How can I define extruder endstops?

[properN00b 1]

Hi everyone!

 

Before I start off:  I am working with an UM2+, Cura 4.3.0 on Windows 10 and the tinkergnome UM2+ firmware.

 

I am currently working on a university project. The aim is to convert the regular UM2+ into a printer which can do both regular and bio-printing (bio-printing is in short words the printing of hydrogel in which you can implement cells, so you can print organic material in every desired form). To achieve this I already designed and printed a syringe pump which is driven by more or less the same stepper motor the current extruder is using. This makes it possible to switch from regular to bioprinting by unplugging the extruder motor and plugging in the syringe pump. This leads to my question: In order to keep the syringe pump from crashing every time the syringe gets empty, I want to include two endstops for the extruder motor. I already took a look into TinkerGnome´  s Firmware and I could imagine that it should be possible to include the endstops within the definition of the regular endstops. The desired reaction would be to pause the current print until the material "is changed".

What I am asking for at this point is experience. Has anyone ever tried to do this and could maybe even help me out with some code advises? I have some programming experience, but mostly with Java and Python so I could really use some help. Especially as the firmware is pretty huge and I am not sure which files have to be edited to make this work. Also I am not entirely sure how to compile and upload the edited firmware. I tried setting up the regular Marlin firmware (the way it was explained in a YT tutorial) but all I got was a huge bunch of errors on the Arduino IDE, mostly Index out of bounds... 

I know I am asking for a lot and I could totally understand if nobody is willing to put that much effort into a stranger´  s project. But I promise if you can help me and I should ever run into you in real life I will buy you a couple of beers!

Cheers,
Max

[properN00b 1]

By the way, I also discovered that there is an option to include "virtual endstops".  This sounds like a pretty good solution as well, especially as the hardware modification would not be needed anymore. If this means I have to sacrifice a little bit of extra safety I would be fine with it.

[tinkergnome 772]

3 hours ago, properN00b said:

The desired reaction would be to pause the current print until the material "is changed".

 

Detection of endstops is usually disabled during printing, but this sounds very similar to a simple "filament end detection".

Support for such a function was added to the tinker-firmware in 2015. This would need a simple switch that connects two pins on the Arduino board when the syringe reaches its end position.

It was originally meant to be used with a more complex sensor, but it turned out that this was all what it needs:

https://community.ultimaker.com/topic/5896-more-information-during-print/page/10/?tab=comments#comment-122987

 

There are some instructions and pictures about the cable connections as well - and it's easy to test with a (pair of) wire.

 

The firmware does not do much more than this part:

https://github.com/TinkerGnome/Ultimaker2Marlin/blob/geek_mode/Marlin/filament_sensor.cpp

 

Hope that helps!

 

[properN00b 1]

This sounds like a perfect solution. I will try and see how it goes. Thanks again for the help, remind me of the beer if it works!

[properN00b 1]

Finally got to try it out and it does exactly what I hoped for. I really start loving your firmware more and more. It´  s also great to see that much support in the community. Big ups to you!