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Can someone explain Live Z?
 
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Can someone explain Live Z?  

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Phil
 Phil
(@phil-4)
Trusted Member
Can someone explain Live Z?

So, my understanding is that the Live Z is a "fudge factor" for the nozzle height. Basically, the machine lowers the nozzle to "0", but due to slight variations in PINDA measurements, bed heights, belt settings, etc. the known 0 might not be physical 0 so you have to adjust the actual nozzle height just a small amount, which is the Live Z.

So, my real question, if the bed height is at the same height, the nozzle is at the same height, and I am using filaments that are all 1.75 mm, why do I have to readjust live Z per filament type? What number is changing that causes live Z to need to be reset between PLA and PETG for instance?

Just curious and trying to understand how this all works.

Posted : 26/07/2018 3:42 pm
Zinga
 Zinga
(@zinga)
Trusted Member
Re: Can someone explain Live Z?

The Live Z adjust isn't really a fudge factor. It's the difference between the distance the PINDA triggers and the position of the nozzle. If you were able to print with a Live Z of 0, your PINDA would be exactly the same height as the nozzle and rubbing against the part as it printed. Mesh Bed Leveling is the fudge factor. It creates a 7x7 grid (extrapolated from the 9 measurements it does at the start of the print) and offsets your Live Z as the nozzle moves across the bed.

Posted : 26/07/2018 4:13 pm
bobstro
 bobstro
(@bobstro)
Illustrious Member
Re: Can someone explain Live Z?

It's all about that 1st layer. Individual layers will be the same distance from each other, but the distance between the 1st layer and the build surface is key. With Live Z adjustments, you're tweaking the distance between the nozzle and bed in simple terms. The reasons you might have to make adjustments between individual filament spools include:

  • Variation in actual filament diameter between manufacturers.

  • Consistency of filament and balance between getting the necessary "squish" for good adhesion and being too well stick and distorted.

  • Propensity of the material to stick to the nozzle instead of the bed. This is often cited as the reason for using a slightly higher setting for stick materials like PETG.

    • Changing nozzles or otherwise adjusting the extruder mechanism may also necessitate re-adjustment.

    IME, a lot of adjustment is not necessary if you're not switching materials or filament types frequently. It's a good troubleshooting step if I'm not able to get the 1st layer to adhere properly.

    My notes and disclaimers on 3D printing

    and miscellaneous other tech projects
    He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

    Posted : 26/07/2018 4:23 pm
    JoanTabb
     JoanTabb
    (@joantabb)
    Veteran Member Moderator
    Re: Can someone explain Live Z?

    The relationship between temperature and live Z is a mojor factor
    At higher temperatures. The distance changes due oto expansion and sensitivity of the pinda.

    The mk3 has an integrated thermistor to help offset the differences. But this needs to be calibrated for your printer

    Also petg doesnt need to be squished as much so also affects the process

    Regards 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 : 26/07/2018 6:58 pm
    Phil
     Phil
    (@phil-4)
    Trusted Member
    Topic starter answered:
    Re: Can someone explain Live Z?

    Thanks. That makes a lot of sense. Appreciate the quick answers.

    Posted : 26/07/2018 7:15 pm
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