whats the matter!

[Gary]

It is totally wrong looking for a stepper motor based on the holding torque and also the torque speed curve is useless if you run it at a different voltage to what the curve was done at.

I get people who buy our motors and use a low power 24V driver with them and complain that they are not getting the speed that they need and that is shown in the torque speed curve.
They allways think that the problem is with the motor and not with the driver that they have spent the last 4 weeks making or spent £70 on ebay buying from China.
The selection of stepper motors seems to be done at the wrong stage in most situations, just last week i had a customer tell me he has this 4 axis stepper driver that is rated to 3A and 36 V and he wants to have the biggest motors as possible for his 1.2m by 2m router he is making, he wanted to go for the largest 34 motors we had, but was a bit disipointed when i told him his driver is too small for the motors.
The result of this is to talk to someone who knows stepper motors and systems before spending your money.
Also you will get far more output power if the motor is in parallel over series, but you do need twice the current.

Well nothing really just that I have just come to the decision that there is no REAL information available for stepper motors and their use.
I had thought that when converting my X1 mill to cnc I had gleaned all the information that was on offer. In selecting the steppers I went with 1.8Nm from ArcEuro as this seemed to be about right( obviously wrong as Zaxis is to weak). I then decided to fit ball screws to try and get better efficiency but completely forget that the pitch was a lot higher that the original screws and therefore making the motors appear weaker. I am in the process of fiting a 3Ncm motor to the z-axis, in so doing I noticed the torque curves for the motor and was amazed at just how weak it was in parallel against series connection.
In hind sight I should have waited and bought a ready made KX1 and saved the headaches.

I have still to try a head counter weight or spring. So I am left wondering why the only info we normally hacve on steppers is their holding torgue wherease we relay need their stepping torque so as to compare them.

I am surprised that anything works at all perhaps its all down to gearing.

The one thing I have learnt is that you never can have enough tooling.

Peter

[ptjw7uk]

Gary,
I totally agree with all you have said but I thought that I was following in well trodden paths in choosing steppers that others had pointed out as being strong enough. The mistake I made was in not doing as they had done in dropping the 2 to 1 gearing by using toothed belts etc nad going with direct drive this coupled with the coarser pitch of the ball screws I think has left the z-axis under powered.
I have also just found references to the fitting of dampers to the steppers to alleviate resonance, not that I know what to look for if I have got it!!
On the web the videos supposedly showing stepper resonance and displaying missing steps for the life of me I couldnt hear any difference.

Peter