New 12" user and I am LOST!

[rhonal89]

Do you level the printer hot or cold. It depends. Heatbed warps when hot. Maybe if you used the zipties provided they are not tie enough on the switch.

Found this post by gmay3

If you haven't seen these parts from Clough42, they are highly recommended as improvements on the stock endstops and use screws instead of zipties.

http://www.thingiverse.com/thing:321810

Parts ordered this morning. Going to install the ABL too. I just can't wrap my head around the z endstop madness I am having. Everytime I home the printer I get a different result! If I hit home, it will place the nozzle below the glass. I hit home again and it back up and stops. it never goes back down. I hit it again, different position! My understanding is the endstop sets the nozzle height. Is this not the case? Can you guys describe what your machines do when you hot the home button. This is in pronterface and via the LCD.

My thought this the switch is either faulty or just is very inaccurate. Is there something I can write into the Gcode manually to set my bed height manually and not let the machine handle it?

For example, after manually setting the Z height and leveling the bed move the x and y axis to home manually and run this code at the beginning of the print...

G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G92 Z0 ;Sets Z position as home position
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing...

[printbus]

...Maybe if you used the zipties provided they are not tie enough on the switch...

Definitely true. Sometimes I get confused between the different people I'm helping in the threads, by PM, and now on IRC. If I didn't bring that up earlier in this thread, it was an oversight on my part.

[tsteever]

Did not use the zip ties. Saw that in the guide and kinda chuckled. Seemed like everything else was very well thought out and that was an afterthought. I will take a look at those parts and see if I should incorporate them into my machine.

What about the code idea?

[printbus]

What about the code idea?

For the gcode approach to work, you'd still need to be convinced that whatever problem you're having doesn't manifest itself during a print. For example, you'd need to know that there are no issues with mechanical slop in the x-carriage/extruder/hot end or issues in properly driving the Z motors or the print may suffer even if it starts properly.

There are some issues with the tentative gcode you listed -

• In your text, you mention manually homing X and Y, yet a G28 X0 Y0 command is shown. Don't bother with the manual homing.
• If you are manually adjusting the nozzle gap for Z, don't include the G28 Z0 command
• The G1 Z15.0 will raise the x-carriage 15mm, presumably for the purpose of priming the extruder. You need to return Z to 0 or the print will attempt to start at that 15mm height

I have a new question related to your original problem - where have you located the clips attaching the glass to the heat bed? I try to locate clips close to the corners, thereby helping to mechanically tie the glass to the corner adjustments. If you only have clips nearer the center of the heat bed, the levelness and Z orientation of the glass could shift slightly as changes in the heat bed temperature alter how flat it is.

[tsteever]

Clips in the corners.

Thanks, I am still learning a lot about the code and really (if you can't tell) do not know what I am doing...yet.

I plan, was to manually set the Z axis myself cause every time I autohome the z axis is in a different spot. I am not exaggerating. Right now I have things tore apart for cleaning but my intention is to replace the Z endstop with a printed setup from thingiverse. Before tear down I hit autohome. The bed wend to the corner and the z descended to a level below the glass. Previously i had adjusted it to be a paper height from the glass.

My glass is clipped at the corners and the home is actually off the glass (in case of the nozzle going below glass level). When I hit home and the machine was at zero I moved the extruder over to verify that the nozzle was at "paper height". I then hit home again and this time it descended below the glass level by almost .6mm (estimate). I immediately hit home again without moving anything and the z went up and stopped. It never descended down again. This time the axis was .4 above the glass!

Every time the machine homes, it is at a different location. I cannot get consistent prints at all. My thought is the switch takes too much pressure, has too much play, or is simply faulty. I am going to replace it with a new switch once it arrives.

Going back to the nozzle rising thing. I notice this behavior a lot when the machine homes below the glass. I will hit home again and the Z will rise but not descent again. It is my understanding that homeming on the Z axis is a 3 part move.

