after stripping printer due to bad pully again today when I print now everything is much taller than it should be , its like the gaps between layers is too big
ive not changed firmware or anything , this would mean motor is moving 2 far so it cant be binding anywhere can it , never had this before when in axis move the z axis moves freely
any ideas anyone im currently a bit lost with this
can the stepper be doing double micro steps for some reason ? stumped 
Recheck your steps/mm setting with repetier.
Is the āgrowthā evenly or does it just hit on some layers?
If you changed the pulleys, maybe the new ones are slightly bigger in diameter.
ive not changed pulleys just tapped new holes in existing ones , but the problems is only on z axis not x and y
Oops! 
Ok, i was mislead.
I donāt know the Vertex that good (i donāt have one)
but i think itās Z axis isnāt belt driven, is it?
just printed 25mm test cube it came out
24.76 y axis
24.70 x axis
49.37 z axis
its like its double stepping
no no belts its madness
You could check the reference voltage on the drivers.
Instructions are in this link.
http://manuals.velleman.eu/article/1-frequently-asked-questions-39.html#SHIFTEDLAYERS
Maybe reload the firmware.
The reference voltage would not cause twice the amount of Z movement (just guessing).
So I would guess it is either incorrect settings of the steps/mm or somehow one of the pins on the DRV8825 steper driver has disconnected (or connected).
What is your current settings (steps/mm) for the Z-axis?
I donāt remember what microstepping the Z-axis uses, but this should be possible to find out. Then compare the settings with measured values on the Z-axis DRV8825 (see datasheet on ti.com/lit/ds/symlink/drv8825.pdf)
Good point!
I already thought about that.
Does the vertex use jumpers to adjust the microstepping or solder bridges as the K8200 does?
If the latter, check the solder joints on the pcb for the Z axis, if the are connected as they should.
Otherwise check the jumper settings.
PS: Nice simple solution for a pulley. Iāll remember that in case my pulleys go bad. Tnx
Now I can lay of the superglue. 
The Vertex uses pcb trace bridges for microstepping selection. So there is not much chance of a bad connection there, but checking to make sure only takes a few seconds (the 6 pads under the driver are connected in pairs with a trace.
It is indeed a very strange occurrenceā¦ Have you tried switching driver boards to make sure the Z driver itself isnāt at fault?
Bang!
Should have suggested that earlier ā¦
it was indeed the driver board swapped and seems fine on z are these a suitable replacement ive orderd one
If they are pin compatible they āshouldā work.
Please let us know your experience.
If you have to adjust the voltage of this brand of driver youāll need to use the potentiometer as the test point (I use a screwdriver with a metallic tip and crocodile clips to connect the screwdriver to the + probe of my voltmeter).
thanks I was not sure if the through plate above the 2 resistors on the right middle was for this
so I need 3 hands or tape 
excellent thnx
So you obviously have them running raby.
Do they work similar or maybe even better than the stock types?
No noticeable difference with the stock type. BTW you can adjust the stock drivers the same way. Itās far safer ā¦ (I burned one trying to adjust it the way proposed in the manual : the tip of my probe slipped from the test point)
