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  1. #1
    I have recently purchased a CNC with the following configuration:
    2.2KW spindle.
    DM860A controllers
    KK01 interface board (from cnc4you.co.uk)
    34Nema motors.

    Jogging the machine across the x or y axis sounds sweet. No problems. When I run a programme though it does certain moves and the whole thing sounds terrible, I made a video:
    https://youtu.be/aSbQEHxy5Uo

    Does that sound normal to you?

    I must also say that if I speed it up it almost eliminates that vibration noise but then it runs at a feed rate that would break bits.

  2. #2
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 2 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,765. Received thanks 339 times, giving thanks to others 8 times.
    Couple questions to start.

    Does it still do it with the spindle not running?

    Is the machine maintaining the correct position?
    I.e. if you start at X0Y0, run the program, then command a move back to X0Y0, does it return to the same position.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  4. #3
    No, it does not sound right. I'm leaning towards electrical problem rather than mechanical, especially running at a higher feed rate removes it. Check all the electrical connections are tight.

    Interesting that jogging is OK but running code is not. Are these both at the same feed rate? If you use feed rate override then jog the machine slower manually is it still OK?

    Which software generated the g-code? Maybe paste it here in case there is something odd there.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  6. #4
    Quote Originally Posted by grantx View Post
    Does that sound normal to you?
    Oh, here we go again, I'm truly sorry to have to say this but for that particular machine then yes it's about right.!! That doesn't mean it's correct, it's very wrong.

    The problem and the noises you are hearing won't be from one thing, it's a mixture of things. I have had plenty of experience with these machines bought from eBay and they are so badly engineered and constructed that a good percentage of the noise will be from poor alignment and setup of the ball-screws.

    The next issue is that they are never set up regards motor tuning and micro-steps etc, don't know if you bought it directly from the guy in Peterlee or not but nearly everyone I've encountered hasn't come with Mach3 setup at all.

    The third issue is that they use Nema 34 motors and often with a low voltage PSU which when combined with cheap drives or poorly setup drives they perform like a can of marbles due to resonance, this resonance is mostly what your hearing as the drives are either setup wrong regards micros steps or just not dealing with the resonance, which is also compounded by the poorly aligned and setup ball-screws. Resonance can and does cripple the performance of a machine and not to be underestimated.

    The first port of call is to check what micro-steps are set on the drives.?
    Do you know the voltage of the PSU feeding the drives.?

    Is this using the UC100 controller.? ( This connects to the KK01 and goes to the PC)

    Quote Originally Posted by grantx View Post
    I must also say that if I speed it up it almost eliminates that vibration noise but then it runs at a feed rate that would break bits.
    What speed does it go away at.? Also, knowing these machines the reason they would break bits above 3mm diameter if cutting in wood's or MDF, etc is that they can not travel fast enough and the machine design is weak and poorly built which causes vibrations so together they can't reach the feed-rates to cut correctly.!

    New users often believe it's their fault they are breaking cutters due to wrong feeds and speeds, often wrongly slowing down when they should be cutting faster. However, this machine in particular while being built from steel is so badly constructed, set up, and poorly specified then they are fighting a losing battle from the get-go.!

    The reason for them not being able to reach the feeds is two-fold, 1st they only have 5mm pitch ball screws, and 2nd they have Nema 34 motors with low volts.
    Large motors like Nema34 when run on low voltage don't spin very fast and the torque drops away very quickly when they are at higher rpm's, they struggle to reach much above 1000rpm and have any usable torque left if run on voltages lower than 60Vdc.
    Combine this with a 5mm pitch and your maximum velocity is 5000 mm/min, which in practice would actually be more like 4500mm/min to avoid losing steps.
    However, This would be your Rapid feed rate and wouldn't be of any use for cutting as the torque will be quite low. So your usable cutting velocity would be more in the range of 3500mm/min which simply isn't fast enough to cut most woods or MDF correctly with any tools above 3mm.
    Combine this with the vibrations and flex from the machine and you are always going to break cutters and struggle to get a decent finish on the material, also tool wear will be excessive due to wrong cutting parameters causing excess heat.!