1) it depends at the home feedrate until the switch is hit
2) it will then rise up at home federate
3) it will descend again at homefeedrate/2

Where in the code can I change step 2? My thought is that due to the inaccurate switch that when it descends too far in step 1 that the rise is not enough to move the switch to an open state. I'd like to test that theory by changing this rise to a taller number and move the z slightly higher before making the 2nd higher resolution z home descent.

[printbus]

Others can jump in at any time, but before I provide any additional help I want to know that the MAX endstops have been disabled. As I said before, leaving them enabled without actually having the MAX switches on the printer can and sometimes does create homing problems. The symptoms are different, but I simply want to know that any issues with the unconnected/floating max endstop inputs are out of the picture.

Mine looks like this in the config.h file.

// Disable max endstops for compatibility with endstop checking routine
#if defined(COREXY) && !defined(DISABLE_MAX_ENDSTOPS)
#define DISABLE_MAX_ENDSTOPS
#endif

I believe I've quoted the last response regarding the max endstops. The code in the quote block has nothing to do with how the max endstop settings are configured, since that code only applies if we have a COREXY printer. Look just above those lines in the configuration.h file. Remove the comment slashes off the first DISABLE_MAX_ENDSTOP line so it looks like the following. I've included the same block of COREXY code for reference:

#define DISABLE_MAX_ENDSTOPS     
//#define DISABLE_MIN_ENDSTOPS

// Disable max endstops for compatibility with endstop checking routine
#if defined(COREXY) && !defined(DISABLE_MAX_ENDSTOPS)
  #define DISABLE_MAX_ENDSTOPS
#endif

[tsteever]

Okay, I modified the configuration.h file and it now looks like this...

#define DISABLE_MAX_ENDSTOPS
//#define DISABLE_MIN_ENDSTOPS


// Disable max endstops for compatibility with endstop checking routine
#if defined(COREXY) && !defined(DISABLE_MAX_ENDSTOPS)
#define DISABLE_MAX_ENDSTOPS
#endif

[printbus]

... It is my understanding that homeming on the Z axis is a 3 part move.

1) it descends at the home feedrate until the endstop switch contacts close
2) it will then retract up at home feed rate for a predetermined distance
3) it will descend again at homefeedrate/2 until the endstop switch contacts close again

Where in the code can I change step 2?

Yes, that is the homing sequence, although I've fixed some autocorrect errors and enhanced the words a bit. The retract distance used in step 2 is easy to change - it is defined in the configuration_adv.h file. Look for these lines:

//homing hits the endstop, then retracts by this distance, before it tries to slowly bump again:
#define X_HOME_RETRACT_MM 5
#define Y_HOME_RETRACT_MM 5
#define Z_HOME_RETRACT_MM 2

While you are in that file, consider increasing X and Y retract distances too. That has nothing to do with your troubles, but I changed mine to 10mm some time ago so that the X and Y homing doesn't seem to be just be a bounce.
--------------

There does seem to be a problem in how Marlin is reading the state of your Z endstop switch. This likely boils down to one of three things: 1) the switch is bad, 2) the wiring to the switch is bad, 3) there's a problem with the input pin for the Z min endstop switch in the AVR processor on the MEGA2560.

Obtaining a replacement switch was a good idea.

MakerFarm usually ships extra wires in the kits. While you wait on the switch, you could try running new wires between the switch you have and the connection on RAMPS. That would at least confirm there isn't a frayed wire or some other issue involved.

We could also make a firmware change to move what pin is used to sample the Z min endstop and try that while you wait on the switch.

Finally, if you have a multimeter, we could connect it to the switch contacts and monitor what the switch is doing as you fiddle with the lever on it.

Your call on any of these.

[printbus]

BTW - I remember now you saying you didn't use the zip ties to mount the Z endstop switch. Good. BUT!! Don't overtighten the small screws that mount the switch to the endstop bracket. The switches are pretty delicate and can easily be distorted if the hardware is too tight. Distorted switch = imprecise operation.

[tsteever]

No Zip ties. I used a dab of hot glue which works great. If I need to take it off I can pop it off and peel the glue off. My new parts did arrive so I am going to print some mounts up.