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Thread: Surface grinder issues, any experienced users around?

  1. #1
    Join Date
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    Surface grinder issues, any experienced users around?

    If anyone has experience with surface grinders, and may have an opinion on the cause of this problem i would appreciate the help.

    So i was skimming some parts on the surface grinder and had been using it for an hour or more, when the head moved down on it's own, for no apparent reason.
    So the machine is automatic, but the vertical is manual.so what made the vertical adjust on its own?
    It did it several times, lowered the head and ground into the finished part. requiring me to do a lot more work to remove the deep pass.
    It seemed to do this completely randomly.
    I would do dozens of passes with no problem, and turn the handwheel each pass to lower the head, then out of the blue, it would lower all by itself.
    I don't know how far it would go, as i would quickly turn the handwheel to raise the head as soon as it started.
    It would go deep enough to see the sparks increase, hear the difference , and see the ruined surface.
    So the machine has a hydraulic left to right travel, an electric front to back step over. and an electric rapid vertical, and a manual vertical for cut depth.
    I am going to take it apart to see whats going on, maybe something has come loose. The machine is not an ancient worn out machine by any stretch.

    When i started to take it apart i have found another issue; the guides system for the head vertical travel is eight bearings and two machined tracks; four bearings on the inside and four on the outside.
    I noticed that only three of the bearings on the outside were in contact with the tracks. The bearings are cam bearings, so they can be adjusted 0.010" but one of them even at its max is still a few thou shy of touching.
    One of the problems is i can't get access to adjust the inside ones without removing the entire head and tracks. Plus there is going to be a lot of work to align and verify the head if i have to go messing with the bearings.
    So i may have to take the head off. I could just make a new plug for the one bearing and bore and grind the hole further off center so that i can adjust it to touch without adjusting anything else, but i guess i will have to check the head alignment first to find out which way to proceed.

    Anyone with experience that can offer some advice would be appreciated.

    1-20190315_103126[1].jpg2-20190315_103402[1].jpg3-20190315_103512[1].jpg

  2. #2
    It sounds me like your vertical motion is not being locked. One possibility is your electric drive is getting voltage spikes or loss of voltage or perhaps the switch is being randomly actuated via some vibration from the sliding table. Perhaps frayed insulation somewhere in the electric raise lower wiring. Can you connect a volt meter across the raise lower motor terminals and run the unit as if you were grinding and watch the volt meter while it is running.

    It could also be a function of your loose guide rollers, so that when the motor lowers the head an increment the head doesn't always move the same amount due to the loose guides.
    Lee Schierer
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  3. #3
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    Thanks Lee, I hadn't thought about it being an electrical issue, i will check that.

    The guide roller issue is a little confusing; Maybe the machine got bumped around in transport and moved the rollers, but i find that a little hard to believe, which leaves the thought that it was like that from the factory, also hard to believe.
    I can't see that they would have drilled the holes off of spec far enough that the roller wouldn't contact. So i will have to check to see if the head is accurate and tight with the seven rollers, then i can just make a new plug for the eighth; and put it down to a factory error in either boring the holes or setting up the head. If the head is not accurate and tight with the seven rollers, then maybe the rollers have moved and i will have to disassemble the head and reset all of the rollers; which sounds like fun, because the manual show some pretty tight specs.

    The roller issue may be related to the head movement.
    I could be vibration; I should balance the wheel.
    I will also check the handwheel and vertical rod assembly to see if it can be tightened, as it does seem quite loose and easy, it also has a bit of backlash, which i am not happy with.

    Thanks.


    Quote Originally Posted by Lee Schierer View Post
    It sounds me like your vertical motion is not being locked. One possibility is your electric drive is getting voltage spikes or loss of voltage or perhaps the switch is being randomly actuated via some vibration from the sliding table. Perhaps frayed insulation somewhere in the electric raise lower wiring. Can you connect a volt meter across the raise lower motor terminals and run the unit as if you were grinding and watch the volt meter while it is running.

    It could also be a function of your loose guide rollers, so that when the motor lowers the head an increment the head doesn't always move the same amount due to the loose guides.