    Again I'm very sorry to have to point these things out and these machines make my blood boil because I see people getting ripped off all the time with these poorly built, poorly specified, and set up machines with no support from the supplier and it's not fair.
    However, I don't know how I can let people know what they have and are facing without being blunt and to the point informing them of what they have in front of them. We can help you regards setup etc and possibly getting it running a little better but the rest isn't anything we can help with other than to advise you to sell it rather than try to upgrade or improve it.
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

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  8. #5
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 2 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,765. Received thanks 339 times, giving thanks to others 8 times.
    After Jazz's post, I've just realised who's machine it is.

    I was thinking it was somebody's secondhand home built machine you had purchased.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  9. #6
    Watching the video again I can hear as the machine stops a thud noise, can also hear it in the movement.! This sounds very much like one of the ball-screws is floating in the BK end bearing which causes backlash. So check that the nut hasn't come loose which can be common on the cheap BK bearings which are fitted on this machine.

    To check for end float grab the screw firmly and push/pull towards the bearings, there should be NO axial movement.

    But you also have issues with micro-step setup and motor tuning as well which is most of the strange noise (resonance)
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

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  11. #7
    Quote Originally Posted by m_c View Post
    After Jazz's post, I've just realised who's machine it is.

    I was thinking it was somebody's secondhand home built machine you had purchased.
    MC You can easily spot them because every other bolt is missing from the rails..
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

  12. #8
    Doesn`t sound good.

    Did you buy it new ?
    If so, surely you should be able to send it back or at least get it repaired under warranty or something.

    Ollie

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  14. #9
    Quote Originally Posted by JAZZCNC View Post
    Oh, here we go again, I

    The reason for them not being able to reach the feeds is two-fold, 1st they only have 5mm pitch ball screws, and 2nd they have Nema 34 motors with low volts.
    Large motors like Nema34 when run on low voltage don't spin very fast and the torque drops away very quickly when they are at higher rpm's, they struggle to reach much above 1000rpm and have any usable torque left if run on voltages lower than 60Vdc.
    Combine this with a 5mm pitch and your maximum velocity is 5000 mm/min, which in practice would actually be more like 4500mm/min
    Even 60Vdc isn't enough to reliably run 34's in my view.
    I know I'm talking of a mill with gibs here and routers are looser running, but still., I could not get my 1080oz reliably above 450rpm (2250mm/min).
    I've bought a new driver for that particular motor (110vdc/80Vac) and upping to 80Vdc as a tester to see if there's any increase in performance. (Will be a while yet, still building new control box).
    Will eventually go all AC.

    With the X & Y I swapped motors to 566oz nema 24's keeping voltage 60vdc and 860 drivers the same.
    It's twice as fast with those 2 on there.

    It's shocking how many people get screwed over these days with misleading specs and advertising.
    At least if you D.I.Y. it you can over engineer the damn things!. (you can also go too far there though).

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  16. #10
    Quote Originally Posted by dazp1976 View Post
    Even 60Vdc isn't enough to reliably run 34's in my view.
    I know I'm talking of a mill with gibs here and routers are looser running, but still., I could not get my 1080oz reliably above 450rpm (2250mm/min).
    I've bought a new driver for that particular motor (110vdc/80Vac) and upping to 80Vdc as a tester to see if there's any increase in performance. (Will be a while yet, still building new control box).
    Will eventually go all AC.
    Yes, I agree but in this case, with small Nm NEMA 34's like fitted on this machine then 60Vdc or more should get them to close 1000rpm. It's a combo of 5mm and low rpm which cripples the speed.

    Quote Originally Posted by dazp1976 View Post
    Will eventually go all AC.
    Don't get hung up on AC, the only advantage is you don't have to mess around building DC PSU's. Even with AC power the drives convert this to DC for the motors.
    -use common sense, if you lack it, there is no software to help that.

    Email: dean@jazzcnc.co.uk

    Web site: www.jazzcnc.co.uk

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