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  • derekm
    replied
    no load (no belts) motor rpm1500 rpm
    with belts set for ratio 8 out of 9 motor rpm 1430 rpm
    with belts set for ratio 9 out of 9 motor rpm 1360 rpm and very slowly increasing
    note mill warmed up at this point
    note the last 1%- 5% of these speeds took a few minutes to achieve.
    Note some more grease was expelled again.

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  • J Tiers
    replied
    Originally posted by derekm
    The motor is 1425 rpm 50hz 900w dual 380/440 -220/ 250V 2.1-3.6A motor

    The Drive is a 200-240V Single in 3 three phase out 4kVA 9A. The drive has its defaults at 1450 50Hz 9A constant torque profile. it runs fine no load it runs ok if the spindle is warmed up
    Ah HA.....................

    THAT isn't going to be bothered by a bit of slowdown in the motor...........

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  • derekm
    replied
    Originally posted by mbensema
    If your problem was with the spindle, I would expect the drive to trip before experiencing the problem you are reporting. It sounds like the VFD is not set up correctly, or might have a problem on the output. If the parameters are not set up for the proper voltage and frequency, you will experience the problem you describe.

    Need to cross off the obvious things first, is the motor wired correctly? Is the drive kVA larger then your motor? Is the input voltage to the VFD same as for the motor? 230V input cannot run a 400V motor on a VFD, but a 400V input can run a 230V motor if programmed properly. Will the motor run at the proper speed with the belt off?

    I would suggest removing the belt and checking the motor solo by checking the output voltage of each phase, you will need an analog volt meter since most digital multimeters are effected by the high frequency carrier frequency. You want to check to make sure the voltages are within a couple percent. If they are off significantly, that can cause your problem. At 100% speed, it should be outputting the motor rated voltage. I would also check the amps on each phase to make sure there are not any bad windings in the motor, or you can bring it to a motor shop and have them megger it.
    The motor is 1425 rpm 50hz 900w dual 380/440 -220/ 250V 2.1-3.6A motor, wiring double checked as delta and the resistance phase to phase is identical at 7.9 ohms.

    The Drive is a 200-240V Single in 3 three phase out 4kVA 9A. The drive has its defaults at 1450 50Hz 9A constant torque profile. it runs fine no load it runs ok if the spindle is warmed up
    Last edited by derekm; 08-16-2008, 06:50 AM.

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  • J Tiers
    replied
    You will likely want a true RMS voltmeter for good voltage readings. Even analog meters can be thrown off by the pulse outputs. Any meter that has an average-to-rms conversion factor built-in can be fooled when the waveform is not a sine wave. That includes digital AND analog.

    Non-true-rms meters are usually calibrated with a conversion factor from average to RMS. That is all right for sine, but will lie for some types of pulse output.

    I had understood that the motor voltage settings were stated to be OK, but it is certainly possible to set the VFD to cause problems.

    And if the motor is set for 400, it will NOT have the right power on 230 and could do what is being seen. Wasn't that checked and found OK? If not, proceed directly to checking that!

    I have , however, seen motors slow down and yet not trip the drive, depending on relative size of drive and motor, as well as the delay for trip-out set in the drive, etc, etc.

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  • mbensema
    replied
    If your problem was with the spindle, I would expect the drive to trip before experiencing the problem you are reporting. It sounds like the VFD is not set up correctly, or might have a problem on the output. If the parameters are not set up for the proper voltage and frequency, you will experience the problem you describe.

    Need to cross off the obvious things first, is the motor wired correctly? Is the drive kVA larger then your motor? Is the input voltage to the VFD same as for the motor? 230V input cannot run a 400V motor on a VFD, but a 400V input can run a 230V motor if programmed properly. Will the motor run at the proper speed with the belt off?

    I would suggest removing the belt and checking the motor solo by checking the output voltage of each phase, you will need an analog volt meter since most digital multimeters are effected by the high frequency carrier frequency. You want to check to make sure the voltages are within a couple percent. If they are off significantly, that can cause your problem. At 100% speed, it should be outputting the motor rated voltage. I would also check the amps on each phase to make sure there are not any bad windings in the motor, or you can bring it to a motor shop and have them megger it.

