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Ramps 1.4 Z axis working backwards

Posted by pintokitkat 
Ramps 1.4 Z axis working backwards
June 16, 2017 10:42AM
I've been converting an old Makerbot Replicator to Ramps1.4 and very nearly succeeded But I've hit a problem that I just cannot work out.

The axes home correctly, which in a Replicator is in the top back right corner. Using Pronterface, I can check the axes move the extruder and heated bed in the direction I'd expect and the hard endstops work correctly. Using Slic3r to generate the gcode, the code looks right, however, when it gets to the first G1 Z0.2, it sends the print bed all the way down, beyond (if it could) the bottom of the printer, causing the z axis stepper to complain bitterly. In fact if I remove the first G1 Z0.2, it happily prints the first layer (albeit very thin as the bed is still at 'home' ie not 0.2mm lower), then as soon as it gets to the next G1 Z, it send the bed all the way down again,

To get the printer to home in the right direction, I've changed the X, Y and Z_home_dir to 1 and so am using the max hard end stops. Here's a snippet of the configuration.h code so you can see;

// @section homing

#define Z_HOMING_HEIGHT 0 // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
// Be sure you have this distance over your Z_MAX_POS in case.

// Sets direction of endstops when homing; 1=MAX, -1=MIN
// :[-1,1]
#define X_HOME_DIR 1
#define Y_HOME_DIR 1
#define Z_HOME_DIR 1

#define min_software_endstops true // If true, axis won't move to coordinates less than HOME_POS.
#define max_software_endstops true // If true, axis won't move to coordinates greater than the defined lengths below.

// @section machine

// Travel limits after homing (units are in mm)
#define X_MIN_POS -46
#define Y_MIN_POS -11
#define Z_MIN_POS 0
#define X_MAX_POS 215
#define Y_MAX_POS 134
#define Z_MAX_POS 140

I appreciate that there must be a lot more information you might need to help diagnose the problem, but as I'm a stumbling newbie, I'm not sure what that might be. Just met me know.

Thank you for your thought cycles.

Re: Ramps 1.4 Z axis working backwards
June 26, 2017 09:17AM
just a point is the printer configuration correct in pronterface for z home postion

Check my rubbish blog for my prusa i3

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