Can't get back to Z offset after G29

I have a Folger Tech FT5 that's been running for about 4 months now. Running a BLTOUCH just like on my FT 2020 i3.

I don't know whether to scream, cry, or beat the dog (oh wait, I don't have a dog). I'm running an order on the FT5 running the 'FT modified version of 1.1.0 RC6'. After 8 consecutive successful prints, the ninth one is giving me the fits. After G28 and G29, the nozzle does not drop down to the print height but stays up about 4 mm. On previous prints at the end of the g29, the nozzle would raise up after probing and then drop down the 5 mm that set by #define Z_RAISE_AFTER_PROBING 5 plus the Z probe offset I have entered. Now it prints in midair
I tried the program on the SD card, the Octopi, and the laptop with the same results, I reloaded the program with the same results. I changed the Z probe offset slightly, saved it to EEPROM with same results.
I finally just gave up and am using old faithful FT 2020 i3 to finish the order. When I gather the strength to face the 'beast', I guess I'll pull the BLTOUCH apart to see if the magnet has come loose from the pin. I can't think of anything else to try.
When it homes on G28, I get 7.11, which is the 5 from above plus my offset of 2.11, so that's correct. I am at a loss.

Any help would be appreciated.

NOTE: It appears that the Z offset is not being applied as it moves from the end of the G29 to begin the print. What would disable that?

Edited 1 time(s). Last edit at 12/18/2016 10:45PM by tjnamtiw.

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

Since I'm not getting any comments, I'm assuming that my explanation sucked.

I'm running a Folger Tech FT-5 now for about 3 months with no problems. I'm running their version of 1.1.0 RC6. I've been using a BLTOUCH since day one on this machine and on my FT 2020 i3 (for 1 1/2 years). My start GCode script is
M140 S70
M280 P0 S160
G4 P5000 : wait for alarm reset to clear
M280 P0 S90 ;pin up
G28 ; home all axes
G29
G1 Z4

The G1 Z4 was to give me room to remove the ooze before it starts printing.

I had a large order to run, which required me to run the FT5 multiple times with the same program. After the 8th successful run, when the 9th run started, it homed (G28) and showed X as 7.11 instead of the usual 2.11, which is my offset (-2.11). It continued to G29 and every measurement was 5 mm more than previously measured. At the end of G29, the nozzle came down the 4 mm from the starting script but not the extra 5 mm that was somehow inserted into the equation. I made no changes to anything between the successful run and this one.

Since then, I've tried the program from the SD card, Octopi, and from my laptop. I also tried other programs that I created on the spot using S3D. Always the same result. I even removed the G1 Z4 from the start up script and then after the G29 sequence, the nozzle stays at the 5 mm height, I get a beep from the LCD panel, and it starts to print 5 mm in the air.

Obviously, this is baffling. I thought that something changed in the program so I reloaded the program with Arduino IDE and same result. I compared every section of the program with the original version from FT using Winmerge and they are the same except for the required changes for the BLTOUCH.

I hope someone can shed some light on this one!

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

Did you check the functionality of the BLTouch? To me it looks like the trigger signal is not stable or got misread ( ground-issues, noise or insufficient voltage level)

Sidenote: why do you have to ABL your FT5 every time? It's not a delta and looks rock solid

Edited 2 time(s). Last edit at 12/20/2016 06:14AM by o_lampe.

Quote
o_lampe
Did you check the functionality of the BLTouch? To me it looks like the trigger signal is not stable or got misread ( ground-issues, noise or insufficient voltage level)

Sidenote: why do you have to ABL your FT5 every time? It's not a delta and looks rock solid

Thanks for the reply! I just did an M48 V4 on my machine and the Sigma is 0.008084 mm for 10 samples so I'd say that's pretty darn stable. The fact that the common denominator is an even 5 mm is the clue here and most certainly is program related. I plan to download and compile from scratch the company's program in case my copy got screwed up somehow. Also, I'd like to try the RC8 version but I need to use the newer version of Arduino; however, it won't compile the RC3 marlin I've been running in my FT 202 i3 for well over a year. The darn programs (Arduinoe) aren't backwards compatible. grrrrrrrrrrrr. And you can't have two versions on the same computer.

As to you sidenote, while the structure of the FT5 is like a brick, the moveable plate is melamine and not very rigid plus the 12" square heated plate is notoriously subject to warpage and distortion even with my mirror tile on top. To do ABL once means you do it every time. It takes all of a minute and works (well, once you get the program debugged!) great.

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

Since no one is awake or this forum is dead, I'll give an update. I gave up on the Folger Tech Marlin and went to RC8, which is now working perfectly using the BLTOUCH.

I have to say I'm disappointed that no one, save O_lampe, had any suggestions. I KNOW I've read MANY comments on many different machines using many different ABL sensing devices about the nozzle printing in mid air yet no one seems to have a clue as to what is going on within Marlin. I know it's a complicated program but I was hoping someone from Github would chime in. Going directly to Github in the past has been a lesson in futility and frustration for the layman.

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Folger Tech 2020 i3 and FT-5 as well as modified JGAurora A5 with direct drive E3D/Titan. All running the BLTOUCH.
Great kits. Having fun and running the heck out of them.
Running Marlin 1.1.0 RC8 on the i3 and FT5. Custom firmware on A5.
Folger Tech Wiki board >[folgertech.wikia.com]

I agree, this forum has moved away from marlin ( including me ) and turned towards RRF. This is because DC42 is the most competent and responsive programmer here.
Maybe the marlin team has also left this forum, so marlin users only get second hand or outdated information.