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  • derekm
    replied
    Originally posted by J Tiers
    190F is getting a bit warm I'd say, but......


    The movement of grease isn't the BIG movement out of the case, but the small movement away from the track of the balls/rollers. There just needs to be a trace there, for the cage. if there is a glob, and it keeps running back in with heat, it may absorb too much power in "stirring", especially with a step-up belting/gearing system.
    The 70C /90C was with reference to standard industrial grease temperatures and bearings of the mid 1970s. These bearings are reaching about 50C to 60C

    I concur with your analysis of the movement of the grease but "its better out than in"

    The grease is still coming out when it up to temperature so some of those globs might be migrating downwards through the bearings and out when the mill is standing but hot.

    I'm considering going to a lighter grease e.g. NLG 1 by using the Castrol Spheerol LP 1 - your thoughts?
    Last edited by derekm; 08-15-2008, 01:42 PM.

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  • J Tiers
    replied
    190F is getting a bit warm I'd say, but......


    The movement of grease isn't the BIG movement out of the case, but the small movement away from the track of the balls/rollers. There just needs to be a trace there, for the cage. if there is a glob, and it keeps running back in with heat, it may absorb too much power in "stirring", especially with a step-up belting/gearing system.

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  • derekm
    replied
    Originally posted by J Tiers
    It's also affected by whether or not your grease is "tracking".... i.e. getting out of the way AND STAYING OUT OF THE WAY.

    A client is having a lot of trouble with a high speed (38k rpm +) grease bearing, despite close contact with the bearing manufacturer on application and so forth..

    However, the mfgr uses a special grease, and has a specific 4 hour break-in procedure to move the grease away from the middle of the races. The client's problem IMO is not in the grease but elsewhere in the system. They have just come around to my point of view recently.

    But, it is very instructive to see the time-to-temperature coming down with each run of a new bearing, during the break-in, as the grease is displaced.

    In your case, you may just have so much grease it cannot get away, and/or will not stay away. But 3000 rpm is a lot less than 38k rpm.

    One air bearing used by a client cannot be RUN below 5k, as it will not develop the air film. The shaft has to be sped up to and past 5k quickly. Your 3k is slow by comparison, and should cause much less problem with heating.

    But you may have a lot of trouble with the power needed to stir the grease.

    Can you REMOVE the grease effectively? Someone was mentioning this earlier, I haven't gone back through the whole thread for it.

    Removal and re-application of a smaller amount might be good.
    The machine was designed to shed the surplus grease through vents however, when blocked with old grease and dirt they dont work. After flushing through with oil, and cleaning out all the old grease, these now work.
    And by running at a lower speed to warm up the surplus now comes out.
    I had forgotten how yukky messy horrible cleaning out bearings was... But this is better than the first time I did this. Ten large 125mm pillow blocks hold alot more yuk than this though.

    Back then bearings reaching a temp of 70C was considered normal - but 90C too hot. Is this still the case?

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  • J Tiers
    replied
    It's also affected by whether or not your grease is "tracking".... i.e. getting out of the way AND STAYING OUT OF THE WAY.

    A client is having a lot of trouble with a high speed (38k rpm +) grease bearing, despite close contact with the bearing manufacturer on application and so forth..

    However, the mfgr uses a special grease, and has a specific 4 hour break-in procedure to move the grease away from the middle of the races. The client's problem IMO is not in the grease but elsewhere in the system. They have just come around to my point of view recently.

    But, it is very instructive to see the time-to-temperature coming down with each run of a new bearing, during the break-in, as the grease is displaced.

    In your case, you may just have so much grease it cannot get away, and/or will not stay away. But 3000 rpm is a lot less than 38k rpm.

    One air bearing used by a client cannot be RUN below 5k, as it will not develop the air film. The shaft has to be sped up to and past 5k quickly. Your 3k is slow by comparison, and should cause much less problem with heating.

    But you may have a lot of trouble with the power needed to stir the grease.

