Hi,
Thank you for posting your question on National Instruments' forums.
You posted your question in an English thread of the forum. Therefore, I will answer in English. If you want to post questions in French, you should do so in the appropriate part of the forum i.e. Discussions de produit de NI.
Concerning the problem you are facing, have you checked the way you programmed your motion control application?
It might be possible that you are not using the correct functions/configuration to drive your NEMA34.
Here is a tutorial on the basic functions of motion control that might help you: Configuring a Motion Control System
As you are using a stepped motor, you can also check this link: NI Motion Control Technical Library
The two documents contain important information about how to use and configure a stepped motor and you should be able to improve greatly your application by using those.
I hope this will help you.
Best regards
Guillaume H.
National Instruments France