SAE Z-axis Steps per MM

Greetings,

I have been fighting these 5/16-18 threaded rods on my z-axis for weeks now. Finally, I believe I've found a solution. Forget all of these magic numbers you find in other forums, google, etc. Everything I have read since the first sickly looking calibration object popped from the print bed and my wife thought it was her christmas present told me to use 2267.716 for Z steps per mm. Negative.

Try this out:
2267.712 Steps per mm.
Here are some layer heights you can try:

.127
.1905
.254
.381
.508

You should be able to multiply any of these by 1.5 for your first layer height if desired. I have had good results in doing so.

Before and after:
Any number that divides equally into 2267.712 works for me. Anyone with 1.8 degree stepper motors should benefit as well. I had some really gnarly stuff coming out of this thing, the ribbing is 100% gone.


I hope this helps anyone building an SAE Reprap.
Kerkove

Edit: Crap, I totally read that wrong lol... Please ignore...

With lead screws you have a thread pitch and how many thread starts there are.

steps per mm = (motor_steps_per_rev * driver_microstep) / thread_pitch*starts

Edited 1 time(s). Last edit at 11/02/2015 08:26PM by madmike8.

The problem appeared to be that the thread pitch in mm is a recurring decimal. 1/18 x 25.4 = 1.41111.... Finding a layer height and steps per unit value that divide into each other equally to avoid the software having to round up every few layers was the challenge here, as well as being close enough to the actual value to avoid affecting dimensional accuracy. Any information (forum thread, howto, magazine article, anything) i could find states the magic number is 2267.716 with a layer height of .1905 or .254. Possibly there was a typographical error somewhere along the way and it became misleading tribal knowledge.

.

Edited 1 time(s). Last edit at 11/02/2015 09:15PM by kerkove.

Btw, after drinking coffee and rereading, that makes good sense.