mad noise and vibrations at slow speed

[eggplant]

Hi all,

My machine is now functional and calibrated as much as I can with a ruler and magnifying glass - waiting on a DTI arriving.

It runs smoothly but if I move X and Y at once, with a small amount on one axis but large on the other it makes a horrible noise and vibrates.
For eg, from 0,0 I can do G1 X50 F500  and it works fine as does G1 Y50 F500 but, if I have say G1 X50 Y1 F100 it hates it and sounds a bit like when you have the step timing wrong on a stepper or try to use too low a voltage for a set speed - not exactly the same but similar.

Hard to explain, I know but Im sure someone must have come accross this problem too. If anyone can offer any assistance? All 3 axis work fine and can move together at all speeds except when one has a small distance to go and one has a lot more to go.


Thanks

[Tweakie.CNC]

You could try reducing your X and Y axis acceleration in motor tuning, this should smooth the sudden steps of the slow moving motor and reduce vibration.

Tweakie.

[eggplant]

Thanks,

Seemed to improve a little. MY stepper drivers only do 1/2 step, would microstepping affect this ?


Calv

[Tweakie.CNC]

I think so.
Microstepping does improve the smoothness of operation considerably. I use 1/8th step but 1/16th is rapidly becoming the norm for low cost drivers now.

Tweakie.

[eggplant]

Thanks,

For some reason it seems worse if the Y axis has to move the lager amount and the X the smaller. Im looking at increasing the size of the machine and making some other changes so I think I'll build one new motor driver at first and see how it goes. I'll post back with my results but wont be for a few weeks. I did ok with this machine, was very cheap to make and is plenty accurate for what it is, and now I know a little more about it all I can plan better and make parts on this machine where possible for the "upgrade". 

Calv

[Tweakie.CNC]

Calv,

In an X,Y move where one axis has farther to go than the other they both start and finish at the same time - one axis moves continuously and smoothly whilst the other starts and stops in jerks. This is why I said that reducing the acceleration would smooth the jerky movement and show some improvement in the situation.
(My router stands on castors and if I have the accel. set too high the whole thing starts to rock  )

Tweakie.

[eggplant]

In an X,Y move where one axis has farther to go than the other they both start and finish at the same time - one axis moves continuously and smoothly whilst the other starts and stops in jerks.

I must be having a slow week ! Is blatently obvious now ! It cant NOT jerk to some extent can it if one axis has a fair distance to go but the other a small amount, makes total sense now and also in theory microsteppoing should help as the steps are smaller so more steps to move the smaller amount should be smoother (I think...)!

Calv

[Tweakie.CNC]

Hi Calv,

Microstepping is the way to go 

Tweakie.