Z Axis stutter on up, X axis homing issue

steve4545

Hi, I have 2 issues with a Prusa I3 that is using Arduino mega and Ramps 1.4.
1): Have set and uploaded the latest version on firmware that varifies and loads fine. The printer has an X Axis home offset from the 0,0 (front/side corner of the board) of (X) -45mm. There doesn't seem to be anyway of correcting for this offset, meaning that the outer edge of the plate is never reached. From what appears to happen, the firmware takes an absolute measurement from the -45 point of home then adds 220 (plate width) and only allows 175mm travel across the plate. I have tried resetting the EEPROM values, and also adding 4500 steps to the extruder offset. (this step offset worked somewhat, but parked the extruder on the corner of the plate i.e: 0,0). I would have thought that being a negative number, the width of the heatbed would have started from '0', which is stated as the default point in the firmware. I have also tried re configuring to 265mm X axis to compensate, but then this will throw out the center of the bed by 45mm. Any ideas how to correct this?

2) I have a stutter in both Z Axis motors only on the up direction. They act as though there is a broken wire and rapidly vibrate back and forth as though stuck between steps. I have the 3 jumper connectors fitted to the ramps board to increase the step ability of the driver. I have also carefully checked all the wiring and found nothing. Both motors were working perfect before changing to a ramps setup. I have also changed the driver board with a good spare, and still have the issue. Both motors work perfect in the (opposite) down direction without any stutter. (There is no bed level installed). If I do a 50mm up movement it will stutter at least twice within the first 20mm. Could this be an issue with the Ramps board (such as a dry joint) or more related to firmware/ software?

Using Repetier server 0.70.1 and Repetier software.

I can post more info if rqd.
Cheers

Repetier

1) There are 2 solutions

#define X_MIN_POS -45and add length. Homing will of course stop at X = -45 and you can tell server that it goes till X=-45 but bed starts at X=0
Second solution is #define ENDSTOP_X_BACK_ON_HOME 45This will move extruder over bed after x homing and that is x=0 (if x min is 0). Then x length is width of bed,2) Hard to say. Friction may be higher up and motor can not compensate the force. Especially if the rods are not square to guides (left or right side higher) Or you are just moving too fast. I guess when they stutter the height is also wrong? You could use 2 motor drivers and mirror z signal to a second stepper driver so each motor has it's own driver and thus more force and driver stays cooler. Or test with lower speeds/acceleration, grease rods.

steve4545

Okay, thanks. I will have a look at the rods and nuts first, then play with different/separate drivers. I get the impression it's an electronic fault or overload of some sort mainly as it does still raise/lower smoothly after about 50mm height. I couldn't feel any heat from either motor, during a test print, but they only traveled half the distance that the software and screen reported.

I take it those commands would go/be under configuration.h tab?

Repetier

The defines yes. x min might also be in eeprom.

steve4545

Hey, just a quick update. Took me a while to get back to it but the second #define option worked a treat.
The z axis turned out to be a fault in the brass nut and printed bracket, with the bracket not flat on top causing the nut to load up one side. Thanks again!