[bwprice100]

.
Hi

This is my first post here and still finding my way around the site.

I am currently building a 4 axis milling machine using a converted Taylor hobson engraving machine.

Using Mach3
breakout boards from here
http://medw.co.uk/wiki/index.php?pag...Breakout+Board
Stepper motors and driver from here
http://www.arceurotrade.co.uk/Catalogue/Stepper-Motors

Now on my horizontal X and Y axis everything seems fine, motors tuned and turning fine with no missed steps. However on the Z axis I have a much bigger motor 650Ncm (http://www.arceurotrade.co.uk/Catalo...Stepper-Motors) and the 4.2A driver (http://www.arceurotrade.co.uk/Catalo...tepper-Drivers)

Now I have mounted the motor directly on to the exisiting axis spindle drive and although the the required torque is well below the specification of the motor I am having problems I am still seem to be loosing steps. The motor has to turn very slowly or the missed steps get worse. I have improved things by increasing the steps per rev on the motor driver (via dip switches) but stiil not right. I can easily turn the spindle by hand so the motor shouldn't be working that hard

Now the questions is how slow can these motors turn?
Is there an optimal speed range they work best?
Should I look at driving indirectly via a reduction mechanism (gears or pulleys)?

Thanks Brian

[Kipper]

Steppers can turn extremely slowly....a single step if you like.

I find most steppers get flaky at higher speeds.... Is a setting incorrect or something binding?

[bwprice100]

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thanks for the quick reply Keith.

It makes it a bit easier if the motor is ok turning slowly, thanks. I am not happy with the mechanical setting but there does not appear to be any binding. With the power off the motor it is relatively easy to turn and hence move the axis with the existing hand wheel, however I am going to strip it mechanically and check it over. At present there is an intermediate shaft that moves the lead screw via a pair of helical gears and I do suspect excessive end float, which moves the gears out of mesh and could cause binding.
I could drive the lead screw directly via toothed pulley to up the ration so the motor could turn faster but this means extra work that may not be needed.

I have also been increasing the steps per rev on the motor driver via dip switches, it was at 1600 step/rev and is now on 10000 and tomorrow I will try increasing it again but I am not sure why this should make a difference?

Cheers Brian

[amishx64]

Those DIP switches you are changing control microstepping - they tell the driver to turn the motor a fraction of a step per computer pulse vs a whole step. This is good for things that need vibration dampening or more precision. This is most likely not what you want to be doing.

Increasing the voltage to your driver increases max potential torque. What's your voltage?

[bwprice100]

Those DIP switches you are changing control microstepping - they tell the driver to turn the motor a fraction of a step per computer pulse vs a whole step. This is good for things that need vibration dampening or more precision. This is most likely not what you want to be doing.

Increasing the voltage to your driver increases max potential torque. What's your voltage?

Hi

The voltage output from the motor driver is 5V and cannot be changed There is a higher current setting available, presently on 8.08Amps but when I up it to the highest setting 9.04Amp the over current circuit cuts in and stops the motor for some reason.

With regard to the steps per rev it was as an experiment and has definitely improved things but not sure why.

Cheers Brian

[Kipper]

Hi

The voltage output from the motor driver is 5V and cannot be changed There is a higher current setting available, presently on 8.08Amps but when I up it to the highest setting 9.04Amp the over current circuit cuts in and stops the motor for some reason.

With regard to the steps per rev it was as an experiment and has definitely improved things but not sure why.

Cheers Brian

It's a 50V driver with 4.2A max output....5V and 8.08A is an odd figure?

Personally I never go past 1/8th stepping as the loss in torque makes the resolution less appealing.....full steps with reduction are more my thoughts....full steps are stronger/more positive.