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Z calibration revisited  

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Henry Casson
(@henry-casson)
Trusted Member
Z calibration revisited

This is a continuation of my original thread " Calibration failed". I started a new thread to save you a long read. I got another intractable clog, and took down my hot end again. On reassembly I once again got the calibration error.. "check axes and try again." This time my messing around with the Z axis did not work. So I thought some more. Calibrate XYZ starts with calibrating Z. So how does the device' s teinsy brain know where the head is in Z. It certainly does, as it displays the value. The stepper can count turns, but it must do so from a sensed Zero. This is provided by the PINDA sensing the bed. So calibrate Z should start by the head going down until the PInda sees the bed . Then it goes up to 5 mm. Now suppose the PINDA is stuck on " yes I sense the bed" . The head does not go down and keeps going up, because there is never a signal " Now I don't sense the bed". It keeps going up
until it hits the top z stops and stops, showing Z = 5. The clue was a chance remark from St Joan of Halifax, " change in the red light is not enough to prove that the PINDA works .. you need to check via the end stop display" . I thought that my PINDA was intermittent when I assembled the machine but the machine worked. I think I fixed it in a working position, but it eventually failed. So I chatted , since PRUSA should have replaced the probe ( 5 month old machine). Chat was so slow that I could do a sudoku between replies, and wanted pictures and movies. I realized that if, in my conceit I value my time at minimum wage, I would save by just buying one, which I did, and it worked. I learned a second lesson also. X calibration will fail at the first point of 4 if the head does not go close enough to the left side of the X axis. You need to see just about Zero of the shiny smooth rod at the left end. In my case I just needed to tuck in the left sided fan wires better. I redid the cable wrap for the PINDA wire. I may be approaching half of my ZIP tie supply.! 🙂

Retired doc, should have been an engineer.

Posted : 04/07/2018 6:47 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
Re: Z calibration revisited

That Joan... doesn't half go on! some times... 😯

regards....

er.... Joan 😳

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 04/07/2018 7:12 pm
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