sludge from the sump of my cylindrical grinder because the previous owner could not be bothered to do the annual maintenance.
    The sump was reserved for the pistons only. The way oil was on a separate tank. In spite of this the grit managed to get into the sump.


    The advantage of grinding steel is that the iron fines combine with the oxygen trapped in the oil to form a durable solid sludge. If you are grinding ceramics there is no glue holding the sludge together at the bottom of the tank.

    The recommended procedure is to pump out the tank once a year. The clean out cover is then removed and you go in with gloves and a scrapper and remove the sludge. The sump is then wiped down with lint free rags and then refilled. The old oil can be run through a filter and reused if the corrosion inhibitors and other additives have not been depleted.

    Filtration on a monthly basis from the bottom of the sump as described in the earlier post would prevent the sludge layer from forming and make the annual maintenance a easier job. The grinder would be shut off during the filtration and remain idle long enough for any remaining grit in the oil to sink to the bottom of the sump.

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    Robert,

    Thank you for sharing your knowledge; are you an Okamoto tech? I still don't understand the "dust" comment. we are running with flood coolant; we get a mist, but I wouldn't say an excessive amount. And when you mention "carriage", do you mean a cabinet surrounding the work envelope?

    I just received word that a replacement valve body is 10 weeks out....I guess that I will be taking it apart.

    Below is a copy of the maintenance instructions provided to us.

    HYDRAULIC SYSTEM CLEANING PROCEDURES

    1) Purchase Exxon/Mobil Oil Corporation product ‘Exxon System Cleaner’.

    2) Add 5% to 10% of ‘Exxon System Cleaner’ by volume to old hydraulic oil in reservoir if it isn’t very dirty. Or remove old oil first, then add ‘Exxon System Cleaner’ to fresh oil
    Example: 5 gallons (maximum) of ‘Exxon System Cleaner’ mixed with 45 gallons of oil in a 50 gallon hydraulic tank. This provides a 10% mixture.

    3) Run the machine with the hydraulics on for 4 to 8 hours. Do not run the machine for more than 16 hours because, as hydraulic seal damage could occur.

    4) Drain the reservoir, clean the bottom, and remove the sediment. Remove the filter located in the bottom of tank; clean and replace.

    5) Refill the reservoir with new hydraulic oil.

    The recommended hydraulic oil is Mobil Oil Corporation product Mobil Vactra 1

    The hydraulic system should be flushed at least once every five years.


    I guess that the definition of "dirty" wasn't well defined.

    Does anyone know anyone other than the factory rep that services these machines, and is local to Delaware?

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    I have three Okamoto two axis hydraulic machines. Two are 8 x 20's from the 1980's and one 12 x 24 was purchased 15 years ago. We don't ever...never run cleaner through them. We just replace the oil then let the machine sit a day or two. Last oil change was eight years ago, but we clean the filter once a month. If oil gets contaminated, particles could stick the solenoids that moves the table in either direction. This would cause the table to stop at the far end of the throw. This happened a few times with the 8 x 20's. We used to just replace the solenoids but now they are very expensive so we just take them apart and clean them. Good as new.

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    Quote Originally Posted by mneuro View Post
    Put the machine back together and it is running like a dream.

    I would say you should pull the valve body out yourself and inspect it. There isnt really anything to fail within the valve body unless there is some sort of catastrophic failure.

    Have you done any testing to make sure the solenoid valves are working properly?
    Actually there is in most grinders but the machine should still work. I have a B&S Micromaster that gets a little sluggish once it warms up. Pulled everything apart and found no obstructions or obvious damage, but I did measure all the bores and spools/pistons and there is some wear. There should only be a tenth or two clearance in there as new I'd guess and mine have more like .0015" clearance on some. Probably going to have to hone the valve bodies and then electroplate, grind and lap the spools/pistons to refurb it.

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    Guys,

    Thanks to everyone that has replied to my post regarding this topic. No, we have not pulled the solenoids out to check them; we were going by the recommendation of the last Okamoto tech that was in. In talking, someone suggested that we "hard chrome" the piston/bore of the valve body and re-grind/lap them to spec...are they already hard chromed? I have never had one apart to know, but reading one of the previous threads, there are no O-rings on the piston that rides against the cylinder bore? Again, I just don't know. I still say that none of this would have happened if we just left it alone....I know, I know..."If it ain't broke, don't fix it!"

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    Quote Originally Posted by eKretz View Post
    Actually there is in most grinders but the machine should still work. I have a B&S Micromaster that gets a little sluggish once it warms up. Pulled everything apart and found no obstructions or obvious damage, but I did measure all the bores and spools/pistons and there is some wear. There should only be a tenth or two clearance in there as new I'd guess and mine have more like .0015" clearance on some. Probably going to have to hone the valve bodies and then electroplate, grind and lap the spools/pistons to refurb it.
    Thats a good point. Our machines have never been used for high volume work so I dont usually need to worry about those kinds of things on our machines. After some cleaning and polishing, we had better than a .0005" fit. But if there was slow movement, checking clearances would be a good idea.

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    Quote Originally Posted by M. Roberts View Post
    Guys,

    Thanks to everyone that has replied to my post regarding this topic. No, we have not pulled the solenoids out to check them; we were going by the recommendation of the last Okamoto tech that was in. In talking, someone suggested that we "hard chrome" the piston/bore of the valve body and re-grind/lap them to spec...are they already hard chromed? I have never had one apart to know, but reading one of the previous threads, there are no O-rings on the piston that rides against the cylinder bore? Again, I just don't know. I still say that none of this would have happened if we just left it alone....I know, I know..."If it ain't broke, don't fix it!"

    The ones on our machine were not hard chromed. They are just hardened and ground. See the attached picture of what it looks like mostly taken apart.

    If I remember right, it was 6 or 7 hoses, and 6 bolts to remove the entire assembly.

    20210514_153442.jpg

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    I was looking at our machine, specifically the hydraulic oil reservoir and how the oil returns to the sump. My understanding is that for the Y axis, the oil is pumped to the top of the screw, and dripped down to provide lubrication; the excess dripping back into the sump.
    Standing behind the machine, looking at the left hand V slideway, I see what appears to be a drain tube that carries the oil back to the sump, but nothing on the right side...the oil which accumulates in/on the center of the casting under the Z axis screw, where does it go? Please correct me if I am wrong about this. I don't see any means of a return of the oil from the x axis ways....there has to be something.
    We did order a replacement valve body from Okamoto, and it as well as a tech is due in today for the installation. Given the previous history, does anyone have any suggestions as to what we should do differently that=n previous?

    Thanks

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    The original spools are probably just hardened steel. They suggested hard chrome as a way to build them up to give you stock to regrind and lap back to a good fit. Electroplating methods such as hard chroming don't distort the item being plated, so they are a good low impact way to restore fits.


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