RoBo 3D Arduino Board

That's what I'm seeing in the code is that if the switch is already active, when you get the G28 home, I'm not seeing a check to make sure it's not already fired... causing the nuts to back out. That's why after homing, it's moving back up the 5mm to deactivate the switch. That to me is a silly and stupid way of doing things. It would be trivial to just check the state of the switch! I think I'm going to open a bug against this in the firmware and try to see if I can make the code change myself (once I get my printer going again) so that I could submit the patch as part of the bug. I'd backed out those nuts at least 4-6 times in my first few attempts at printing. I can only suspect others are as well. Then you have to adjust the bed for level, again, and again, and again. Nuts to that!!! This can be fixed even with the current switch by just making better choices in the firmware about checking the state of the limit switch!

 

Yupyup! Yeah the ability to back out is a must, it just shouldn't be as easy to occur due to a simple code change. The code is easy... just tossing in an extra check or two here and there for the limit switches, all of 'em, not just Z. Really, it should be doing that anyway because you want to know if you hit home or limit (yeah I know we only have home switches on the R3D) in all aspects of the print... bad G-Code would otherwise potentially keep banging against the limit for the Y or Z axis at max travel as well. The switches need to function as an interrupt in the code and throw an E-Stop, just like in industrial CNC operations. Not seeing that code support in the firmware (as a former software tester) is making my pull my hair out! LOL

I can tell already I'm gonna end up eventually being a contributor to the firmware as I RTFC and delve deeper into the code. I'm seeing LOTS of spots that can use fixes/improvements.

 

Thank you.

Regards. Manolo.

 

The Nuts problem has been driving me... This needs to get fixed. On a few occasions I hit the home Z while the extruder was cold and had a blob of plastic on it. Other times were "random" but the evidence to figure out what when wrong was destroyed when the nuts backed out. (example if you had the far Z stepper loosing sync; nut not seating properly; dunno). Side data point is I think I am seeing the homed Z height change by 0.2-0.3mm as the extruder head heats up. Couple of thoughts. We really want the nuts to be able to back out as a safety feature. What about adding a second microswitch with a lever arm that trips when the nuts back part way out? This micro should trip the emergency stop, which is ok, because you could restart without loosing the leveling. Question: Is there an emergency stop input configured into Marlin/Taurino? If not, there are other input pins that cold be re-purposed with a code hack.?

 

Are there not emergency stops on some LCDs? It doesn't seem like that would be a hard thing to implement, and adding the switch would be nothing.

 

I have some ideas, when I get home ill sketch them out

 

Seshan* - Don't have my LCD connected yet, but what about Robo's that don't or have different LCD...thinking we need a general purpose solution. Emergency stop function has to exist in the Marlin code since it is being punched by the LCD.

tesseract* - Did a peek at the pin interface on Marlin, and did not see anything that looked like a Estop pin. Functionality has to be there, since LCD can punch Estop as well as Repetier. Maybe find the Mcode that is used by Repetier and call that routine.

Also "printed" up a looooong extension knob (1.75") for a 4mm hex head screw to replace the PITA limit screw. Knob body about 0.425" dia. Hex slot in core keeps screw from rotating. Retaining nut on outside bottom of knob to hold screw in place. Drop of CA added to thread and cured before inserting to keep from rotating freely.

I'll make some measurements as to how much my extruder length changes by when it gets hot. Still guessing on the order of 0.27mm.

 

I think it would be possible to wire it up to other end stop?
As for allowing the bolt to move I was thinking one of those micro switches with a roller lever, placed vertical on the side, some bracket will need to be designed, But I think that would work fine.

 

In the firmware there is max pin support already there. The pins for our configuration are:
X_MAX_PIN 2
Y_MAX_PIN 15
Z_MAX_PIN 19

These correlate also to the schematic for the RAMPS board:
http://reprap.org/mediawiki/images/3/3f/Arduinomegapololushieldschematic.png

There is also a KILL pin, which I'm assuming is eStop:
KILL_PIN 41

This pin 41 -=IS=- utilized by the AUX4 connector on pin 7 on the RAMPS board, but if you aren't utilizing the AUX connector, then it can it still be able to be treated as a free pin as near as I can tell. I'm not sure how the LCD connects to RAMPS, and that might be via the AUX connector. If so, then there is your connection previously wondered about with how the LCD has the eStop functionality, and how it's currently working. If I had the schematic for the LCD I might be able to figure out if that's how it's connecting or not, but the wiki for RepRap is too lean on info to figure that out... of course, sombody with a display could do a continuity test between the button and pin 41 and tell for sure. So to wire this bad boy up, you'd just need to take +5v off of the RAMPS or mega, run that to your switch, and back to pin 41. When activated, it goes HI, and as I read the firmware, everything should stop right there in the kill() function which turns everything off... heater, steppers, hotend... and throws a error to the serial line as well as the LCD. I think we won't even require a firmware update to effect this change, but if so, it would be a minor update in Configuration.h (I think the stock config is disabling the endstops, so that line would just have to be commented out again, easy enough) so I think everything is there in the code to make this happen already. Booyah Grandma. Booyah!

So I'm thinking to enable eStop functionality you just need to wire to either 19 or 41 to a switch for when the system starts to throw it's nuts. I would recommend using pin 41 for the thrown nuts sensor, and keep 2, 15, and 19 free for sensors for the limit switches (rather than home). I'm still spelunking through the stepper code. There might be a simple fix here also to just add some checks for the checkHitEndstops function in there. Presently checks for kill, checking the home/limit switches, heater management, and updating the LCD is all performed in the main function.

 

we're all on the same page "What about adding a second microswitch with a lever arm that trips when the nuts back part way out? This micro should trip the emergency stop, which is ok, because you could restart without loosing the leveling."

KILL_PIN is being configured as an input to Marlin with possibly a pull up (internal/external?). Question is do the LCD controllers actively drive this pin high? According to the code, if configured, the KILL_PIN pin being driven to "0" causes the kill() routine to be called. Before the end of the kill() routine, a call is made to suicide() which "turns off the power supply". kill() then goes into a while(1) -hangs waiting for the reset. Do we really want to do power cycle? I don't have good schematics, what is the SUICIDE_PIN connected to? kill() is also called based on an inactivity timeout.

We might want to post input for a best fix recommendation to the Marlin community. Anybody hooked in to them?

At a minimum, we have to make some kind of code change to make this work. At that point, it might be easiest to hack one of the unused limit switches.

Looks like Repetier does an emergency stop via hard reset through the USB and the ATMEGA16U2. Looking at the code it has something to do with a change in the connection status. Did not dig into it. I have observed this on other Arduino boards.

 

while(1) -we take a watchdog timeout?

 

Z -Math. Turn your printer on from a cold start and carefully calibrate the Z so it zeros with a piece of notebook paper (0.1mm) between the extruder and bed. Back off Z to 10mm or so. Turn extruder heater on to a temp of 190C running fan 100% for 15 minutes. Extruder has now expanded and is 0.2mm longer. If you were very careful to calibrate, the nuts will eject the next time you home the Z because the nozzle tip will keep the Z micro from closing. So only Z home after the Robo 3D is back up to full temp.

Ran two cool down cycles with a dial indicator and was seeing just shy of 0.008" extruder contraction after the heater power was shut off and extruder was allowed to cool to room temp 20C with initial temp of 190C. Indicator was quickly zeroed at the start of each cool down when it came into contact with the extruder tip to minimize initial thermal expansion of the indicator itself.