    Can you REMOVE the grease effectively? Someone was mentioning this earlier, I haven't gone back through the whole thread for it.

    Removal and re-application of a smaller amount might be good.

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  • derekm
    replied
    nickh,
    I think the default settings are pretty close apart from current limit and setting the VFD to constant speed.

    I think I learnt a bit about this from a number of runs and come up with a simple and rather obvious fact.

    Grease lubricated bearings need warming up before you run them at high speed.
    5 minutes at 1000 rpm getting it warm letting the machine expell any excess grease means I can go to 3200 rpm no problem no motor overheating.

    A few other points are the correct belt tension (which is tighter than you think) and correct belt alignment also help.

    My father who had 40 years of setting up very very large industrial fans told me about the importance of belt tension and alignment (I have his belt tensioning gauges, tacho, and balancing gear) but I didnt pick up on the warming the bearings for high speed.

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  • NickH
    replied
    Are the default settings on your VFD the correct settings for the motor?
    If not you're on a hiding to nothing, I have 4 different VFD's from 4 different manufacturers and all required several parameters to be set from figures on the motor plate.
    My Siemens and ABB also have an option to sense the motor, all require an operator panel to configure.
    Are you sure this is suposed to work without configuration?
    Regards,
    Nick

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  • derekm
    replied
    well that didnt work but top and bottom of the spindle do turn more easily but that isnt it

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  • derekm
    replied
    Tried it again with the mill cold this morning back to square one- must be the cold old grease.
    Later to day I will drop the quill and flush it through with ISO 100 oil and attempt to do the same with the top end pulley. I use the oil because its a solvent for the grease but a good lubricant for the bearing so I can go straight back reload with grease without worrying about dry bearings
    This is what I did with the idler/intermediate pulley to get it to run freely a few months ago.
    Last edited by derekm; 08-12-2008, 06:15 AM.

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  • derekm
    replied
    Originally posted by J Tiers
    ....
    One question is, since it appears from your statements to have a couple belts, whether the belts themselves might be part of the problem. Setting belt tension etc, can have a distinct effect on the operation. Tight can make it quite draggy.

    If idler bearings are ratty and draggy in some way, that also subtracts from power.

    If there seems to be significant friction when you turn the motor by hand in a particular speed, it is probably too much. Generally the drive should feel free, so that most of the power goes to the cutter. You can check out each part of the drive and see if any particular area seems to be "it".

    If that is the spindle, your guess of old grease may be very good. Crummy old grease really causes a problem, and it may not be fixed by running. You might have to actively clean it.

    Grease is also not always the material of choice. Even though there are 'zerks", it might have been intended to use oil. I think Bridgeport has been guilty of that. But naturally, if it says grease, then use grease.
    Belt tension -not as tight as they should be so thats not the problem
    The drag is at the spindle.
    I suppose I could drop the quill out of head to see if it is the head pulley bearings as opposed to the spindle quill bearings.
    15 Zerks - only 4 use grease the rest oil

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  • J Tiers
    replied
    The 1450 motor is only increased a bout 2.5x. That's significant, but by no means crazy. A drill press might do that, or close to it.

    If the motor runs slower than it should, then it is probably overloaded, as you already knew.

    One question is, since it appears from your statements to have a couple belts, whether the belts themselves might be part of the problem. Setting belt tension etc, can have a distinct effect on the operation. Tight can make it quite draggy.

    If idler bearings are ratty and draggy in some way, that also subtracts from power.

    If there seems to be significant friction when you turn the motor by hand in a particular speed, it is probably too much. Generally the drive should feel free, so that most of the power goes to the cutter. You can check out each part of the drive and see if any particular area seems to be "it".

    If that is the spindle, your guess of old grease may be very good. Crummy old grease really causes a problem, and it may not be fixed by running. You might have to actively clean it.

    Grease is also not always the material of choice. Even though there are 'zerks", it might have been intended to use oil. I think Bridgeport has been guilty of that. But naturally, if it says grease, then use grease.
    Last edited by J Tiers; 08-11-2008, 10:53 PM.

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