Homing Retraction Not Working

I have an older UP! printer that had no electronics (I got it that way from Craigslist) and I've been restoring it with the RAMPS 1.4 board. It has been going well an I've made a few prints and so far they have been okay. One of the issues I've been dealing with is I cannot get retraction to work when homing. With this printer, the print head only moves in the X axis and the Y axis is cantalievered on the Z axis. The Z axis homes to the bottom, away from the print head. Right now, I have to physically hold the Z axis up before I send a home command so that it does not start past the trip point of the homing switch, which is mechanical.

There is no sign that any of the axis are retracting. I've attached my configuration files. Anyone have any suggestions on what to do to get it working?

Thanks,

Veen

I forgot to mention that I am running Marlin firmware.

Hi,

I am doing the same conversion too on Up! printer with the Ramps board. I had burnt my motherboard and chip recently.

Currently I am using Marlin, Pronterface, Slic3r and Ramps 1.4

I had did some hardware change too. I noticed Ramps is a 12V system, all the heater and thermistor need to change to 12V system also.

I guess we can home at the bottom limit switch but setting need to be made in Slic3r to tell the printer to move the platform up to position before we start print. Do keep me update if you solve the problem. Thanks.

a picture of your printer would be a help . I can kind of understand the cantilever Y axis but would like to see it.

Your Z axis home position is set to move away from the print head in your config.h file
// ENDSTOP SETTINGS:
// Sets direction of endstops when homing; 1=MAX, -1=MIN
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR 1

I suppose if you could relocate the endstop you could alter the config.h file and have it home "to" the print head.

I was also a bit confused by your Z max position
#define Z_MAX_POS 140 //137.8
as ive never seen (on the forums ) this being expressed in such a way. Not saying its wrong mind you , just that its unusual.
If i were you i'd set it to 120 to start experimenting with. You can always go back to it later to get your full build height.

Good luck ( and do post some pics)

Hi,

I have attached the photo of the UP! printer internal. By default when unpowered, the Z-axis will be sitting on the bottom of the printer due to gravity. (about 140mm away from extruder head)

The construction.
- 140mm x 140mm x 140mm
- All X Y Z axis uses 2GT belt and pulley system (no lead screw)
- All X Y Z axis uses a linear rail to guide the axis
- see attached pic for mech limit switches

I did not open the cover to expose the X axis, but all the axis construction is identical. It is almost impossible to re-locate the limit switch as there is still a metal cover on top of all the axis.

you can visit this link for better quality picture. [tinkerworks.blogspot.sg]

Thank you.

Hey,

I haven't checked the forums in a while but it's cool someone else is trying to do the same thing.

The confusion over "#define Z_MAX_POS 140 //137.8" is simply that I have it set for 140 but have 137.8 commented out so I can keep track of previous Z positions since I set the distance between the print head and the build platform by changing the Z Max Position. (I have since written some code that allows me to do this automatically with the RepRap Discount Smart Controller)

I'm still unable to get homing retraction to function properly. Have you had any luck changfrancis?

Veen

I had successfully done my first print. Check up Up! forum for my post.
[pp3dp.com]

My solution comes in 2 parts.
First, I set marlin to Home Z at 140mm. Home at bottom. (Normally Reprap default home Z at 0mm, which Up! printer can't as there is a missing limit switch.) See attached Marlin Code.

Second, use Pronterface software to manually shift the the bed until it just touch the extruder nozzle. Records the height of the Z position, should be between 0 to 10mm. Lets assume the reading taken is 6.4mm. Next, I use Slic3r software to do the setting. Go to set the Z offset and start code, see attached.

Best of luck with the Mod. Cheers and keep printing.


