[tef9]

Hello,

Sadly my BF30 is making a horrible grinding noise from all 3 axis. I have made a video that can be found [ame="http://www.youtube.com/watch?v=c9kyqHz9Szk"]here[/ame]

It can take a while for all three to start grinding, however sometimes its as soon as I switch the controller on.

Any ideas?

Thanks,

Andy

[Dano523]

Sounds like servo strain more than grinding,
Just how tight do you have the gibs on all the axis?
Also, what are us using for lube for the table axis as well?


Without laying a hand on the machine, would dare to say that the X gibs are too tight now, and as the Y and Z axis metal heats up from friction, they are also too tight (or dry locking from lack of lube) and straining the servo's later as well.

[waltpermenter]

Sounds like servo strain more than grinding,
Just how tight do you have the gibs on all the axis?
Also, what are us using for lube for the table axis as well?


Without laying a hand on the machine, would dare to say that the X gibs are too tight now, and as the Y and Z axis metal heats up from friction, they are also too tight (or dry locking from lack of lube) and straining the servo's later as well.

he's running steppers not servos, you ever build a cnc machine?

andy, you need to provide more info, stepper sizes, drivers, power supply, mach 3?,etc. you're likely under powered for this sized machine and are getting resonance issues.
walt

[tef9]

Hi,

I tried altering the gibs - no joy, everything is lubricated with grease.

Motor size = Nema 23
Torque = 3.1Nm
Power 42v 15amp
Controller = Mach 3
Drivers 5amp Drv50's from DIYcnc

Thanks,

Andy

[Connor]

You micro stepping? If so, which one?

[LongRat]

Sounds a lot like resonance. Are there any tuning pots you can adjust on those drives? Failing that, you could try attaching a heavy disk to the motor shafts, although that would be a lot easier if they were dual shaft motors.

[tef9]

Hi,

Connor9220 if I recal they are set 1/4 step.

Long rat, there are no pots, is resonance curable? or do I need bigger motors?
Also is it weight on the stepper motor or the stepper motor spindle thats important?

Thanks,

A

[LongRat]

Its on the motor shaft. Look up stepper motor resonance and see how others have mounted these weighted discs. It isn't damping, it just moves the system resonance to a different frequency, hopefully out of the range of motor vibrations. I have never seen this with Gecko drives, but they have electrical resonance damping built in.

[arizonavideo]

I have seen this myself not too long ago.

The step and direction leads may be reversed going into the driver.

If it is only one motor then change the two leads and give it a try.

Before each pulse the computer tells the driver what direction to go so you have to pules for each step.

If you put a indicator on the X you may find some missing or extra steps too.

[LongRat]

You also have the pulse duration options in the motor tuning in Mach.

[tef9]

Ok So I tried a new motor on the machine and that made no differance, however the new motor is dual spindle so the a balance wheel is an option.

Interestingly I have managed to get this working at 1/2 step @1200 mm/m this is the best result yet. :cheers:

Operating at 1/2 step am I loosing anything?

Is 1200 mm/m a good speed for this sized mill?

Thanks,

Andy

[LongRat]

Don't worry about speed on the mill, concentrate on the cutting performance. For reference, my bf30 runs at 1700mm/min rapids but my system is probably totally different. Half step will limit your resolution which probably isn't a problem, but it also changes the torque performance of the motors. I would search out the gecko drive stepper motor white paper which will really help your understanding.

[digits]

If you switch to 1/2 steps, aren't you going to limit your resolution to 0.9 degrees. Which on 5mm pitch screws I make to be 12.5um. Probably not a problem for most uses though.

As to speeds - I get 1800mm rapids, and that is damn slow on a 500mm travel macine IMHO.

[tef9]

Longrat/Digits

Thanks for the responses, I did indeed take a look at that document. Verry interesting, thank you so much digits - I think 12.5um is not going to be an issue. Having spent this amount of time converting the mill i just now want to use it...still 3000mm/m would be nice, I think if I was ever to do this again...I would go with servos and a decent enclosure

Or Just buy a Wabeco.....

Thanks,

Andy

[LongRat]

Servos are not foolproof and can come with their own set of problems. For a start they are more complex so there are more things to go wrong and reduce reliability. I have found that once correctly set up, my stepper systems have performed without fault for many years. And HONESTLY, just don't worry about rapids. You will curse poor accuracy or missed steps a hundred times more aggressively than you ever will your machine going a bit slow.
The Wabeco is great but having converted one of those too, you will enjoy your 30 just a much when it is working right. The BF is more rigid and for most general model making tasks the Wabeco will not really be any better, just a bit nicer quality. I can hold sub 10 micron tolerances with mine which isn't going to happen easily with the BF. But then I don't need that either so i'm happy.

[tef9]

Yes I have seen people sweat when setting up servo motors...however if I was to do another system (which I would like to) then servos is the way I would go, probably DC...and perhaps a Digits style AC servo for a spindle.

The mill i keep comming back to is that Tormach supprisingly...I hear very good things, just a pain to import. Their CNC lathe also look awesome, still they are expensive.

Yes I did loose steps on a job recently have not had a problem since I sorted the resonance issue out. It is very anoying...my big problem is enclosing the mill. I have seen what you did however I am not keen to go that way... I was thinking of enclosing the table.

Never used a Webeco, however the do look good. I would really like their lathe atm.

A