Today I finished building and adjusting a Prusa-Clone printer. The brain is a 32bit board with Smoothieware on in. To run the auto bed leveling routine I installed a 3DTouch (BLTouch clone, sorry low on cash). After many headaches, I got everything working fine and I'm happy with the result. Except for one thing...

When the 3DTouch is probing, it is triggered when the nozzle is about 1 mm from the bed. If I set the probe higher, the nozzle crashes onto the bed. If I set the probe lower, the probe would be on the same level of the nozzle, not so good for print time.

Anyone with similar experience or how to sole it? google doesn't show up much regarding this.

Thanks in advance!

  • $\begingroup$ So guessing from your story, you are running Marlin? Have you changed the Z-offset on the printer itself? $\endgroup$
    – Granny
    Jan 15 '18 at 14:00
  • $\begingroup$ No, actually I'm not. I'm running on a Smoothieware powered board (no flag found about that). The question is not about the software, which I know how to manipulate with the offsets, but regarding the hardware, the 3DTouch (also no flag) $\endgroup$ Jan 16 '18 at 14:41
  • $\begingroup$ I installed a 3D touch yesterday on my Anet A8 and i had 0 problems setting it up. Are you sure you wired it correctly? And also set it up correctly in the firmware? How are you sure its not firmware related? $\endgroup$
    – Granny
    Jan 17 '18 at 7:36
  • $\begingroup$ The probe works ok and it does what it's supposed to do, it justs triggers way too late. The pin has to be introduced quite a bit before it triggers. $\endgroup$ Jan 20 '18 at 13:03
  • $\begingroup$ Probably something wrong with the probe itself then. Cause i have a clone aswell and it touches very lightly. $\endgroup$
    – Granny
    Jan 22 '18 at 7:40

That it triggers when the nozzle is about 1 mm from the build plate is how it is supposed to work. The installation manual describes how to setup the sensor.

The mount needs to be adjustable so that the distance between the bottom of the sensor (not the pin) needs to be 8.3mm above the tip of the nozzle.

When taking the above distance into account, the probe should be hitting the build plate first when it is extended. When the probe triggers, it triggers at a certain distance from the nozzle. It is this distance that you need to add as an offset so that the printer knows where the actual Z=0 is. To determine the offset, you home the printer, then lower the head until a piece of paper gives a little drag when pulled under the nozzle. From the display you can read the offset, e.g. -1.4. With command M851 Z-1.4 you set the offset between level and trigger point. Use M500 to store the new settings.


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