Print jumps 7mm in Y direction after initial layers

[gmay3]

OME, I have been having this exact same problem in the Y axis with mine lately, I have tried and failed many times to get the large extruder gear printed at 30% hexagonal infill and it fails as you have shown in the last 20 minutes of the print. So frustrating since its about a 2.5 hour print.

I tried putting a fan near the RAMPS stepper driver heatsinks to see if cooling them down helped. This seemed to allow the print to only fail at 10 mins before being complete. (progress?) I do not have any active cooling on any of the stepper motors themselves.

I also noticed that after the print failed while printing, I was able to pull the bed and cause the belt to slip over the teeth on the Y stepper gear and by doing this, the print error was even worse. Point being, I think the belt is heating up and becoming less rigid and allowing a little more flexibility in the belt.

I've had this issue before with the set screw on the y pulley coming loose and causing this issue but I think this time it was because my y belt was just tight and now super tight. I've tightened it as much as I could and will try this print out again to see where we are.

[printbus]

... I do not have any active cooling on any of the stepper motors themselves.

...I think the belt is heating up and becoming less rigid and allowing a little more flexibility in the belt.

One thought is to check how hot the Y-motor gets during your print. For those of us with the "hot" running motors, I found the Y-motor got the hottest of them all, likely since it is so boxed in when mounted in the frame. Maybe that heat is causing the Y-motor to skip or is soaking through the pulley to the belt?

For a while I printed with a small desk fan angled towards the Y-motor, and then with a 40mm fan sitting on the table in front of the motor. Now the 40mm fan is mounted to a piece of wood that is in turn bolted to the bottom side of the v-rails. It only takes a small amount of airflow to keep the motor case at what feels like a reasonable temperature.

EDIT: More info on mounting a Y-motor cooling fan to the v-rails is in this post of my build thread - Y MOTOR COOLING FAN

[gmay3]

That's a good idea printbus! I will try moving the RAMPS fan to the Y motor to see if that helps.

[old man emu]

I really think that my problem is trying to print somewhere that the room temperature is 100F. Nothing cools down under those conditions, even with an industrial sized fan blowing across it.

During my wanderings I can across this: http://reprap.org/wiki/G-code#M906:_Set_motor_currents

M906: Set motor currents

Example: M906 X300 Y500 Z200 E350
Sets the currents to send to the stepper motors for each axis. The values are in milliamps.

Has anyone used this during set up and calibration?

Old Man Emu

[printbus]

...M906: Set motor currents

Example: M906 X300 Y500 Z200 E350
Sets the currents to send to the stepper motors for each axis. The values are in milliamps.

Has anyone used this during set up and calibration?

You'd have to check your source code to see if M906 is supported. My bet is that it's not. M906 could be what is used with the Rambo electronics board, where some form of digital adjustment is involved instead of the microscopic trimpots we're familiar with on the Pololu-type driver boards used on RAMPs.