10" i3V Lead Screw Calibration

Hi everyone, I've recently upgraded my Makerfarm 10" i3V with lead screws and it's been a struggle to get it working properly.

I purchased some of the parts separately from Makerfarm and the leadscrew from Amazon.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The instructions from maker farm had me change the z steps from 4000 to 800 but I'm not sure if that's correct. When I tell the printer to autohome the Z motors move ungodly slow.
I'm basically experiencing the same problem as this Youtube video: https://www.youtube.com/watch?v=6c3Eh-fIInA

Thanks!

800 would be correct if your electronics is set for 32 microsteps per step. If your electronics is set for the more common 16 microsteps per step, 400 would be the correct value.

This is determined from the "lead" spec on your Acme rods. The value of 8mm means the screw advances 8mm per revolution of the rod. Typical stepper motors use 200 full-size steps per revolution. For level 16 microstepping, this is 200*16 or 3200 microsteps per rev. For level 32 microstepping, this is 200*32 or 6400 microsteps per rev . Taking the 32 microstepping as an example, 3200 microsteps per rev on the motor * 1 rev per 8mm travel on the rods gives 800 microsteps per mm of travel.

Is the z-axis also slow to move when just doing a z-axis move and not a three-axis autohome? I'd focus on that. I don't have acme screws but I believe they can require a lot of torque to get the carriage moving. You probably want the stepper driver set for as high of a current as you can. Start with low values for z-axis acceleration and feedrate. Work your way up until you figure out what your new limits are. You might find you have to stick to a low acceleration factor on the z-axis.

There have been a few that have converted to acme screws. Maybe one of them will catch your thread and chime in on any other details.

I just upgraded to those exact Lead screws on my 10" i3v. I used 400 steps. Works perfectly. So glad I did this upgrade (my threaded rods were pretty bent after a recent move.)

What mounting method did you use? Just out of curiosity. I used http://www.thingiverse.com/thing:842213 which has been working great for about 2 weeks.

After watching the video you linked, you might want to to look at your acceleration as well as your max feedrate. My DEFAULT_MAX_FEEDRATE for Z is 50 (the stock was 5, too slow for me) and my DEFAULT_MAX_ACCELERATION is 100. Hope that helps, I'll try to answer any questions you have.

The default firmware is set up for acceleration, jerk, and feed rate appropriate to the thread rods. When you go to Acme rods, they can be changed to make things work faster. There is no problem with leaving them on the "slow" settings. The Z axis never needs to move very fast with normal printing.

If your head is crashing into the bed, that has nothing to do with the screws. The crash is controlled by your Z axis limit switch.

Calibrating the steps / mm is fairly straightforward: Tell it to move 100 mm and measure how far it moved. If it moved 50 mm, your steps / mm number is too small. (you told it it would take 100 steps and it really needs 200). If it moved 200 mm, your steps / mm number is to large.

Bob