Hi Steve,

Thanks for the reply, 500.000 step/second is in total for all axises? or per axis?

So u are also suggesting to decrease the micro stepping did i understand correct?

Hakan

The 500,000 steps applies to each axis individually. The sum of steps for all axes does not matter.

If you are approaching this limit, then decreasing the micro stepping would be my suggestion.

Hi,

u mean instead of g28 it should code g92?

No, I just mean that these are two codes that can produce unexpected excursions of the machine, and often not recognised if you are reading code trying to determine a fault.

Craig

Hi,

I decreased the microsteps 1/10 and ran the same code, it finished it without any error. It seems that the problem was high microstepping which lead to high pulse numbers because of the 5mm pitch of ballscrew in small movements(helixes), machine moves very fast in those areas and Mach4+ESS generates very high number of pulses in less than a second which the stepper drives can not accept. The 3 phase 16NM stepper driver accepts max. 200khz signal so when pulse generator exceeds 200khz momentarily, stepper driver looses it.

So the correct approach in microstepping should be adjusting it to a lowest value which is enough for the required movement precision, 2 micron is what i adjusted it for today, before it was very high like below 0.05 microns of electronic precision which the machine can never perform mechanically.

To be sure i need to run at least 10 jobs but it didnt make any absurd movements in 3 jobs i ran today, so thanks to you all for the help and support.

Regards,

Hakan

Hi,

So the correct approach in microstepping should be adjusting it to a lowest value which is enough for the required movement precision, 2 micron is what i adjusted it for today,

Close, but not quite. Increasing microstepping does not increase resolution, its nice to think it would but in practice 1/2 stepping is the highest practical and reliable resolution. You might
get an increase at 1/4 stepping but it will not be consistent. This derives from the fact the the differential torque between microsteps diminishes rapidly with increasing microstepping, and
consequently there is insufficient torque to step one micro step, but there is enough to step 1/2 step, and sometimes enuogh to step 1/4 step, but not enough to step 1/8 step.

The true value of microstepping is increased smoothness of motion. Microstepping was first proposed and implemented by astronomers whom were wishing to acieve a smoother motion from
the steppers in their telescope mounts. Microstepping, to some reasonable value, will reduce or eliminate mid-band resonance, which plagues steppers. Microstepping beyond that value it pointless,
you gain little extra 'smoothness', no extra resolution and an increased signal rate. In practice microstepping of 1/8, 1/10, and 1/16 are the maximum practical microstep regimes.

Craig

Hi Graig,

well as manufacturers say smooth motion is the gain of microstepping but the aim is dividing 1 rotation to higher number of pulses which should increase the precision of motion u are getting from the motor/ballscrew. So 1.2 degree motor should receive 300 pulse for 1 full turn but with microstepping u double, triple or increase the pulse number 10 times, the resolution of motion with 300 pulse and 3000 pulse for 1 turn can not be same i think, if u are not loosing steps u are increasing the resolution(precision) of motion u get out of the ballscrew.

If the pitch is 5mm, in 300pulse case u get 0.016mm movement for every pulse and in 3000pulse case u get 0.0016mm movement am i right? or wrong?

U are saying in real world driver can not do 10 times microstepping but if thats the case the drivers should not work and machine wont be able to move as u command but it is moving. for example in that driver there is 30000 pulse microstepping and in that microstep resolution when i command the axis to move 1 microns it moves 1 microns.

Hakan 

Hi,

increase the pulse number 10 times, the resolution of motion with 300 pulse and 3000 pulse for 1 turn can not be same i think

Does not work, it would be nice but anything beyond 1/2 stepping, that is 400 pulses/rev does NOT result in increased resolution.

Let say that you have set 10 microsteps per full step, ie 2000 pulse per rev, and the current location of the rotor is at fullstep position 0.
The current in the A winding is max, say 1A, and the current in the B winding is 0A. If the driver gets a pulse it will alter the currents to:
A will reduce by 1/10th, ie 0.9A and the B winding will increase to 0.1A. The rotor would like to assume a postion 1/10th of one fullstep (1.8⁰)
or 0.18⁰, but the torque available to make that move is the difference between the holding torque at position 0 verses the torque at position 0.1
and that is ONLY 1/10th of the RATED holding torque. It is highly probable that the load will exceed the available torque and the rotor WILL NOT move as you had hoped.

If the drive gets a second pulse, now the A current will be 0.8A and the B current will be 0.2A. The torque from position 0 to position 0.2 is 2/10ths of the holding torque, again
probably not enough to overcome the load.

If the drive gets yet another pulse then A=0.7A and B=0.3A and the torque from 0 to 0.3 is 3/10ths which may or may not be enough to cause the rotor to move.

So you can see because of the very much reduced torque between each partial steps  the rotor will probably not move, until some indefinite number of steps
have accumulated until the is sufficient torque to overcome the load and then the rotor will move a number of microsteps and once. This is not ideal. You'd want
the rotor to move exactly 1/10th a full step at each pulse, but you may get three, four or five pulses where the rotor does not move, then all of a sudden it will, and
catch up.

If you were using 1/2 stepping most drives apply A=1A and B=1A for a torque from position 0 to position 0.5, ie 1/2 a step of 1.41 times the holding
torque and surely the rotor will move.

For this reason 1/2 stepping, ie 400 pulse per rev is the highest reliable resolution you can get from a two phase stepper.

Craig

For stepper motors, the issue is with how much torque is available at the target location. The manufactures torque spec relates to how much torque is available just before the motor fails to hold position and jumps to the next set of winding poles. With a traditional two phase stepper motor, this happens at a shaft angle displacement equivalent to 1/2 of a full step.

If you are micro stepping you do not get the full torque if you only displace the shaft a small fraction of a full step. This is why the full enhanced resolution is not available in the real world. If your load required very low torque, then you could get closer to the ideal target location. Microstepping can offer significant advantages in some light duty instruments such as telescopes, but does not gain you much resolution for a router or milling machine.

Hi,
one of the few advantages of closed loop steppers is increased resolution.

As I posted earlier open loop steppers can reliably step in 1/2 steps, ie 0.9⁰ per pulse, but even with microstepping cannot reliably achieve any higher resolution.
With a closed loop stepper however the feedback to the drive will allow the drive to alter the A and B currents UNTIL the rotor shifts to it desired position as measured by the feedback
encoder. Thus the drive could be commanded to shift the rotor by 1/10th of a step, ie 0.18⁰ and the drive will alter the A & B currents until 0.18⁰ has been achieved.

Craig

Hi Steve,

If you are micro stepping you do not get the full torque if you only displace the shaft a small fraction of a full step. This is why the full enhanced resolution is not available in the real world. If your load required very low torque, then you could get closer to the ideal target location. Microstepping can offer significant advantages in some light duty instruments such as telescopes, but does not gain you much resolution for a router or milling machine.

Very nicely and concisely  worded.

Craig