Nema 17 shaft broken

Hi,

Yesterday i had for the second time a broken shaft on 1 of my Nema 17 steppers both times on the motor.
I was using this motor for only 2 months now, its from the motor thats moving the Y axis (i have printer with a H frame) .
Is this just a bad quallity steppers or is there something wrong in my printer, the only thing i can think of to change is less tension on my timing belt and putting the pulley closer to the stepper ( mount it up side down screws on the end of the shaft)
I have now 4mm distance between motor and pulley.

could it be caused by a not 100% round pulley? i used the same pulley on both motors ?
I will look add this when its finished printing.

Edited 1 time(s). Last edit at 03/01/2016 11:43AM by Michel000.

... could be, you're over-tensioning the belt, so it's bending the shaft more, than it can handle.

A solution is to embed the other end of the shaft in a bearing to reduce the bending forces ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

But putting a extra bearing on the shaft only works if you use a high precision part to hold the bearing and motor exactly inline else it will only put more tension on the shaft.

... this is normally done with milled aluminium holders, but plastic parts will do too.

The hole for the counter-bearing is fixed, the fixing holes for the motor screws will give the displacement to align the motor ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I used these bearings while switching to a one motor Z setup. [www.aliexpress.com]