//===========================================================================
//=============================Mechanical Settings===========================
//===========================================================================

// Uncomment the following line to enable CoreXY kinematics
// #define COREXY

// corse Endstop Settings
#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors

#ifndef ENDSTOPPULLUPS
// fine Enstop settings: Individual Pullups. will be ignord if ENDSTOPPULLUPS is defined
#define ENDSTOPPULLUP_XMAX
#define ENDSTOPPULLUP_YMAX
#define ENDSTOPPULLUP_ZMAX
#define ENDSTOPPULLUP_XMIN
#define ENDSTOPPULLUP_YMIN
#define ENDSTOPPULLUP_ZMIN
#endif

#ifdef ENDSTOPPULLUPS
#define ENDSTOPPULLUP_XMAX
#define ENDSTOPPULLUP_YMAX
#define ENDSTOPPULLUP_ZMAX
#define ENDSTOPPULLUP_XMIN
#define ENDSTOPPULLUP_YMIN
#define ENDSTOPPULLUP_ZMIN
#endif

// The pullups are needed if you directly connect a mechanical endswitch between the signal and ground pins.
const bool X_ENDSTOPS_INVERTING = false; // set to true to invert the logic of the endstops.
const bool Y_ENDSTOPS_INVERTING = false; // set to true to invert the logic of the endstops.
const bool Z_ENDSTOPS_INVERTING = false; // set to true to invert the logic of the endstops.
//#define DISABLE_MAX_ENDSTOPS

// For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
#define X_ENABLE_ON 0
#define Y_ENABLE_ON 0
#define Z_ENABLE_ON 0
#define E_ENABLE_ON 0 // For all extruders

// Disables axis when it's not being used.
#define DISABLE_X false
#define DISABLE_Y false
#define DISABLE_Z false
#define DISABLE_E false // For all extruders

#define INVERT_X_DIR true // for Mendel set to false, for Orca set to true
#define INVERT_Y_DIR false // for Mendel set to true, for Orca set to false
#define INVERT_Z_DIR false // for Mendel set to false, for Orca set to true
#define INVERT_E0_DIR false // for direct drive extruder v9 set to true, for geared extruder set to false
#define INVERT_E1_DIR false // for direct drive extruder v9 set to true, for geared extruder set to false
#define INVERT_E2_DIR false // for direct drive extruder v9 set to true, for geared extruder set to false

// ENDSTOP SETTINGS:
// Sets direction of endstops when homing; 1=MAX, -1=MIN
#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.
// Travel limits after homing
#define X_MAX_POS 140
#define X_MIN_POS 0
#define Y_MAX_POS 140
#define Y_MIN_POS 0
#define Z_MAX_POS 140
#define Z_MIN_POS 0

#define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
#define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)
#define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)

// The position of the homing switches
//#define MANUAL_HOME_POSITIONS // If defined, MANUAL_*_HOME_POS below will be used
//#define BED_CENTER_AT_0_0 // If defined, the center of the bed is at (X=0, Y=0)

//Manual homing switch locations:
#define MANUAL_X_HOME_POS 0
#define MANUAL_Y_HOME_POS 0
#define MANUAL_Z_HOME_POS 0

Edited 1 time(s). Last edit at 06/11/2013 10:08PM by changfrancis.

Good news Francis , im sure Veen will like your result as well

I did notice in your pic that you have names the axes the wrong way round well at least as far as is the norm for rep raps. Normally the X axis is the one on which the print head moves and the Y axis is the one for the print bed. Not sure if this will effect your prints at all.

Good luck

Yes. I noticed too. (You meant the white label that is on the print ?)

I had re-connected them, thanks. Havent got a chance to print anything major yet.

I had only been print square cube for testing .

I am currently using a 12V 40W heater element for the printed bed. I noticed that it is not sufficient to keep the bed at 100degree. When i measure the voltage, it is at 12V. Hence, I am sure that the PID and circuit is ok but the heater cartridge is just not powerful enough.

The solution i guess is to put 2 element in the same heater bed. Haven't got a chance to try. Will update again.

I've homed that way in the past. I'm trying to do printing without a computer using just SD, LCD and rotary encoder. I've made updates to the code in ultrapanel.cpp that lets you set the z offset without a computer. It uses the homing offset in the marlin firmware which I can update and store in EEPROM. I did it that way so I wouldn't have to re-slice a part just because my offset changed. I'll upload that code when I get a chance, hopefully tonight.

My problem is that the when the printer is powered off, the gantry falls far into the end stop. If it would retract up and out of the end stop and then back into I would get very consistent homing but right now I can't get it to retract.

It might take me a couple days to get the code uploaded as I just moved and everything is packed away.

I put two 40W heaters in my bed as well, now the bed gets to 100C in just a few minutes.

Edited 1 time(s). Last edit at 06/18/2013 10:53AM by Veen.