Piezoelectric sensors and printhead angle detection

Hi everyone,

i’ve built a five-axis-printer based on the K8800, for my university. The fourth and fifth axis are uncoupled from the xyz-movement, so i can still use the original hardware and marlin firmware of the printer for now. Now i have two questions:

  1. In the product description video (‘Vertex Delta 3D Printer’ on youtube.com at 2:25) a printhead angle detection is mentioned, that halts the printer in case someone bumps into it. For my purpose i have to deactivate this safety feature, how can i do that?

  2. The printhead has a small backlash in z direction due to the Dynamixel motors i use. This causes some problems with the automatic calibration. When the nozzle touches the bed during the height calibration, sometimes the piezoelectric sensors don’t realize it because of the backlash. I’ve already set the sensitivity to the maximum with the potentiometer, but it’s not enough. Is there an option to increase the sensitivity beyond the maximum? Maybe by replacing the potentiometer with a larger resistor or an external circuit?

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Hello @Simon01

Sorry not knowing marlin firmware well, the built-in “accelerometer” or “Printhead angle detection” implementation or configuration dont pop to my eyes in the K8800 marlin Configuration.h. But seem logical to start looking in the firmware :

(cause i don’t know what is for, Maybee the “KILL_PIN” in the “pins_K8800.h” but i’m totally not sure …)

I haven’t really searched / found a schematic of the head PCB or info. for the piezo sensors sensitivity of the K8800. Maybee a careful search on the forum ?

But i’m really intrigued by the five-axis-printer concept … ( like are you using the head to prind in other angles than the basic vertical angle easy to do filaments deposit ?)

I ll be happy to have a view of your modified printer.

Wishing you will find what you need

Have a good day !

Hi PPAC,

thanks for your hints. I’ve had a look at the marlin code already and i couldn’t find anything related to the angle detection either. But i found a circuit diagram of the K8800 here in the forum, this helps me a lot:

The µC at the hotend sends a single kill-signal to the mainboard for both overheat and angle fault via pin: ‘PCBHOTEND-EXT1-KIL’
So i chose the trivial solution and removed this cable from the plug and it works :slight_smile:
I just have to be careful now about the temperature.

Auto calibration is possible when i ‘reinforce’ the hotend with some zip ties, although it’s also not the best solution. Relating to the circuit diagram it is a trial-and-error task to find the right level to trigger the BED-LEVEL-signal.
Maybe i’ll find another way, but for now i use the zip ties.

I’m glad that you are interested in my project. I would like to try out how swiveling the nozzle affects the printing of overhangs. Since there is no software for a five axis printer, i decided to uncouple the kinematic of the fourth and fifth axis from the xyz-movement. So i just need to write a little program to swivel the nozzle and use the standard firmware for the rest.

Both axes of rotation intersect at the nozzle tip, so the whole hotend rotates around the nozzle tip.

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Hello @Simon01

I’m impressed ! :star_struck:
Well beyond my skills.

You seem to have the skills to advance in your project / research.

Like choosing to uncouple the added axes. To avoid recreating the firmware and slicing software. ( On your first post, I was like : no way ! 5 axes means you have to totally rework all the softwares : unreachable project. But now, I see this is achievable)

Well ! “Bravo !”

Hoping you will subjugate this new techno-beast.
Have a good day !

Thank you very much.

Unfortunately i had no clue about 3D printing :sweat_smile:. But i’m learning and it’s a very interesting topic.

Thanks for your help.
Have a good day as well.

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