Prusa Mendel/Splinter - Using 12mm rod instead of 8mm for Z axis

Hi,

I'm using a 12mm rod instead of 8mm for Z axis. I'm planning to upload Splinter firmware to the Sanguino board. I went through the configuration file to see what parameters I have to modify but couldn't zero in on any of them. Or is it in the Math file?

Can anyone let me know if this is possible? I know it should be, but need to figure out how hard it will be.

Thanks

Do you mean for the threaded or smooth rod? Smooth rod you don't have to change anything at all. If you meant the threaded rod, it's probably much better to go for smaller than m8 if anything, say M5, and avoid the z-wobble you'll get with larger rods.

HI James,

Whether M12 or M8, basically I'm using a different rod than M8, then what changes to I need to make in the firmware? How does it calculate how much has to be moved? and where are those settings?

Thanks

hi
what you need to know is the pitch of the thread your using
see Metric thread ptich

i,e how much your Z axis will raise ( or lower depending on which way you turn it) by 1 revolution of your rod

then depending on whether you have direct drive ( 2 stepper motors , 1 above each rod directly connected) or single drive ( 1 stepper motor driving a belt that turns the Z rods simultaneously) you need to figure out the steps needed to turn your m12 rod 1 revolution

As an example if you have direct drive stepper motors that are 200 steps per 1 revolution ( of the stepper motor out put shaft) and your ptich is 1.75 then simply divide 200 / 1.75 = 114.28 this is in theory how many steps are needed to make your z axis move 1 mm

In actual fact you need to take micro steps into account so it would be 200 X 16 ( for 16 micro steps) = 3200 then divide this by your ptich
so 3200 / 1.75 ( M12 with a 1.75 pitch) = 1828.571428

then look for the default axis steps per unit in your FW config
in configuration.h file look for
#define _AXIS_STEP_PER_UNIT {X, Y, Z, E}

Edited 1 time(s). Last edit at 03/13/2013 03:46PM by bigfilsing.

Thanks a ton! The exact piece of info I was looking for!