Need help with Auto Bed Levelling

I have a P3Steel running with Marlin and slic3r.
I have set up the auto bed levelling and start up is good.
It warms up the bed, does a G28 then a G29 and then waits for the hotend to warmup.
Now the problem. When the print starts the hotend stays at the same height. It does not come down to the bed. I have set the offset probe values in Marlin.

Any help please. I am stuck.

Riaan

Well, we don't really have enough to go on here...

Couple of questions...

After you run G28, enter M119 in the command window of Prontrface (assuming prontrface). This tells you the end stop activations.
let's assume you have only X and Y end stops and the Z probe. In some situations, people have both a Z probe and Z end stop. Since I don't know what you have, I'll guess.

After the Homing of X and Y, the M119 should show only X and Y end stop switches triggered. If it shows Z triggered, and it in fact is not triggered, you might have an endstop inverted. You can change the behavior in marlin or check your connection.

I also don't know what kind of end stops you have... switches only? switches on little PCB with LED? (these require 3 connections, power, ground, signal).
On the probe, it is likely just a switch. Does the G29 command spit back any results at all? Is it actually going up and down and touching the bed?

Lot's of questions.

post a video on you tube it is worth a thousand words

Cheers,
Mark

if you have a lcd you will have to make sure its also set in your eeprom

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

I just want to confirm.
I replaced the old end stop on the ramps with the new end stop switch that will be used as the probe. Lets now call that the probe(End stop Switch).
The probe i then plug into the Z min end stop pins on the ramps board. Where the previous end stop was.

Think this is starting to sound wrong.

Riaan

When i give a G 28 command X will move to end stop then Y to end stop. Then move to center of bed swicht acting as a probe will come down and the z will move down till end stop is triggered.
G29 command will then move to the four different probe setting points and do the probe thing moving up and down twice on each probe. It will then stay at the position of the last probe and wait for the hot end to warm up. After the hot end has come to temp the print will start but the hot end will stay in that position of z height. It should come down to the offset position of z and print on the bed.
I will make an you tube video and post this. See attached my config h file. I think this is correct. But please double check.
I am using repetierhost and slic3r.

Riaan

have you measured the distance from your prob to hotend?

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

Yes i have.
I got
X -33.30 witch I entered as positive 33. (I could not get Marlin to verify with the .30 so i left it out for now.
Y -20.00 witch i entered as positive 20
Z 11.40 witch I entered as negative -11.40

What i have found is that after homing all axis I can not move the z down further. So it is reading Z as 0 but does not go to minus. If i override that lets saqy by G92 Z20 i can then get Z to go down.

In Marlin I have done this: #define min_software_endstops false // If true, axis won't move to coordinates less than HOME_POS.

So Z is supposed to go to less than zero. Here is my robe offset in Marlin.

// these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
// X and Y offsets must be integers
#define X_PROBE_OFFSET_FROM_EXTRUDER 33
#define Y_PROBE_OFFSET_FROM_EXTRUDER 20
#define Z_PROBE_OFFSET_FROM_EXTRUDER -11.40

I am busy with the video.

Riaan

have you tried it without the minus i cant check mine as im not near my pc

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

Here is a link to the video i have made to illustrate what is happening.

[www.youtube.com]

Riaan

To me, it won't come down any further owing to the way your machine is set up. The video looks like the nozzle isn't anywhere near the hotbed during the calibration. So its calibrating right and printing where it thinks the bed is. Can join shorten the arm with the switch? Or failing that your offset is way off so its not compensating right.

Edited 1 time(s). Last edit at 05/08/2015 02:22PM by Phytone.

nope u have it set offset -11.20 try 11.20 but get ready to stop the printer if it crashes in bed also that servo is very twitchy


ill be at my printer around 9pm uktime i have to go into my settings and check if its minus or not but sure i did same thing and its actual distance from probe to hotend making it plus if it was hotend to probe then it be minus

Phytone it should not matter how far down because you set the offset

Edited 1 time(s). Last edit at 05/08/2015 02:41PM by chris33.

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

Did you change this setting:

#define min_software_endstops false //If true, axis won't move to coordinates less than HOME_POS.

it is true by default. you need to set it to false that so that after probing, marlin will let the nozzle go down below 0 up to your z offset value.

Edited 3 time(s). Last edit at 05/08/2015 03:24PM by thetazzbot.

There is a line in the ABL area for servo delay or something to that effect. Uncomment it for 300ms and it should stop your servo twitch

I have set this to false

#define min_software_endstops false //If true, axis won't move to coordinates less than HOME_POS.

I have my config h file uploaded in higher up. Maybe if some one could have a look and see if thy can pick up any mistakes.

I will look at the ABL settings. Thanks. It is a digital servo and might replace it with a analog HXT 900.

In my startup g code corrct.

; generated by Slic3r 1.1.7 on 2015-05-08 at 22:19:37

; perimeters extrusion width = 0.40mm
; infill extrusion width = 0.67mm
; solid infill extrusion width = 0.26mm
; top infill extrusion width = 0.26mm

G21 ; set units to millimeters
M107
M190 S100 ; wait for bed temperature to be reached
M104 S230 ; set temperature
G28 ; home all axis
G29
M106 S255 ; start fan speed to S
M109 S230 ; wait for temperature to be reached
G90 ; use absolute coordinates
G92 E0
M82 ; use absolute distances for extrusion

Riaan

Have a look at my g code when starting.
; generated by Slic3r 1.1.7 on 2015-05-09 at 01:11:02

; perimeters extrusion width = 0.40mm
; infill extrusion width = 0.67mm
; solid infill extrusion width = 0.26mm
; top infill extrusion width = 0.26mm

G21 ; set units to millimeters
M107
M190 S100 ; wait for bed temperature to be reached
M104 S230 ; set temperature
G28 ; home all axis
G29
M106 S255 ; start fan speed to S
M109 S230 ; wait for temperature to be reached
G90 ; use absolute coordinates
G92 E0
M82 ; use absolute distances for extrusion
G1 Z0.300 F6000.000

The z axis is told to go to .300. Would that be normal or should it actually say the -(probe value).

Riaan

I have sorted my problem. The best way to learn in live is via trial and error.

In Marlin I had to change one of my speed settings from 5 to 3. The z axis could not get down fast enough and got stuck.

#define DEFAULT_MAX_FEEDRATE {500, 500, 3, 25} // (mm/sec)

Riaan

Sorry to bring up an old thread, i am having a similar issue (prusa i3 - Marlin) installed auto bed levelling (servo arm and switch) g28 and g29 commands operate as they are meant to, calibrated my #define Z_PROBE_OFFSET_FROM_EXTRUDER correctly to the -2.7 from setting the hot end at a point and homing then putting switch in same place etc. So g28 and g29 work as they should, as soon as i go to print my hot end crashes into the bed. I have tried increasing and decreasing offset and it still does the same. I also tried experimenting with #define min_software_endstops false and changing to true, this allowed me to do a g28 and g29, then manually lower the hot end down to the correct position before the software put a stop to it going any lower, but then when i go to print it crashes into the bed again :/. Any help advise would be much appreciated, im assuming i have a simple setting wrong somewhere but im fairly new to all this.
Thanks
James

i am having similar problems and was wondering you had ever figured out the problem?