  4. #4
    If this is a new or fairly new machine give the factory a call. They can probably get you to the right cause faster than any of us can.
    Lee Schierer
    USNA- '71
    Captain USN(Ret)

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  5. #5
    The randomness would make me think of a stiction issue. Something hanging, backlash, some issue with lowering the head and the head hangs but the backlash is still uncompensated, and then a given amount of vibration, heat, or "voodoo" and it drops taking out the backlash? Just a guess?
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  6. #6
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    Quote Originally Posted by Lee Schierer View Post
    If this is a new or fairly new machine .......
    That's what I'm also wondering.
    Never, under any circumstances, combine a laxative and sleeping pill, on the same night

  7. #7
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    The machine is a few years old, but hardly seen any use. So I cant see it as a wear issue.
    I contacted the North american distributor and spoke to their tech, and he didn't have any idea what the problem would be. I will contact the company in Germany.
    But thought that this must be a known if not common problem with surface grinders, there must be millions in use and i figure this is not unique, so there may be folks who have encountered this before, and could point me to the solution.
    I would like to see whats going on anyway, its always nice to take a machine apart and get up close and personal with everything, just to be familiar with all of the mechanics.

  8. #8
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    No experience with surface grinders, but I was thinking backlash also as most WW machines have that issue to an exaggerated extent.
    NOW you tell me...

  9. #9
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    Do you know that the grinder is set up level and all casting feet are touching the ground?

  10. #10
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    No, i haven't checked it recently. I am leaning towards a backlash issue as the most probable cause.

    Quote Originally Posted by michael langman View Post
    Do you know that the grinder is set up level and all casting feet are touching the ground?

  11. #11
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    First off, are you using coolant of mist spray while grinding? Are you sure the head is actually dropping? The reason I ask is after over 25 yrs in machine shop, I've never seen that happen. I have seen grinding wheels suddenly dig in due to getting the work too hot where it warps slightly, or expands, making the wheel dig in even more. Make sure the wheels you are using are a good fit on the spindle. If you have access to an indicator, plunge type would be best in this situation, set it, and if you can operate manually, run the table back and forth a number of times, move down a few thousandths repeat, etc to see if it will drop while not actually grinding a workpiece, or if it hangs up at any point, then go from there.

  12. #12
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    Hi Tony,
    You have never seen it happen; that makes it a little more mysterious.

    I wasn't using any coolant, These were 1" square bar, parts from an old machine that i was just skimming on all four sides, purely cosmetic cleanup. I was only taking a few tenths of with each pass, and moving fast, so i don't think that it was heat, also it was randomly happening, and instantly, it wasn't a gradual lowering, it would just plow down over a stroke distance of 6-8". When i say " plow down" we are talking in relative terms, so it may have been an extra few tenths or more, before i caught it. which is still going to mess up a part that you were doing to spec. So this wasn't a gradual heating up and expanding without me noticing, this was instantly noticeable, and would make me jump. I will check the wheel fit on the shaft also
    I have several indicators, and i will test manually.

    I appreciate any and all opinions as it will help me investigate.
    Thanks.

    Quote Originally Posted by Tony Pisano View Post
    First off, are you using coolant of mist spray while grinding? Are you sure the head is actually dropping? The reason I ask is after over 25 yrs in machine shop, I've never seen that happen. I have seen grinding wheels suddenly dig in due to getting the work too hot where it warps slightly, or expands, making the wheel dig in even more. Make sure the wheels you are using are a good fit on the spindle. If you have access to an indicator, plunge type would be best in this situation, set it, and if you can operate manually, run the table back and forth a number of times, move down a few thousandths repeat, etc to see if it will drop while not actually grinding a workpiece, or if it hangs up at any point, then go from there.

  13. #13
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    Sounds like backlash to me. I think you crank down the head and it comes down except for a fraction at the end. With vibration it settles down that last little bit. After lowering the head you should crank it back up to remove any backlash. If the handwheel is unbalanced it may be rotating to move the handle down. My lathe cross slide did that when the gib was looser.
    How much backlash do you have on the head adjustment wheel. How much rotation would cause the unexpected drop?

  14. #14
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    What Tony describes is very common when grinding without coolant. Also if the part is not flat to begin with it could be moving into the wheel. But usually the wheel gets loaded and heats up then heating up the part. Some metals are problems to grind and the correct wheel for the type of metal is important.

  15. #15
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    I woulds post over at "Practical Machinist". you will get many experienced answers very soon. I would post i nthe General section for quickest response.
    Bill D.

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